ICAO 9137 Airport Services Manual Part 2 Pavement Surface Conditions 4th Ed
ICAO 9137 Airport Services Manual Part 2 Pavement Surface Conditions 4th Ed
ICAO 9137 Airport Services Manual Part 2 Pavement Surface Conditions 4th Ed
AN/898
Airport
Services Manual
Part 2
Pavement Surface Conditions
Doc 9137
AN/898
Airport
Services Manual
Part 2
Pavement Surface Conditions
AMENDMENTS
The issue of amendments is announced regularly in the ICAO Journal and in the
supplements to the Catalogue of ICAO Publications and Audio-visual Training
Aids, which holders of this publication should consult. The space below is provided
to keep a record of such amendments.
Date
CORRIGENDA
Entered by
No.
(ii)
Date
Entered by
Foreword
(iii)
Table of Contents
Page
Chapter 1. General . . . . . . . . . . . . . . . . . . . . . . . .
1-1
1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . .
1.2 Importance of runway surface friction
characteristics/aeroplane braking
performance . . . . . . . . . . . . . . . . . . . . . . . .
1.3 Need for assessment of runway surface
conditions. . . . . . . . . . . . . . . . . . . . . . . . . .
1.4 Contaminant drag . . . . . . . . . . . . . . . . . . . .
1.5 Explanation of terms . . . . . . . . . . . . . . . . . .
1-1
2-1
2-3
2-4
2-6
3-1
1-2
1-3
1-3
2-1
General. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Measurement . . . . . . . . . . . . . . . . . . . . . . . .
Reporting . . . . . . . . . . . . . . . . . . . . . . . . . . .
Interpretation of low friction
characteristics. . . . . . . . . . . . . . . . . . . . . . .
1-1
3.1
3.2
3.3
3.4
Page
3-1
3-2
3-4
6.1 General. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.2 Wet surface state information . . . . . . . . . . .
6.3 Snow-, slush- or ice-covered surface state
information . . . . . . . . . . . . . . . . . . . . . . . .
6.4 SNOWTAM format. . . . . . . . . . . . . . . . . . .
3-4
Chapter 7.
5-1
5-1
5-1
5-2
5-6
5-7
5-7
5-8
5-8
5-8
5-13
5-14
5-15
5-16
6-1
6-1
6-1
6-3
6-4
7-1
4-1
7.1
7.2
7.3
7.4
7.5
General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1
Snow committee . . . . . . . . . . . . . . . . . . . . . 7-2
Snow plan procedure. . . . . . . . . . . . . . . . . . 7-2
Mechanical methods . . . . . . . . . . . . . . . . . . 7-4
Equipment for snow removal and
ice control . . . . . . . . . . . . . . . . . . . . . . . . . 7-5
7.6 Thermal methods. . . . . . . . . . . . . . . . . . . . . 7-21
7.7 Chemical methods . . . . . . . . . . . . . . . . . . . . 7-23
4-1
4-1
4-2
4-3
4-3
(v)
(vi)
Page
8-1
8.1 General. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.2 Chemical removal . . . . . . . . . . . . . . . . . . . .
8.3 Mechanical removal . . . . . . . . . . . . . . . . . .
8-1
8-1
8-2
9-1
9.1 General. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9-1
Appendix 8.
Chapter 1
General
problem of taking off from slush- or water-covered runways is contained in the Airworthiness Technical Manual
(Doc 9051).
1.1
1.1.3 Further, it is essential that adequate information on the runway surface friction characteristics/aeroplane braking performance be available to the pilot and
operations personnel in order to allow them to adjust
operating technique and apply performance corrections. If
the runway is contaminated with snow or ice, the condition
of the runway should be assessed, the friction coefficient
measured and the results provided to the pilot. If the
runway is contaminated with water and the runway
becomes slippery when wet, the pilot should be made
aware of the potentially hazardous conditions.
INTRODUCTION
1.1.4 Before giving detailed consideration to the need
for, and methods of, assessing runway surface friction, or to
the drag effect due to the presence of meteorological contaminants such as snow, slush, ice or water, it cannot be
overemphasized that the goal of the airport authority should
be the removal of all contaminants as rapidly and completely as possible and elimination of any other conditions
on the runway surface that would adversely affect aeroplane performance.
1-2
surface be not less than 1.0 mm. This normally requires
some form of special surface treatment.
1.2.2 Adequate runway friction characteristics are
needed for three distinct purposes:
a) deceleration of the aeroplane after landing or a rejected
take-off;
b) maintaining directional control during the ground roll
on take-off or landing, in particular in the presence of
cross-wind, asymmetric engine power or technical
malfunctions; and
c) wheel spin-up at touchdown.
1.2.3 With respect to either aeroplane braking or
directional control capability, it is to be noted that an aeroplane, even though operating on the ground, is still subject
to considerable aerodynamic or other forces which can
affect aeroplane braking performance or create moments
about the yaw axis. Such moments can also be induced by
asymmetric engine power (e.g. engine failure on take-off),
asymmetric wheel brake application or by cross-wind. The
result may critically affect directional stability. In each
case, runway surface friction plays a vital role in counteracting these forces or moments. In the case of directional
control, all aeroplanes are subject to specific limits
regarding acceptable cross-wind components. These limits
decrease as the runway surface friction decreases.
1.2.4 Reduced runway surface friction has a different
significance for the landing case compared with the
rejected take-off case because of different operating
criteria.
1.2.5 On landing, runway surface friction is particularly significant at touchdown for the spin-up of the wheels
to full rotational speed. This is a most important provision
for optimum operation of the electronically and mechanically controlled anti-skid braking systems (installed in
most current aeroplanes) and for obtaining the best possible
steering capability. Moreover, the armed autospoilers
which destroy residual lift and increase aerodynamic drag,
as well as the armed autobrake systems, are only triggered
when proper wheel spin-up has been obtained. It is not
unusual in actual operations for spin-up to be delayed as a
result of inadequate runway surface friction caused
generally by excessive rubber deposits. In extreme cases,
individual wheels may fail to spin up at all, thereby creating a potentially dangerous situation and possibly leading
to tire failure.
1.2.6 Generally, aeroplane certification performance
and operating requirements are based upon the friction
1-3
1) at a very busy airport or at an airport that frequently
experiences the conditions of impaired friction
adequate runway cleaning equipment and frictionmeasuring devices to check the results;
2) at a fairly busy airport that infrequently experiences
the conditions of impaired friction but where operations must continue despite inadequate runway
cleaning equipment measurement of runway
friction, assessment of slush contaminant drag
potential, and position and height of significant
snowbanks; and
3) at an airport where operations can be suspended
under unfavourable runway conditions but where
a warning of the onset of such conditions is
required measurement of runway friction,
assessment of slush contaminant drag potential, and
position and height of significant snowbanks.
1.4
CONTAMINANT DRAG
1-4
first considering some of the basic phenomena which occur
both under and around a rolling tire. For the sake of simplicity, these can, however, be given in a qualitative
manner.
Percentage slip
1.5.2 Brakes in the older aeroplane models were not
equipped with an anti-skid system; i.e. the harder the pilot
applied the brakes, the more braking torque developed. In
applying the brake pressure, the wheel slowed down and,
provided there was sufficient braking torque, could be
locked. Assuming an aeroplane speed of 185 km/h (100 kt)
and the speed of the tire at its point of contact with the
ground 148 km/h (80 kt), the tire would slip over the
ground at a speed of 37 km/h (20 kt). This is termed 20 per
cent slip. Similarly, at 100 per cent slip, the wheel is
locked. The importance of this term lies in the fact that as
the percentage slip varies, so does the amount of friction
force produced by the wheel, as shown in diagrammatic
form in Figure 1-1 for a wet runway. Therefore the maximum friction force occurs between 10 to 20 per cent slip,
a fact which modern braking systems make use of to
increase braking efficiency. This is achieved by permitting
the wheels to slip within these percentages.
1.5.3 The importance of this curve from the viewpoint of runway friction coefficient measurement is that the
value at the peak of the curve (termed maximum) can,
when plotted against speed, represent a characteristic of the
runway surface, its contamination, or the friction-measuring device carrying out the measurement and is, therefore,
a standard reproducible value. This type of device can thus
be used to measure the runway friction coefficient. On
snow- or ice-covered runways, the measured value can be
given in a meaningful form to a pilot. On wet runways, the
measured value can be used as an assessment of the friction
characteristics of the runway when wet.
Locked wheel
1.5.4 The term locked wheel is exactly as implied
and the friction coefficient skid produced in this
condition is that at 100 per cent slip in Figure 1-1. It will
be noted that this value is less than the max attained at
the optimum slip. Tests have shown that for an aeroplane
tire, skid varies between 40 and 90 per cent of max,
subject to runway conditions. Even so, vehicles using a
locked wheel mode have also been used to measure the
runway friction coefficient. In this case, the measured value
would be indicative for the wheel spin-up potential at
touchdown.
1-5
0.4
max
skid
0.2
Tire pressure: 13.5 kg/cm2
Speed: 75 kt
20
40
80
60
100
Locked wheel
Free rotation
Slip ratio (percentage)
Figure 1-1.
0.6
Dry concrete surface
Friction coefficient ()
0.6
0.4
0.2
Ice
10
20
30
40
50
Figure 1-2.
60
1-6
increases are explained by the combined effect of
viscous/dynamic water pressures to which the tire/surface
is subjected. This pressure causes partial loss of dry
contact, the extent of which tends to increase with speed.
There are conditions where the loss is practically total and
the friction drops to negligible values. This is identified as
either viscous, dynamic or reverted rubber aquaplaning.
The manner in which these phenomena affect different
areas of the tire/surface interface and how they change in
size with speed is illustrated in Figure 1-3, which is based
on the three zone concept suggested by Gough. In Zone 1
where there is dynamic pressure and in Zone 2 where there
is viscous pressure, friction is virtually zero, whereas one
can assume dry friction in Zone 3. Zone 3 will gradually
decrease in size as speed increases and the friction
coefficient will be reduced in proportion to the reduction
in the size of Zone 3. It can be assumed that the proportion
between the zones will be the same if two wheels are
running at the same fraction of their aquaplaning speed.
1.5.9 In the case of viscous aquaplaning, loss of
traction can occur at relatively low speeds due to the effect
of viscosity in preventing water from escaping from under
the tire footprint. However, a very smooth runway surface
is required; such a surface can be encountered in areas that
have become heavily coated with rubber deposited by tires
during wheel spin-up at touchdown or that have been
subjected to polishing by traffic. Viscous aquaplaning is
associated with damp/wet runways or on wet ice-covered
runways and, once begun, can persist down to very low
speeds. Viscous aquaplaning can occur during the braking
portion of either a rejected take-off or a landing ground roll.
1.5.10 Dynamic aquaplaning will occur beyond a
critical speed which is a function of tire pressure. The
condition is a result of an inertial effect of the water in
which the downward pressure (inflation pressure) of the tire
is insufficient to displace the water away from the footprint
in the short time of contact. Dynamic aquaplaning can
occur on a runway with inadequate macrotexture at speeds
beyond the critical aquaplaning speed provided the fluid is
deep enough. It is associated with a coverage of fluid of
measurable depth on the runway and occurs at a critical
velocity which is a direct function of the tire pressure. The
higher the tire pressure, the higher the velocity at which
(dynamic) aquaplaning will occur. However, the trade-off
will be that with increasing tire pressure, the achievable wet
friction will generally decrease in the speed range up to
aquaplaning. Dynamic aquaplaning is experienced during
the higher speeds of landing and take-off ground roll. As
little as 0.5 mm of standing water has been found to be
sufficient to support dynamic aquaplaning. This relatively
small depth can occur in heavy rain showers or can result
from water pools due to surface irregularities.
