VSKYLABS Maule M-7-235B
MANUAL / POH
Supplement A - Lycoming Engine Data
The VSKYLABS Maule M-7-235B is powered by the Lycoming O-540-B series engine. The real-world Maule POH does not include engine performance charts. As a reference for flight planning and maintenance, here are some useful charts:
Specifications - O-540-B Series:
FAA Type Certificate ........................295
Rated horsepower.............................235
Rated speed RPM..............................2575
Bore, inches.................................5.125
Stroke, inches...............................4.375
Displacement, cubic inches...................541.5
Compression ratio ...........................7.2:1
Firing order ................................1-4-5-2-3-6
Spark occurs, degrees BTC....................25
Valve rocker clearance (hydraulic tappets collapsed) ...............0.028-0.080
Prop. drive ratio ...........................1:1
Prop. driven rotation .......................Clockwise
Operating Instructions:
STARTING PROCEDURES:
a. O-540 Series
Perform pre-flight inspection.
Set carburetor heat control in “cold” position.
Set propeller governor (if applicable) in “Full RPM” position.
Turn fuel valve to “on” position.
Move mixture control to “Full Rich”.
Turn on boost pump.
Pump throttle to full open and back to idle position for 2 to 3 strokes for a cold engine. If engine is equipped with a priming system, cold engines may be primed with 1 to 3 strokes of the priming pump.
Open throttle approximately ¼ travel.
Set magneto selector switch. Consult airframe manufacturer’s handbook for correct position.
Engage starter.
When engine starts, place magneto selector switch in “Both” position.
Check oil pressure gage for indicated pressure. If oil pressure is not indicated within thirty seconds, stop engine and determine trouble.
b. IO-540 Series (Cold Engine).
Perform pre-flight inspection.
Set propeller governor in “Full RPM”.
Turn fuel valve to “on” position.
Open throttle approximately ¼ travel.
Turn boost pump on and move mixture control to “Full Rich” position until a slight but steady flow is indicated.
Return mixture control to “Idle Cut-Off” position.
Set magneto selector switch. Consult airframe manufacturer’s handbook for correct position.
Engage starter.
When engine starts, place magneto selector switch in “Both” position.
Move mixture control slowly and smoothly to “Full Rich”.
Check oil pressure gage for indicated pressure. If oil pressure is not indicated within thirty seconds, stop the engine and determine trouble.
NOTE: If engine fails to achieve a normal start, assume it to be flooded. Crank engine over with
throttle wide open and ignition off. Then repeat above procedure.
GROUND RUNNING AND WARM-UP:
Subject engines are air pressure cooled and depend on the forward movement of the aircraft to maintain proper cooling. Particular care is necessary, therefore, when operating these engines on the ground. To prevent overheating, it is recommended that the following precautions be observed.
NOTE: Any ground check that requires full throttle operation must be limited to three minutes, or less if indicated cylinder head temperature should exceed the maximum stated in this manual.
Head the aircraft into the wind.
Leave mixture in “Full Rich”.
Operate the engine on the ground only with the propeller in minimum blade angle setting.
Warm up at approximately 1000-1200 RPM. Avoid prolonged idling and do not exceed 2200 RPM on the ground.
Engine is warm enough for take-off when the throttle can be opened without the engine faltering.
GROUND CHECK:
Warm up as directed above.
Check both oil pressure and oil temperature.
Leave mixture in “Full Rich”.
(Where applicable) Move the propeller control through its complete range to check operation and return to full low pitch position. Full feathering check (twin engine) on the ground is not recommended but the feathering action can be checked by running the engine between 1000-1500 RPM; then momentarily pulling the propeller control into the feathering position. Do not allow the RPM to drop more than 500 RPM.
A proper magneto check is important. Additional factors, other than the ignition system, affect magneto drop-off. They are load-power output, propeller pitch and mixture strength. The important thing is that the engine runs smoothly because magneto drop-off is affected by the variables listed above. Make the magneto check in accordance with the following procedures:
(Controllable Pitch Propeller) With propeller in minimum pitch angle, set the engine to produce 50-65% power as indicated by the manifold pressure gage unless other specified in the aircraft manufacturer’s manual. Set the mixture control to the full rich position. 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. Mag checks at low power settings will only indicate fuel-air distribution quality.
NOTE: Aircraft that are equipped with fixed pitch propellers, or not
equipped with manifold pressure gage, may check magneto drop-off with engine operating at approximately 2100- 2200 RPM.
Switch from both magnetos to one and note drop-off; return to both until engine regains speed and switch to the other magneto and not 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 the normal specification of 175 RPM is usually a sign of a too lean or too rich mixture.
If the RPM drop exceeds 175 RPM, slowly lean the mixture until the RPM peaks. Then retard the throttle to the RPM specified in step e. (1) for the magneto check and repeat the check. If the dropoff does not exceed 175 RPM, the difference between the magnetos does not exceed 50 RPM, and the engine is running smoothly, then the ignition system is operating properly. Return the mixture to full rich.
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 plug fouling.
OPERATING IN FLIGHT:
Subject engines are equipped with a dynamic counterweight system and must be operated accordingly. Use a smooth, steady movement (avoid rapid opening and closing) of the throttle.
See airframe manufacturer’s instructions for recommended power settings.
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 leaning the mixture, the following general rules should be observed by the operator of Lycoming aircraft engines.
LEANING - GENERAL RULES:
Never exceed the maximum red line cylinder head temperature limit.
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.
On engines with manual mixture control, maintain mixture control in “Full Rich” position for rated takeoff, climb and maximum cruise powers (above approximately 75%). However, during take-off from high elevation airport or during climb, roughness or loss of power may result from over-richness. In such a case adjust mixture control only enough to obtain smooth operation – not for economy. Observe instruments for temperature rise. Rough operation due to over-rich fuel/air mixture is most likely to be encountered at altitudes above 5,000 feet.
Always return the mixture to full rich before increasing power settings.
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.
During let-down flight operations it may be necessary to manually lean carbureted or fuel injected engines to obtain smooth operation.
LEANING TO EXHAUST GAS TEMPERATURE GAGE:
Normally aspirated engines with fuel injectors or carburetors:
Maximum Power Cruise (approximately 75% power) – Never lean beyond 150°F on rich side of peak EGT unless aircraft operator’s manual shows otherwise. Monitor cylinder head temperatures.
Best Economy Cruise (approximately 75% power and below) – Operate at peak EGT.
LEANING TO FLOWMETER:
Lean to applicable fuel-flow tables or lean to indicator marked for correct fuel-flow for each power setting.
LEANING WITH MANUAL MIXTURE CONTROL
(Without flowmeter or EGT gage):
Carbureted Engines:
Slowly move mixture control from “Full Rich” position toward lean position.
Continue leaning until engine roughness is noted. (c) Enrich until engine runs smoothly and power is regained.
OPERATING CONDITIONS:
PERFORMANCE CHARTS - O-540-B SERIES - LEANING TRENDS:
PERFORMANCE CHARTS - O-540-B SERIES - PART THROTTLE FUEL CONSUMPTION:
PERFORMANCE CHARTS - O-540-B SERIES - SEA LEVEL POWER CURVE:
PERFORMANCE CHARTS - O-540-B SERIES - PERFORMANCE DATA:
