Owners Manual
Owners Manual
Owners Manual
Owners Manual
Introduction
The DA150 was designed to provide the highest quality and performance in Giant
Scale modeling. Unlike most other large gas engines on the market, the
DA150 is not a combination of various industrial motor parts. Desert Aircraft computer
designed the DA150 from the ground up as a high performance aircraft engine. We did
not cut any corners. Existing cylinders, pistons and crankshafts were plentiful and
cheap, but did not offer the performance and other features that we needed. The DA 150
pistons, cylinders and crankshaft were designed by, and manufactured exclusively for,
Desert Aircraft.
The design features long connecting rods and high piston pin location for better rod
angularity and piston tracking with less cylinder and piston wear. Three large crankshaft
bearings are used to offer maximum stability and longevity. The pistons and crankshaft
are very well balanced, providing the smoothest vibration levels for your airframe and
radio system in its class.
Rather than use a shaft extension to gain clearance between the prop and the
cylinders and carburetor, the front section of the case is long, with a bearing right behind
the prop hub. Not only does this provide a very stable crankshaft, it also makes fitting
the engine and mufflers in the cowl, much easier.
The crankcases are CNC milled from 7075 T6 aluminum alloy. Along with excellent fit
and finish, precise bearing alignment is insured, which is critical to engine performance.
The reliable Desert Aircraft auto advance, electronic ignition system insures easy
starting and high performance. This ignition provides a powerful spark, yet is fully
shielded to insure protection from R/F noise.
The DA150 has proven to be the ultimate aerobatic engine by dominating and winning
the 1999 World Aerobatic Masters, the 2000 Tournament of Champions, 2001/2003
IMAC Nats, 2001/2003 Tucson Shootouts, 2002 and 2003 JR Challenge.
Congratulations and thank you from all of us at Desert Aircraft for choosing to own the
best in Giant Scale engines!
1
Safety Instructions
WARNING! This motor can cause severe harm to you, and or others, if misused or if
these safety precautions and instructions are not observed. Desert Aircraft is not
responsible for any loss, injury or damage resulting from the miss-use of its products.
You alone are responsible for the safe operation of your motor.
If you do not agree with the above, do not operate the engine.
Recommended Props
Always inspect your prop and spinner and tighten prop bolts before each flight!
While special break-in props are not required, they can help speed up the break-in
process and reduce the risk of over loading the motor.
The following props are recommended:
For break-in: Bolly 30x12, Menz 30x10, 32x10 Mejzlik 30x10
For normal use: Bolly 30x12, 30x15, 32.5x11
Menz 30x10, 30x12, 32x10, 32x12
Mejzlik 30x10, 30x12, 32x10 2 blades, and 28x12, 29x12 3 blades
AirModels 32.5x11 2 blade, 28x12, 29x12 3 Blades
Smaller diameter props with more pitch will help reduce noise.
The DA150 has a very wide power band. The "normal" peak operating rpm for
aerobatics is 5,500 to 6,500 rpm, depending on prop selection, sound requirements
and pilot preference. While with fine tuning it is possible to have an idle as low as 800
rpm, normal reliable idle rpm is 1,200 to 1,400.
Always use a drill guide to drill your props.
Always check the balance of your prop.
For safety, we recommend painting the tips of your props (front and back) with a
bright color, especially black props.
Never use a damaged or repaired prop, or a prop that has struck the ground or any
other object. Damage that can be hard to see, could turn into disaster when turning
at thousands of RPM.
5
Starting
1. Check that prop bolts are tight and spinner is secure.
2. Make sure the starting area is free of dirt, sand, gravel, or other loose debris
3. Turn on the radio system and check the throttle operation and position.
4. Have someone (with eye protection) firmly hold the plane.
5. Close the choke completely.
6. Open the throttle to approximately 1/4 position.
7. Turn on the ignition. ALWAYS BE PREPARED FOR THE MOTOR TO START
ON ANY FLIP OF THE PROP!
8. Always wear a heavy leather glove when starting the motor.
9. Give the prop a quick, firm, flip counter clockwise. Follow through quickly as you
flip the prop so your hand is out of the propeller's path. Repeat until the motor
fires or pops.