1-7
Direction of motion
Zone 2
Low speed
Zone 3
Boundary of static
tire-ground contact area
Zone 2
High speed
Zone 1
Figure 1-3.
Zone 3
Friction/speed curves
1.5.15 Water is one of the best lubricants for rubber,
and displacement of water and penetration of thin water
films in the tire contact area take time. There are a number
of runway surface parameters that affect the drainage
capability in the tire contact area. If a runway has a good
macrotexture allowing the water to escape beneath the tire,
then the friction value will be less affected by speed.
Conversely, a low macrotexture surface will produce a
larger drop in friction with increase in speed. Another
parameter is the sharpness of the texture (microtexture),
which determines basically the friction level of a surface, as
illustrated in Figure 1-4.
1.5.16 As speed increases, the friction coefficients
of the two open-textured surfaces A and D drop slightly,
whereas the friction coefficients for surfaces B and C drop
more appreciably. This suggests that the slope of the friction/speed curve is primarily affected by the macrotexture
provided. The magnitude of the friction coefficient is predominantly affected by the roughness of the asperities, A
and B having a sharp microtexture, C and D being smooth.
From the friction point of view, therefore, runway surfaces
Surface texture
1.5.17 The surface texture between the tire and the
runway depends on a number of factors, such as speed,
surface texture, type of runway contamination, depth of
contamination, tire rubber compound, tire structure, tire
tread pattern, tread surface temperature, tire wear, tire
pressure, braking system efficiency, brake torque, wheel
slip ratio and season of the year. Some of these factors have
effects on each other, and their individual effect on the
magnitude of the friction coefficient varies in significance.
The parameter, however, that determines most significantly the magnitude of achievable wet friction and the
friction/speed relationship is runway surface micro/macrotexture. Additional information on the influence of surface
micro/macrotexture characteristics on tire friction performance is given in Appendix 2.
1-8
Friction coefficient ()
0.8
A
B
0.6
C
D
0.4
Poli
Fine text ur
ed
s h ed
concr
et
3/8 po
li
asphalt
shed gra
vel
0.2
10
20
30
40
50
60
70
80
90
Velocity (km/h)
Chapter 2
Assessment of Basic Factors Affecting Friction
2.1
2-2
10
15
10
10
30
20
Velocity (m/s)
Figure 2-1.
Variation of total drag of a small tire with wheel RPM and speed
30
20
90 kg
73 kg
45 kg
23 kg
10
10
20
30
Figure 2-2.
2-3
2.5
a
2.0
0.5
0
Pa
7k
kP
27
ret
dc
o nc
s he
1.0
e8
1.5
B ru
2.5
3
te 1
79
kP a
82
cr e
co n
et e
r
d
c
e
Pa
con B r u sh
79 k
r ed
3
o
1
Sc
rete
onc
c
d
re
Sco
7.5
10
12.5
15
2.2
SURFACE CONTAMINANTS
2-4
2.2.2 During operation on runways with measurable
depths of fluids, in addition to the presence of critically low
levels of friction and the adverse effects of aquaplaning,
there exists the retardation effect referred to as precipitant
drag. More specifically, precipitant drag can be broken
down to include:
a) fluid displacement drag;
b) wheel spin-down characteristics; and
c) wheel spray patterns and fluid spray (impingement)
drag. Based on actual aeroplane testing and ground-run
tests, the levels of precipitant drag attained are a direct
function of the following variables and their applied
combination, namely, square of ground speed, vertical
load, tire pressure, fluid density, fluid depth and wheel
location.
2.2.3 When an unbraked tire rolls on a fluid-covered
runway, the moving tire contacts and displaces the stationary runway fluid. The resulting change in momen-tum of
the fluid creates hydrodynamic pressures that react on the
tire and the runway surfaces. The horizontal component of
the resulting hydrodynamic pressure force is termed fluid
displacement drag or a retarding force to forward movement. The vertical component of this reaction is termed
fluid displacement lift or the reacting force introducing
potential dynamic aquaplaning and wheel spin-down
tendencies. Additional fluid forces reacting to forward
movements are fluid spray drag and fluid spray lift
created on the aeroplane when some of the displaced runway fluid in the form of spray subsequently impinges on
other parts of the aeroplane, such as the tires, landing gear,
high lift/drag devices and rear-mounted engines.
2.2.4 Fluid displacement drag is primarily critical for
the acceleration characteristics of the aeroplane on take-off.
The effects of fluid displacement drag are also experienced
during deceleration; however, the advantages of the retardation during deceleration are largely offset by the general
reduction of the friction coefficient and the possible
occurrence of aquaplaning.
2.2.5 The problem of precipitant drag due to surface
contaminants is related to take-off. Bearing in mind that
precipitant drag increases with the square of speed, a
critical speed can be reached at which the precipitant drag
is equal to the thrust. If the aeroplane is then below lift-off
velocity, it will never leave the ground. In addition to
speed, the precipitant drag will vary with the depth of the
contamination and with its density. Since both, particularly
the former, can vary throughout the runway length, the
complexity of the problem can well be appreciated. Furthermore, the fact that precipitant drag on an aeroplane
2.3
SURFACE TEXTURE
2-5
4. A rubber-faced aluminium or wooden squeegee, some
30-40 mm in width.
5. Masking tape.
B.
Test procedure
Apparatus required
Apparatus required
2. Putty knife.
B.
Test procedure
2-6
2.4 UNEVENNESS
e) the carbon print. By means of carbon paper, a copy of
the surface of a piece of the pavement is printed on
scribbling paper. The length of a profile constructed
therefrom is measured;
f) the water-flow measurement. Determination is made of
a quantity of water flowing during a certain time from
the bottom of a flat cylinder placed on the pavement
(loss of height).
2.3.8 By means of such measurements, an approximate indication of the surface roughness may be obtained.
From volume measurement, the area of the smoothed sand
or grease gives such an indication. The quotient of the
volume of the smoothed material and its area is called the
mean depth of the texture. The quotient of the length of a
line measured along the profile of a diagonal section
through the pavement and the length of a basis line is called
Chapter 3
Determining and Expressing Friction Characteristics
of Wet Paved Surfaces
3.1
GENERAL
3-2
3.2
MEASUREMENT
3-3
3.2.14 To minimize variations in the friction measurements caused by the techniques used in applying a textural
finish to the surface, runs should be made in both directions
and a mean value taken. Significant variations between the
readings obtained in both directions should be investigated.
Additionally, if measurement of the friction is made along
a track 5 m from the runway edge, it will provide a datum
of the unworn and uncontaminated surface for comparison
with the centre track(s) subjected to traffic.
3.2.11
follows:
3-4
Test tire
Test equipment
Type
(1)
Pressure
(kPa)
Test speed
(km/h)
Test water
depth
(mm)
Design
objective
for new
surface
Maintenance
planning
level
Minimum
friction
level
(3)
(4)
(5)
(6)
(7)
(2)
Mu-meter Trailer
A
A
70
70
65
95
1.0
1.0
0.72
0.66
0.52
0.38
0.42
0.26
Skiddometer Trailer
B
B
210
210
65
95
1.0
1.0
0.82
0.74
0.60
0.47
0.50
0.34
Surface Friction
Tester Vehicle
B
B
210
210
65
95
1.0
1.0
0.82
0.74
0.60
0.47
0.50
0.34
Runway Friction
Tester Vehicle
B
B
210
210
65
95
1.0
1.0
0.82
0.74
0.60
0.54
0.50
0.41
TATRA Friction
Tester Vehicle
B
B
210
210
65
95
1.0
1.0
0.76
0.67
0.57
0.52
0.48
0.42
RUNAR
Trailer
B
B
210
210
65
95
1.0
1.0
0.69
0.63
0.52
0.42
0.45
0.32
GRIPTESTER
Trailer
C
C
140
140
65
95
1.0
1.0
0.74
0.64
0.53
0.36
0.43
0.24
and have been correlated with at least one of the types mentioned in Chapter 5. A method of estimating the friction
value when no friction-measuring devices are available at
the airport is described in Appendix 6.
3.3
REPORTING
3.4 INTERPRETATION OF
LOW FRICTION CHARACTERISTICS
3.4.1 The information that, due to poor friction
characteristics, a runway or portion thereof may be slippery
when wet must be made available since there may be a
significant deterioration both in aeroplane braking performance and in directional control.
3.4.2 It is advisable to ensure that the landing
distance required for slippery runway pavement conditions,
as specified in the Aeroplane Flight Manual, does not
exceed the landing distance available. When the possibility
of a rejected take-off is being considered, periodic investigations should be undertaken to ensure that the surface
friction characteristics are adequate for braking on that
portion of the runway which would be used for an emergency stop. A safe stop from V1 (decision speed) may not be
possible, and depending on the distance available and other
limiting conditions, the aeroplane take-off mass may have
to be reduced or take-off may need to be delayed awaiting
improved conditions.
Chapter 4
Measurement of Compacted Snow- or Ice-Covered
Paved Surface Friction Characteristics
4.1
GENERAL
4.1.2 The measurement of the surface friction coefficient provides the best basis for determining surface
friction conditions. The value of surface friction should be
the maximum value that occurs when a wheel is slipping
but still rolling. Various friction-measuring devices may be
used. As there is an operational need for uniformity in the
method of assessing and reporting runway friction, the
measurement should preferably be made with devices that
provide continuous measuring of the maximum friction
along the entire runway. Chapter 5 provides a description
of several different ground friction-measuring devices that
meet these requirements. The possibility of standardization
is discussed, together with correlation between ground
vehicles and between ground vehicles and aeroplane tire
braking performance.
4.2
4.2.3 The reliability of conducting tests using frictionmeasuring devices in conditions other than compacted snow
and/or ice may be compromised due to non-uniform
conditions. This will apply in particular when there is a thin
layer of slush, water film over ice, or uncompacted dry or
wet snow on a runway. In such cases, the wheels of the
friction-measuring device or of an aeroplane may penetrate
the runway contaminant layer differently which would result
in a significant difference in the friction performance
indication. The results of friction tests obtained with
different friction-measuring devices in such cases may be at
great variance because of differences in test methods and,
for a particular method, because of different characteristics
of the vehicle and different individual techniques in
performing the test. Care is also essential in providing
runway friction information to pilots under conditions when
a water film is observed on top of ice.
4-2
can be achieved with the actual stopping performance of
the aeroplane. This information is undoubtedly required to
assist the airport authority in making operational judgements, but in the case of ice-covered runways, the
measuring and reporting of friction coefficients should only
be regarded as an interim procedure while clearing and
other remedial measures to restore the runway to full
serviceability are being completed. Although the coefficient of friction for a wet surface decreases with an
increase in speed, tests on ice or compacted snow do not
indicate an appreciable difference in friction coefficient
values between the comparatively low friction-measuring
device speeds and aeroplane speeds. However, the
measured friction coefficient value on a runway covered
with ice patches at regular, short intervals may differ from
that experienced by the pilot due to the reaction time of the
aeroplane antiskid system.
