04 - C208B - ND (Rev 3) - Part 6 - EDDY CURRENT

Model 208 Nondestructive Testing Manual (Rev 3)
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EDDY CURRENT BOLT HOLE TECHNIQUES - GENERAL

1. Description.
A. This procedure presents the general requirements for eddy current inspection of open fastener holes and may be used as
a standalone procedure or in conjunction with inspection procedures listed in Part 6.
B. This procedure shall not supersede inspection requirements when defined by a specific inspection procedure listed in Part
6 of this manual.
C. When a specific inspection procedure does not exist in Part 6 and where no specific inspection requirements are defined,
this procedure may be used.
D. This procedure gives set up instructions for both manual bolt hole inspection and semiautomatic bolt hole inspections for
impedance plane instruments.
E. This procedure gives general set up instructions which can be utilized by a variety of instruments. It does not give specific
instructions regarding instrument specific settings. It is the responsibility of the inspecting organization to be familiar with
the instruments being used.
2. Personnel Requirements.
A. For personnel certification requirements, refer to Part 1 - Personnel And Facilities of this manual.
3. Eddy Current Test System.
A. The eddy current test system shall consist, at a minimum of the following components.
(1) Eddy current instrument
(2) Probe
(3) Reference standard
(4) Cable
B. The test system shall demonstrate a repeatable signal response of a minimum of a 3:1 signal to noise ratio from the EDM
notch in the reference standard when compared to a defect free area of the reference standard.
C. The functional performance of the eddy current instrument shall be verified on an annual basis.
4. Materials and Equipment.
A. Tape.
(1) The tape used to help reduce noise and protect the coil on the probe should be Polytetrafluoroethylene (PTFE) or
similar type adhesive backed tape commonly known as Teflon™ tape.
(2) Other types of tape are allowed but it should be slick to allow the probe to rotate freely in the hole and have an
adhesive backing to adhere to the probe.
(3) Tape thickness for eddy current inspection will generally be in the range of 0.002 to 0.010 inches thick.
(4) If used, tape shall be applied prior to calibration to verify that the proper sensitivity is achieved. Refer to Table 3 or
Table 5.
(5) Calibration will be verified if a different thickness of tape is applied then what was used for the original calibration.
B. Instrument.
(1) The eddy current instrument will be an impedance plane type. Metered instruments are not allowed using this
procedure.
C. Probes.
(1) The probe may have an absolute, differential/reflection or differential/bridge coil arrangement. A differential/reflection
or differential/bridge coil arrangement is necessary for semiautomatic rotary bolt hole inspection, and highly
recommended for manual bolt hole inspections.
(2) Probes may be shielded or unshielded but must be able to provide the sensitivity and signal to noise ratio described
in this procedure.
(3) Probes for manual inspection shall have an adjustable collar to control and maintain the depth that the probe is
inserted into the hole.
(4) The probe shall not give interfering responses from normal handling pressures, or normal operating pressure
variations on the sensing coil.
Copyright © Textron Aviation Inc. Page 1 of 27

Retain printed data for historical reference only. For future maintenance, use only current data. Print Date: Sat Feb 03 18:37:07 CST 2018
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(5) An adjustable, self-expanding probe is recommended for semiautomatic inspection to ensure consistent coil contact
with the side of the hole.
(6) If a solid non-expanding probe is used it must fit the hole to allow for a minimum amount of lift-off. The difference
between the diameter of the probe and the diameter of the hole shall not exceed 0.005 inches either without tape
applied over the coil or after application of tape.
(7) Choose a probe that fits the hole snugly while still allowing for free probe travel.
(8) Teflon™ or similar tape may be used to help improve the signal to noise ratio and to decrease the wear on the eddy
current probe coil.
(9) The probe shall be capable of operating at the frequency required for the material being inspected. Refer to Table 1
for guidance on probe operating frequencies.
Table 1. Materials
Condition Material Type (NOTE 1) Frequency (NOTE 2)
Aluminum, Magnesium (15% or greater
Nonmagnetic, High conductivity 200kHz-500kHz
IACS)
Magnesium (< 15% IACS), Titanium,
Nonmagnetic, Low conductivity 1MHz-3MHz
Inconel and Nickel alloys
400 series Stainless, 17-7 TH1050,
High permeability 4130 or 4300 series Steels, in any heat 400kHz-1MHz
treat condition
301 series, 304 series stainless, 17-7
Low permeability or Nonmagnetic 1MHz-3MHz
PH annealed
NOTE 1: Material types listed are for information only, these are examples of common materials that
would fall into the ranges listed under the heading, "Condition"
NOTE 2: The frequencies listed above are generally recognized to provide the optimum sensitivity in
the materials listed. Use of frequencies outside of those listed are allowed providing that the
sensitivity can be verified on the correct size EDM notch on a reference standard of similar
material.
D. Reference Standards.
(1) Reference standards should be constructed of an alloy similar to the base metal of the test object and conform to the
requirements listed in Table 2.
(2) Reference standards shall have a minimum surface finish of 150 RHR or RMS 165.
(3) Reference standards used in accordance with this procedure shall at a minimum, have 1 corner EDM notch of 0.030
inch x 0.030 inch x 0.007 inch for the hole size being inspected.
(4) A 0.030 inch x 0.030 inch corner notch or 0.050 inch x 0.050 inch corner notch shall be used for calibration unless
otherwise specified. Refer to Table 3 and Table 4 in the calibration sections for sensitivity levels for the different sized
notches.
(5) The dimensional accuracy of EDM notches shall be documented and traceable to the National Institute of Standards
and Technology (NIST).
(6) A typical eddy current bolt hole reference standard is shown in Figure 1.
Table 2. Materials
Inspection Material Type Material for Reference Standard (Note 1)
All conductive non-ferromagnetic alloys with Non-ferromagnetic alloy with a conductivity that 2024-T3 27.5-32.5
conductivities of 15 percent IACS or greater. is within ±15 percent IACS of the test material %IACS 7075-T6 30.5-
range, but not lower than 15 percent IACS. 36 %IACS 7075-
T76XX 38-42 %IACS
6013-T6X 40-43
%IACS 6061-T6 40-50
%IACS

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All conductive non-ferromagnetic alloys with a Non-ferromagnetic alloy with a conductivity that Titanium 6AL-4V 1.01
conductivity of 0.8 percent IACS to less than 15 is not more than 1.0 percent IACS greater than %IACS Inconel 1.7%
percent IACS. the test material range or less than 0.8 percent IACS Magnesium
IACS. AM100A-T4, AZ91C-
T4, AZ91E-T4 9.9
%IACS
High permeability steel 400 series Stainless, 17-7 TH1050, 4130 or 4300 series steels in any
heat treat condition.
400 series stainless steel alloys. Any 400 series stainless steel alloy.
Low permeability alloys. 304 stainless or 17-7 PH annealed.
NOTE 1: Materials listed are for information only. These are some common materials available and may be
used. Reference standard material needs to conform to the requirements of Table 2.
5. Inspection Preparation.
A. Hole bores shall be round and smooth enough to not cause eddy current signals that would exceed a 3:1 signal to noise
ratio. Refer to Figure 10 and Figure 11.
B. Visually inspect hole bores for nicks, burrs, scoring or other conditions that may cause an excessive noise signal.
C. Any hole condition that would cause damage to the probe is not suitable for inspection. The condition must be corrected
prior to inspection.
D. If necessary, clean up the holes prior to the inspection utilizing one or more of the following methods.
(1) Methods generally considered acceptable for cleaning are, (but are not limited to).
(a) Solvent moistened cotton swab.
(b) Scotch bright.
(c) Flex Hone.
E. Do not oversize the hole during the cleaning process unless specifically allowed per the Maintenance Manual, the
Structural Repair Manual, the Component Maintenance Manual, or on direction from Cessna Engineering.
F. If allowed per the Maintenance Manual, Structural Repair Manual, Component Maintenance Manual, or other maintenance
document or Engineering, a 1/64th inch, or the amount as directed, clean up ream may be performed if needed to achieve
a satisfactory surface condition of the hole.
G. If the hole cannot be satisfactorily cleaned up to allow for an inspection, contact Citation Customer Service for instructions.
Refer to the Introduction for contact information.
H. Continue to Section 6 for Manual Probe Calibration or Section 7 for Calibration for Semiautomatic Hole Inspection.
6. Manual Probe Calibration.
A. The instrument shall be calibrated and operated in accordance with this procedure and the manufacturer's instructions.
B. The minimum single layer material thickness that can be examined using a manual probe hole inspection is 0.063 inch.
C. Instrument calibration shall be performed prior to inspection. Calibration shall be checked periodically during continuous
use and at the conclusion of the inspection. If the calibration is below the levels originally established, all holes inspected
since the last known good calibration check shall be reinspected. The instrument calibration shall be verified if any part of
the system is replaced or if any calibrated control settings are changed.
D. Teflon™ Tape is highly recommended to be placed over the probe coil. It will act as a wear surface and on high
permeability steel will greatly improve signal to noise ratio.
E. Positioning the thumb screw in line with the coil will help to define the position of the coil when the coil is in the hole. Refer
to Figure 2.
F. The use of a Low Pass Filter will help to improve the signal to noise ratio. Set it to the highest value that does not cause
the signal to be unstable.
NOTE: Do not use the High Pass filter with the manual probe, regardless of the coil type.
G. Setting Lift-Off for Absolute Probe.
(1) Select the probe for the best fit in the hole to be inspected and based on the requirements of Table 1.
(2) Select the standard for the material being inspected based on the requirements of Table 2.

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(3) Turn on the instrument.

(4) Connect the probe to the instrument using the proper cable and or balance coil.
(5) Set the instrument frequency as appropriate per Table 1, for the material type being inspected.
(6) Position the trace dot in the lower right hand quadrant of the screen, approximately 80% horizontal and 20% vertical
for non-ferromagnetic materials and 50-60% horizontal and 20% vertical for ferromagnetic materials.
(7) Place the probe on the surface of the standard with the collar hanging over the edge so the coil is in contact with the
surface of the standard. Refer to Figure 3.
(8) Ensure that there is no influence on the coil from any EDM notch, edge of the standard or hole edges.
(9) Press the null/balance button.
(10) Lift the probe off of the standard and adjust the phase or rotation so lift-off is traveling horizontal and to the left. Refer
to Figure 3.
(11) With the probe on the standard, rock the probe a little, if the dot moves to the right of null, re-null if necessary.
H. Setting Lift-Off for Differential Probe:
(1) Select the probe for the best fit in the hole to be inspected and based on material type per Table 1.
(2) Select the standard for the material being inspected based on the requirements of Table 2.
(3) Turn on the instrument.
(4) Connect the probe to the instrument using the proper cable and or balance coil.
(5) Set the instrument frequency as appropriate per Table 1 for the material type being inspected.
(6) Set the screen position of the dot to 50% horizontal and 50% vertical.
(7) Place the probe on the surface of the standard with the collar hanging over the edge so the coils are in contact with
the surface of the standard. Refer to Figure 4.
(8) Ensure that there is no influence on the coil from any EDM notch, edge of the standard or hole edges.
(10) Roll the probe from side to side while monitoring the display. Do not lift the probe from the standard.
(11) The dot should move back and forth from the center position as the probe is rolled back and forth. Reference Figure
4.
(12) Adjust the phase/rotation to position the trace going horizontal. Refer to Figure 4.
NOTE: If the dot moves farther in one direction than the other, the coils were not perfectly centered on
the surface of the standard when the null button was pressed. For setting the "Lift-Off" it is not
that important that the signal is symmetrical.
I. Adjusting Gain:
(1) Adjust lift-off for the probe being used. Refer to Setting Lift-Off for Absolute Probe or Setting Lift-Off for Differential
Probe before continuing.
(2) Apply Teflon™ tape to probe over coil if needed.
(3) Position the probe collar so as to position the center of the coil approximately 0.030 inches below the edge of the
collar and tighten the thumb screw. Use this dimension for either the 0.030 inch x 0.030 inch or the 0.050 inch x 0.050
inch notch. Refer to Figure 2.
NOTE: Typical shielded probe coils on most bolt hole probes are 0.060 inches in diameter, and
unshielded probe coils are 0.090 inches in diameter. Use these diameters as a guide in
positioning the edge of the collar.
(4) Place the probe in the appropriate hole of the reference standard with the coil away from the EDM notch.
(6) Rotate the probe in the hole so as to pass the coil over the corner EDM notch.
(7) Adjust the gain to obtain a minimum signal response from the corner EDM Notch. Refer to Table 3.

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Table 3. Calibration levels.

EDM Notch Size (in Absolute Probe Figure Differential Probe Figure
inches) Minimum Peak Minimum Peak to
Signal Response Peak Signal
Response
0.030 X 0.030 3 Divisions Figure 5 30% Figure 7
0.050 X 0.050 7 Divisions Figure 6 70% Figure 8
J. Continue to Section 8 to Determine Layer Thicknesses and Section 9 for the Manual Probe Inspection.
7. Calibration for Semiautomatic Hole Inspection.
A. The instrument shall be calibrated and operated in accordance with this technique and the manufacturer's instructions.
B. The minimum material thickness that can be examined using semiautomatic hole inspection is 0.020 inch
C. Adjusting filter settings is very helpful in reducing noise and fine tuning the signal on the display and is necessary to
achieve satisfactory results.
NOTE: Filter settings must be set correctly to achieve satisfactory results. To much input or not enough
input from either, or both of the filter settings can be very detrimental to the inspection and may
result in missed flaws. Consult the manufacturers instructions regarding your specific instrument
for specifics about setting the filters.
D. The High Pass Filter (HPF) should always be set to a value lower than the Low Pass Filter (LPF).
E. As a general rule, as hole sizes increase in diameter and or scanner rotation speed increases, the HPF and LPF settings
will need to be increased.
F. Most Nortec instruments default to filter settings of 500 for the LPF and 200 for the HPF. These are generally good
numbers and may not need to be changed. Other manufactures may have different systems for setting the filters such as
possibly a Band Pass filter option. Refer to the scope manufacturer's, owners manual for setting the filters if needed.
G. The HPF should be set to optimize the response from the EDM notch. The HPF allows high frequencies to pass, (crack
indications would be considered a high frequency response) or suppresses low frequencies produced by changes
occurring over a longer period of time of coil contact such as, the hole being out of round, or minor surface blemishes.
H. The LPF should be set to minimize the high frequency responses typically caused by noise generated by the probe and or
the instrument while allowing lower relative frequency signals to pass such as from relevant crack indications. The LPF
allows low frequencies to pass, or rejects high frequencies typically caused by noise generated by the probe or instrument.
I. Instrument calibration shall be performed prior to inspection. Calibration shall be checked periodically during continuous
use and at the conclusion of the inspection. If the calibration is below the levels originally established, all holes inspected
since the last known good calibration check shall be reinspected. The instrument calibration shall be verified if any part of
(1) Setting Lift-Off.
(a) Select the probe for the best fit in the hole to be inspected and based on material type per Table 1.
(b) Select the standard for the material being inspected based on the requirements of Table 2.
(c) Apply Teflon™ tape to probe over coil if needed.
NOTE: Teflon™ tape is highly recommended and will greatly improve signal to noise ratio when
inspecting high permeability steels.
(d) Insert probe into scanner.
(e) Connect scanner to the using the appropriate cable.
(f) Turn instrument on.
(g) Set the frequency based on the material being inspected. Refer to Table 1.
(h) Turn the Sweep function off and adjust the instrument to have a flying dot or impedance plane display.
(i) If your instrument doesn't automatically position the dot at the center of the screen, adjust the X and Y position
controls to position the dot at the horizontal and vertical center of the screen.
(j) Set the instrument initial gain setting to a 1:1 ratio.
(k) Refer to Table 4 and set initial filter settings based on probe diameter. Continue with Setting Filters, Calibration

