SERVICE
|
652 Oliver Street
Williamsport, PA 17701 USA
570/323-6181
| DATE: | August 18, 1999 |
Service Instruction No.1498 |
| 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. | |
The fuel system is more susceptible to vapor formation and its effects during operation in warm weather. Following are a list of symptoms which indicate the presence of vapor and the corrective action to use to purge vapor from the system.
NOTE
These procedures constitute an expansion of Cessna's published operating procedures.
A. Recognition of Problem:
Vapor may form in the hid system during ground operations when the ambient temperature exceeds 15 degrees F. The symptoms of fuel vapor as it affects engine operation are:
1. Fluctuation of idle speed and fuel flow.
2. Poor engine response to throttle movement.
3. Engine will not run when throttle is closed.
4. High RPM drop (>150 RPM) when checking magnetos.
B. Corrective Action:
If you notice one of the above during ground operation, perform the following:
1. Advance throttle to obtain an engine speed of 1800-2000 RPM. Maintain This speed for 1 - 2 minutes or until operation becomes smooth. Make sure oil temperature stays within limits.
2. Retard the throttle to idle to verify normal operation.
3. Advance throttle to 1200 RPM and lean for taxi.
4. Immediately prior to brake release for takeoff roll, set mixture, advance to full throttle and hold position of full throttle for 10 seconds (coordinate with ATC as necessary).
NOTE
When the engine is operated above 1800 RPM, fuel flow is increased and fuel temperatures throughout the fuel system are greatly reduced. The increased flow purges any vapor and the cool fuel stops vapor from forming.