4.2.5 In considering the relative merits of measuring
the friction coefficient on a compacted snow- and/or icecovered runway, compared with effective measures to maintain a surface free of any contaminants at all times, it should
be noted that immediate removal of snow and ice should
receive the highest priority. Nevertheless, there are circumstances that justify a requirement for friction measurement
and, therefore, the development of acceptable methods. For
example, incidents have occurred involving loss of braking
action or of directional control on runways that were
apparently clean and dry. Such deterioration in the friction
coefficient, while not visually apparent, could have been
revealed by measurement. Incidents of this kind can occur at
an airport having few or no traffic movements at night, when
flight operations are resumed in the early morning and frost
is observed, or when, under freezing conditions, the runway
surface temperature falls below the dew point (e.g. through
radiation). It should be noted that while the airport temperature reported may still be above the freezing point, the
runway surface temperature may fall below the freezing
point and the surface can have extremely low friction within
a very short time due to sudden ice formation.
4.2.6 When a runway is icy, the friction value is liable
to change. Under these circumstances, frequent measurements of runway friction coefficient are essential and call
for cooperation and development of suitable procedures
between the appropriate air traffic service units, the airport
authority, and the crew operating the friction-measuring
device.
4.2.7 At an airport that regularly experiences heavy
snowstorms, it is sometimes necessary to discontinue snow
removal operations for a short period in order to permit
flight operations to continue. Under these circumstances, it
is unlikely that the runway will be completely clean, and
4-3
4.4
MEASUREMENT
4.5
REPORTING
4.5.1
There is a requirement to report the presence
of snow, slush or ice on a runway or a taxiway. To be able
to report meteorological contaminants with some degree of
reliability and consistency, a uniform method for describing
them must be established. Therefore, the following
definitions for slush and snow on the ground have been
incorporated in Annex 14, Volume I.
Slush. Water-saturated snow which with a heel-and-toe
slap-down motion against the ground will be displaced with
a splatter; specific gravity: 0.5 up to 0.8.
4-4
0.40 and
0.39 to
0.35 to
0.29 to
0.25 and
Code
Good
Medium to good
Medium
Medium to poor
Poor
5
4
3
2
1
above
0.36
0.30
0.26
below
Chapter 5
Runway Friction-Measuring Devices
2.
3.
The Eighth Air Navigation Conference (1974) recommended that ICAO develop criteria for the basic
technical and operational characteristics of equipment used
to measure runway friction. In response to this recommendation, some relevant criteria were developed and transmitted to States. It was thought that the material would
assist those States which might be planning to develop new
friction-measuring devices. States, however, were informed
of the uncertainty of obtaining, on wet runway surfaces, a
more acceptable correlation between friction-measuring
devices and aeroplane braking performance using any new
measuring equipment developed in accordance with the
proposed criteria. These criteria, which were reviewed and
updated in 1991, are summarized below. The criteria are
5-1
4.
5.
5-2
6.
7.
Presentation of the results of measurements. The equipment should be able to provide a permanent record of
the continuous graphic trace of the friction values for
the runway, as well as allowing the person conducting
the survey to record any observations and the date and
time of the recording (see Figure 5-1).
8.
9.
5-3
Type of equipment
Time
Location
Date of test
Wind
Direction
Weather
Programme No.
Runway
Surface description
Surface texture tests
Grease (mm)
Water (seconds)
Position 1
Position 2
Position 3
Tire wear test
Left
Right
Total
Tests conducted by
Towing vehicle
(if applicable)
Method of wetting
Depth of water
(mm)
Test speeds
Starting at
Ending at
32
65
95
130
145
160
145
160
1st third
Middle third
3rd third
Recorder chart reference number and means of identification of individual run and speed:
Speed km/h
32
65
95
Section of runway
45 m from centre
line giving lowest
coefficient of
friction (excluding
paint markings)
Note. The original recorder chart or a print of it must be attached to this form.
Figure 5-1.
130
5-4
0.62
0.60
Friction values
0.60
0.56
0.50
0.50
0.48
0.40
SKD
SFT
RFT
Notes:
1. Test speed 65 km/h; water depth 1 mm.
2. Mu-meter value of 0.50 used as base in the correlation. The range quoted is two standard deviations.
5-5
attributed to differential changes in water depths caused by
variations in the pavement surface. For this reason, it is
very important to control water depth when classifying
pavements for maintenance purposes. For compacted snowand/or ice-covered surfaces, fewer interacting variables
affect the friction values because the braking action on
these surfaces is not speed-dependent.
5.3.6 The correlation between the various frictionmeasuring devices when pavement surfaces are covered
with compacted snow and/or ice is presented in Figure 5-3.
The following practices for tests should be employed:
A. Continuous friction-measuring devices (e.g. Mu-meter,
Grip Tester, Surface Friction Tester, Runway Friction
Tester or Skiddometer)
Test speeds: 65 km/h, except under icy conditions when
a lower speed may be used.
0.5
Friction values
B
0.4
D
E
0.3
Skiddometer
(SKD)
Surface Friction
Tester (SFT)
Mu-meter
Runway Friction
Tester (RFT)
Tapley Meter
BrakemeterDynometer
5-6
B. Decelerometer
Dynometer)
(e.g.
Tapley
Meter,
Brakemeter-
1. Vehicle specifications
a) The vehicle should have a mass in the order of 1 to
2 tonnes.
b) It should be equipped with winter tires without
studs, with the tire pressure set at manufacturers
recommendation. Tire wear should not exceed
75 per cent.
c) It must have 4 brakes properly adjusted to ensure a
balanced action.
d) The vehicle should have minimum pitching tendency and maintain satisfactory directional stability
under braking.
2. The decelerometer should be installed in the vehicle
according to the manufacturers instructions. It should
also be located and placed in the vehicle so it cannot be
disturbed or displaced by either airport personnel or
vehicle movement. The decelerometer should be maintained and calibrated according to the manufacturers
recommendations.
3. Speed at brake application should be approximately
40 km/h.
4. Friction survey techniques
a) Brakes should be applied sufficiently hard to lock
all four wheels of the vehicle and then should be
released immediately. The time during which the
wheels are locked should not exceed one second.
b) The decelerometer used should record or retain the
maximum retardation braking force occurring
during the test.
c) Random very high or very low readings may be
ignored when calculating the average values.
5.3.7 Since decelerometers require the test vehicle to
be accelerated to given test speeds, which takes a finite
distance, the intervals at which the test readings can be
taken are necessarily greater than those taken by the continuous friction-measuring devices. These devices, therefore, can be considered only as spot reading frictionmeasuring devices.
5.4
5.4.1
In order to be operationally meaningful, it is
necessary to first determine the correlation between the
friction data produced by the friction-measuring devices
and the effective braking friction performance of different
aeroplane types. Once this relationship is defined for the
ground operational speed range of a given aeroplane, the
aeroplane flight crew should be able to determine aeroplane
stopping performance for a particular runway landing
operation by considering the other factors including
touchdown speed, wind, pressure/altitude and aeroplane
mass, all of which significantly influence the stopping
performance. At present, there is general agreement that
success in this respect is greater for the compacted snowand/or ice-covered surface conditions since fewer
parameters affecting tire frictional behaviour are involved
compared to the more complex and variable wet runway
case.
5.4.2 In 1984, the United States undertook a fiveyear programme to study the relationship between aeroplane tire braking performance and ground vehicle friction
measurements. Several types of surface conditions were
evaluated: dry, truck-wet, rain-wet and snow-, slush- and
ice-covered. The ground friction-measuring devices used in
this study were the diagonal-braked vehicle, Runway
Friction Tester, Mu-meter, BV-11 Skiddometer, Surface
Friction Tester and two decelerometers (Tapley and
Brakemeter-Dynometer). The results of this investigation
showed that the ground vehicle friction measurements did
not directly correlate with the aeroplane tire effective
braking friction on wet surfaces. However, agreement was
achieved using the combined viscous/dynamic aquaplaning
theory (see Appendix 1).
5-7
update and certify that the operator maintains a high
proficiency level. If this is not done, then personnel fail to
maintain their experience level over time and lose touch
with the new developments in calibration, maintenance and
operating techniques. All friction-measuring devices should
periodically have their calibration checked to ensure that it
is maintained within the tolerances given by the manufacturer. Friction-measuring devices furnished with selfwatering systems should be calibrated periodically to
ensure that the water flow rate is maintained within the
manufacturers tolerances, and that the amount of water
produced for the required water depth is always consistent
and applied evenly in front of the friction-measuring tire(s)
throughout the speed range of the vehicle.
5.6 MU-METER
5.6.1 The Mu-meter is a 245 kg trailer designed to
measure side force friction generated between the frictionmeasuring tires passing over the runway pavement surface
at an included angle of 15 degrees. The friction-measuring
tires on the Mu-meter are made to ASTM E670, Annex A2,
specification. The trailer is constructed with a triangular
frame on which are mounted two friction-measuring wheels
and a rear wheel. The rear wheel provides stability to the
trailer during its operation. Figure 5-4 shows the over-all
configuration of the trailer. A vertical load of 78 kg is
generated by ballast via a shock absorber on each of the
friction-measuring wheels. The friction-measuring wheels
operate at an apparent slip ratio of 13.5 per cent. The
Mu-meter also has a rear wheel which has a patterned tread
tire, size 4.00 - 8 (16 4.0, 6 ply, RL2). The tire operates
with an inflation pressure of 70 kPa. The Mu-meter, being
a trailer device, requires a tow vehicle; if the self-water
system is required, a water tank must be mounted on the
tow vehicle to supply water to the nozzles.
5.6.2 The distance sensor is a sealed photo-electric
shaft encoder mounted on the rear wheel of the trailer. The
distance sensor reads digital pulses in increments of a
thousand-per-wheel revolution, transmitting them to the
signal conditioner for calculation each time the trailer
travels one metre. The load cell is an electronic transducer
mounted between the fixed and movable members of the
triangular frame. The load cell reads minute tension
changes from the friction-measuring wheels. The signal
conditioner is mounted on the frame and amplifies analog
data received from the load cell and digital data from the
distance sensor. The signals from the rear wheel distance
sensor provide both distance measurement and, combined
with increments of real time, speed measurement. The
computer located in the tow vehicle is called a processor
5-8
5.7
5.8
SKIDDOMETER
5.9
5-10
5-12
5.10
GRIP TESTER
5-14
5-15
the constant slip ratio of the measuring wheel may be set to
any percentage between 5% and 100%. In the variable slipmeasuring mode, the test is conducted by applying wheel
braking from free rolling to fully locked on the runway
surface and measuring the braking friction force which the
runway surface exerts against the braking wheel.
5-16
DECELEROMETERS
General
5.13.1 Decelerometers provide the most reliable
information when pavement surfaces are covered with
compacted snow and/or ice. Decelerometers should not be
used on wet pavement surfaces, and tests should not be
conducted when pavement surfaces are covered with loose
or dry snow exceeding 51 mm depth or with slush
exceeding 13 mm depth.
5.13.2 Since decelerometers have to be mounted
inside a vehicle, certain requirements for the vehicle have
to be met to ensure that reliable and consistent measurements are obtained. Acceptable vehicles are large sedans,
station wagons, intermediate or full-size automobiles,
utility and passenger-cargo trucks, vehicles that have frontwheel or four-wheel drive, and vehicles that have an antilocking braking system (ABS) on the rear axle.
5.13.3 Tires on the vehicle can significantly influence friction measurements. Therefore, they should all
have tread patterns that do not exceed 50 per cent wear, and
tire pressure should always be maintained at all times
according to the manufacturers specifications.
5.13.4 The vehicle brakes should always be properly
adjusted to ensure a balanced action. The vehicle should
have minimum pitching tendency and satisfactory directional stability when the brakes are applied.