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for Semiautomatic Hole Inspection Calibration after setting lift-off to ensure filter settings are optimized for the
inspection.
(l) Turn on the scanner.
NOTE: If the scanner rotation speed is adjustable, set it for a minimum of 1,000 RPM's. For larger
diameter holes scan speeds over 1500 to 2000 RPM may be necessary to ensure
complete coverage unless scan index speeds are kept very slow.
1 Slower scanner rotation speeds will require slower scan indexing speed in the hole.
2 For steel or other high permeable materials, a slower scan rotation is often helpful in reducing interference
from noise. If necessary, reduce scanner rotation speed until an acceptable signal to noise ratio is
achieved.
3 Do the Determining Maximum Scan Index Speed steps after final adjustment in scanner rotation speed.
(m) If the dot is not at the center of the screen, press the null button.
(n) Hold the scanner so the probe is parallel to the surface of the standard. Refer to Figure 9.
(o) Place the probe in contact with the standard using light pressure, keeping the coil away from edges and EDM
notches. This will generate a lift-off signal as the coil rotates. Refer to Figure 9.
(p) Adjust the phase or rotation to position the flat portion of the signal from lift-off horizontal, along the X axis. Refer
to Figure 9.
NOTE: The signal from lift-off should be a flattened figure 8 pattern. The less vertical spread there
is in the signal from the lift-off, the less base line noise there will be on the sweep trace. If
the signal from lift-off exceeds 2 major divisions in total vertical spread, reduce the gain
until the signal from lift-off is less than 2 major divisions vertically and all or mostly on
screen in the horizontal direction. Refer to Figure 9.
(2) Setting Filters
(a) Use the values in Table 4and or the following steps for initial filter settings:
1 With the scanner on and the probe in the appropriate hole in the reference standard.
2 Set the HPF to the lowest value.
3 Increase the HPF value until the signal sweep flattens out. Depending on where the LPF is set the signal
may look a little noisy at this point.
4 Set the LPF to it's highest value.
5 Decrease the LPF value to get a stable dot or until the spikes from the noise signals decrease and the
signal from the notch in the reference standard just starts to decrease.
Table 4. Probe Diameters
Probe Diameter (in inches) 5/32 to 7/32 7/32 to 5/16 5/16 to 7/16 7/16 to 3/4
LPF 500 500 700 1500
HPF 150 200 300 500
NOTE 1: The values in Table 4 are meant as a guide. They will generally provide good results.
Use them as a starting place and adjust them as needed to obtain the best signal to
noise ratio and the most uniform response from the EDM notch.
(3) Setting Inspection Gain.
(a) Follow the steps for Setting Lift-Off and Setting Filters prior to setting the gain.
(b) Follow equipment manufacturer's directions on how to turn the Sweep on, and set the scope to display the
sweep trace.
NOTE: Do not set the display to a Waterfall, Timed or Sync type display. Those displays are for
use with an automatic scanner and specialized equipment.
(c) Turn on the scanner.
(d) Insert the probe into the appropriate sized hole in the reference standard.
(e) Maximize the signal from the corner EDM notch at the surface of the standard by moving the probe in and out of

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the hole until the best signal is achieved.

(f) Adjust the gain and probe drive controls to achieve a minimum signal response from the reference notch as
defined in Table 5.
NOTE: A probe drive of low or medium will usually provide better results than a probe drive of
high. High probe drive can easily over drive the coils in the probe causing a saturated
condition and loss of signal and sensitivity.
(g) Adjustments may need to be made in the Filter settings after setting the inspection gain as one does affect the
other. After setting the gain, if the signal from the EDM notch is distorted or asymmetrical, or if the noise level is
to high, make some adjustments to the HPF, or LPF as required. You may need to go back and forth between
Filter and Gain settings a couple of times to achieve satisfactory results.
Table 5. Notch Size Values
EDM Notch Size (in inches) Peak to Peak Signal Response Figure
0.030 X 0.030 30% Figure 10
0.050 X 0.050 60% Figure 11
(4) Determining Scanner Zero or 12 O'clock Position.
NOTE: When the scanner is on, the sweep trace from the left side to the right side of the screen
represents one 360 degree revolution of the probe in the hole, regardless of the size of the
hole or the speed of the scanner. So determining the circumferential position of an indication
is a matter of determining where "zero" is on your scanner. Most manufacturers scanners will
position the indication from the notch at the left (0 ) and right (100 percent) edge of the screen
simultaneously when the top or front of the scanner is pointed at the indication. Refer to
Figure 12. The steps below will set the zero position from the notch indication as stated above.
(a) Find a notch that you know the position of in the reference standard.
(b) With the scanner turned on, insert the probe into the appropriate size hole in the reference standard.
(c) Maximize the signal from the notch you are going to use to determine zero.
(d) Rotate the scanner while keeping the signal from the notch visible on the display. As the scanner is rotated, the
notch signal will move to the left or right along the sweep line depending on which direction you move the
scanner.
(e) Stop when the front or top of the scanner is pointing in the direction of the notch. Refer to Figure 12.
(f) The indication from the notch should be at the left hand and right hand side of the screen simultaneously, 0 and
100 percent. Reference this as the Zero or 12 O'clock position. Refer to Figure 12.
(g) With the scanner oriented in this position, an indication that was at the opposite side of the hole, towards the
rear of the scanner or 6 O'clock, would be at the 50 percent screen width on the sweep trace. Refer to Figure 13.
(h) An indication at 9 O'clock would show on the sweep trace at approximately 25% and an indication at 3 O'clock
would show at approximately 75%. Refer to Figure 13.
NOTE: If the indication from the notch using your scanner is at a different screen position than
stated above, that is okay. Make a note of the location on the screen of the indication
when the top of the scanner is pointed towards the notch. Make adjustments to the other
clock positions by the same amount as the zero position is off.
(5) Determining Maximum Scan Index Speed.
(a) Insert the probe into the appropriate hole in the reference standard and locate the corner notch at the interface of
the first and second layers.
1 If using a single layer standard, insert the probe from the side opposite the notch and move towards the
notch, stopping before the probe exits the hole and reversing direction of travel back towards the entry
surface.
(b) Monitor the display while moving the probe in and out over the notch.
(c) Gradually increase the probe travel speed until the peak height of the notch response begins to decrease below
30% Peak to Peak.
(d) This is the maximum probe scan index speed.

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J. Continue to Section 10 for the Semiautomatic Inspection.

8. Determine Layer Thicknesses.
A. For manual probe inspection using an absolute probe the thickness of the layers to be inspected must be known for proper
indexing. If the layer thicknesses are already known, continue to Section 9 for the Manual Probe Inspection. If not, continue
with the following steps to determine the thickness of the layers.
B. If inspections will be performed with a differential probe, you do not have to measure the layer thicknesses. If you choose
not to measure the layers continue to Section 9 for the Manual Probe Inspection and index per step 9.A.(2).
C. Inspection steps to determine layer thicknesses if they are not known.
NOTE: The following steps must be performed using an absolute coil hole probe.
(1) Set the collar to a depth so the coil will not be influenced by any edge or interface.
(2) Insert the probe into the hole.
(3) Press the Null/Balance button.
(4) Loosen the collar set screw and push the shaft of the probe into the hole toward the interface.
(5) When you reach the interface, you will get a crack like indication from the interface.
(6) Stop moving the probe when the indication is at maximum amplitude.
(7) If the indication is off screen, record the current the gain setting and reduce the gain until you can pass the interface
and keep the indication from the interface on screen.
(8) When the indication from the interface is at the maximum amplitude, stop moving the probe and tighten the collar set
screw.
(9) Remove the probe and measure the thickness of the layer from the bottom of the collar to the center of the coil.
NOTE: If there are multiple layers that will need to be measured for thickness, do not move the
position of the collar.
(10) Inspect the layer per the indexing in Table 6.
D. If there are multiple layers, make a note of this measurement and continue determining the remaining layer thicknesses as
follows.
(1) Without adjusting the depth of the probe collar, insert the probe into the hole until the collar is seated on the surface of
the structure.
(2) The dot position should return to where it was in step C.(8).
(3) Loosen the set screw and push the probe slowly in to the hole. The dot should return to the null position.
NOTE: If the layers are not all the same materiel alloy and heat treat, the dot may not return to the
exact null position as in step C.(3). As long as it's in the same general area that's fine. If it's off
screen, press the null/balance button to bring it back on screen.
(4) Continue pushing the probe into the hole until the next interface is reached. When you reach the interface, you will get
a crack like indication from the interface.
(5) Stop when the signal from the interface is at maximum amplitude.
(6) Tighten the collar set screw and remove the probe from the hole.
(7) Measure from the bottom of the collar to the center of the coil.
(8) Subtract the measurement of the previous layer/layers from this measurement.
(9) Make a note of the layer thickness.
(10) Repeat steps D.(1) thru .(9) as needed until all layers have been measured.
NOTE: After all of the layers have been measured, if the instruments gain setting was changed in step
8.C.(7), set it back to the value that you recorded.
E. When all layers have been measured, continue to Section 9 for the Manual Probe Inspection.
9. Manual Probe Inspection.
A. The following instructions will provide inspection guidance for manual bolt hole probes using a differential or absolute coil
arrangement.
(1) To determine layer thicknesses if they are not known, do the steps in Determine Layer Thicknesses.

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(2) If using a differential probe. It is optional to set the collar for a depth of 0.030 inches and index every 0.060 inches to
within 0.030 inches of the opposite surface.
NOTE: With a differential probe there will be very little or no impact from the interfaces of the different
layers.
(3) Calibrate manual probe, refer to Manual Probe Calibration.
(4) Set the collar for a depth as directed per Table 6 or section 6, Manual Probe Calibration for differential probe collar
depth.
(5) Insert the probe into the hole, hold the probe steady with the collar firmly seated on the surface of the structure.
(6) Press the Null/Balance button on the instrument.
(7) Rotate the probe through the entire diameter of the hole for each index depth required.
(8) Monitor the display through each rotation for any crack like indications.
NOTE: If there is dot movement not consistent with that of a crack. You may have nulled on or very
close to a crack. Position the probe in another spot in the hole at the same depth and re null,
and re inspect the hole at the same depth.
NOTE: As in a surface inspection, dot travel will follow the same direction relative to lift-off for a crack.
Dot movement in directions other than that which would be consistent for a crack in the
material being inspected need to be investigated for relevance before being rejected as a
crack.
(9) If an indication is noted, refer to the Evaluation section, for characterization instructions.
Table 6. Scan Index For Layer Thickness
Layer Thickness (in inches) Scan Index
.063 to 0.090 Middle of the layer.
0.090 to 0.120 .030 inch from each edge/interface.
Greater than 0.120 to 0.180 0.030 inch from each edge/interface plus the middle of the layer.
Greater than 0.180 0.030 inch from each edge/interface plus 0.060 inch index.
10. Semiautomatic Inspection.
A. Inspection steps for semiautomatic hole inspection.
(1) Calibrate per steps in the Calibration for Semiautomatic Hole Inspection section 7.
(2) Set the instrument to Sweep display.
(3) Visually inspect holes per the Inspection Preparation section, and correct any conditions that would prevent an
acceptable scan.
(4) Check fit the probe to the hole/holes being inspected to ensure that the correct probe size is being used. Adjust fit if
needed.
(5) With the probe scanner turned on, slowly insert the probe into the hole while monitoring the display.
(6) Make a complete scan of the entire length of the bore of the hole.
NOTE: A complete scan consists of monitoring the display as the probe is inserted all of the way into
and through the hole and then back out of the hole.
NOTE: Do not exceed the index speed established in the calibration section.
B. Any indication while in sweep mode that differentiates itself from baseline noise, needs to be investigated for the
possibility of it being a crack.
(1) With the probe in the hole and the scanner on, maximize the indication.
(1) Turn the Sweep mode off so the flying dot or impedance plane mode is on.
NOTE: As in a surface inspection, dot travel will follow the same direction relative to lift-off for a crack.
Dot movement in directions other than that which would be consistent for a crack in the
material being inspected need to be investigated for relevance before being rejected as a
crack. Refer to Figure 14, for examples of crack indications in different materials.
NOTE: If the indication in the display is traveling in a direction not consistent with a crack for the

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material being tested, it is probably not a crack. It still may be a rejectable condition though.
Determine what the cause of the indication is to determine if it is rejectable.
C. If an indication is noted, refer to the Evaluation section, for characterization instructions.
11. Evaluation.
A. General
(1) Any vertical deflection that is distinguishable from the null position and lift-off, and is not caused by noise, lift-off or
part geometry is cause for further investigation regardless of signal amplitude. There are no acceptable cracks.
(2) Unless otherwise specified, all cracks are rejectable regardless of length or signal amplitude.
(3) Indications with a phase response different from the reference notch may indicate hole contamination or damage. If
indications exceed a 3:1 signal to noise ratio, additional hole preparation, reaming and/or cleaning, may be required.
(4) If horizontal lift-off is greater than 40% FSW on the impedance display check for out-of-round condition or interface
noise. If allowed, have the hole reamed and then reinspect.
NOTE: Any damage to the bore of the hole that cannot be corrected through limits established in the
Structural Repair Manual must be reported to Citation Customer Service Engineering, refer to
Introduction for contact information. Nicks and gouges are a rejectable condition as they
could easily develop into a crack. These should be reported the same as reporting a crack
indication.
(5) Do not report the depth of the crack radially (distance into the material from the edge of the hole). Due to the nature of
how a crack forms as compared to an EDM notch, depth measurements are very unreliable and should not be
reported.
(6) The use of a borescope, flashlight or other visual aids may be necessary to determine the cause of an indication.
(a) If a crack like indication is found:
1 Identify the circumferential position of the indication.
2 Using an approved marker, mark the position around the hole to define the orientation of the crack.
3 If the indication is repeatable, verify that it is not due to foreign material stuck to the side of the hole or
some other non relevant indication.
4 After the circumferential position has been established, inspect the hole again, if the circumferential
position of the indication changes, it is not a crack.
5 Look into the hole using any means suitable to determine if any foreign material in the hole could be
causing the indication.
6 If the fasteners were cadmium (cad) plated, pay particular attention to the possibility that some of the cad
plating could be stuck to the side of the hole. Cad plating will give a very strong crack like indication on
sweep mode but it will appear going near vertical when in the flying dot mode. Cad plating stuck to the side
of the hole will usually be small, darker grey specs and would be located in line with the circumferential
position of the crack indication.
NOTE: An X-ACTO™ blade or small dental pick can be useful to help remove a piece of cad
plating stuck to the side of the hole. Use care to not gouge or damage the bore of the
hole.
B. Manual Probe.
(1) For manual hole inspection, when the eddy current probe is centered over a crack, the signal will be at maximum and
a small movement of the probe will cause the signal to diminish, returning to the null point. Corrosion pits, foreign
material, gouges or other damage, will generally be apparent for a longer degree of probe rotation before the signal
from the indication returns to the null point.
(2) A crack indication will follow the same phase direction as a crack indication would in a surface inspection for the
material being inspected.
(3) If the indication in the display is traveling in a direction not consistent with a crack for the material being inspected, it
is probably not a crack. It still may be a rejectable condition though. Determine what the cause of the indication is to
determine if it is rejectable.
(4) Nicks and gouges may have a signal similar in phase to a crack but the indication on the screen will usually be wider