10. Open the choke.
11. Set throttle to idle position. (carb butterfly plate slightly open)
12. Flip the prop again until the motor runs.
13. Let the motor warm up for 15 or 20 seconds before advancing the throttle.
Needle Adjustments
The needle farthest from the motor is the High End needle. The needle closest to
motor is the Low End needle. Turning the needles clockwise leans the fuel
mixture. Turning the needles counter-clockwise richens the fuel mixture.
Settings will vary with altitude, temperature, humidity, fuel, carb variances, etc. A
consistently good starting point is: 5/8 of a turn open on the Low needle, 2 turns
open on the High needle. The Low needle is very sensitive and should not vary
much, if at all, from the 5/8's setting.
Adjusting either needle can have a slight effect on the other. Example: leaning the
low needle can "slightly" lean the high range.
Adjust the High End needle to peak rpm. A tachometer is a great help, but remember
that the RPM may drop a little after every start due to heat build up. Dont lean the
mixture any more than necessary. If the rpm steadily drops at full throttle or fades on
long vertical maneuvers, the motor is too lean and is over heating.
Adjust the Low End needle until you achieve a smooth idle and a reliable transition to
high throttle. Generally if the motor stutters or coughs in the mid range or when the
throttle is advanced, the low end needle is too rich and possibly even the high end
needle. If the motor dies quickly, the low end is probably lean.
Operating the motor overly rich not only reduces power, it creates other problems
such as poor transition, pre-mature carbon build up, fouled plugs, excessive exhaust
residue, sticking rings, and rough running.
6
Trouble Shooting
Motor won't start
Check battery voltage ( should be 5.0+ volts) and all ignition connections, wiring and
switches. Wires can break from vibration near connectors.
Check tank venting, clunk position, and fuel flow.
Is the case pressure tap sealed? ( 1/4" 28 threaded hole in the rear case, near carb)
Does fuel move towards the carb when the prop is flipped?
If carb isnt priming, is choke plate closing completely? Is the carb or carb mount
loose causing an air leak? Look for fuel seepage.
Is throttle set at idle or slightly higher after motor pops and choke is opened?
Make sure prop is flipped over with authority. The ignition wont fire at low speed.
If a lot of fuel drips from carb, the motor might be flooded. If so, remove and dry, or
replace, the spark plugs. Try starting again without using the choke.
The motor might be too rich. Make sure both needles are adjusted to peak
performance.
Check that the fuel clunk is not stuck in the wrong position.
The most common cause of this problem on gas aircraft motors is the variation of
airflow around the carb inlet and the carb pump metering hole (located on the shiny
carb diaphragm cover). The carb has a hard time adjusting to positive and negative
pressures in and around the cowl. If the meter hole senses the prop blast or some
other pressure variance, it will usually cause the carb to pump more fuel, which in
turn makes the motor run rich. One symptom is that the motor becomes rich on take
off. Sometimes the metering hole is in side the cowl and the carb intake is out side in
a very different environment. Even with both inside the cowl, there can be enough of
a variance to affect the performance. The optimum is to have both operating in the
same environment. These problems, and the cures for them, vary from plane to
plane. Since the problem usually only occurs in flight, bench testing wont help much.
It may take several test flights to sort it out. Here are some things to try:
1) Fasten a small shield over the diaphragm hole. Thin aluminum works well
(soda can!). This protects the hole from direct blasts of air.
2) Horizontal cooling shroud plates in front of the cylinders, not only help lower
engine temperatures, but also help protect the carb area from turbulent airflow
in the cowl.
(continued)
7
Trouble Shooting (continued)
3) If the carb is exposed, try to create positive pressure over the carb inlet.
This can be done with a small aluminum plate protruding out from the rear side
of the intake or a beveled velocity stack. This lets the carb see a positive
airflow regardless of the planes attitude.
4) Caution! If the diaphragm plate is removed for any reason, be sure the
diaphragm pin on the center of the diaphragm is inserted in the metering lever
fork.
DESERT AIRCRAFT
1815 S. Research Loop
Tucson, AZ 85710 USA
Ph 520 722 0607 Fax 520 722 5622
Email desertaircraft@theriver.com
DA150 WARRANTY
Your DA150 motor and ignition system are covered with a 2 year warranty
by Desert Aircraft, starting from the date of purchase.
NOTE: Warranty replacement items will not be shipped until suspect items are
received, and deemed faulty by, Desert Aircraft.
8 02/2004