5.13.5 The decelerometer should be installed in the
vehicle according to the manufacturers instructions. It
should be placed in the vehicle so that it is not displaced by
any vehicle movement. The decelerometer should be maintained and calibrated according to the manufacturers
recommendations.
5.13.6 It is necessary to take a certain number of
readings to obtain a reasonable appraisal of the runway
surface condition. The total runway length is divided into
three equal portions the touchdown, mid-point and rollout zones. A minimum of three tests at the speed of
35 km/h should be conducted in each zone. An averaged
number should be determined for each zone. The averaged
numbers are always recorded in the same direction the
aeroplane lands.
5.13.7 The following procedures should be used in
conducting friction surveys.
Brakemeter-Dynometer
5.13.9 The Brakemeter-Dynometer consists of a
finely balanced pendulum free to respond to any changes in
speed and angle, working through a quadrant gear train to
rotate a needle around a dial (see Figure 5-14). The dial is
calibrated in percentage of g, the accepted standard for
measuring acceleration and deceleration. To stop all
vibration, the instrument is filled with a fluid not sensitive
to changes in temperature. The meter, which requires a
vehicle for transport, should always be used with a floormounting stand. This device should only be used on
runway surfaces covered with ice and/or compacted snow.
It is not recommended for operation on wet runway pavement surfaces. The procedures for conducting friction tests
are given in 5.13.7.
Tapley Meter
5.13.10 Two versions of the Tapley Meter are available
on the market: the original Tapley (a standard mechanical
decelerometer) and the Tapley Electronic Airfield Friction
Meter. Both require a vehicle for transport and are
recommended for use only on compacted snow and/or icecovered runway surfaces. They are not recommended for
operation on wet runway pavement surfaces.
5.13.11 Mechanical decelerometer. The mechanical
version is a small pendulum-based decelerometer, consisting
of a dynamically calibrated, oil-damped pendulum in a
sealed housing (see Figure 5-15). The pendulum is
magnetically linked to a lightweight gear mechanism to
Chapter 6
Collection and Dissemination of
Pavement Surface State Information
6.1
GENERAL
6.1.3
Before take-off or landing, the pilot needs
information on all aspects of an airport, its aids and operational facilities. In many cases, an adverse combination of
available take-off or landing distance, tail or cross-wind
components, visibility and poor friction characteristics will
make a take-off or landing impossible.
6.1.4 In order to enable aeroplane operators and pilots
to readily appraise and use the information received, it is
necessary to have the information and its presentation
standardized. Reports must be in the form of a positive
statement and must be as complete as possible. This, in
turn, generates a great deal of information. A standardized
code is, therefore, necessary in order to streamline the communications processes, particularly when severe meteorological conditions prevail over a large area, and to allow
rapid updating.
6.2
6-2
(COM
heading)
(ADDRESSES)
(Abbreviated
heading)
(ORIGINATORS
( INDICATOR)
SNOWTAM
(LOCATION INDICATOR)
DATE/TIME OF OBSERVATION
(OPTIONAL GROUP)
(Serial number)
A)
B)
(RUNWAY DESIGNATORS)
C)
D)
(CLEARED RUNWAY WIDTH, IF LESS THAN PUBLISHED WIDTH (m; if offset left or right
of centre line add L or R))
E)
F)
G)
H)
MEASURED OR CALCULATED
COEFFICIENT
or
GOOD
MEDIUM/GOOD
MEDIUM
MEDIUM/POOR
POOR
UNRELIABLE
5
4
3
2
1
9
(When quoting a measured coefficient, use the observed two figures, followed by the abbreviation
of the friction-measuring device used. When quoting an estimate, use single digit))
(CRITICAL SNOWBANKS (If present, insert height (cm)/distance from the edge of runway (m)
followed by L, R or LR if applicable))
J)
K)
L)
M)
N)
(TAXIWAY SNOWBANKS (If more than 60 cm, insert YES followed by distance apart, m))
P)
R)
S)
(PLAIN LANGUAGE REMARKS (Including contaminant coverage and other operationally significant
information, e.g. sanding, de-icing))
T)
NOTES:
6.3
6.3.1 For long- and medium-term planning, aeroplane operators need to be able to assess the degree of
regularity of operations which can be expected at an airport
in winter conditions. Airport authorities also need to define
the relevant parameters for their own purposes. Therefore,
the State and airport authorities must give a clear and
accurate statement of their intentions regarding:
allocation of responsibility;
methods of clearance (including chemicals used, if
any);
equipment to be used;
order of clearance priorities;
methods of measurement;
table of friction coefficients for snow- and ice-covered
surfaces;
methods for improving friction characteristics;
criteria for snowbank reporting;
availability of information and dissemination procedures; and
local deviations from national practice.
6-3
6-4
1. General
a) When reporting on two or three runways, repeat
Items C to P inclusive.
Item G
Mean depth in millimetres deposit for each third of
total runway length, or XX if not measurable or
operationally not significant; the assessment to be
made to an accuracy of 20 mm for dry snow, 10 mm
for wet snow and 3 mm for slush.
9.
Item H
Friction measurements on each third of the runway and
friction-measuring device. Measured or calculated coefficient (two digits) or, if not available, estimated
surface friction (single digit) in the order from the
threshold having the lower runway designation
number. Insert a code 9 when surface conditions or
available friction-measuring device do not permit a
reliable surface friction measurement to be made. Use
the following abbreviations to indicate the type of
friction-measuring device used:
Item A
Aerodrome location indicator (four-letter location
indicator).
3.
Item B
Eight-figure date/time group giving time of
observation as month, day, hour and minute in UTC;
this item must always be completed.
4.
Item C
Lower runway designation number.
5.
Item D
Cleared runway length in metres, if less than published
length (see Item T on reporting on part of runway not
cleared).
6.
7.
Item E
Cleared runway width in metres, if less than published
width; if offset left or right of centre line, add L or
R, as viewed from the threshold having the lower
runway designation number.
Item F
Deposit over total runway length as explained in
SNOWTAM format. Suitable combinations of these
numbers may be used to indicate varying conditions
over runway segments. If more than one deposit is
present on the same portion of the runway, they should
be reported in sequence from the top to the bottom.
Drifts, depths of deposit appreciably greater than the
6-5
BRD
GRT
MUM
RFT
SFH
SFL
SKH
SKL
TAP
Brakemeter-Dynometer
Grip tester
Mu-meter
Runway friction tester
Surface friction tester (high-pressure tire)
Surface friction tester (low-pressure tire)
Skiddometer (high-pressure tire)
Skiddometer (low-pressure tire)
Tapley meter
6-6
13. Item M
Enter the anticipated time of completion in UTC.
14. Item N
The code for Item F may be used to describe taxiway
conditions; enter NO if no taxiways serving the
associated runway are available.
15. Item P
If applicable, enter YES followed by the lateral
distance in metres.
16. Item R
The code for Item F may be used to describe apron
conditions; enter NO if apron unusable.
17. Item S
Enter the anticipated time of next observation/measurement in UTC.
18. Item T
Describe in plain language any operationally
significant information but always report on length of
uncleared runway (Item D) and extent of runway
contamination (Item F) for each third of the runway (if
appropriate) in accordance with the following scale:
runway contamination:
10% if less than 10% of runway contaminated
25% if 11-25% of runway contaminated
50% if 26-50% of runway contaminated
100% if 51-100% of runway contaminated.
6.4.4 The following material provides further
guidance for the completion of the SNOWTAM format.
General comments
1. The codes for Item F may be used for describing
conditions on taxiways and aprons.
2. Metric units must be used and the unit of measurement not reported. Include unit of measurement in
Item T, if needed for clarification.
Specific comments for each item
Item A Enter the four-letter location indicator for the
aerodrome.
Item B Enter the date the assessment was made by
giving an eight-digit date/time group indicating the month,
day, hour and minute of the observation in UTC (e.g.
02010850, meaning 1 February at 0850 UTC). This time
Brakemeter-Dynometer
Grip tester
Mu-meter
Runway friction tester
Surface friction tester (high-pressure tire)
Surface friction tester (low-pressure tire)
Skiddometer (high-pressure tire)
Skiddometer (low-pressure tire)
Tapley meter
6-7
6-8
(COM
heading)
(Abbreviated
heading)
(ADDRESSES)
GG
070645
(Serial number)
LSZHYNYX
(LOCATION INDICATOR)
L S 0 1 4 9 L
SNOWTAM
(ORIGINATORS
( INDICATOR)
DATE/TIME OF OBSERVATION
(OPTIONAL GROUP)
1 1 0 7 0 6 2 0
149
(RUNWAY DESIGNATORS)
C)
D)
LSZH
11070620
10
2 200
(CLEARED RUNWAY WIDTH, IF LESS THAN PUBLISHED WIDTH (m; if offset left or right
of centre line add L or R))
E)
40 L
F)
4/5/4
G)
20/10/20
H)
30/35/30
MUM
(CRITICAL SNOWBANKS (If present, insert height (cm)/distance from the edge of runway (m)
followed by L, R or LR if applicable))
J)
30/5 L
K)
YES L
L)
TOTAL
M)
N)
(TAXIWAY SNOWBANKS (If more than 60 cm, insert YES followed by distance apart, m))
P)
R)
S)
0900
---YES 12
---11070920
(PLAIN LANGUAGE REMARKS (Including contaminant coverage and other operationally significant
information, e.g. sanding, de-icing))
T)
A)
B)
MEASURED OR CALCULATED
COEFFICIENT
or
5
4
3
2
1
9
(When quoting a measured coefficient, use the observed two figures, followed by the abbreviation
of the friction-measuring device used. When quoting an estimate, use single digit))
NOTES:
Figure 6-2.
Chapter 7
Snow Removal and Ice Control
7.1
GENERAL
7.1.5
Clearance of snow, slush, ice and standing
water from the movement area should be based on flight
safety and schedule considerations. In most circumstances,
the priority will be:
a) runway(s) in use;
7.1.6
It is recognized that airport operating
authorities throughout the world have developed their own
equipment and techniques to effect the clearance and
removal of contaminants. Although equipment combinations and techniques of application vary, the objective to
speedily provide clean and dry airport pavements is
constant.
7.1.7
There are many factors to be considered when
determining the equipment necessary for the removal of
surface contaminants encountered on airport pavements.
Topography, climate, airport location, type of aeroplane,
density of movements, characteristics of operating surfaces
and navigational facilities are but a few of the considerations.
7.1.8
Airports located in tropical or sub-tropical
zones may be concerned with problems associated with
heavy and frequent rain squalls leading to standing water
7.1.4
Whatever technique may be employed for the
removal of snow, slush, ice and standing water, the aim is
7-1
7-2
7.2
7.3.2
All mechanical equipment should be functioning and be backed up with a good system for
replacements. Work shifts, including mechanical repair
staff, should be posted and call out procedures clearly
detailed. Many airports prominently display a map of the
site in the maintenance crew room detailing the priority
areas for each storm as it occurs, to avoid any confusion
about the designated work areas.
7.3.3
The availability of the latest weather reports
and the advance warning of impending storms are essential
to an efficient organization; this facet of the operations
should be arranged with the meteorological staff in advance
of the season.
7.3.4
ATS unit staff and the Snow Committee
influence what equipment is used at the airport. To ensure
a minimum of lost time from active areas due to
manoeuvring aeroplanes, a good working relationship must
be established between field supervisors and the ATS unit
staff. It is essential that the installation of runway markers,
snow fencing and obstruction marking take place before the
first snowfall. These installations may also be marked on
the site map for ready reference. Finally, any operator
training necessary should have been accomplished long
before the first operation of the season is required. These
are the more fundamental arrangements that should be
implemented prior to the commencement of each snow
removal season.