20-00-01-0 (Rev 3)
and more vertical and may apparent for a longer duration of probe rotation.
(5) Determining the length of a crack.
(a) Insert the probe into the hole to approximately the depth of the crack.
(b) Locate the crack and peak the amplitude from the crack.
(c) If the peak amplitude from the indication is off screen, reduce the gain until the whole indication is visible in the
display.
(d) Rotate the probe back and forth across the crack while moving the probe towards the end of the crack until a
point is reached where the crack signal peak amplitude has been reduced by 50 percent.
(e) Tighten the set screw.
(f) If the crack is located common to the near surface, remove the probe and measure from the center of the coil to
the edge of the collar. Report this dimension as the length of the crack.
(g) If the crack is common to an interface or the far edge, tighten the set screw on the collar and make a mark on the
probe shaft with a sharp pencil at the end of the collar.
(h) Loosen the set screw and move the probe towards the interface or far edge, once the interface or edge is
determined, tighten the set screw and make another mark on the probe shaft.
NOTE: The interface or far edge can be determined by rotating the probe so the coil is not
influenced by the crack and nulling the instrument. Slowly push the probe in towards the
interface or edge. Both will give an indication very similar to a crack. Use the same
method as finding the end of the crack to locate the edge of the interface or far edge of
the part.
(i) Measure the distance between the center of the two marks. Report this dimension as the length of the crack.
C. Semiautomatic Probe.
(1) Characterization to determine relevance of a crack indication should always be done with the display in the flying dot
or phase analysis mode.
(2) Maximize the signal from the indication.
(3) With the display set to the flying dot mode, observe the signal characteristics of the indication.
(a) A crack will follow the same phase direction as a crack would in a surface inspection for the material being
inspected, up and to the left for aluminum and vertical for steel. Semiautomatic inspection indications will have
both a positive and negative component although they may not be equal.
(b) Corrosion will have a response that is very random and will have vertical and horizontal components to the
indication. The signal will have the look of a birds nest on the display in the flying dot mode and on the sweep
mode will most likely have multiple indications along the sweep base line similar to a noisy hole.
(4) Determining the length of a crack.
(a) Set the display on the scope to Sweep mode.
(b) With scanner turned on, insert the probe into hole with crack indication.
(c) Peak the signal from the crack indication.
(d) If the peak amplitude from the indication is off screen, reduce the gain until the whole indication is visible in the
display.
(e) Move the probe in the hole until the signal from the crack is reduced by 50%.
(f) Hold the scanner steady while maintaining the signal from the crack at 50%.
(g) Using a sharp pencil or other fine point marker, lay it on the surface of the part so that the point is at the same
level as the surface of the part.
(h) Slowly move the pencil towards the shaft of the probe as it's rotating and make a mark on the probe shaft even
with the surface of the part. Refer to Figure 15.
(i) If the crack is located common to the near surface, remove the probe and measure from the center of the coil to
the center of the mark on the probe shaft. Report this dimension as the length of the crack.
(j) If the crack is common to an interface or the far edge, continue moving the probe in the hole until the interface or
edge is defined or by a reduction in the signal amplitude of the crack indication of 50%.

20-00-01-0 (Rev 3)
(k) Hold the scanner and probe steady in the hole and make another mark on the probe shaft. Refer to Figure 15.
(l) Remove the probe from the hole and measure the distance from the center of the two marks. Report this
dimension as the length of the crack.
12. Reporting Results.
A. If part disposition has not been specified, contact Citation Customer Service for disposition. Refer to Introduction for
contact information. Make sure to provide the following information:
(1) Location of the hole with observed discontinuity.
(2) Length of crack in the bore of the hole.
(3) If applicable, material layer or layers that are affected.
(4) Discontinuity orientation relative to hole. The 12 O'clock position is typically referred to as Up in a hole that is oriented
forward to aft or left to right and Forward in a hole that is oriented up and down.

20-00-01-0 (Rev 3)
Figure 1 : Sheet 1 : Typical Surface Reference Standard

A16318

20-00-01-0 (Rev 3)
Figure 2 : Sheet 1 : Probe Coil

A101044
ORIENT COLLAR
THUMB SCREW
0.030 INCH WITH COIL.
(0.762 mm)
DETAILA
0.030 INCH
(0.762 mm)
MANUAL PROBE CALIBRATION

20-00-01-0 (Rev 3)
Figure 3 : Sheet 1 : Lift-Off Display

20-00-01-0 (Rev 3)
Figure 4 : Sheet 1 : Lift-Off Display

20-00-01-0 (Rev 3)
Figure 5 : Sheet 1 : Notch Signal Response

20-00-01-0 (Rev 3)

20-00-01-0 (Rev 3)

20-00-01-0 (Rev 3)

20-00-01-0 (Rev 3)
Figure 9 : Sheet 1 : Scanner On Reference Standard

20-00-01-0 (Rev 3)

20-00-01-0 (Rev 3)

20-00-01-0 (Rev 3)
Figure 12 : Sheet 1 : Determining Scanner Position

20-00-01-0 (Rev 3)
Figure 13 : Sheet 1 : Determining Scanner Position

20-00-01-0 (Rev 3)
Figure 14 : Sheet 1 : Crack Indications

20-00-01-0 (Rev 3)
Figure 15 : Sheet 1 : Determining Crack Length

A101057
REFERENCE STANDARD FOR ILLUSTRATION ONLY.

USE SURFACE OF PART BEING INSPECTED WHEN MARKING
PROBE FOR CRACK LENGTH.
PENCIL

20-00-02-0 (Rev 3)
EDDY CURRENT SURFACE TECHNIQUES - GENERAL

1. Description
A. Eddy current inspection is good for the detection of surface or near-surface cracks in most metals. This method is done
when eddy currents are put into the part and then monitored for electrical changes of the induced field. The field change is
interpreted to find the type of defect. Eddy current inspection can be used on airframe parts or assemblies where the
inspection area is accessible to contact by the eddy current probe. An important use of eddy current inspection is to find
cracks caused by corrosion and stress around fastener holes with the fasteners installed.
B. This section gives the general requirements for the use of the eddy current method to find surface defects. Use this section
with specific instructions for the location of the inspection and the types of discontinuities to be detected.
2. Personnel Requirements
A. Personnel certification requirements are found in Part 1of this manual.
3. Instrument Requirements: Surface Inspection
A. Instrument Sensitivity
(1) Some inspection techniques require the use of instruments that show both phase and amplitude information on a
storage cathode ray tube for impedance plane analysis. Impedance plane instruments can be used in place of
metered instruments. Metered instruments must not be used in place of impedance plane instruments where the
ability to distinguish phase information is necessary.
(2) The instrument must have a repeatable signal response that has a signal-to-noise ratio of greater than 3 to 1 for the
test in which it is to be used. Impedance plane instruments must be able to resolve the signal within the guidelines
shown in Figure 1 and Figure 2.
A10766
MINIMUM
SENSITIVITY
LEVEL
LIFT-OFF NULL POINT

20°
ABSOLUTE PROBE CALIBRATION RANGE

Figure 1
A16316
MINIMUM
SENSITIVITY
LEVEL IS 3
DIVISIONS F ROM
20° PEAK TO PEAK
LIFT-OFF
NULL POINT 20°

20-00-02-0 (Rev 3)
DIFFERENTIAL PROBE CALIBRATION RANGE

Figure 2
(3) Make sure the functional performance of the eddy current instrumentation is verified on an annual basis.
B. Probe Sensitivity
(1) The probe can have an absolute or differential coil arrangement.
(2) The probe can be shielded or unshielded. A shielded probe is usually recommended.
(3) The probe must have an operating frequency that gives the required test sensitivity and depth of penetration.
(a) Inspections done on aluminum must be done at an operating frequency of 200 kHz.
(b) Inspections done on titanium must be done at an operating frequency of 1 MHz to 2 MHz.
(c) Inspections done on steel must be done at an operating frequency of 500 kHz to 800 kHz.
NOTE: The approximate frequencies must be used unless a different frequency is shown in a specific
procedure. The actual frequency used will depend on the ability of the test systems (probe
and instruments) to meet the required test sensitivity.
(4) Smaller coil diameters are better for detection of cracks. A coil diameter of 1/8 inch is usually used.
(5) For crack detection, the coil will usually contain a ferrite core.
(6) The probe must not give interference responses caused by pressure of use, probe movement or normal operating
pressure variations on the sense coil which cause the signal-to-noise ratio to be less than 3 to 1.
(7) Teflon tape can be used to decrease the wear on the eddy current probe coil. When Teflon tape is used, a new
instrument calibration must be done.
4. Instrument Calibration Standards
A. Nonferrous reference standards must be of an alloy that has the same major base metal, basic temper, and the
approximate electrical conductivity as the material to be inspected.
B. Reference standards must have a minimum surface finish of 150 RHR or RMS 165.
C. The dimensional accuracy of EDM notches must be documented and traceable to the National Institute of Standards and
Technology (NIST).
D. In some cases a specially fabricated reference standard will be necessary to simulate a part's geometry, configuration,
and/or the specific discontinuity location. Artificial discontinuities can be used in the reference standard.
5. Inspection Considerations
A. Temperature: Inspections must not be done until the temperature of the probe, the standard, and the material are equal.
B. Surface Condition:
(1) Finish: The surface finish of the area to be tested must be 150 RHR or RMS 165 or smoother.
(2) Cleanliness: The test area must be free of dirt, grease, oil, or other contaminants.
(3) Probe Contact: Eddy current inspection must be done with good contact made between the probe and the part
unless a specific procedure requires an offset. Lightly corroded parts must be cleaned lightly with emery cloth.
Severely corroded or painted parts must be lightly abraded and cleaned locally in the area on which the probe will be
put.
6. Instrument Calibration
A. The instrument must be calibrated and operated in accordance with this technique and the manufacturer's instructions.
B. Instrument calibration must be done before inspection. Calibration must be checked at intervals as necessary to maintain
calibration during continuous use and at the end of the inspection. The instrument must be calibrated again if any part of
C. A 0.020 inch surface notch must be used for surface inspections unless another dimension is given in the procedure. A
typical eddy current surface reference standard with EDM notch depths of 0.010 inch, 0.020 inch, and 0.040 inch is shown
in Figure 3.

20-00-02-0 (Rev 3)
A16317
TYPICAL SURFACE REFERENCE STANDARD

Figure 3
D. Adjust the instrument to get a minimum separation of three major screen divisions between the null/balance point and the
applicable reference notch. The signal from a differential probe must be considered peak-to-peak.
E. Filters can be used to make the signal-to-noise ratio better.
7. Inspection
A. When possible, the area of inspection must be inspected from two different directions which are at paths 90 degrees to
each other.
B. Do the inspection in sections that are not wider than the eddy current test coil. The part edge must be scanned if response
from edge effect does not prevent the display of the calibration notch response. Areas where edge effect is greater than
the calibration notch signal must not be inspected using eddy current.
C. When possible, fillets and radii must be scanned both transverse and parallel to the axis of the radius. The edge of the fillet
or radius must be scanned transverse to the axis of the radius.
8. Interpretation
A. If an indication is found, carefully repeat the inspection in the opposite direction of probe movement to make sure of the
indication. If the indication is found for left and right probe movement, carefully monitor the amount of probe movement or
turn needed to cause the instrument to move off from the maximum indication.
B. Unless specified differently, cracks are not allowed.
C. Find the end of a crack using the 50 percent method. Move the probe slowly across the end of the crack until a point is
found where the crack signal amplitude has been reduced by 50 percent. The center of the probe coil at this point is the
end of the crack.
9. Reporting Results
A. If the inspection procedure has not told you what to do with the damaged part, contact Cessna Propeller Aircraft Product
Support, P.O. Box 7706, Wichita, KS 67277 USA. Telephone 316-517-5800 Fax 316-942-9006. Include sufficient
information in all written descriptions so that someone not involved with the inspection can interpret the results. Give the
following information:
(1) Location of the discontinuity.
(2) The discontinuity size.
(3) The discontinuity orientation.

20-00-03-0 (Original Issue)
EDDY CURRENT CONDUCTIVITY TESTING: ALUMINUM

1. Description
A. This is a general inspection procedure that is used to find the conductivity of aluminum structures by use of the eddy
current method. This procedure is to be used with the applicable material specification and structural engineering
drawings to find if the conductivity values are acceptable or unacceptable.
B. Conductivity testing is an effective method for determining the material properties of aluminum structures. Eddy currents
are put into the part and the variations in the electrical field caused by conductivity changes are observed. Indications are
recorded and compared to acceptable ranges for the material tested. However, other materials or geometric changes in
the area can influence the conductivity indication of the instrument. Therefore, accurate determination of material
properties cannot be made based on conductivity without access to the appropriate material specification and
engineering drawings.
C. A typical field application is to determine material properties after heat has been applied. Such situations include:
structure heated by an engine or APU, fire damage, and lightning strike.
3. Instrument Requirements: Conductivity Testing
A. Inspection Frequency: The instrument used must have an operating frequency of 60 kHz.
B. Instrument Accuracy: The instrument used must be an eddy current instrument capable of determining the conductivity of
aluminum alloys as a percentage of the International Annealed Copper Standard (% IACS) with an accuracy of within 1.0%
IACS or better through electrically nonconductive films and coatings up to at least 0.003 inch (0.08 mm) thick.
C. Instrument Sensitivity: The instrument must have a sensitivity such that changes of at least 0.5% IACS are clearly
distinguishable over the conductivity range of the aluminum alloys under test.
D. Probe: The probe to measure conductivity must have a flat contact surface. The contact surface diameter must not be
greater than 0.500 inch (13 mm).
E. Test lift-off compensation as follows: put the probe on a bare standard, then put a 0.003 inch (0.08 mm) thick
nonconductive flat shim between the probe and the standard. The difference in the two readings must not exceed 0.5%
IACS. If it does, return the instrument to the calibration laboratory for repair and recertification.
F. The functional performance of the conductivity instrument must be verified at the intervals required by the controlling
specification or the manufacturer's recommendation, whichever is less.
4. Calibration Reference Standards
A. Each instrument must have a minimum of two aluminum alloy instrument conductivity standards that are always kept with
the instrument.
(1) One must have a value in the range of 25% to 32% IACS.
(2) One must have a value in the range of 38% to 62% IACS.
B. There must be a minimum spread of 10% IACS between the standard with the low range and the one with the high range.
C. The instrument conductivity standards must be certified to be accurate within plus or minus 0.85% IACS by the comparison
method to the laboratory conductivity standards in accordance with ASTM B193 procedure in a system per ISO 10012-1
ANSI/NCSL Z540-1.
D. Calibration must be made initially and at intervals such that they coincide with the conductivity instrument recalibration
cycle.
5. Inspection Considerations
A. Temperature: Inspections must not be done until the temperature of the probe, the standard, and the material are equal.
The temperatures must stay equalized and constant throughout the test within 3°C (5.4°F) of each other.
B. Surface Condition
(1) Finish: The surface finish of the area to be tested must be 150 RHR or RMS 165 or finer.
(2) Cleanliness: The areas to be tested must be free of dirt, grease, oil, or other contaminants.
(3) Nonconductive Coatings: Conductivity measurements may be made through anodize, chemical film, primer, paint, or
other nonconductive coatings, if these coatings do not exceed 0.003 inch (0.08 mm) thickness. Coatings with a
thickness greater than this must be removed prior to conductivity testing.

