Magnetic Drop-Off Check; Step 3. Complete The Engine Run-Up - Lycoming IO-360-N1A Installation And Operation Manual

16. Complete a magneto drop-off check as follows for all three cycles RIGHT/LEFT/BOTH.
A. Move the propeller control through its complete range as a check for operation and return
to the full low pitch position. Full feathering check (twin engine) on the ground is not
recommended but a check of the feathering action can be done by operating the engine
between 1000 to 1500 rpm, then momentarily pulling the propeller control into the
feathering position. Do not allow the rpm to drop more than 500 rpm.
B. With the propeller in minimum pitch angle, set the engine to produce 50 to 65% power
per the manifold pressure gage unless otherwise specified in the aircraft manufacturer's
manual. At these settings, the ignition system and spark plugs must work harder because
of the greater pressure within the cylinders. Under these conditions, ignition problems can
occur. Magneto checks at low power settings will only indicate fuel/air distribution
quality.
NOTICE: To prevent spark plug fouling, do not operate on a single magneto for too long a
period. A few seconds is usually sufficient for the magneto drop-off check.
C. Switch from BOTH magnetos to one magneto and note the drop-off; return to BOTH
until the engine regains speed and switch to the other magneto and note the drop-off, then
return to BOTH. Drop-off must not exceed 175 rpm and must not exceed 50 rpm between
magnetos.
D. If the rpm drop exceeds 175 rpm, slowly lean the mixture until the rpm peaks. Then
retard the throttle to the specified rpm, for the magneto drop-off check and repeat the
check. If the drop-off does not exceed 175 rpm and the difference between the drop-off
values for both magnetos does not exceed 50 rpm, and the engine is running smoothly,
the ignition system is operating properly.
E. Smooth operation of the engine with a drop-off that exceeds the specification of 175 rpm
is usually an indication of a propeller load condition at a rich mixture.
17. Look for any illuminated caution or warning lights in the cockpit.

Step 3. Complete the Engine Run-Up

IF DURING ENGINE RUN-UP OR ENGINE IDLE, ANY OPERATIONAL
PROBLEMS OCCUR, DO NOT TAKE-OFF. IDENTIFY AND CORRECT
THE CAUSE OF THE PROBLEM AND COMPLETE THE OPERATIONAL
TEST AGAIN.
Complete the engine run-up as follows:
1. With the engine running, turn the Fuel Selector to FULLEST or BOTH.
2. Make sure the oil temperature is above the specified minimum (Appendix A).
3. Operate the engine on the ground (with the propeller at minimum blade angle setting).
4. Make sure the oil pressure and oil temperatures are within the specified operating range in
Appendix A.
5. With the mixture control at FULL RICH, increase the throttle to 1800 rpm.
Engine Start and Operation
Page 28
IF THE ENGINE IS OPERATED AT LOW OIL PRESSURE OR LOW OIL
LEVEL, THE ENGINE CAN MALFUNCTION OR STOP.
AVOID PROLONGED IDLING AND DO NOT EXCEED 2200 RPM ON
THE GROUND. THE ENGINE IS WARM ENOUGH FOR TAKE-OFF
WHEN THE THROTTLE CAN BE OPENED WITHOUT THE ENGINE
FALTERING.
IO-360-N1A Engine Installation and Operation Manual
© 2016 Avco Corporation. All Rights Reserved
February 2016