SNOW COMMITTEE
7.3
7.3.1
There are several procedures essential to
efficient snow removal from airport pavements. All
7-3
Edge lights
3 m (10 ft)
0.3 m (1 ft)
1.5 m (5 ft)
1 m (3 ft)
Runway
15 m (50 ft)
5 m (16 ft)
5 m (16 ft)
25 m (83 ft)
A. Runways used by very large aircraft (such as B-747, DC-10, L-1011) (see 7.3.5)
Edge lights
3 m (10 ft)
0.3 m (1 ft)
Runway
0.6 m (2 ft)
5 m (16 ft)
5 m (16 ft)
15 m (50 ft)
1 m (3 ft)
5 m (16 ft)
1.5 m (5 ft)
5 m (16 ft)
5 m (16 ft)
7-4
7.4
MECHANICAL METHODS
7-5
mean annual snowfall and serving piston-engine
aeroplanes only or serving scheduled air services with
two flights or less per day may find that the most
economical solution is to contract their snow removal
to off-airport contractors or earth-moving contractors,
on a priority basis, during periods of snowfall.
General considerations
7.5.1 Timely and complete snow/ice control is
equipment-oriented. The selection of an optimum equipment inventory is discussed below. In a typical process for
selection of airport snow removal and ice control equipment (SRICE), the airport authority is faced with many
considerations. The more critical are:
a) economics obtaining the financial resources;
b) facility size area to be maintained and number of
operations;
c) spare part and repair facilities maintenance/service
arrangements and availability of service; and
d) weather snowfall, temperature and ice formation.
Weather
7.5.2 Since snow and ice control equipment needs
are closely related to snowfall incidence, the following
factors help to establish a need for snow/ice control
equipment at an airport.
a) The incidence of snow, the average depth of snow per
storm, the density of the snow, the volume and nature
of the air traffic served by the airport, and the pavement
area to be cleared of snow/ice by SRICE are factors to
be considered when purchasing snow removal
equipment.
b) Weather data indicate that communities having a mean
annual snowfall of about 40 cm or less generally
receive deposits of less than 5 cm per storm. Normally,
it would not be economically practical to provide large
amounts of expensive snow removal equipment that
may be needed infrequently or for a very short period
of the year. Airports receiving less than about 40 cm
7-6
Plough
type
Blade
angling
Low-speed
displacement
type
Casting-type
high-speed
Swath
width
Cost
Rubber
edge
Wear
One way
No
Single
direction
Single
direction
Large
Low
Yes
Acceptable
Reversible
Yes
Both
directions
Both
directions
Large
Medium
Yes
Acceptable
Roll-over
Yes
No
Excellent
both
directions
Medium
Medium
No
Minimum
Apron
Yes
Both
directions
No
Large
High
No
Acceptable
Large/folding
wings
Yes
Both
directions
Both
directions
Very
large
Highest
Yes
Acceptable
Articulated
Both
directions
No
Medium
Medium
No
Minimum
Loader
bucket
7.5.7
Plough types. Figure 7-3 illustrates the different plough types.
a) Tapered blade, one way, left or right hand. Designed
for high-volume, high-speed runway snowploughing,
this snowplough is a conventional, one-way type with a
tapered mould-board, operated by hydraulic power with
conventional controls.
b) Power-reversible, with standard or non-metal cutting
edge. This snowplough is intended for high-volume,
high-speed runway snowploughing requiring the ability
to discharge snow to the right or left at a fixed cutting
angle. The unit is not intended for use on areas
equipped with in-pavement lighting.
c) Roll-over, steel edge. This plough is designed for snow
removal operations requiring the ability to discharge
snow to the right or left at a fixed cutting angle. The
unit is not intended for use on areas equipped with inpavement lighting.
d) Levelling wing, left or right hand. This levelling wing
is intended for heavy-duty snow removal operations
and will provide blade operation at varying heights for
wind-row and snowbank levelling and trimming
operations.
7-7
Single stage,
single fan with cutter bar,
single plough wing
Figure 7-2.
Single stage,
dual fan with cutter bars
h) Apron snow blade. This plough is designed for wideswath operations in confined apron areas. This unit is
suitable for pushing snow and slush away from terminal
buildings, aeroplane stands and apron areas and is not
intended for use on areas with in-pavement lighting.
i) Snow buckets (general purpose). Snow buckets are for
use in snow-loading operations and should function
similarly to a standard bucket. The snow bucket is
intended for use on front-end, loader-type vehicles in
lieu of a standard bucket.
7-8
Extension wing
right or left
fixed bla
de
Pow
er r
eve
rs
ible
Roll-over blade
Figure 7-3.
Blade types
One-wa
y
Favourable conditio
ns
Se
Casting-type ploughs
(Limit of use)
ve r
ec
li m
a te
li n
e
Figure 7-4.
7-9
b) friction reduction The friction coefficient of polycarbonate is less than steel and plough/snow skin
friction is decreased, producing less drag; thus, less
ploughing power is required.
c) corrosion-free material The polycarbonate mouldboard will not rust or corrode, and the portion of the
ploughing assembly made of steel is generally protected by the polycarbonate mould-board.
Ploughing costs/distance
Travel distance
Figure 7-5.
Ploughing costs/distance
7-10
Steel hop
per
Electric start
engine
Figure 7-6.
Sander/spreader device
Small swath, light duty 3.6 m swath towed type with integral blower
Large swath, heavy duty over 3.6 m pushed type with integral engine
and rear blower raised cab
Large swath, heavy duty over 3.6 m pushed type with two engines,
front blower conventional cab
7-11
7-12
7-13
h) relative humidity and dew-point temperature; and
i) chemical factor (an indication of the relative concentration of anti-icing chemicals still remaining in
solution on the pavement surface).
7.5.19 The system works automatically 24 hours a
day, permitting the detection of changing conditions before
other methods.
7.5.20 Depending on the number of input heads in
the pavement surface, the system can detect varying and
rapidly changing conditions. Accordingly, rapid formation
of ice will be detected electronically on a wet runway even
if the air temperature remains above freezing. It is to be
noted that airport personnel would not be alerted to the
problem by conventional means.
7.5.21 Maintenance personnel time is better spent in
preventing ice traction problems rather than continuously
measuring them.
7.5.22 A continuous system provides more current
information since the most recent dynamic friction
measurement or pilot report may quickly become invalid
when climatic conditions are rapidly changing. The task of
reporting SNOWTAM data may be less complex and more
rapid during manual data entry on the systems video
display. The previous SNOWTAM data will remain until
changed; only the automatic functions will continuously
update. The display data can show a history, trends,
graphics, or any format programme the user selects, and all
or any portion of it may be sent to any geographic location
over standard telephone lines. The display unit can also
present the current status of other field conditions or
operational safety data entered manually or by radio link.
7.5.23 Experience has shown that the system provides
the following benefits:
a) safety Advance warning of incipient icing conditions allows ice control materials to be applied prior
to the formation of runway ice. Anti-icing opposed to
de-icing provides better runway friction characteristics,
improves runway utilization, and reduces the use of
abrasives;
b) cost Use of chemicals and abrasives only when the
sensors indicate a need and the use of lighter anti-icing
applications when an advance warning is provided will
result in substantial reduction of ice control materials.
7.5.24 Selection of the correct number of sensors in
each runway is dependent on many factors. These factors
are presented in Figure 7-13.
7-14
Figure 7-10.
Front-end loader
Elevation difference
T,, T, = Potential temperature difference
7-16
Figure 7-14.
equipment may be considered the basis of the snowblower/plough team concept (see Figure 7-14).
7-17
from one primary runway, or that runway providing the
maximum wind coverage, one principal taxiway connecting
the runway to the apron, and 20 per cent of the apron.
7.5.32 The recommended minimum snow removal
equipment for general aviation airports served exclusively
by aeroplanes having a gross mass of less than 5 700 kg
should include one or more high-speed snowblowers having
a demonstrated or manufacturers certified capacity sufficient to remove snow which has a density of 400 kg/m3,
with a minimum casting distance of 15 m (measured from
the blower to the point of maximum deposition) from the
areas described in 7.5.31 under the following criteria:
a) 40 000 or more annual operations: 2.5 cm of snow
should be removed within two hours;
b) 6 000 to 40 000 annual operations: 2.5 cm of snow
should be removed within four hours; and
c) 6 000 or less annual operations: 2.5 cm of snow should
be removed within four hours, when practical.
7.5.33 Each high-speed snowblower should be
supported by at least one snowplough having similar
performance characteristics.
7-18
6
5
r e)
mo
s(
or
on
3
nn
0a
50
00
ua
lo
ra t
i
pe
Medium
Small
Intermediate
Large
3
2
1
2
1
0
00
10
o
0t
0
50
to
000
10 0
00
00
20
ra
pe
00 0
ss
or le
t io
ns
ra
ope
t i on
at i on
oper
Snowblower capacities
0.25
0.50
0.75
1.00
1.25
1.50
Figure 7-15.
1.75
2.00
7-19
157 000
Snowblower selection
4 500
2 000
Blast pads (2 at 75 30 m)
Miscellaneous
m2
126 000
17 000
2 000
2 000
4 000
7-20
obtained from Figure 7-15 without calculation, assuming
the essential airport operational area to be cleared is known.
7.5.42 In general, the current team concept of snow
removal indicates the desirability of using the larger snowblowers to meet capacity requirements; i.e. if an airport has
a snow removal capacity requirement of 2 000 t/h, one
large snowblower should be selected instead of three small
snowblowers. This also reduces equipment outlay since
each snowblower is normally supported by two ploughs.
7.5.43 Sweeper selection. Paragraph 7.5.29 indicates
that one high-speed sweeper should be provided for each
70 000 m2 of primary runway. A simple graphic solution is
provided in Figure 7-16 such an airport will require two
sweepers.
7.5.44 Sander selection. Using the graphic solution
(Figure 7-16), two sander/spreader vehicles are selected
(from 7.5.29).
Plough theory/selection
7.5.45 Two snowploughs should accompany each
snowblower, and the total plough displacement should
equal or exceed the snowblower capacity at the normal
plough speed.
7.5.46 When the high-speed team concept of snow
removal using one or more snowploughs is utilized at an
airport, it becomes important to match plough and snowblower capabilities. It is essential that the rate or capacity of
the snowblower be equalled or exceeded by the displacement
capabilities of the accompanying snowplough(s), since rapid
snow removal operations should make the most efficient use
of all equipment, particularly the snowblower.
7.5.47 The plough size classification is not intended
to rigidly establish blade lengths. Instead, the classification
is intended to aid in matching vehicle performance levels,
i.e. large snowblowers should be supported by large
ploughs. Plough size only establishes a range of blade
lengths for each size.
7.5.48 The plough and snowblower matching concept is described in the following paragraphs so as to
ensure that team ploughs do not have a smaller capacity
than the accompanying snowblower.
7.5.49 In the team concept, snowblower capacity is
determined in part by the time required to clear the runway
and by the amount of snow on the runway.
7-21
10
15
20
25
30
35
Figure 7-16.
