Operation In Flight; Leaning Procedure - Lycoming O-320 76 Series Operator's Manual

SECTION 3
OPERATING INSTRUCTIONS
(2) Switch from both magnetos to one and note drop-off, return to both until engine regains speed and
switch to the other magneto and note drop-off, then return to both. Drop-off should not exceed 175
RPM and should not exceed 50 RPM between magnetos. A smooth drop-off past normal is usually
a sign of a too lean or too rich mixture.
f. Do not operate on a single magneto for too long a period, a few seconds is usually sufficient to check
drop-off and will minimize the possibility of plug fouling.

7. OPERATION IN FLIGHT.

See airframe manufacturer's instructions for recommended power settings.
a. Fuel Mixture Leaning Procedure.
Improper fuel/air mixture during flight is responsible for many engine problems, particularly during
take-off and climb power settings. The procedures described in this manual provide proper fuel/air
mixture when leaning Lycoming engines; they have proven to be both economical and practical by
eliminating excessive fuel consumption and reducing damaged parts replacement. It is therefore
recommended that operators, of all Lycoming aircraft power plants, utilize the instructions in this
publication any time the fuel/air mixture is adjusted during flight.
Manual leaning may be monitored by exhaust gas temperature indication, fuel flow indication, and
by observation of engine speed and/or airspeed. However, whatever instruments are used in
monitoring the mixture, the following general rules should be observed by the operator of Lycoming
aircraft engines.
Never exceed the maximum red line cylinder head temperature of 500°F.
For maximum service life, cylinder head temperatures should be maintained below 435°F
(224°C) during high performance cruise operation and below 400°F (205°C) for economy
cruise powers.
Never lean the mixture from full rich during take-off, climb or high performance cruise
operation unless the airplane owners manual advises otherwise. However, during take-off
from high elevation airports or during climb at higher altitudes, roughness or reduction of
power may occur at full rich mixture. In such a case the mixture may be adjusted only
enough to obtain smooth engine operation. Careful observation of temperature instruments
should be practiced.
Operate the engine at maximum power mixture for performance cruise powers and at best
economy mixture for economy cruise power; unless otherwise specified in the airplane
owners manual.
Always return the mixture to full rich before increasing power settings.
3-4
LYCOMING
GENERAL RULES
SERIES OPERATOR'S MANUAL
O-320