Break-In Phase - Desert Aircraft DA50R Owner's Manual

Break-in phase

• The engine should run well from the beginning and improve as flight hours accumulate. We do not
recommend breaking the engine in on a test stand. The stationary load and lack of air ducting can
lead to engine over heating. Proceed with flying once the engine is tuned and running correctly.
Engine break-in can be a slow process, taking place over many hours of flight time. Peak RPM will
improve along with idle characteristics as run time accumulates.
• Special "break in only" props are not required. Preferably start with a prop that allows peak RPM
over 6,400 during the break-in process.
• The High needle can be set for optimum RPM or just slightly rich during break-in. Too rich will cause
problems with excess residue and carbon build up. Adjust the needles as needed and give the
engine a few test flights using a variety of throttle settings and engine loads. Avoid extended high
rpm or extended hovering conditions for these first few flights. After a few test flights the needles
may need adjustment as the engine settles in and other things change such as different props,
exhaust, weather, and altitude.
Starting
1. Always wear a heavy leather glove when starting the motor.
2. Check that prop bolts are tight and spinner is secure.
3. Make sure the starting area is free of dirt, sand, gravel, or other loose debris
4. Turn on the radio system and check the throttle operation and position.
5. Have someone (with eye protection) firmly hold the plane from a position behind the wing.
6. Close the choke completely.
7. Open the throttle to approximately 1/4 position.
8. Turn on the ignition. ALWAYS BE PREPARED FOR THE MOTOR TO START ON ANY FLIP OF
THE PROP, whether the ignition switch is on or off!
9. Give the prop a quick, firm, flip counter clockwise. Follow through quickly as you flip the prop so that
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 in/clockwise "leans" the fuel mixture. Turning the needles
out/counter-clockwise "richens" the fuel mixture.
• Settings will vary with altitude, temperature, humidity, fuel, carb variances, etc. A "general" starting
point for the DA50 is: 1 5/8's open on the Low needle, 1 7/8's open on the High needle.
• Adjusting either needle can have a slight effect on the other. Example: Leaning the low needle can
"slightly" lean the high rpm range.
• Adjust the High End needle to peak rpm. A tachometer can help, but remember that the RPM
normally drops a little bit after every start due to residual heat build up. Don't 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 overheating.
(Cont'd)
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