Spreader/sweeper selector
two snowblowers;
two snow sweepers;
7-22
25
20
15
La
lo
ep
rg
ug
10
In te
ll
Sma
d
rme
p
i a te
10
20
l ou
plou
gh
gh
30
40
1.8 m length
3.0 m length
4.5 m length
50
Thermal melt
7.6.3 Thermal melting has not yet proven to be
competitive when compared to conventional methods of
snow disposal. Both the mobile and static pit hot water bath
installations have encountered frequent mechanical difficulties and the rate of disposal is relatively low. Fuel costs
are high and installation costs cannot be expected to drop
until the system is accepted on a much larger scale with the
consequent drop in production costs. The drainage problem
with snow-melt water is another factor affecting the
acceptance of this system, particularly the mobile units that
discharge into street or field drainage facilities where the
water is liable to refreeze prior to reaching the drains.
7.7
CHEMICAL METHODS
7-23
materials used in the manufacture of aeroplanes. A
thorough analysis of these chemicals must be carried out to
ensure that they will not have a deleterious effect on
aeroplane components. Calcium or sodium chlorides are
not approved for use in the movement area.
7.7.2 Whenever possible, chemicals should be used to
prevent ice from forming rather than to remove it. If,
however, liquid chemicals are used as a de-icing agent (i.e.
applying liquid chemicals on snow- or ice-covered
surfaces), then it should be realized that a viscous substance
on top of ice reduces braking action to a dangerous degree
for up to an hour. Solid chemicals, however, when spread
on an icy surface, will penetrate the ice and, though taking
a much longer time period, will eventually break the
ice/surface bond so that the contaminant can be swept
away. The melting water on top of the ice may also present
viscous aquaplaning conditions. It must be remembered
that water or liquid chemicals on top of ice constitute one
of the most slippery surfaces likely to be encountered at all
speeds including those associated with taxiing.
7.7.3 The use of chemicals, both liquid and solid,
should be very carefully controlled and monitored in order
to ensure that the local environment and hence
environmental groups are affected as little as possible.
They should not be toxic or unacceptable in public drainage
systems, should not constitute a severe fire risk, and should
not in themselves lower the braking action significantly.
7-24
Although urea possesses de-icing qualities, it is considered
to be essentially an anti-icer. It is most effective when the
pavement is wet and a freezing temperature is forecast, or
when rain is forecast and the pavement temperature is
below freezing. The action of urea in lowering the freezing
point of water allows time for the removal of water by
sweeping to prevent the formation of ice on the pavement.
When used as a de-icer, as much snow and surface ice as
possible should first be removed by conventional means.
To facilitate the removal of ice by the use of urea, the
ambient temperature should be higher than 3C. If
extreme low temperature conditions occur after the
application of urea, the surface may become slushy; immediate removal by sweeping is necessary. Because of
appreciable material cost, equipment calibration and
application should be precisely controlled. When used as an
anti-icer, a spreading rate of 20 gr/m2 should be sufficient.
Application should only be made to a 22.5 m central
portion disposed symmetrically about the runway centre
line. This rate equals approximately 135 kg per 300 linear
metres.
7.7.7 To assist in the removal of ice, the temperature
should be higher than 3C; the quantity of urea will vary
depending upon the surface temperature and the thickness
of the ice. The effectiveness of urea is determined by the
amount of dilution. Urea has a residual effect lasting
several days.
7.7.8 Its density, which is 0.72 kg/dm3, is approximately one-half that of sand. Urea can be displaced by
wind; the current practice is to pre-wet the pavement or wet
the urea prill with water or a liquid de-icer (water or spray)
prior to application with a special vehicle (see 7.5.13).
Abrasives
7-25
Sieve opening
(mm)
4.75
2.36
1.18
.30
.18
100
97-100
30-60
0-10
0-2
7-26
gradation requirements in the suggested specifications can
be adjusted somewhat to accommodate local materials that
have proven to be satisfactory based on experience.
7.7.16 The effectiveness of sanding can be increased
and the risk of engine ingestion reduced if the sand is set
(embedded) into the iced surface. Sand can be spread most
effectively when it is warm and dry, since any retained
heat assists in setting the sand in ice. One method of
setting the sand, though difficult to implement, is to apply
heat after the sand has been spread by using weed burners
or other open flame sources. Another method is to apply
liquid anti-icing/de-icing chemicals diluted 1:1 at the rate
of 10 L/900 m2 to soften the surface of the ice prior to
spreading the sand.
7.7.17 Sand is generally applied at about 0.5 kg per
m2. Higher rates may be required, especially when using
equipment that does not provide uniform coverage. Often,
older equipment requires higher average application rates to
ensure that all parts of the distribution pattern are receiving
adequate sand coverage. It is recommended that a test area
be used to determine the optimum rate of sand application
to achieve the desired surface texture.
7.7.18 Small piles of sand that accumulate when the
spreading vehicle stops momentarily are dangerous to aeroplane operations and should be removed before permitting
aeroplanes to use the treated surface. Sand should be
removed as soon as the ice melts and the water evaporates
to minimize engine ingestion and displacement by engine
blast.
7.7.19 Care should be exercised in the storage of
sand or other aggregate since any moisture will freeze the
stock into unmanageable large pieces which can cause
serious damage to engines.
7.9
CLEARANCE OF SLUSH
Chapter 8
Removal of Rubber
8.1
GENERAL
8.1.5 The hot compressed air technique uses hightemperature gases to burn away the rubber deposits left by
aeroplane tires and can be used on both Portland cement
concrete and asphaltic concrete runways. It has been
claimed that as no mechanical action takes place at the
runway surface, there is little danger of the surfacing
material becoming loose and causing foreign object
ingestion. However, caution should be exercised and the
condition of the pavement should be closely monitored
when using this technique on asphaltic concrete runways.
a) chemical solvents;
b) high-pressure water blasting;
c) chemical solvents and high-pressure water blasting; and
d) hot compressed air.
8.1.2 In assessing the effectiveness of any system
for rubber removal, the objective must be clearly understood, i.e. to restore a good coefficient of friction in wet
conditions so as to provide safe operational conditions for
all aeroplanes. A change in surface colour, for example,
from black to grey on Portland cement concrete can be very
misleading, because even a small amount of residual rubber
in the pores of the pavement can produce low friction
values, while giving an overall clean appearance. It is
therefore essential to quantify the friction coefficient by
means of a reliable friction-measuring device.
8.2
CHEMICAL REMOVAL
8-2
Chapter 9
Clearance of Oil and/or Grease
9.1 GENERAL
9.1.1 Free deposits of these materials may be blotted
up with rags, sawdust, sand, etc., and the residue then
scrubbed with detergent using a rotary power broom. It will
likely be necessary to remove the deteriorated portions of
the oil-impregnated asphalt areas in order to successfully
repair or seal the surface.
9.1.2 Oil-soaked and stained areas on concrete
surfaces are washed to remove imbedded material using a
detergent compound of sodium metasilicate and resin soap
applied with water and scrubbed with a power broom. The
loosened contaminants are flushed away with water. For
asphaltic concrete pavements, an absorbent or blotting
material, such as sawdust or sand, combined with a
powdered alkaline degreaser, is used.
9-1
Chapter 10
Clearance of Debris
10.1
GENERAL
10-2
10.1.9 Other apron users, such as aeroplane caterers,
fuel suppliers, forwarding agents and handling agents, do
not come under the direct supervision of the operators.
Airport authorities should check that those engaged in the
provision of such services have also taken steps to instruct
their staff properly regarding the prevention of litter and the
disposal of waste material. Widespread use of polythene
bags and sheets by the catering services and aeroplane
maintenance personnel, and as temporary protection for
freight or components against weather, considerably
increases the chance of engine ingestion of this type of
material. Engine failures have occurred as a direct consequence. Sand used to clean fuel and oil spillage from
aprons is a further potential cause of turbine engine and
propeller damage and should be immediately and
efficiently removed after use.
10.1.10 Cargo areas, by the very nature of the operations they support, are particularly susceptible to contamination from strapping, nails, paper and wood, which
may become detached from crates or other containers in the
course of freight handling. Other equipment which has
been found in cargo areas includes loose buckles from
cargo tiedown nets, loose turnbuckles and large sheets of
polythene film. To the extent that forwarding agents
operate in these areas, the airport authority should require
that they assume their share of the responsibility for
keeping it in good condition. Where night activities are frequently involved, good illumination is necessary so that the
areas can be kept clean.
10.1.11 On taxiways, bypass areas and holding bays,
and on runways themselves, the presence of stones and
other debris as a result of erosion of the adjacent areas can
constitute a problem, and guidance on preventive measures,
including the sealing of runway and taxiway shoulders, is
already contained in Part 2 of the Aerodrome Design
Manual (Doc 9157). The need for adequate sealing has
been highlighted by the introduction of large jet aeroplanes
with greater engine overhang. Until runway and taxiway
shoulders are adequately sealed, care is needed to ensure
that vegetation and grass cuttings do not present an ingestion problem to overhanging engines. Moreover, the areas
immediately adjacent to the paved and sealed surfaces
should also receive regular inspection and attention to
ensure that debris which could subsequently find its way
onto the more critical areas is not present.
10.1.12 Deterioration of the bearing surface itself,
leaving loose sand, fragments of concrete and bitumen, is
another possibility, and concrete joints, if not properly
filled, are excellent traps for debris. Such joints should be
filled to permit effective sweeping. There is also an
indication that kerosene spillage on bitumen taxiways and
runways, caused by the venting of fuel tanks of aeroplanes
10.3
SWEEPER TESTS
10.3.1 Sweepers should be tested regularly by a performance test. A description of the practice being used by
one State for performance testing is given below.
a) Select a flat, smooth, bituminous, concrete area and
mark out a section 6 m 2 m on the surface.
b) Assemble a 0.45 kg mixture comprising equal portions
of each of the materials (dry) specified as medium/fine
gravel, coarse sand and medium/fine sand.
1) Medium/fine gravel. The gradation of this material
is such that 100 per cent shall pass a 9.5 mm screen
size and not more than 2 per cent pass a 2.4 mm
screen size.
10-3
2) Coarse sand. The gradation of this material is such
that 100 per cent shall pass a 2.4 mm screen size
and no particles pass a 0.6 mm screen size.
3) Medium/fine sand. The gradation of this material is
such that 100 per cent shall pass a 0.6 mm screen
size and no particles pass a 0.3 mm screen size.
c) Obtain eight stones, spherical in shape, 50 mm
diameter, and one of each of the following: 6 cm nail,
12 mm diameter ball-bearing, a piece of aluminium
(50 mm square 1.2 mm thick), and 12 mm nut.
d) Spread the mixture of medium/fine gravel, coarse sand
and medium/fine sand evenly over the test area. Along
one diagonal of the test area, place the eight stones at
equal spacings, and along the other diagonal, place the
nail, ball-bearing, aluminium square and nut at equal
spacings.
e) The sweeper shall be operating normally and, on
passing over the prepared test area at 16 km/h, shall
pick up and retain 98 per cent of the sand and gravel
and 100 per cent of the stones and miscellaneous
objects.
10.3.2 In the event of a sweeper failing to comply
with a performance test, action should be taken to restore
the sweeper to the acceptable operational standard of performance. The frequency of sweeper tests will depend
largely on the utilization of the unit. It is common practice
to undertake such tests on a regular weekly basis.
Appendix 1
Method for Determining the Minimum Friction Level
Vref
VTouch
15 m
(50 ft)
VB
Air distance, SA
V=0
Dry braking
distance, SD
Transition distance, ST
Dry landing distance, SL
A1-2
3.5
3.0
1/2 dry runway average MU-EFF
2.5
2.0
1.5
1.0
0
.05
.1
.15
.2
.25
.3
.35
.4
Average MU-EFF
Figure A1-2.
