652 Oliver Street
Williamsport, PA 17701 USA
|DATE:||August 13, 1999||
Service Instruction No.1497
|SUBJECT:||Recommended Engine Procedures for Purging Vapor During Ground Operations|
|MODELS AFFECTED:||Textron Lycoming IO-360-L2A engines installed in Cessna C172R aircraft used in training operations.|
|TIME OF COMPLIANCE:||As required during aircraft operations.|
Flight training operations often present an environment that makes an engine more susceptible to spark plug fouling, reduced efficiency, and excessive fuel consumption. Some of the flight training profiles that cause these conditions are overpriming, prolonged idling and taxiing at low engine speeds, and extended operation at full rich mixture.
Following these recommended engine operating procedures can result in improved service experience.
These procedures constitute an expansion of Cessna's published operating procedures.
New, newly remanufactured, and newly overhauled engines have special break-in requirements and should be operated for the first fifty (50) hours in accordance with the procedures given in the appropriate Engine Operator's Handbook.
A. Start-up and Ground Operations.
1. Start the engine in accordance with the procedures given in the Pilot's Operating Handbook (POH) or Airplane Flight Manual (AFM). Do not overprime, as overpriming can delay starting and promote spark plug fouling.
2. When the engine is firing evenly, advance the throttle to operate the engine at 1200 RPM for warm-up.
3. Lean mixture to Best Power (lean until RPM drops; then enrich to recover to peak RPM).
4. Reset throttle to 1000 RPM.
5. Move throttle as necessary for normal operation.
6. Conduct pre-take-off check list in accordance with the POFI or AFM.
7. Set mixture to Full Rich for magento check. Do not operate on a singlemagneto for more than the few seconds necessary to check drop-off.
8. Following magneto check reset engine to 1200 RPM and recheck mixture to confirm Best Power.
9. Reset throttle to 1000 RPM, and maintain this setting until clearance for takeoff.
10. For takeoff, set mixture Full Rich. (For high elevation fields, leaning may be required for smooth engine operation. Refer to POH or AFM.)
B. Flight Operations.
1. Climb: Below 3000 feet density altitude, use Full Rich mixture. Above 3000 feet density altitude, lean to maximum RPM. Leaning technique -- Slowly lean until the RPM shows a drop. Enrich until obtaining smooth operation, then enrich an additional 1/2 turn of the mixture knob (approximately 180 degrees rotation).
2. Cruise: Lean to maximum RPM (all altitudes). Leaning technique - Slowly lean until the RPM shows a drop. Enrich until obtaining smooth operation, then enrich an additional 1/2 turn of the mixture knob (approximately 180 degrees rotation).
3. Move engine controls smoothly and slowly. Always return mixture to Full Rich before increasing power settings.
C. Landing Operations.
1. On approach, set the mixture at Full Rich.
D. Engine Shut-Down.
1. If extended taxi is expected, lean to best power during taxi.
2. After engine temperature gages are stabilized within normal readings at 1000 to 1200 RPM, move mixture control to Idle Cut-Off.