(4) Surface Curvature: On concave surfaces, a curvature radius of 10 inches (250 mm) or more is required. On convex
surfaces, a curvature radius of 3 inches (8 mm) or larger is required.
(a) A correction factor must be applied for smaller radii.
(5) Probe Contact Area: The surface of the part to which the conductivity measuring probe is applied must be at least as
large as the outside diameter of the probe. If the part dimension is very nearly equal to the probe diameter, the probe
must be centered on the part.
6. Instrument Calibration
A. Calibration Reference Standards
(1) Each instrument must have a minimum of two aluminum alloy instrument conductivity standards which must always be
kept with the conductivity instrument. One standard must be in the range of 25% to 32% IACS and one in the range of
38% to 62% IACS. There must be a minimum spread of 10% IACS between the standard for the low range and the
standard for the high range. The instrument conductivity standards must be certified to be accurate within 0.85%
IACS by the comparison method to the laboratory conductivity standards in accordance with ASTM B193 procedure
in a system per ISO 10012-1 ANSI/NCSL Z540-1. Calibration must be made initially and at intervals such that they
coincide with the conductivity instrument recalibration cycle.
B. The instrument must be calibrated and operated as specified in this technique and the manufacturer's instructions.
C. Each time the conductivity instrument is used, it must be calibrated (standardized) using the instrument conductivity
standards before checks are made and rechecked at 15 minute intervals during continuous operation. If the instrument is
found to be out of calibration, all measurements done since the last calibration must be rechecked.
7. Instrument Calibration Standards
A. Nonferrous reference standards must be of an alloy that has the same major base metal, basic temper and the
approximate electrical conductivity of the material to be inspected.
B. Reference standards must have a minimum surface finish of 150 RHR or RMS 165.
8. Inspection
A. The purpose of the inspection is to collect information to let the responsible engineering group determine the material
properties in the affected area.
NOTE: Because variations in material properties, material stacking, and geometry cause changes of
conductivity readings, conductivity readings alone must not be used to determine if the affected
area is accepted. Reference must be made to the applicable material specifications and
engineering drawings.
B. Visual
(1) Clean the area to be examined with methods specified in the appropriate maintenance manual. Remove all dirt, grit,
soot, and other debris that will not let the probe maintain good contact with the structure.
(2) Examine the area visually for indications of possible heat damage. Some signs include paint/metal discoloration and
bubbled or peeled paint.
(3) Record the location and description of the heat damaged area. This description will be used along with the
conductivity readings to determine the type of repair. If photographs are used to describe the area, take the picture
before the conductivity test is done.
C. Eddy Current Conductivity
(1) Use the appropriate reference standards to make sure of proper instrument calibration within the general conductivity
range of aluminum structures .
(2) After the visual inspection, set a reference point. If there is visual evidence of possible heat damage, set the
reference point at the center of the area that appears to have been the most affected. If there is no visual evidence of
possible heat damage, set the reference point at the center of the area to be inspected. In either case, the reference
point will locate approximately the center of the area of interest.
NOTE: A detailed map will need to be made of the inspection area. It must include dimensions to
locate the reference point and enough information to let the engineering personnel that do the
review of the information locate the places the conductivity readings were taken.
(3) The total area to be examined, and the distance between readings will depend on the specific situation. It is
recommended that the distance between conductivity readings not exceed 1.0 inch (25 mm). If the visual evidence or

the conductivity readings suggest rapid changes in severity, decrease the distance between test points. It is
recommended that the total area to be examined exceed the area of visual evidence by at least 2.0 inches (50 mm). If
the conductivity readings continue to change, the area of examination should be expanded until readings remain fairly
constant to make sure a complete map of the area is prepared.
(4) Locate the reference point at the corner of a square, refer to Figure 1. Take conductivity readings as you work away
from the reference point in the increments and distance determined in the previous step. Enough information must be
recorded along with the conductivity reading to allow a person not familiar with the inspection to locate the data point.
NOTE: Structural considerations may make it necessary that the test points do not follow the pattern
of Figure 1. It is up to the inspector to set a pattern that best covers the area to be inspected.
A16319
INTERVAL BETWEEN REFERENCE POINTS

INSPECTION POINTS
INSPECTION LOCATIONS AT THE CORNERS

OF THE "SQUARES"
SAMPLE INSPECTION GRID

Figure 1
9. Reporting Results
A. If the inspection procedure has not told you what to do with the damaged part, contact Cessna Propeller Aircraft Product
Support, P.O. Box 7706, Wichita, KS 67277 USA. Telephone 316-517-5800 Fax 316-942-9006. Include sufficient
information in all written descriptions so that someone not involved with the inspection can interpret the results. Give the
following information:
(1) Location of the affected area.
(2) A visual description of the affected area.
(3) Location of the reference point and the relative location and interval between conductivity readings.
(4) A map of the area with the conductivity readings recorded on it.

53-10-01-0 (Rev 1)
FUSELAGE ENGINE MOUNT FITTINGS

1. Description
A. This procedure will show you how to find cracks in the engine mount fittings on the fuselage.
B. This inspection satisfies requirements of Maintenance Manual, Chapter 5, (Refer to Table 1).
Table 1. Item Codes
AIRPLANE ITEM CODE TASK NUMBER
MODEL 208 A531008 53-10-00-250
3. Preparation
A. Remove the engine and truss. Refer to the Maintenance Manual Chapter 71, Engine Mount - Maintenance Practices.
B. Clean the area to be examined of any unwanted material and/or burrs.
4. Equipment
NOTE: This equipment was used to do this procedure. You can use replacements for the items below if they
have the necessary parameters. You can use metered instruments as replacements. The metered
equipment must have the parameters specified in the general sections of this manual.
NAME NUMBER MANUFACTURER USE
Eddy Current Instrument Nortec 2000 Staveley NDT Technologies To find cracks
421 N. Quay St.
Kennewick, WA 99336
Web: www.staveleyndt.com
Shielded Surface Probe MP902-60/1-3M NDT Engineering Corp. To find cracks
1/8 inch diameter 19620 Russell Rd.
Kent, WA 98032
Web: www.ndteng.com
Shielded Surface Probe MP902-60 NDT Engineering Corp. To find cracks
1/8 inch diameter
Shielded Bolt Hole Probe VM101BS-1/2 VM Products To find cracks
1/2 inch diameter PO Box 44926
Tacoma, WA 98444
Web: www.vmproducts.net
Aluminum Reference HRS-15A NDT Engineering Corp. To calibrate test equipment
Standard
Steel Reference Standard SRS-10S NDT Engineering Corp. To calibrate test equipment
Micrometer or caliper Locally available To position probe collar
Inspection Plate NOTE 1 To have a stable surface for the
bolt hole inspection
NOTE 1: If plate is made from a different thickness material, all probe depths must be adjusted. Refer to Figure 2.
5. Calibration
A. Calibrate the 200 kHz Surface Probe.
(1) Connect the probe to the instrument.
(2) Set the eddy current instrument frequency to 200 kHz.
(3) Put the probe on the face of the aluminum standard away from the notch.
(4) Push the null (balance) button.
(5) Lift the probe away from the standard. Monitor the display.
(a) Adjust the instrument so that the lift-off signal goes horizontal and to the left.

53-10-01-0 (Rev 1)
(6) Move the probe over the notch. Monitor the display to make sure the signal moves up and toward the left as the probe
moves across the notch.
(a) Adjust the instrument to get a minimum of three major screen divisions between the null point and the notch
point.
B. Calibrate the 1 MHz Surface Probe.
(2) Set the eddy current instrument frequency to 1 MHz.
(3) Put the probe on the face of the steel standard away from the notch.
point.
C. Calibrate the 200 kHz Bolt Hole Probe.
(3) Put the probe in the 1/2 inch hole in the standard with the probe coil away from the notch.
(5) Move the probe coil across the notch. Monitor the display to make sure the signal moves up and toward the left as the
probe moves across the notch.
(a) Adjust the instrument to get three major screen divisions between the null point and the notch point.
6. Inspection
A. Top and Bottom Outboard Mounts Surface Inspection (Refer to Figure 1 and Figure 2).
(1) Calibrate the 200 kHz surface probe and instrument. Refer to Calibrate the 200 kHz Surface Probe.
(2) Use the 200 kHz surface probe to examine all of the countersunk area of each of the top and bottom outboard
mounts.
B. Airplanes 20800330 and On Bottom Mount Bolt Hole Inspection
(1) Calibrate the bolt hole probe and instrument. Refer to Calibrate the 200 kHz Bolt Hole Probe.
(2) Set the probe at a depth of 0.62 inch (15.75 mm), measurement is from the edge of the collar to the center of the coil.
(3) Put the inspection plate over one of the bottom mount holes.
NOTE: The plate will rest on the heads of the fasteners.
(a) Put the probe in the hole until the collar is against the inspection plate.
(b) Turn the probe a minimum of 360 degrees while you monitor the display for cracks.
(4) Adjust the collar of the probe so that it is at 0.74 inch (18.80 mm) away from the center of the coil.
(6) Do the inspection on the other bottom hole.
C. Airplanes 20800001 thru 20800329 and 208B Bottom Mount Bolt Hole Inspection
NOTE: Airplanes 20800001 thru 20800329 with a lower reinforcement assembly installed, use the

53-10-01-0 (Rev 1)
inspection depths for Airplanes 20800330 and On.

(2) Set the probe at a depth of 0.55 inch (13.97 mm), measurement is from the edge of the collar to the center of the coil.
(3) Put the inspection plate over one of the bottom mount holes.
NOTE: The plate will rest on the heads of the fasteners.
(6) Do the inspection on the bottom hole.
D. Top Outboard Mounts Bolt Hole Inspection
(2) Set the probe at a depth of 0.58 inch (14.73 mm), measurement is from the collar to the center of the coil.
(3) Put the inspection plate on one of the top mount holes.
(4) Do the inspection at each of the index number depths in Table 1.
(5) Do the inspection on the other upper hole.
Table 2. Top Outboard Holes
Index Number Depth (Inches) Depth (mm)
1 0.58 14.73
2 0.72 18.29
3 0.86 21.84
4 1.00 25.40
5 1.14 28.96
6 1.28 32.51
7 1.42 36.07
8 1.56 39.62
E. Top Center Mount Surface Inspection
(1) Calibrate the 1 MHz surface probe and instrument. Refer to Calibrate the 1 MHz Surface Probe.
(2) Refer to Figure 1. Examine around the circumference of the truss attach hole. Keep the probe as near to the edge of
the hole as possible but try to avoid any edge effect.
7. Part Disposition
A. If a crack is found, contact Cessna Propeller Aircraft Product Support, P.O. Box 7706, Wichita, KS 67277 USA.
Telephone 316-517-5800. FAX 316-942-9006. Provide the following information:
(1) Crack location.
(2) Crack length.
(3) Crack orientation.

53-10-01-0 (Rev 1)
Figure 1 : Sheet 1 : Engine Mount Fittings

A29100
UPPER CENTER
ENGINE MOUNT
UPPER RIGHT
ENGINE MOUNT UPPER LEFT
ENGINE MOUNT
LOWER RIGHT LOWER LEFT

ENGINE MOUNT ENGINE MOUNT A
REINFORCEMENT
FITTING NOTE 1: REINFORCEMENT
(NOTE 1) FITTING IS INSTALLED
ON SOME MODEL
208 AIRPLANES
BOLT HOLE
COUNTERSINK INSPECTION
INSPECTION AREA
AREA
DETAIL A 2613T3007A
A2613T1016

53-10-01-0 (Rev 1)
Figure 2 : Sheet 1 : Inspection Plate

A29103
0.60 INCHES (15 mm)

2.5 INCHES (64 mm) DIAMETER
DIAMETER
MAKE FROM 0.040 INCH THICK ALUMINUM SHEET
A2683T1001

53-20-01-0 (Rev 1)
CARGO AND PASSENGER DOOR DOUBLERS

1. Description
A. This procedure will show you how to find cracks in the door doublers on the cargo and passenger door corners.
Table 1. Item Codes
MODEL 208 A532003 53-10-00-251
A. Personnel certification procedures are found in Part 1of this manual.
3. Preparation
A. Clean the area to be examined of any unwanted material and/or burrs.
4. Equipment
421 N. Quay St.
Kennewick, WA 99336
Kent, WA 98032
Web: www.ndteng.com
Aluminum Reference HRS-15A NDT Engineering Corp. To calibrate system
Standard
5. Calibration
(3) Put the probe on the face of the standard away from the notch.
point.
6. Inspection
A. Door Doubler (Refer to Figure 1).
(1) Calibrate the surface probe and instrument. Refer to Calibrate the 200 kHz Surface Probe.
(2) Insert the surface probe through a door frame lightning hole and do an inspection of the doubler for cracks.
7. Part Disposition

53-20-01-0 (Rev 1)
(1) Crack location.

(2) Crack length.

53-20-01-0 (Rev 1)
Figure 1 : Sheet 1 : Cargo and Crew Door Doublers

53-20-01-0 (Rev 1)
Figure 1 : Sheet 2 : Cargo and Crew Door Doublers

53-20-02-0 (Rev 1)
FUSELAGE TO WING ATTACH FITTING LUGS

1. Description
A. This procedure will show you how to find cracks in the fuselage to wing attach fitting lugs.
Table 1. Item Codes
MODEL 208 A532007 53-10-00-252
3. Preparation
A. Remove the wing. Refer to the Maintenance Manual Chapter 57, Wing - Removal/Installation.
C. Remove the eccentric bushings from the aft lugs.
4. Equipment
421 N. Quay St.
Kennewick, WA 99336
Tacoma, WA 98444
15/16 inch diameter
Micrometer or Caliper Commercially available To position probe collar
Standard 19620 Russell Rd.
Kent, WA 98032
Web: www.ndteng.com
5. Calibration
A. Calibrate the 200 kHz Bolt Hole Probe.
(3) Put the probe in the appropriate hole in the standard with the probe coil away from the notch.
point.
6. Inspection

53-20-02-0 (Rev 1)
NOTE: Inspections must be done on both the left and right side of the airplane.
A. Forward Attach Fitting Bolt Hole Inspection (Refer to Figure 1).
(1) Calibrate the 7/8 inch bolt hole probe and instrument. Refer to Calibrate the 200 kHz Bolt Hole Probe.
(2) Set the probe at a depth of 0.050 inch (1.27 mm). Measure from the collar to the center of the coil.
(3) Put the probe in the hole from the forward side of the lugs.
(4) Turn the probe a minimum of 360 degrees while you monitor the display.
(5) Do the inspection at each of the probe depths in Table 1.
Table 2. Forward Lugs
1 0.050 1.27
2 0.150 3.81
3 0.250 6.35
4 0.862 21.89
5 0.962 24.43
6 1.062 26.97
(6) Do the inspection from the aft side of the lugs.
(7) Do the inspection for each of the attach fittings.
B. Aft Attach Fitting Bolt Hole Inspection (Refer to Figure 1).
Table 3. Aft Lugs
1 0.050 1.27
2 0.140 3.56
3 0.230 5.84
4 0.778 19.76
5 0.868 22.05
6 0.958 24.33
(6) Do the inspection from the aft side of the lugs.
(7) Do the inspection for each of the attach fittings.
7. Part Disposition
(1) Crack location.
(2) Crack length.