A = +0.411922
B = 2.6458E-2
C = +2.05336E-3
D = 1.01815E-4
E = +2.22342E-5
Calculation procedure
5. The NASA Combined Viscous/Dynamic Hydroplaning Theory (refer to references 1 and 3 at the end of
this appendix) suggests that the friction/speed curves generated on wet pavements by tires having different sizes, tread
rubber compounds, and inflation pressures can be normalized by using non-dimensional ratios for both friction
(MU/MU-ULT) and speed (V/VC). Using this approach,
the following equations have been derived to estimate the
aeroplane effective braking coefficient (MU-EFF)
A1-3
(1)
(2)
(3)
(4)
(5)
Tester:
(MU-ULT)T must be determined from experimental
low-speed test (1.63.2 km/h) on dry pavement
(Table A1-1)
(MU)T obtained from friction tester wet runway data
(V)T friction tester test speed to obtain (MU)T
PA aeroplane tire inflation pressure, kPa
Subscripts: A = aeroplane; T = runway friction tester
7. Sample calculation. The minimum friction level
(MFL) for a runway friction tester is 0.5 at 65 km/h and
0.41 at 95 km/h (refer to reference 4 at the end of this appendix). The following step-by-step procedure transforms
these friction and speed values into equivalent MU-EFF
and speed values for the 2-engine jet transport aeroplane
shown in Figure A1-2. These MU-EFF values will be averaged over a 0278 km/h (0150 knot) aeroplane braking
speed range to obtain a value for this aeroplane which can
be used in Figure A1-2 to obtain its braked SDR, which
then can be compared with the SDR obtained from using
half the dry runway aeroplane MU-EFF. Thus, it becomes
possible to determine whether or not the friction tester
MFL values at 65 km/h and 95 km/h test speeds are conservative or unconservative in terms of the 2-engine jet
transport wet runway.
(6)
A1-4
REFERENCES
SDR = 1.91
This SDR value (1.91) compares with the aeroplane
wet/dry SDR = 1.68 (from Figure A1-2) and indicates that
the friction tester values for the wet runway MFL are
reasonable for the Law runway friction tester.
Concluding remarks. Similar calculations were made
for brake application speeds of 278 km/h (150 knots),
259 km/h (140 knots), 241 km/h (130 knots) and 222 km/h
(120 knots) for both the 2-engine and 3-engine jet transport,
using the MFL method. The results are shown in
Table A1-2. These calculations suggest that the 278 km/h
(150 knots) brake application speed is more representative
of an aborted take-off at or near V1 speed, while the lower
brake application speeds are more representative of
typical aeroplane landing conditions. It can be seen from
Table A1-1.
Friction-measuring
device/aeroplane
Test tire
pressure
(kPa)
Characteristic
friction
coefficient
(MU-ULT)
207
207
207
69
1 069
1 207
1.0
1.1
1.15
1.1
0.76
0.738
Characteristic
hydroplaning
speed VC
(km/h)
91.2
91.2
91.2
80.5
207.5
220.5
A1-5
Table A1-2. Effect of brake application speed on actual and estimated aeroplane
wet/dry braked stopping distance ratio using the MFL Method
Brake application
speed (km/h (kt))
278
259
241
222
(150)
(140)
(130)
(120)
(150)
(140)
(130)
(120)
*RFT estimated
aeroplane
MU-EFF
*RFT estimated
aeroplane
wet/dry SDR
**Calculated
aeroplane
wet/dry SDR
0.1467
0.1552
0.1637
0.1722
1.91
1.84
1.77
1.71
1.63
1.73
1.76
1.78
2-engine jet
transport
0.1469
0.1547
0.1624
0.1702
2.04
1.96
1.89
1.82
1.76
1.80
1.83
1.86
3-engine jet
transport
Aeroplane type
Appendix 2
Procedures for Conducting Visual Inspection Runway
Maintenance Surveys at Airports that Serve Turbo-jet
Aeroplane Operations When Friction Equipment Is Not Available
represent values obtained from continuous friction-measuring devices that operate in the fixed braking slip mode.
Table A2-3 shows a method for coding the condition of
grooves in pavements, and Table A2-4 shows a method for
coding the pavement surface type. These codes are provided as a short-cut method for preparing notes concerning
the pavement surface condition.
A2-2
Table A2-1.
Daily turbo-jet
aeroplane arrivals
for runway end
Minimum friction
survey frequency
Less than 15
16 to 30
448 to 838
31 to 90
839 to 2 404
91 to 150
2 405 to 3 969
151 to 210
3 970 to 5 535
Note. After calculating the first two columns according to the procedures given
in Appendix 6, the airport operator must select the column which has the higher value
and then select the appropriate value in the last column.
Classification
of rubber
deposit
accumulation
Very light
Estimated percentage
of rubber covering
pavement texture in
touchdown zone of runway
Less than 5%
Estimated range of
Mu values averaged
150 m segments in
touchdown zone
Suggested level
of action to be
taken by
airport authority
0.65 or greater
None
Light
6-20%
0.55 to 0.64
None
Light to
medium
21-40%
0.50 to 0.54
Monitor deterioration
closely
Medium
41-60%
0.40 to 0.49
Medium to
dense
61-80%
0.30 to 0.39
Dense
81-95%
0.20 to 0.29
Very dense
96-100%
Table A2-2.
Note. With respect to rubber accumulation, there are other factors to be considered by the airport operator: the type and age of the
pavement, annual climatic conditions, time of year, number of wide-body aeroplanes that operate on the runways, and length of runways.
Accordingly, the recommended level of action may vary according to conditions encountered at the airport. The Mu ranges shown in the above
table are from continuous friction-measuring devices that operate in the fixed braking slip mode. The Mu ranges are approximate and are to
be used by the airport operator only when these devices are not available. When the devices are available, the airport operator should conduct
friction surveys on the runways to establish the actual rubber classification level.
A2-3
A2-4
Groove type
Groove condition
0 none
l sawed grooves
2 plastic grooves
0
1
2
3
4
5
6
7
8
9
50%
60%
70%
80%
90%
of
of
of
of
of
grooves
grooves
grooves
grooves
grooves
not
not
not
not
not
effective*
effective
effective
effective
effective
* When this level is exceeded, the airport operator should take corrective action to improve
groove efficiency.
Alpha code
Asphalt concrete
pavement
Portland cement
concrete pavement
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
belt finished
microtextured, predominately fine aggregate
macrotextured, predominately coarse aggregate
worn surface, coarse aggregate protrudes and/or abraded out
burlap dragged
broomed or brushed
wire comb
wire tined
float grooved
other
A2-5
LENGTH,.!.
cm.)
.8 1
.6
I
1.5
.8
1.0
1.2
1.4
INSIDE DIAMETER, d, in.
2.0
2.5
3.0
3.5
INSIDE DIAMETER, d, cm.
A2-6
Figure A2-4.
Appendix 3
NASA Certification Test Procedure for
New Continuous Friction-Measuring Equipment
Used at Airport Facilities
TEST PROCEDURE
INTRODUCTION
General
PRIMARY OBJECTIVES
1.
Steps
2.
1.
Check CFME test hardware, tire(s), and data acquisition system for proper configuration and working
condition.
3.
2.
4.
3.
A3-1
A3-2
water flow rate that will achieve average water depth
on the surface of 1 mm.
4.
5.
6.
7.
8.
9.
Appendix 4
Standard Test Method for
Skid Resistance on Paved Surfaces Using a Continuous
Fixed Braking Slip Technique
1.
E670
SCOPE
E867
E1551
E1844
F377
F457
2.
E178
E274
REFERENCED DOCUMENTS
2.1
ASTM Standards
A4-1
A4-2
SUMMARY OF METHOD
5.
APPARATUS
Instrumentation
5.5 General requirements for measuring system. The
instrumentation system shall conform to the following
overall requirements at ambient temperatures between 4C
and 40C (40F and 100F):
Overall static system accuracy 2% of the full scale
Time stability calibration 1 year minimum
The exposed portions of the system shall tolerate 100%
relative humidity (rain or spray) and other adverse
conditions, such as dust, shock, and vibrations, that may be
encountered in pavement test operations.
5.6 Force-measuring transducer. The tire forcemeasuring transducer shall be of such design as to measure
A4-3
5.12 Ideally, the instrument calibration shall allow the
whole measuring system including strain gage transducers
to be calibrated (BS 598 Draft Standard on Measuring
Surface Friction refers). If this is not possible, then all
strain gage transducers shall be equipped with resistance
shunt calibration resistors or equivalent that can be
connected before or after test sequences. The calibration
signal shall be at least 50% of the normal vertical load and
shall be recorded.
5.13 Tire friction force or torque and any additional
desired inputs, such as vertical load and wheel speed, shall
be recorded in phase (5 degrees over a bandwidth of 0 to
20 Hz). All signals shall be referenced to a common time
base.
5.14 The signal-to-noise ratio shall be at least 20 to 1
on all recording channels and the noise must be reduced to
2% or less of the signal.
6.
SAFETY PRECAUTIONS
A4-4
7. CALIBRATION
7.1 Speed. Calibrate the test vehicle speed indicator at
the test speed by determining the time for traversing, at
constant speed, a reasonably level and straight, accurately
measured pavement of a length appropriate for the method
of timing. Load the test vehicle to its normal operating
weight for this calibration. Make a minimum of three runs
at each test speed to complete the calibration. Other
methods of equivalent accuracy may be used. Calibration
of a fifth wheel shall be performed in accordance with
ASTM test method F457.
7.2 Braking (fixed slip) force. Place the test wheel of
the assembled unit, with its own instrumentation, on a
suitable calibration platform, which has been calibrated in
accordance with ASTM test method F377, and load vertically to the test load. Measure the test load within 0.5%
accuracy whenever the transducer is calibrated. Level the
transducers longitudinally and laterally such that the
tractive force sensitive axis is horizontal. This can be
accomplished by minimizing the tractive force output for
large variations in vertical load. The system (vehicle or
trailer) should be approximately level during this procedure. The calibration platform shall utilize minimum
friction bearings, have an accuracy of 0.5% of the applied
load, and have a maximum hysteresis of 0.25% of the
applied loading up to the maximum expected loading. Take
care to ensure that the applied load and the transducersensitive axis are in the same vertical line. Perform the
tractive force calibration incrementally until the test tire
starts to slip on the calibration platform, but at least up to
50% of the static vertical load. For other fixed slip testers,
refer to related manufacturers handbooks listed in 2.2.
8.
GENERAL
9.
PROCEDURE
10.
FAULTY TESTS
11.
A4-5
REPORT
weather conditions
wheel path tested
ambient and surface temperature
average, high, and low braking slip number for the
test section, and speed and per cent braking slip at
which the tests were made. (If values not used in
computing the average are reported, this fact should
be stated.)
the date of the last calibration
12.