53-20-02-0 (Rev 1)
Figure 1 : Sheet 1 : Wing Attach Fitting Lug

53-20-03-0 (Rev 1)
LOWER FORWARD CARRY THRU BULKHEAD

1. Description
A. This procedure will show you how to find cracks in the wing strut attach fittings in the bottom forward carry through
bulkhead.
Table 1. Item Codes
MODEL 208 A532004 53-10-00-253
3. Preparation
A. Remove any of the interior necessary to get access to the fittings from the inside of the fuselage. Refer to the Maintenance
Manual.
4. Equipment
421 N. Quay St.
Kennewick, WA 99336
Kent, WA 98032
Web: www.ndteng.com
Tacoma, WA 98444
1/4 inch diameter
Shielded Surface Probe MP905-120FX NDT Engineering Corp. To find cracks
1/8 inch diameter with
Flexible Copper Shaft
Standard
5. Calibration

53-20-03-0 (Rev 1)
point.
B. Calibrate the 200 kHz Bolt Hole Probe.
point.
6. Inspection
A. Stiffener and Top Bulkhead Surface Inspection (Refer to Figure 1).
(2) Remove one bolt from the structure at a time.
(a) Remove nut from aft side.
(b) Remove the bolt.
NOTE: If there is not enough clearance to remove the bolt, it may be necessary to cut the head of
the bolt off.
1 Remove the bolt far enough to cut off the head.
2 Remove the shank of the bolt from the aft side.
(3) Examine around the circumference of the hole.
(4) Do a bolt hole inspection on the hole from the aft side. Refer to the appropriate Attach Fitting Bolt Hole Inspection.
(5) Install a new bolt from the aft side of the hole.
(6) Use the previous steps to examine each hole shown in Figure 1.
B. Attach Fitting Bolt Hole Inspection for Holes 4, 5, and 6
NOTE: Bolts 4, 5 and 6 may be removed at same time for Model 208B only.
(2) Set the probe at a depth of 0.201 inch measuring from the collar to the center of the coil.
(3) Put the probe in the hole.
(5) Do the inspection at each of the probe depths of Table 1 for holes 4, 5, and 6.
Table 2. Holes 4, 5, and 6
1 0.201 5.11
2 0.321 8.15
3 0.441 11.20
4 0.561 14.25
5 0.801 20.35
6 0.921 23.39

53-20-03-0 (Rev 1)
7 1.041 26.44
8 1.061 26.95
9 1.226 31.14
10 1.329 33.76
11 1.449 36.80
12 1.569 39.85
13 1.689 42.90
14 1.809 45.95
15 1.929 49.00
16 2.049 52.04
17 2.169 55.09
18 2.289 58.14
19 2.354 59.79
C. Attach Fitting Bolt Hole Inspection for Holes 1, 2, and 3. (Refer to Figure 1).
(5) Do the inspection for holes 1, 2, and 3.
NOTE: Inspection for holes 1, 2, and 3 must be done from the forward and aft sides of the bulkhead.
D. Attach Fitting Inspection for Holes 7, 8, and 9. (Refer to Figure 1).
(1) Calibrate the flexible surface probe and instrument. Refer to Calibrate the 200 kHz Surface Probe.
(2) Do a surface probe around the nuts of holes 7, 8, and 9.
(a) Insert the flexible surface probe through a lightning hole to do the inspection.
NOTE: Inspection for holes 7, 8, and 9 must be done on the forward and aft sides of the
bulkhead.
7. Part Disposition
(1) Crack location.
(2) Crack length.

53-20-03-0 (Rev 1)
Figure 1 : Sheet 1 : Wing Strut Attach Fittings

53-20-04-0 (Rev 1)
MAIN LANDING GEAR FITTING

1. Description
A. This procedure will show you how to find cracks in the main landing gear fittings on the fuselage.
Table 1. Item Codes
MODEL 208 A532005 53-10-00-254
3. Preparation
A. Remove the main landing gear. Refer to the Maintenance Manual Chapter 32, Main Landing Gear - Maintenance
Practices.
4. Equipment
421 N. Quay St.
Kennewick, WA 99336
Kent, WA 98032
Web: www.ndteng.com
Standard with 0.020 inch
Deep Surface EDM notch
5. Calibration
(5) Lift the probe away from the standard. Monitor the display
point.
6. Inspection
A. Main Gear Forgings (Refer to Figure 1, Figure 2, Figure 3, and Figure 4).
(2) Examine around the circumference of the four cap attach holes in the forward and aft fitting.

53-20-04-0 (Rev 1)
(a) Keep the probe as near to the edge of the hole as possible but try to avoid any edge effect.
(3) Examine around the circumference of the main landing gear forging slot. (Refer to Figure 3).
(a) Keep the probe as near to the edge of the hole as possible, but try to avoid any edge effect.
(4) Examine the inner radii around the circumference of the main landing gear forging slot. (Refer to Figure 4).
7. Part Disposition
Telephone 316-517-5800. FAX 316-942-9006. Give the following information:
(1) Crack location.
(2) Crack length.

53-20-04-0 (Rev 1)
Figure 1 : Sheet 1 : Main Gear Support Forging

53-20-04-0 (Rev 1)
Figure 2 : Sheet 1 : Cap Attach Hole

53-20-04-0 (Rev 1)
Figure 3 : Sheet 1 : Support Forging Slot

53-20-04-0 (Rev 1)
Figure 4 : Sheet 1 : Support Forging Slot Inner Radius

53-20-05-0 (Rev 2)
MAIN LANDING GEAR ATTACH FITTINGS AND AFT CARRY-THRU BULKHEAD

1. Description
A. This procedure will show you how to find cracks in the main landing gear attach fittings and bottom aft carry thru bulkhead
at FS 194.40 and 208.00.
Table 1. Item Codes
MODEL 208 A532006 53-10-00-255
3. Preparation
Manual.
4. Equipment
Eddy Current Instrument Nortec 2000 Staveley NDT Technologies To find cracks.
421 N. Quay St.
Kennewick, WA 99336
Kent, WA 98032
Web: www.ndteng.com
Tacoma, WA 98444
1/4 inch diameter
Micrometer or caliper Commercially available To position probe collar
Standard
5. Calibration

53-20-05-0 (Rev 2)
point.
point.
6. Inspection
NOTE: Inspections on the bottom fittings must be done on both the left and right and forward and aft sides of
the bulkhead.
A. Bottom Bulkhead Surface Inspection (Refer to Figure 1).
(2) Remove one bolt.
(4) Do a bolt hole inspection on the hole. Use the procedure that applies to each hole.
(5) Install the bolt before removing the next bolt.
(6) Examine each hole using the previous steps.
B. Attach Fitting Bolt Hole Inspection for Holes 4, 5, and 6 (Refer to Figure 1).
NOTE: Holes 4, 5, and 6 go into the brace between the fittings.
(2) Set the probe at a depth of 0.180 inch (4.57 mm).
(3) Measure from the collar to the center of the coil.
NOTE: Due to lack of accessibility to perform the bolt hole eddy current inspection, it is permissible to
perform a surface eddy current inspection on any or all of these bolt holes. Refer to Bottom
Bulkhead Surface Inspection.
(6) Install the bolt before removing the next bolt.
1 0.193 4.90
2 0.313 7.95
3 0.433 11.00
4 0.553 14.05
5 0.673 17.09
6 0.793 20.14
7 0.913 23.19
8 1.033 26.24
9 1.123 28.52
(7) Do the inspection at each of the depths for holes 4, 5, and 6, forward and aft, left and right..

53-20-05-0 (Rev 2)
C. Attach Fitting Bolt Hole Inspection for Holes 1, 2, and 3 (Refer to Figure 1).
(5) Do the inspection for holes 1, 2, and 3.
7. Part Disposition
(1) Crack location.
(2) Crack length.

53-20-05-0 (Rev 2)
Figure 1 : Sheet 1 : Aft Bulkhead Gear Support Fitting

53-20-06-0 (Rev 3)
FUSELAGE TO WING CARRY-THRU ATTACH FITTING

1. Description
A. This procedure will show you how to find cracks in the wing attach fittings in the forward and aft carry through bulkheads.
Table 1. Item Codes
MODEL 208 A532016 53-10-00-256
3. Preparation
Manual.
4. Equipment
421 N. Quay St.
Kennewick, WA 99336
Kent, WA 98032
Web: www.ndteng.com
Adjustable Bolt Hole BXM-10/12 NDT Engineering Corp. To find cracks
Probe
Tacoma, WA 98444
Micrometer or caliper Commercially available To position probe collar
Standard
5. Calibration

53-20-06-0 (Rev 3)
point.
point.
6. Inspection
A. Top Bulkhead Surface Inspection (Refer to Figure 1).
(2) Remove one bolt.
(4) Do a bolt hole inspection on the hole. Refer to the appropriate Attach Fitting Bolt Hole Inspection.
(5) Use the previous steps to examine each hole shown in Figure 1.
B. Forward Attach Fitting Bolt Hole Inspection For Bolt Holes 1, 2, 3 and 4 (Refer to Figure 1).
(3) Remove only one bolt.
(4) Put the probe in the hole from the aft side of the bulkhead.
(6) Do the inspection at each of the probe depths of Table 2.
(7) Install the bolt.
(8) Remove the next bolt.
(9) Do the complete inspection of each of the bolt holes shown on the forward top carry-thru bulkhead.
Table 2. Forward Bolt Holes
1 0.130 3.30
2 0.210 5.33
3 0.290 7.37
4 0.370 9.40
5 0.450 11.43
6 0.530 13.46
7 0.610 15.49
8 0.690 17.53
9 0.770 19.56
10 0.850 21.59
11 0.930 23.62
12 1.010 25.65

53-20-06-0 (Rev 3)
13 1.090 27.69
14 1.155 29.34
15 1.255 31.88
16 1.335 33.91
17 1.415 35.94
18 1.495 37.91
19 1.575 40.01
20 1.655 42.04
21 1.735 44.07
22 1.815 46.10
23 1.895 48.13
24 1.975 50.17
25 2.055 52.20
26 2.135 54.23
27 2.215 56.26
28 2.280 57.91
C. Attach Fitting Bolt Hole Inspection for Holes 5A, 5B, 6A, 6B, 7A, 7B (Refer to Figure 1).
(1) Calibrate the adjustable bolt hole probe and instrument. Refer to Calibrate the 200 kHz Bolt Hole Probe.
(6) Do the inspection for holes 5A, 5B, 6A, 6B, 7A, 7B.
D. Aft Attach Fitting Bolt Hole Inspection (Refer to Figure 1).
(2) Set the probe at a depth of 0.180 inch ( mm). Measure from the collar to the center of the coil.
(4) Put the probe in the hole fron the forward side.
(6) Do the inspection at each of the probe depths of Table 3.
(7) Install the bolt.
(8) Remove the next bolt.
(9) Do the complete inspection of each of the bolt holes shown on the aft top carry-thru bulkhead.
Table 3. Aft Bolt Holes
1 0.180 4.57
2 0.260 6.60
3 0.340 8.64
4 0.420 10.67
5 0.500 12.70
6 0.580 14.73
7 0.660 16.76

53-20-06-0 (Rev 3)
8 0.740 18.80
9 0.820 20.82
10 0.900 22.86
11 0.980 24.89
12 1.060 26.92
13 1.180 29.97
14 1.260 32.00
15 1.340 34.04
16 1.420 36.07
17 1.500 38.10
18 1.580 40.13
19 1.660 42.16
20 1.740 44.20
21 1.820 46.23
22 1.900 48.26
23 1.980 50.29
24 2.060 52.32
7. Part Disposition
(1) Crack location.
(2) Crack length.

53-20-06-0 (Rev 3)
Figure 1 : Sheet 1 : Wing Attach Fitting

53-20-06-0 (Rev 3)
Figure 1 : Sheet 2 : Wing Attach Fitting

53-20-07-0 (Rev 2)
FUSELAGE TO LOWER STRUT ATTACH FITTING LUGS

1. Description
A. This procedure will show you how to find cracks in the wing strut attach fitting lugs on the bottom forward carry through
bulkhead.
Table 1. Item Codes
MODEL 208 A531005 53-20-07-250
MODEL 208 A531006 53-20-07-251
MODEL 208 A531010 53-20-07-252
MODEL 208 A531011 53-20-07-253
3. Preparation
A. Remove the strut. Refer to the Maintenance Manual.
4. Equipment
421 N. Quay St.
Kennewick, WA 99336
Kent, WA 98032
Web: www.ndteng.com
Tacoma, WA 98444
Standard
5. Calibration

53-20-07-0 (Rev 2)
point.
6. Inspection
A. Attach Lug Bolt Hole Inspection. (Refer to Figure 1).
(2) Set the probe at a depth of 0.05 inch. Measure from the collar to the center of the coil.
(5) Put the probe in the hole from the aft side of the lugs.
(7) Do the inspection at each of the probe depths of Table 2 for each lug.
Table 2. Attach Lug
1 0.05 1.27
2 0.13 3.30
3 0.21 5.33
4 0.267 6.78
5 0.871 22.12
6 0.951 24.16
7 1.031 26.19
8 1.075 27.31
7. Part Disposition
(1) Crack location.
(2) Crack length.

53-20-07-0 (Rev 2)
Figure 1 : Sheet 1 : Wing Strut Attach Fitting Lugs

53-50-01-0 (Rev 1)
FUSELAGE TO HORIZONTAL STABILIZER ATTACH FITTINGS

1. Description
A. This procedure will show you how to find cracks in the fuselage to horizontal stabilizer attach fittings on the fuselage.
Table 1. Item Codes
MODEL 208 A535001 53-10-00-257
3. Preparation
A. Remove the horizontal stabilizer. Refer to the Maintenance Manual, Chapter 55, Horizontal Stabilizer -
Removal/Installation.
4. Equipment
421 N. Quay St.
Kennewick, WA 99336
Kent, WA 98032
Web: www.ndteng.com
Shielded Bolt Hole Probe BXM-32/40 NDT Engineering Corp. To find cracks
1/2 inch to 5/8 inch
diameter
Tacoma, WA 98444
Micrometer or caliper Commercially available To put the collar in position
Aluminum Reference HRS-15A NDT Engineering Corp. To calibrate the system
Standard
Inspection Plate NOTE 1 Fabricate according to Figure 2 To give a stable surface for the
bolt hole inspection
NOTE 1: If plate is made from a different thickness material, all probe depths must be adjusted.
5. Calibration

53-50-01-0 (Rev 1)
point.
point.
6. Inspection
NOTE: Inspections must be done on the left and right fittings.
A. Do the Forward Attach Fitting Surface Inspection (Refer to Figure 1).
(2) Use the 200 kHz surface probe to examine each of the countersink areas of the fittings.
B. Do an Inspection of the Bolt Hole for the Forward Attach Fitting (Refer to Figure 1 and Figure 2).
(2) Set the probe to a depth of 0.42 inch (10.67 mm).
(4) Put the inspection plate on the probe.
(5) Put the probe in the hole until the collar is against the inspection plate.
(7) Do the inspection at each of the depths in Table 1.
Table 2. Forward Attach Fitting
Index Number Depth (inches) Depth (mm)
1 0.42 10.67
2 0.52 13.21
3 0.62 15.75
4 0.72 18.29
C. Do an Inspection of the Bolt Hole for the Aft Attach Fitting (Refer to Figure 1)
7. Part Disposition
(1) Crack location.
(2) Crack length.

53-50-01-0 (Rev 1)

53-50-01-0 (Rev 1)
Figure 1 : Sheet 1 : Horizontal Stabilizer Attach Points

53-50-01-0 (Rev 1)

A29124
BOLT HOLE
INSPECTION AREA
SURFACE PROBE
INSPECT
VIEW A-A
CROSS SECTION OF FORWARD
FITTING AT THE ATTACH POINT
2683T1005

53-50-01-0 (Rev 1)
Figure 2 : Sheet 1 : Inspection Plate

A29103
0.60 INCHES (15 mm)

2.5 INCHES (64 mm) DIAMETER
DIAMETER
MAKE FROM 0.040 INCH THICK ALUMINUM SHEET
A2683T1001

53-50-02-0 (Rev 1)
VERTICAL STABILIZER ATTACH POINTS

1. Description
A. This procedure will show the techniques used to find cracks in the forward vertical stabilizer attach points on the fuselage.
Table 1. Item Codes
MODEL 208 A535002 53-10-00-258
MODEL 208 A535003 53-10-00-259
3. Preparation
A. Remove the vertical stabilizer. Refer to the Maintenance Manual, Chapter 55, Vertical Stabilizer - Removal/Installation.
B. Clean the attach holes of any unwanted materials and/or burrs that can cause interference with the inspection.
4. Equipment
Eddy Current Unit Nortec 2000 Staveley NDT Technologies To find cracks
421 N. Quay St.
Kennewick, WA 99336
Shielded Bolt Hole Eddy VM101BS-3/8 VM Products To find cracks
Current Probe 3/8 inch PO Box 44926
diameter Tacoma, WA 98444
Shielded Surface Eddy MP902-60 NDT Engineering Corp. To find cracks
Current Probe 1/8 inch 19620 Russell Rd.
diameter Kent, WA 98032
Web: www.ndteng.com
Bolt Hole / Surface HRS-15A NDT Engineering Corp. To calibrate the system
Reference Standard
Micrometer or caliper Commercially available To position the probe collar
5. Calibration
A. Calibrate the 200 kHz Surface Probe
(5) Lift the probe away from the standard.
(a) Monitor the display.
(b) Adjust the instrument so that the lift-off signal goes horizontal and to the left.
(6) Move the probe across the notch.
(a) Monitor the display to make sure the signal moves up and toward the left as the probe moves across the notch.
(a) Adjust the instrument to get a minimum of three major screen areas between the null point and the notch point.

53-50-02-0 (Rev 1)
B. Calibrate the 200 kHz Bolt Hole Probe

(a) Adjust the instrument to get a minimum of three major screen divisions areas the null point and the notch point.
6. Inspection
A. Forward Attach Holes Inspection (Refer to Figure 1).
(1) Bolt hole inspection for the top attach holes.
(a) Calibrate the bolt hole probe and instrument. Refer to Calibrate the 200 kHz Bolt Hole Probe.
(b) Set the depth of the probe to 0.065 inch (1.65 mm).
(c) Adjust the diameter of the probe to the diameter of the hole.
(d) Inspect the bore of each hole from the aft side of the bulkhead.
(e) Set the probe at a depth of 0.130 inch (3.30 mm).
(f) Do an inspection of the bore of each hole from the aft side of the bulkhead.
(g) Set the probe at a depth of 0.170 inch (4.32 mm).
(h) Do an inspection of the bore of each hole from the aft side of the bulkhead.
(2) Bolt hole inspection for the bottom attach holes.
(a) Calibrate the bolt hole probe and instrument. Refer to Calibrate the 200 kHz Bolt Hole Probe.
(b) Set the probe at a depth of 0.080 inch (2.03 mm).
(c) Adjust the diameter of the probe to the diameter of the hole.
(d) Do an inspection of the bore of each hole from the aft side of the bulkhead.
B. Aft Attach Point Holes Inspection (Refer to Figure 2).
(1) Calibrate the surface probe and instrument. Refer to Calibrate the 200 kHz Surface Probe.
(2) Set the probe at a depth of 0.041 inch (1.04 mm).
(3) Adjust the diameter of the probe to the diameter of the hole.
(4) Do the inspection on the bore of each of the holes.
(a) Increase the depth of the scan 0.080 inch (2.08 mm) after each scan for the remainder of the hole depth.
7. Part Disposition
Telephone 316-517-5800. FAX 316-942-9006. Give the information that follows:
(1) Crack location.
(2) Crack length.

53-50-02-0 (Rev 1)
Figure 1 : Sheet 1 : Vertical Stabilizer Forward Attach Points

A29131
LEFT TOP RIGHT TOP

ATTACH HOLE ATTACH HOLE
LEFT BOTTOM RIGHT BOTTOM

ATTACH HOLE ATTACH HOLE
VERTICAL STABILIZER
FORWARD BULKHEAD
2612T1008

53-50-02-0 (Rev 1)
Figure 2 : Sheet 1 : Vertical Stabilizer Aft Attach Points

A29125
LEFT TOP
ATTACH HOLE RIGHT TOP
ATTACH HOLE
RIGHT BOTTOM
LEFT BOTTOM ATTACH HOLE
ATTACH HOLE
AFT CANTED
BULKHEAD
2612T1007

55-10-01-0 (Rev 1)
HORIZONTAL STABILIZER FORWARD AND AFT ATTACH POINTS

1. Description
A. This procedure will show the techniques used to find cracks in the horizontal stabilizer forward and aft attach points.
Table 1. Item Codes
MODEL 208 A551003 55-10-00-250
3. Preparation
B. Clean the attach holes of any unwanted material and/or burrs that can have an affect on the inspection.
4. Equipment
421 N. Quay St.
Kennewick, WA 99336
Shielded Bolt Hole Eddy BPMF-16 NDT Engineering Corp. To find cracks
Current Probe 1/4 inch 19620 Russell Rd.
diameter Kent, WA 98032
Web: www.ndteng.com
Shielded Bolt Hole Eddy BXM-32/40 NDT Engineering Corp. To find cracks
Current Probe 17/32 inch
diameter
Surface Eddy Current MP902-60 NDT Engineering Corp. To find cracks
Probe 1/2 to 5/8 inch
diameter
Bolt Hole Reference HRS-15A NDT Engineering Corp. To calibrate the system
Standard
Micrometer or caliper Commercially available To put the probe collar in
position
5. Calibration

55-10-01-0 (Rev 1)
point.
point.
6. Aft Attach Point Inspection
A. Do the Bolt Hole Inspection (Refer to Figure 1).
(2) Adjust the probe diameter to the diameter of the probe.
(a) Put a non-metallic material in the slot of the probe.
(3) Set the depth of the probe to 0.190 inch (4.83 mm) between the collar and the center of the coil.
(4) Put the probe into the hole and turn it 360 degrees while you watch the eddy current unit for crack signals.
(6) Do the inspection on each of the holes.
Table 2. Aft Attach Point
Index Depth (Inches) Depth (mm)
1 0.190 4.83
2 0.250 6.35
3 0.310 7.87
B. Do the Surface Inspection.
(2) Examine around the circumference of the attach holes.
7. Forward Attach Points Inspection
A. Do an Attach Mount Inspection (Refer to Figure 1).
(2) Adjust the probe diameter to the diameter of the hole with the use of nonmetallic material between the slot in the
probe.
Table 3. Forward Attach Point
Index Depth (Inches) Depth (mm)
1 0.050 1.27
2 0.17 4.32
3 0.29 7.37
4 0.41 10.41

55-10-01-0 (Rev 1)
5 0.53 13.46
6 0.65 16.51
7 0.77 19.56
8 0.89 22.61
9 1.01 25.65
10 1.07 27.18
8. Part Disposition
(1) Crack location.
(2) Crack length.

55-10-01-0 (Rev 1)

55-10-02-0 (Rev 1)
HORIZONTAL STABILIZER SPARS

1. Description
A. This procedure gives the techniques used to find cracks in the forward and aft spars of the horizontal stabilizer.
Table 1. Item Codes
MODEL 208 A551005 55-10-00-251
MODEL 208 A553004 55-10-00-252
3. Preparation
B. Clean the inspection area of any unwanted materials and/or burrs that can have an effect on the inspection.
4. Equipment
421 N. Quay St.
Kennewick, WA 99336
Ring Probe RR206-5/TF 500Hz- NDT Engineering Corp. To find cracks
10kHz 19620 Russell Rd.
Kent, WA 98032
Web: www.ndteng.com
Reference Standard 2683301-1 Cessna Aircraft Company To calibrate system
Material and Process Engineering
Department 352
P.O. Box 67277
Wichita, KS 67277
Phone: (316) 517-0897
Web: ncertprogram@cessna.textron.com
5. Calibration
A. Calibrate the Ring Probe.
(1) Set the eddy current instrument to a frequency of 5 kHz.
(2) Put the ring probe over the good fastener on the reference standard.
(3) Lift the probe away from the standard. Monitor the display for the lift-off response.
(a) Adjust the instrument so that the lift-off signal goes horizontal and to the left. This is the null point.
(4) Put the probe over the fastener with a flaw on the reference standard.
(5) Move the probe until the fastener is in the center of the probe.
(6) Lift the probe away from the standard. Monitor the display for the defect response. This is the defect point.
(7) Adjust the instrument to get a minimum of three major screen divisions between the null point and the defect point.
6. Inspection
A. Inspect the Forward Spar (Refer to Figure 1).

55-10-02-0 (Rev 1)
(1) Calibrate the ring probe and instrument. Refer to Calibrate the Ring Probe.
(2) Inspect each fastener on the top and bottom spar between RSS 9.90 and LSS 9.90.
B. Inspect the Aft Spar (Refer to Figure 1).
(1) Calibrate the ring probe and instrument. Refer to Calibrate the Ring Probe.
(2) Inspect each fastener on the top and bottom spar between RSS 10.60 and LSS 10.60.
7. Part Disposition
(1) Crack location.
(2) Crack length.

55-10-02-0 (Rev 1)
Figure 1 : Sheet 1 : Horizontal Stabilizer Spars

55-30-01-0 (Rev 2)
VERTICAL STABILIZER SPARS

1. Description
A. This procedure will show you how to find cracks in the spars of the vertical stabilizer.
Table 1. Item Codes
MODEL 208 A553001 55-30-00-250
MODEL 208 A553002 55-30-00-251
A. Personnel certification requirements are found in Part 1 of this manual.
3. Preparation
A. Remove the vertical stabilizer. Refer to the Maintenance Manual, Chapter 55, Vertical Stabilizer - Removal/Installation.
4. Equipment
421 N. Quay St.
Kennewick, WA 99336
Kent, WA 98032
Web: www.ndteng.com
Bolt Hole Probe 3/8 inch BPMF-24 NDT Engineering Corp. To find cracks
diameter
Micrometer or caliper Commercially available To put the probe collar in
position
Standard
5. Calibration
point.

55-30-01-0 (Rev 2)

point.
6. Inspection
A. Inspect the Forward Spar Between WL 134.38 and WL 138.00 (Refer to Figure 1).
(2) Examine around each of the fasteners in the circled area on the forward and aft side of the spar.
NOTE: Access to the aft side will be through a lightening hole in the bottom rib.
B. Inspect the Forward Spar Attach Holes (Refer to Figure 1).
(3) Put the probe in the same hole from the forward side of the stabilizer.
(4) Monitor the display for any indications as the probe is turned a minimum of 360 degrees.
(8) Do the steps again for each of the three remaining holes.
C. Inspect the Rear Spar Between WL 126.12 and WL 129.00 (Refer to Figure 1).
(2) Examine around each of the fasteners in the area shown in Figure 1 on the forward and aft side of the spar.
D. Inspect the Rear Spar Attach Holes (Refer to Figure 1).
(6) Put the probe in the same hole from the aft side of the stabilizer.
(8) Do the steps again for each of the three remaining holes.
7. Part Disposition
(1) Crack location.
(2) Crack length.