Appendix 5
An Example of a Runway Friction Assessment Programme
7. Enter values for [G], [H], [K], [M] and [N] on Chart D.
A5-1
A5-2
Aeroplane type
Maximum aeroplane
landing mass (kg)
[A]
A300-B2
127 462
A300-B4
132 996
A300-600
138 000
A310-200
122 000
A310-300
123 000
A320-100
63 000
A320-200
64 500
B707-120B
86 184
B707-[320/420]
93 895
B707-[720/720B]
79 380
B707-320B
97 524
B707-320C
112 039
B727-[100/100C]
64 638
B727-200
73 030
B737-100
44 906
B737-200
46 721
B737-[200C/200QC]
48 535
B737-300
52 527
B737-400
56 246
B737-500
49 896
B747-[100/B/SF/SR]
255 830
B747-[200/B/C/F/P]
285 768
B747-[300/400]
285 768
B747-[200B/300]
290 304
Annual number
aeroplane landings
at airport
[B]
A5-3
Aeroplane type
Maximum aeroplane
landing mass (kg)
[A]
B747-300SR
242 676
B747-SP
210 924
B757-200PF
95 256
B767-200
123 379
B767-200ER
129 276
B767-300
136 080
B767-300ER
145 152
BAC111-[200/400]
31 298
BAC111-500
39 010
BAC CONCORDE
111 132
BAe146-100
32 568
BAe146-200
34 927
BAe146-300
40 824
DC8-[20/30/40]
93 895
DC8-55
98 431
DC8-[55F/61/62/71/72]
108 864
DC8-72AF
113 400
DC8-[63F/73CF/73AF]
124 740
DC8-[61F/71CF/63/73]
117 029
DC9-[10/15/15F]
37 059
DC9-21
43 228
DC9-[32/33F]
44 906
DC9-41
46 267
DC9-51
49 896
DC9-81
58 061
DC9-82
58 968
DC9-83
63 277
DC9-[87/88]
58 968
DC10-[10/10CF/15]
164 884
Annual number
aeroplane landings
at airport
[B]
A5-4
Aeroplane type
Maximum aeroplane
landing mass (kg)
[A]
DC10-40
182 801
DC10-[30CF/KC-10A]
197 770
DC10-[30/40CF]
186 430
F28-[1000/2000]
26 762
F28-[3000/5000]
29 030
F28-[4000/6000]
30 164
L1011-1
162 389
L1011-[100/200/500EW]
166 925
CONVAIR 880
70 308
CONVAIR 990
91 627
SE210
47 583
MD11
195 048
MD11 COMBI
207 749
MD11F
213 872
IL62
114 308
VC10-1100
97 978
VC10-1150
107 503
Annual number
aeroplane landings
at airport
[B]
+ = Wide-body aeroplane
Total annual non-wide-body aeroplane landings
Total annual wide-body aeroplane landings
%
%
%
%
A5-5
Form for computation procedure Chart B
365 days
per annum
__________________
__________________
[D]
[F]
Average annual aeroplane mass for annual aeroplane landings for all runways:
Annual aeroplane
landing mass
Annual aeroplane
landings
__________________
__________________
__________________
[E]
[D]
[J]
RUNWAY ____________
Daily aeroplane landings:
Daily aeroplane landings
all runways
__________________
__________________
__________________
[F]
[G]
[H]
__________________
__________________
__________________
[G]
[D]
[I]
=
__________________
__________________
__________________
[I]
[J]
[K]
A5-6
Minimum friction
survey frequency
[M]
Minimum rubber
removal frequency
[N]
less than 15
16 to 30
31 to 90
91 to 150
151 to 210
greater than 210
Notes:
1. Airports that exceed 31 daily turbo-jet aeroplane landings are more critical with respect to friction deterioration caused by rubber
accumulation due to increased aeroplane activity.
2. In addition to daily turbo-jet aeroplane landings for runway ends, other factors should be considered by the airport operator when
determining rubber removal, such as the type and age of pavement, annual climate conditions, time of year, number of wide-body
aeroplanes that operate on the runways, and length of runways.
3. Reference columns [H] and [K]: After calculating [H] and [K], the airport operator should select the column which has the higher value
and then select the appropriate values in columns [M] and [N].
Airport: _____________________________________________________________
Runway
designation
Per cent
annual
aeroplane
landings per
runway
[G]
Estimated
daily
aeroplane
landings per
runway
[H]
Annual distribution
of aeroplane landing
mass per runway
( 106 kg)
[K]
Type of
runway
pavement
Type of
surface
treatment
Total
runway
length
(m)
Estimated
friction
survey
frequency
[M]
Estimated
rubber
removal
frequency
[N]
Appendix 6
Methods of Measuring or Assessing Braking Action When
No Friction Test Devices Are Available
low, the quote between skid and max varies with the
specific conditions but the factors quoted above are
considered to give acceptable results. The speed at brake
application and the braking tests by this method may be the
same as in the method described in 4.4.2 for measuring
of braking action by braking a truck or car with a decelerometer installed. An example of a form to be used
for recording and processing test results is given in
Figure A6-1.
METEOROLOGICAL OBSERVATIONS
(RELATED TO RUNWAYS COVERED
BY SNOW OR ICE)
V2
2gS
V
time =
tg
where V = speed at brake application, m/s
S = stopping distance, in m
t = stopping time, in s
g = acceleration of gravity, in m/s2.
3. Normally, the friction coefficient based on time is
a little too low because there is a tendency to start the stop
watch an instant before the brakes become effective. On the
other hand, the friction coefficient based on stopping
distance is normally a little too high because the truck is
being braked to some extent before the wheels begin to
skid.
A6-2
Airport
Runway
Date
Time
Temperature
About 10 m east*
centre line of runway
Stop
time
(s)
Distance from
end of runway
Time:
T=
Distance:
D = D East + D West
No. of observations
Average:
Stop
distance
(m)
Sector
About 10 m west**
centre line of runway
Stop
time
(s)
Stop
distance
(m)
T East + T West
No. of observations
T + D
2
Figure A6-1. Example of schema that can be used when recording a friction test
made with skidding wheels of a truck to a full stop from 40 km/h
Remarks
A6-3
b) coefficient of friction between 0.25 and 0.35:
1) snow conditions at temperature just below freezing
point;
2) snow-covered runways at temperatures below
freezing point, exposed to sun.
Appendix 7
Plough Types and Accessories
2. Polymer and composite mould-boards and mouldboard coatings appear to reduce snow/slush/mould-board
skin friction. Skin friction reduction may reduce the power
required to propel the plough vehicle, thus reducing the
ploughs fuel consumption. Substantial plough fuel savings
have been claimed by some manufacturers. Plough mouldboards that physically cast a large volume of snow high and
away from the vehicle instead of simply wind-rowing
or displacing snow could reduce equipment inventories.
At some locations, depending on light snowfall, light
winds, the type of snow, and runway location, lighting, and
shoulder configuration, a high casting plough may not
require a snowblower to move a substantial portion of the
cleared snow over the pavement edge lights. Elimination
of a snowblower can represent substantial fuel and equipment savings, but any selection of a casting plough for such
a double-duty task should be carefully investigated,
recognizing that the required performance may be highly
dependent on the snow conditions at the site. Some
snowplough blade sizes are as follows:
A7-2
a) Tapered blade, one-way, left or right hand. Designed
for high-volume, high-speed runway and associated
snowploughing operations, this snowplough is a conventional, one-way (single direction discharge only)
type with a tapered mould-board, operated by hydraulic power with conventional in-cab, driveroperated controls. The blade, depending on plough
size, can vary from approximately 0.60 m to 0.76 m
high at the intake end, and from 1.27 m to 2.03 m high
at the discharge end. The blade should be equipped
with replaceable cutting edges, either metal or nonmetal, as specified. The unit should include a safety
trip device and a manual or power-adjustable blade
tilt for general purpose work, such as aprons and
runways. When equipped with tungsten carbide cutting
edges, it should not be used on surfaces equipped
with in-pavement lighting. In these areas, rubber or
polyurethane cutting edges are recommended. Ploughs
of this design do not have the versatility of reversible types and are not recommended for general airport
use.
b) Conventional power-reversible. The large size
classification of this snowplough is intended for highvolume, high-speed runway snowploughing requiring
the capability to discharge snow to the right or left at
preselected cutting angles from the bulldozing position.
The snowplough should have a detachable blade
assembly; it should be equipped with replaceable
cutting edges and be operated by hydraulic power with
conventional controls located in the operators cab. The
mould-board design should be such that the tungsten
carbide-tipped cutting edges and rubber/polyurethane
cutting edges can be interchanged. The power-operated
reversing mechanism should enable the blade to be
positioned in a minimum of four positions either side of
the bulldozing position, giving a maximum blade
angle of approximately 35 to 40 degrees. The unit
should be equipped with an automatic blade locking
and unlocking feature, an oscillating or floating drive
frame and, when specified, blade trip devices. The
plough should be equipped with bolt-on replaceable
shoes or castors when a non-metal cutting edge is
specified. Adjustable blade tilt can be specified when
this plough is to be used for general-purpose ploughing.
The mould-board can vary from approximately 1.8 m to
6 m in length at the cutting edge, and from approximately 0.88 m to 1.20 m in height. When the plough is
to be used on pavement areas equipped with inpavement lighting, a rubber or polyurethane cutting
edge is recommended in lieu of tungsten carbide.
Deeply flared inlet/exit ends may be specified to
increase snow-casting capabilities.
A7-3
g) Underbody scraper. This plough is designed for
maximum manoeuvrability in restricted areas without
in-pavement lighting and for breaking and ploughing
packed ice and snow. The unit should be either hydraulically or pneumatically operated with conventional in-cab controls. Depending on plough size, it
should have a blade length range to approximately
3.6 m, with a 30 cm to 50 cm mould-board radius and
a detachable cutting edge made of tungsten carbide
steel. The mould-board should be heavy-duty steel with
a minimum blade thickness of 1.2 cm. The plough
should be power-reversible permitting change of blade
angle to the left or right from the bulldozing position.
The system should be equipped with an adjustable
ground pressure device. A shock-absorbing suspension
trip system to prevent damage from suddenly applied
loads should be provided, and a system to fold or raise
the blade for transport with a minimum of 15 cm road
clearance should also be incorporated. The underbody
blade hanger device should be constructed to provide
the maximum load-bearing distribution surface for the
mould-board. Blade turntable circles should be the
welded type with at least four position indexing locks,
manual or automatic.
h) Apron snow blade. The apron blade should be designed
to be mounted on an aeroplane tug, wheel loader,
industrial tractor, or other similar vehicles that may
differ from a standard type plough vehicle. The plough
is designed for wide-swath, low-speed operations in
confined apron areas. This unit should be suitable for
pushing snow and slush away from terminal building,
gate, and apron areas and is not intended for use in
areas with in-pavement lighting. The unit should have
a mould-board length to 6 m, have a deeply recessed
curvature, be approximately 1.42 m high, and may
have optional full side plates. The replaceable tungsten
carbide steel cutting edge should be fixed in
the bulldoze position. The blade hitch should be of
the vertical slide or similar quick disconnect configuration, and the plough should be equipped with a
minimum of either two shoes or two castors. Parking
legs may be provided as desired; plough shoes may
provide this function on some models.
i) Snow buckets (general purpose). The bucket should be
used by and fit on a standard wheel loader or similar
type vehicle without modification, on a quick disconnect hitch. Snow buckets are designed for snow-loading
operations, removing wind-rows, and stockpiling snow
for storage or transport. They should be constructed of
steel in accordance with the standard techniques of
plough construction. The bucket capacity should be
A7-4
from 1 m3 to 4 m3. The bucket should be capable of a
minimum 20 degree forward tilt, transverse tilt and
level scoop operation. Bucket tilt may be provided by
the articulating mechanism of the vehicle itself.
j) Snow basket. This is intended for use on wheel loadertype vehicles using a quick disconnect hitch. This
basket bucket is for use in snow-loading operations and
Appendix 8
Related Reading Material
Porous Friction Surface Courses, Report No. FAARD-73-l97, dated February 1975.
Laboratory Method for Evaluating Effect of Runway Grooving on Aircraft Tires, Report No.
EAA-RD-74-l2, dated March 1974.
END
A8-1
ICAO 2002
3/02, E/P1/3200
Order No. 9137P2
Printed in ICAO