55-30-01-0 (Rev 2)
Figure 1 : Sheet 1 : Vertical Stabilizer Spars

55-30-01-0 (Rev 2)

55-30-01-0 (Rev 2)

57-20-01-0 (Rev 2)
WING TO CARRY-THRU SPAR ATTACHMENT FITTING

1. Description
A. Examine for fatigue cracks in specific holes of the spar attach fittings.
Table 1. Item Codes
MODEL 208 A570013 57-10-00-250
MODEL 208 A570014 57-10-00-251
A. Personnel certification requirements are in Part 1of this manual.
3. Preparation
A. Remove the wing. Refer to the Maintenance Manual Chapter 57, Wings - Removal/Installation.
B. Remove the four bolts in each fitting, indicated in Figure 1.
C. Clean the area to remove substances that may interfere with the inspection.
4. Equipment
Eddy Current Unit with X-Y storage oscilloscope Nortec Staveley Instruments, To find cracks
1000s Inc.
421 N. Quay
Kennewick, WA
99336
Web:
www.staveleyndt.com
Bolt Hole Probe, 7/8 inch diameter BPM-56 NDT Engineering To find cracks
Corp.
19620 Russell Rd.
Kent, WA 98032
Web:
www.ndteng.com
Bolthole Probe, 15/16 inch diameter BPM-60 NDT Engineering To find cracks
Corp.
Bolt Hole Probe, 5/16 inch diameter BPM-20 NDT Engineering To find cracks
Corp.
Bolthole Probe, 1/4 inch diameter BPM-16 NDT Engineering To find cracks
Corp.
Micrometer or caliper Commercially To position
avilable probe collar
Bolt Hole Reference Standard HRS-15A NDT Engineering To calbrate
Corp. system
5. Calibration

57-20-01-0 (Rev 2)
(3) Put the probe in the applicable hole in the standard with the probe coil away from the notch.
point.
6. Forward Spar Fitting Inspection
A. Wing to Carry-Thru Forward Spar Attach Fitting Bolt Holes (Refer to Figure 1).
(2) Inspect attach fitting holes number 1, 2, 3, and 4.
NOTE: Figure 2 shows a typical hole cross section.
(6) Do the inspection at each of the probe depths of the applicable table for each hole.
Table 2. Hole 1
Index Structure Depth (inches) Depth (mm)
1 Fitting 0.05 1.27
2 Fitting 0.09 2.29
3 Fitting 0.13 3.30
4 Fitting 0.17 4.32
5 Angle 0.25 6.35
6 Spacer 0.32 8.13
7 Web 0.38 9.65
8 Spacer 0.44 11.18
9 Angle 0.51 12.95
10 Fitting 0.6 15.24
11 Fitting 0.64 16.26
12 Fitting 0.68 17.27
13 Fitting 0.72 18.29
Table 3. Hole 2
1 Fitting 0.05 1.27
2 Fitting 0.15 3.81
3 Fitting 0.29 7.37
4 Fitting 0.39 9.91
5 Angle 0.47 11.94
6 Spacer 0.54 13.72
7 Web 0.60 15.24
8 Spacer 0.66 16.76
9 Angle 0.73 18.54

57-20-01-0 (Rev 2)
10 Fitting 0.82 20.83

11 Fitting 0.92 23.37
12 Fitting 1.06 26.92
13 Fitting 1.16 29.46
Table 4. Hole 3
1 Fitting 0.05 1.27
2 Fitting 0.09 2.29
3 Fitting 0.13 3.30
4 Fitting 0.17 4.32
5 Spacer 0.24 6.10
6 Cap 0.31 7.87
7 Web 0.38 9.65
8 Cap 0.45 11.43
9 Spacer 0.52 13.21
10 Fitting 0.6 15.24
11 Fitting 0.64 16.26
12 Fitting 0.68 17.27
13 Fitting 0.72 18.29
Table 5. Hole 4
1 Fitting 0.05 1.27
2 Fitting 0.15 3.81
3 Fitting 0.29 7.37
4 Fitting 0.39 9.91
5 Spacer 0.46 11.68
6 Cap 0.53 13.46
7 Web 0.60 15.24
8 Cap 0.67 17.02
9 Spacer 0.74 18.80
10 Fitting 0.81 20.57
11 Fitting 0.91 23.11
12 Fitting 1.05 26.67
13 Fitting 1.15 29.21
7. Aft Spar Fitting Inspection
A. Wing to Carry-Thru Aft Spar Attach Fitting Bolt Holes (Refer to Figure 1).
(2) Inspect attach fitting holes number 5, 6, 7, and 8.
NOTE: Figure 3 shows a typical hole cross section.

57-20-01-0 (Rev 2)
(6) Do the inspection at each of the probe depths of the applicable table for each hole.
Table 6. Hole 5
1 Fitting 0.05 1.27
2 Fitting 0.10 2.54
3 Fitting 0.15 3.81
4 Angle 0.23 5.84
5 Spacer 0.28 7.11
6 Spacer 0.38 9.65
7 Angle 0.43 10.92
8 Fitting 0.51 12.95
9 Fitting 0.56 14.22
10 Fitting 0.61 15.49
Table 7. Hole 6
1 Fitting 0.05 1.27
2 Fitting 0.18 4.57
3 Fitting 0.31 7.87
4 Angle 0.39 9.91
5 Spacer 0.44 11.18
6 Spacer 0.54 13.72
7 Angle 0.59 14.99
8 Fitting 0.67 17.02
9 Fitting 0.80 20.32
10 Fitting 0.92 23.37
Table 8. Hole 7
1 Fitting 0.05 1.27
2 Fitting 0.10 2.54
3 Fitting 0.15 3.81
4 Spacer 0.22 5.59
5 Cap 0.28 7.11
6 Cap 0.39 9.91
7 Spacer 0.45 11.43
8 Fitting 0.52 13.21
9 Fitting 0.57 14.48
10 Fitting 0.62 15.75
Table 9. Hole 8
1 Fitting 0.05 1.27

57-20-01-0 (Rev 2)
2 Fitting 0.18 4.57

3 Fitting 0.31 7.87
4 Spacer 0.38 9.65
5 Cap 0.44 11.18
6 Cap 0.55 13.97
7 Spacer 0.61 15.49
8 Fitting 0.68 17.27
9 Fitting 0.81 20.57
10 Fitting 0.94 23.88
8. Attach Lug Holes
A. Wing Attach Lug Holes (Forward Spar) (Refer to Figure 1).
(2) Inspect each attach fitting lug hole.
NOTE: Both lugs at each location must be inspected.
(6) Do the inspection at each of the probe depths of Table 9 for each hole.
Table 10. Forward Lug Holes
Index Depth (inches) Depth (mm)
1 0.05 1.27
2 0.15 3.81
3 0.25 6.35
4 0.35 8.89
5 0.45 11.43
B. Wing Attach Lug Holes (Aft Spar) (Refer to Figure 1).
(2) Inspect each attach fitting lug hole.
NOTE: Both lugs at each location must be inspected.
(6) Do the inspection at each of the probe depths of Table 10 for each hole.
Table 11. Aft Lug Holes
Index Depth (inches) Depth (mm)
1 0.05 1.27
2 0.15 3.81
3 0.22 5.59
4 0.29 7.37
5 0.39 9.91
9. Part Disposition

57-20-01-0 (Rev 2)
(1) Crack location.
(2) Crack length.

57-20-01-0 (Rev 2)
Figure 1 : Sheet 1 : Wing to Carry-Thru Spar Attach Fitting Inspection

57-20-01-0 (Rev 2)
Figure 2 : Sheet 1 : Typical Hole Cross Section at Forward Spar Fitting Hole Locations
A29132
WEB
(0.040 INCH THICK) WEB
SPACER SPACER (0.040 INCH THICK)
(0.080 INCH THICK) ANGLE (0.080 INCH THICK)
(0.063 INCH THICK) ANGLE
ANGLE (0.063 INCH THICK)
(0.063 INCH THICK) ANGLE
(0.063 INCH THICK)
FITTING FITTING
(0.220 INCH THICK) (0.440 INCH THICK)
HOLE 1 MATERIAL CROSS SECTION HOLE 2 MATERIAL CROSS SECTION
WEB
(0.040 INCH THICK) WEB
CAP CAP (0.040 INCH THICK)
SPACER
(0.040 INCH THICK) SPACER
SPACER (0.040 INCH THICK)
(0.040 INCH THICK) SPACER
(0.040 INCH THICK)
FITTING FITTING
2683T1003

57-20-01-0 (Rev 2)
Figure 3 : Sheet 1 : Typical Hole Cross Section at Aft Spar Fitting Hole Locations
A29133
WEB WEB
SPACER (0.032 INCH THICK) SPACER (0.032 INCH THICK)
ANGLE ANGLE
ANGLE (0.050 INCH THICK) ANGLE
(0.050 INCH THICK) (0.050 INCH THICK) (0.050 INCH THICK)
FITTING FITTING
WEB WEB
CAP (0.032 INCH THICK) CAP (0.032 INCH THICK)
SPACER SPACER SPACER
SPACER (0.040 INCH THICK) (0.040 INCH THICK)
FITTING FITTING
2683T1004

57-20-02-0 (Rev 3)
FORWARD SPAR LOWER CAP INBOARD OF WS 141.20

1. Description
A. Examine for fatigue cracks in the lower forward spar cap inboard of WS 141.20.
Table 1. Item Codes
MODEL 208 A570010 57-10-00-252
3. Preparation
A. Remove panels 501AB and 601AB to access the inboard end of the bottom forward spar. (Refer to Figure 1).
B. Remove the inboard side bracket of the strut fairing to get access to the skin at the forward spar.
C. Clean the skin and spar cap to remove substances that can interfere with the inspection.
4. Equipment
NOTE: This equipment was used to make this procedure. You can use replacements for the items below if they
have the necessary parameters. Metered instruments are not allowed. There is no alternate for the
Cessna reference standard.
Eddy Current Unit with Nortec 1000s Olympus To find cracks
X-Y storage 48 Woerd Ave
oscilloscope Waitham, Massachusetts 02453
Web: www.olympus-ims.com
Spot Probe (NOTE 1) 9213550 Olympus To find cracks
Shielded Surface Probe MP905-60 Olympus To find cracks
1/8 inch diameter
(NOTE 2)
Cessna Customer Care
Phone: (316) 517-5800
Fax: (316) 517-7271
Email: TMDC@txtav.com
NOTE 1: Reflection spot probe: 1/4 inch diameter, operating frequency of 6 kHz.
NOTE 2: Surface probe: 1/8 inch diameter operating frequency of 200 kHz, shielded (ferrite core), right angle 1/2
inch drop, 6 inches long. Other lengths/styles may be used provided the coil requirements are met.
5. Calibration
point.

57-20-02-0 (Rev 3)
B. Calibrate the Spot Probe.

(2) Set the eddy current instrument frequency to 6 kHz, +1 or -1 kHz.
(3) Put the probe on the standard away from the notch.
NOTE: The spar cap has two angles bonded to a center web. Be sure you use an area on the
standard that best matches the area of the airplane you are to inspect.
point.
C. Alternate Calibration for the Spot Probe.
NOTE: There may be greater edge effect, compared to the reference standard, when you inspect the area
parallel to the edge of a spar cap. This can be caused if the distance between the fasteners and the
edge of the spar cap is smaller than on the reference standard. If edge effect interference is
noticed, use the alternate calibration.
(3) Measure the distance from the edge of the spar cap to the edge of the fastener on the airplane.
(4) Compare that measurement to the same one on the reference standard.
(5) If the edge distance on the airplane is shorter, move the probe the same difference away from the fastener on the
standard.
(a) If the airplane fastener has an edge distance of 0.35 inch (8.9 mm) and the standard has an edge distance of
0.50 inch (12.7 mm), do the calibration on the test standard 0.15 inch (3.8 mm) from the fastener.
(b) Use a nonmetallic straight edge to make sure the probe keeps the proper distance from the fasteners on the
standard.
NOTE: The spar cap consists of two angles bonded to a center web. Be sure you use an area on the
(9) Move the probe over the appropriate notch. Monitor the display to make sure the signal moves up and toward the left
as the probe moves across the notch.
NOTE: You are looking for cracks between the fastener and the edge of the spar cap. Make sure that
the EDM cut on the standard is in the same relative position as the airplane structure you are
looking at.
point.
6. Inspection
A. Bottom Forward Spar Cap (Refer to Figure 1).
(1) Make sure the instrument and probe are calibrated. Refer to Calibrate the 200 kHz Surface Probe.
(2) Use the eddy current surface probe to inspect along the edges of the bottom spar cap at the strut attach point
between the ribs at WS 126.50 and WS 141.20.
(3) Do an inspection around the nut plate fasteners and holes located at the inboard end of the spar.

57-20-02-0 (Rev 3)
B. Use the eddy current spot probe to inspect around each fastener common to the bottom spar and skin from the inboard
end of the wing to the rib at WS 126.50.
(1) Make sure the instrument and probe are calibrated. Refer to Calibrate the Spot Probe.
(2) The spar cap has two angles bonded to a center web.
(3) Do a calibration and inspection parallel to the forward and aft edges of each cap with a nonconductive straight edge
as a guide for the probe.
NOTE: If greater edge effect is sensed, use the Alternate Calibration for the Spot Probe to recalibrate
the equipment.
(4) Do a calibration and inspection with the spot probe around the remaining area of each of the fasteners from the
inboard end of the wing spar to WS 126.50.
7. Part Disposition
(1) Crack location.
(2) Crack length.

57-20-02-0 (Rev 3)
Figure 1 : Sheet 1 : Bottom Forward Spar Cap Inspection Area

57-20-03-0 (Rev 3)
WING AFT SPAR LOWER CAP INBOARD OF WS 141.20

1. Description
A. Examine for fatigue cracks in the bottom aft spar cap inboard of WS 141.20.
Table 1. Item Codes
MODEL 208 A570011 57-10-00-253
3. Preparation
A. Clean skin and spar cap to remove substances that may interfere with the inspection.
4. Equipment
NOTE: This equipment was used to make this procedure. You can use replacements can be used for the items
below if they have the necessary parameters. Metered instruments are not allowed. There is no
alternate for the Cessna reference standard.
Eddy Current Unit with Nortec 1000s Olympus To find cracks
X-Y storage 48 Woerd Ave
oscilloscope Waitham, Massachusetts 02453
Web: www.olympus-ims.com
Spot Probe (NOTE 1) 9213550 Olympus To find cracks
Cessna Customer Care
Phone: (316) 517-5800
Fax: (316) 517-7271
Email: TMDC@txtav.com
NOTE 1: Reflection spot probe: 1/4 inch diameter, operating frequency of 6 kHz.
5. Calibration
A. Calibrate the Spot Probe.
point.
B. Alternate Calibration for the Spot Probe.
NOTE: There may be greater edge effect, compared to the reference standard, when you inspect the area
parallel to the edge of a spar cap. This can be caused if the distance between the fasteners and the
edge of the spar cap is smaller than on the reference standard. If edge effect interference is
noticed, use the alternate calibration.

57-20-03-0 (Rev 3)

(3) Measure the distance from the edge of the spar cap to the edge of the fastener on the airplane.
(4) Compare that measurement to the same one on the reference standard.
(5) If the edge distance on the airplane is shorter, move the probe the same difference away from the fastener on the
standard.
(a) If the airplane fastener has an edge distance of 0.35 inch (8.9 mm) and the standard has an edge distance of
0.50 inch (12.7 mm), do the calibration on the test standard 0.15 inch (3.8 mm) from the fastener.
(b) Use a nonmetallic straight edge to make sure the probe keeps the proper distance from the fasteners on the
standard.
(9) Move the probe over the appropriate notch. Monitor the display to make sure the signal moves up and toward the left
as the probe moves across the notch.
NOTE: You are looking for cracks between the fastener and the edge of the spar cap. Make sure that
the EDM cut on the standard is in the same relative position as the airplane structure you are
looking at.
point.
6. Inspection
A. Bottom Aft Spar Cap (Refer to Figure 1).
(1) Use the eddy current spot probe to inspect around each fastener common to the bottom spar and skin from the
inboard end of the wing to the rib at WS 141.20.
(a) Make sure the instrument and probe are calibrated. Refer to Calibrate the Spot Probe.
(b) Do a calibration and inspection parallel to the forward and aft edges of each cap using a nonconductive straight
edge as a guide for the probe.
NOTE: If greater edge effect is sensed, recalibrate the equipment using the Alternate Calibration
for the Spot Probe.
(c) Do a calibration and inspection with the spot probe around the remaining area of each of the fasteners from the
inboard end of the wing spar to WS 141.20.
7. Part Disposition
(1) Crack location.
(2) Crack length.

57-20-03-0 (Rev 3)
Figure 1 : Sheet 1 : Bottom Aft Spar Cap Inspection Area

57-50-01-0 (Rev 3)
FLAP TRACKS
1. General
A. Included in this section are instructions to do an eddy current inspection for fatigue cracks in the flap tracks.
Table 1. Item Codes
MODEL 208 A575002 57-10-00-254
MODEL 208 A575003 57-10-00-255
3. Tools, Equipment and Materials
A. The equipment used in the development of this procedure is listed in the Table below.
NOTE: Equivalent eddy current equipment may be used provided it meets the sensitivity requirements of
this procedure.
Eddy Current Instrument Nortec 2000 Olympus NDT To inspect flap tracks
48 Woerd Ave
Waltham, MA 02453
Web: http://www.olympus-imsg.com
Calibration Standard SRS-0824A Olympus NDT To calibrate equipment
NOTE: 1
Right Angle Surface MP902-60 Olympus NDT To inspect flap tracks
Probe
NOTE: 2
NOTE: 1. An equivalent calibration standard will be an aluminum alloy with a 0.020 inch deep or less,
surface EDM notch. Refer to Part 6, 20-00-02 for additional guidance.
2. Coil: 200 kHz, 1/8 inch diameter, shielded (ferrite core). Probe body: right angle, 0.2 inch drop, 6
inches long. Other lengths/styles of probes may be used provided the coil requirements are met.
4. Calibration
(6) Move the probe over the 0.020 inch deep EDM notch. Monitor the display to make sure the signal moves up and
toward the left as the probe moves across the notch.
(a) Adjust the instrument to get a minimum of three major screen divisions between the null point and the peak notch
indication.
5. Flap Track Inspection
A. Do the Eddy Current Inspection of the Center, Inboard, and Outboard Flap Tracks (Refer to Figure 1).
(1) Lower the flaps to the fully extended 30 degree position.
(2) Disconnect all electrical power from the airplane. Attach maintenance warning tags to the battery connector(s) and
external power receptacle that have the following written on them:

57-50-01-0 (Rev 3)
WARNING: DO NOT CONNECT ELECTRICAL POWER - MAINTENANCE IN PROGRESS.

(3) Remove the left and right flap assemblies from the airplane. Refer to Maintenance Manual Chapter 57, Flap -
(4) Do an eddy current inspection of the flap tracks.
NOTE: Eddy current inspection of the center, inboard, and outboard flap tracks is typical.
(a) Calibrate the 200 kHz surface probe and instrument. Refer to Calibrate the 200 kHz Surface Probe.
(b) With the probe, scan the top and bottom internal and external surfaces, and inboard and outboard surfaces of
the flap tracks. Scan first in one direction, then the opposite direction.
1 If cracks are not found, no further action is necessary.
(5) Replace the flap track(s) if any cracks are found. Refer to the Model 208 Series Illustrated Parts Catalog for flap track
part number.
(6) Install the left and right flap assemblies. Refer to Maintenance Manual Chapter 57, Flap - Removal/Installation.
(7) Do an operational check of the flap system. Refer to the Maintenance Manual, Chapter 27, Flap Rigging Guide -
Adjustment/Test.
(8) Remove the maintenance warning tag and connect the airplane battery.

57-50-01-0 (Rev 3)
Figure 1 : Sheet 1 : Flap Track Inspection

57-50-01-0 (Rev 3)

A22178
MOVE PROBE IN ONE DIRECTION,

THEN THE OPPOSITE DIRECTION ON THE FLAP TRACK
INTERNAL FLAP TRACK SURFACES,
AS SHOWN BY THE ARROWS.
RIGHT ANGLE
SURFACE PROBE
WING
DETAIL B
TYPICAL INTERNAL SURFACE
FLAP TRACK INSPECTION

THEN THE OPPOSITE DIRECTION ON THE
WING UPPER AND LOWER FLAP TRACK
FLAP TRACK SURFACES, AS SHOWN BY THE ARROWS.
RIGHT ANGLE
SURFACE PROBE
DETAIL C
TYPICAL UPPER AND LOWER EXTERNAL
SURFACE FLAP TRACK INSPECTION
B2622T1027
C2622T1029

57-50-01-0 (Rev 3)

A22180
RIGHT ANGLE
SURFACE PROBE
WING FLAP TRACK

THEN THE OPPOSITE DIRECTION ON
THE INBOARD AND OUTBOARD FLAP
TRACK SURFACES AS SHOWN
BY THE ARROWS.
DETAIL D
TYPICAL INBOARD AND OUTBOARD
SURFACE FLAP TRACK INSPECTION
D2622T1028

57-60-01-0 (Rev 1)
WING STRUT FITTINGS

1. General
A. This procedure agrees with the Model 208 Maintenance Manual, Chapter 5, 5-14-28, Supplemental Inspection Number
57-60-01.
Table 1. Item Codes
MODEL 208 A570008 57-10-01-250
MODEL 208 A570009 57-10-01-251
3. Tools and Materials
NOTE: You can use equivalent alternatives for the following items:
Eddy Current Instrument Nortec 2000 Staveley NDT Technologies To inspect strut fittings
421 N. Quay St.
Kennewick, WA 99336
Right Angle Surface MP902-60 NDT Engineering Corp. To inspect strut fittings
Probe 100 kHz to 500 19620 Russell Rd.
kHz, 0.125 inch Kent, WA 98032
diameter, 11 inches long Web: www.ndteng.com
Bolt Hole Probe BPMF-56 NDT Engineering Inspect Upper Strut Fitting Holes
Bolt Hole Probe BPMF-48 NDT Engineering Inspect Lower Strut Fitting Holes
Calibration Standard HRS-15A NDT Engineering Corp. To calibrate equipment
4. Preparation
A. Remove the Strut.
WARNING: OBEY ALL FUEL SYSTEM FIRE AND SAFETY PRACTICES
(1) Defuel the airplane Refer to the Maintenance Manual Chapter 12, Fuel - Servicing.
(2) Disconnect all electrical power from the airplane. Attach maintenance warning tags to the battery connector(s) and
external power receptacle that have the following written on them: WARNING: DO NOT CONNECT ELECTRICAL
POWER - MAINTENANCE IN PROGRESS.
NOTE: Removal and installation procedures for both left and right wing lift struts are typical.
(3) Remove the wing lift strut fairings. Refer to the Maintenance Manual Chapter 57, Wings - Removal/Installation.
CAUTION: WING MUST STAY AS NEAR TO THE NORMAL DIHEDRAL ANGLE AS POSSIBLE. TOO MUCH
MOTION UP OR DOWN AT THE WING TIP (ONE INCH (25 mm) MAXIMUM UP OR DOWN) WILL
DAMAGE THE WING ATTACH FITTINGS.
(4) Put a support on the outboard section of the wings. Refer to the Maintenance Manual Chapter 57, Wings -
(5) With the outboard section of wings supported, remove the left wing lift strut. Keep the hardware for reinstallation.
Refer to the Maintenance Manual Chapter 57, Wings - Removal/Installation.
5. Calibration

57-60-01-0 (Rev 1)
point.
B. B. Calibrate the 200 kHz bolt hole probe
NOTE: This calibration is for either of the specified bolt hole probes.
(3) Insert the probe into the appropriate hole of the reference standard.
NOTE: Make sure that the probe coil is positioned away from the EDM notch.
(5) Rotate the probe coil across the notch.
NOTE: Monitor the display to make sure the signal moves up and toward the left as the probe moves
across the notch.
point.
6. Inspection Procedure
NOTE: Inspection procedures are typical for all strut fittings.
A. Do the inspection on the necessary areas of the attach fittings for cracks (Refer to Figure 1).
(1) Clean the areas to be inspected.
(3) Do the inspection on the surface of the fitting.
NOTE: The areas to be inspected are the edge of the fitting and the top of the lugs at the machined
step. Refer to Figure 1.
(4) Carefully do the inspection in the opposite direction of probe scanning to make sure of the crack indication.
(5) Do the inspection on the fittings (total of 8). Do the probe scanning in the direction of the arrows around first three
bolts as shown in Figure 1, Sheets 2 and 3, Details B and C
B. Bolt Hole Probe Inspection - Upper Fitting Attach Holes
NOTE: The upper fitting attach holes have a diameter of 0.875 inches (22.225 mm) so you must use the
BPMF-56 bolt hole probe. Each lug has a width of 0.70 inches (17.78 mm).
(1) Calibrate the BPMF-56 bolt hole probe. Refer to Calibrate the 200 kHz bolt hole probe.
(2) Position the collar of the bolt hole probe so it is 0.050 inch (1.270 mm) from the center of the probe coil.
(3) Insert the probe into an upper attach hole.
NOTE: It may be necessary to balance the instrument.
(4) Adjust lift-off so it moves horizontal and to the left.
(5) Monitor the instrument display while you rotate the probe around the entire circumference of the hole so it goes
beyond 360 degrees.
(6) Reposition the collar 0.10 inch (2.54 mm) from its position (0.15 inch (3.81 mm) from the coil center).
NOTE: Do the inspection again.
(7) Repeat the step above five more times.
(a) Reposition the collar 0.10” after each index until the lug as been inspected.

57-60-01-0 (Rev 1)
NOTE: Each upper lug will have seven index positions.

C. Bolt Hole Probe Inspection - Lower Fitting Attach Holes
NOTE: The lower fitting attach holes have a diameter of 0.75 inch (19.05 mm) so you must use the BPMF-
48 bolt hole probe. Each of the lower attach fittings have a width of 0.50 inch (12.7 mm).
(1) Calibrate the BPMF-48 bolt hole probe. Refer to Calibrate the 200 kHz bolt hole probe.
(2) Position the collar of the bolt hole probe so it is 0.050 inch (1.270 mm) from the center of the probe coil.
(3) Insert the probe into an upper attach hole.
NOTE: It may be necessary to balance the instrument.
(4) Adjust lift-off so it moves horizontal and to the left.
(5) Monitor the instrument display while you rotate the probe around the entire circumference of the hole so it goes
beyond 360 degrees.
(6) Reposition the collar 0.10 inch (2.54 mm) from its position (0.15 inch (3.81 mm) from the coil center).
NOTE: Do the inspection again.
(7) Repeat the step above three more times.
(a) Reposition the collar 0.10” after each index until the lug as been inspected.
NOTE: Each lower lug will have five index positions.
7. Disposition
A. If no cracks are found, install the wing struts. Refer to the Maintenance Manual Chapter 57, Wings - Removal/Installation.
B. If cracks are found, replace the wing strut fitting. Refer to the Maintenance Manual Chapter 57, Wings -

57-60-01-0 (Rev 1)
Figure 1 : Sheet 1 : Wing Strut Fitting Inspection

A22184
A
C
A A
TIEDOWN
(REFERENCE) B
VIEWA−A
MS21042L5
NUT
(REFERENCE)
B
OUTBD
DETAILA FWD
LOOKING UP AT LEFT
WING STRUT ASSEMBLY
UP (RIGHT SIDE OPPOSITE)
VIEWB−B
FWD
2610T7005
A2622T1022
AA2622T1024
BB2622T1023

57-60-01-0 (Rev 1)

57-60-01-0 (Rev 1)

57-60-02-0 (Rev 1)
WING STRUT ATTACHMENT TO FRONT SPAR

1. Description
A. Look for fatigue cracks in the fitting of the strut attachment to the front spar.
Table 1. Item Codes
MODEL 208 A570012 57-10-01-252
MODEL 208 A570015 57-10-01-253
MODEL 208 A570016 57-10-01-254
MODEL 208 A570017 57-10-01-255
2. Preparation
NOTE: This procedure must be done while the wing is removed.
A. Remove the wing. Refer to Maintenance Manual Chapter 57, Wings - Removal/Installation.
B. Remove the strut fairings for access to the fittings.
C. Clean the skin and the spar cap to remove materials that can cause interference with the inspection.
3. Equipment
421 N. Quay St.
Kennewick, WA 99336
Shielded Bolt Hole Probe BPM-56 NDT Engineering Corp. To find cracks
Kent, WA 98032
Web: www.ndteng.com
Kent, WA 98032
Web: www.ndteng.com
Micrometer or caliper Commercially available To position the probe collar
Standard
4. Calibration

57-60-02-0 (Rev 1)
point.
point.
5. Inspection
A. Support Fitting Surface Inspection (Refer to Figure 1).
NOTE: This inspection is not necessary for Airplanes 20800001 thru 20800010 and Airplane 20800012.
NOTE: This inspection is necessary for both wings.
(1) Calibrate the surface probe. Refer to Calibrate the 200 kHz Surface Probe
(2) Holes 1 thru 4.
(a) Remove the nut from each bolt one at a time.
(b) Pull the bolt out of the hole far enough to allow you to do a surface inspection around the bolt shank.
(c) Do a surface scan inspection around the bolt on the fitting.
(d) Do a surface scan inspection around the bolt hole on the opposite fitting.
(e) Install the nut and torque to standard torque.
(f) Do the inspection at each of the holes.
(3) Holes 5 thru 7.
(a) Do a surface scan inspection around each of the fastener heads and collars. Do not remove collars.
B. Attach Lug Inspection (Refer to Figure 1).
NOTE: This inspection is for all airplanes.
(5) Do the inspection at each of the depths in Table 1 for each of the lug holes.
Table 2. Attach Lugs
Index Number Depth (inches) Depth (mm)
1 0.05 2.03
2 0.17 4.32
3 0.29 7.37
4 0.41 10.14
5 0.53 13.46
6 0.65 16.51
6. Part Disposition
Telephone 316-517-5800. FAX 316-942-9006. Give the information that follows:

57-60-02-0 (Rev 1)
(1) Crack location.

(2) Crack length.

57-60-02-0 (Rev 1)
Figure 1 : Sheet 1 : Wing Strut Attachment to Front Spar


04 - C208B - ND (Rev 3) - Part 6 - EDDY CURRENT

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What is the purpose of this procedure?

What is the purpose of this procedure?

What are the requirements for eddy current test systems according to this procedure?

What are the requirements for eddy current test systems according to this procedure?

Model 208 Nondestructive Testing Manual (Rev 3)

EDDY CURRENT BOLT HOLE TECHNIQUES - GENERAL

Copyright © Textron Aviation Inc. Page 1 of 27

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(3) Turn on the instrument.

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Table 3. Calibration levels.

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the hole until the best signal is achieved.

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J. Continue to Section 10 for the Semiautomatic Inspection.

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Figure 1 : Sheet 1 : Typical Surface Reference Standard

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Figure 2 : Sheet 1 : Probe Coil

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Figure 3 : Sheet 1 : Lift-Off Display

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Figure 4 : Sheet 1 : Lift-Off Display

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Figure 5 : Sheet 1 : Notch Signal Response

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Figure 6 : Sheet 1 : Notch Signal Response

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Figure 7 : Sheet 1 : Notch Signal Response

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Figure 8 : Sheet 1 : Notch Signal Response

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Figure 9 : Sheet 1 : Scanner On Reference Standard

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Figure 10 : Sheet 1 : Notch Signal Response

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Figure 11 : Sheet 1 : Notch Signal Response

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Figure 12 : Sheet 1 : Determining Scanner Position

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Figure 13 : Sheet 1 : Determining Scanner Position

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Figure 14 : Sheet 1 : Crack Indications

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Figure 15 : Sheet 1 : Determining Crack Length

REFERENCE STANDARD FOR ILLUSTRATION ONLY.

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EDDY CURRENT SURFACE TECHNIQUES - GENERAL

LIFT-OFF NULL POINT

ABSOLUTE PROBE CALIBRATION RANGE

NULL POINT 20°

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DIFFERENTIAL PROBE CALIBRATION RANGE

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