Textron 172R180HP, Pilot Operating Handbook

Page: 120 / 396

SECTION 4 CESSNA
MODEL 172R (180 HP) NORMAL PROCEDURES
FUEL VAPOR PROCEDURES
The engine fuel system can become susceptible to fuel vapor
formation on the ground during warm weather. This will generally
loccur when the outside ambient air temperature is above 80 ° F.
The situation is further aggravated by the fact that the engine fuel
flows are lower at idle and taxi engine speeds. When vapor occurs
as evidenced by idle engine speed and fuel flow fluctuations, the
following procedures are recommended.
1. With the mixture full rich, set the throttle at 1800 RPM to 2000
RPM. Maintain this power setting for 1 to 2 minutes or until
smooth engine operation returns.
2. Retard the throttle to idle to verify normal engine operation.
3. Advance the throttle to 1200 RPM and lean the mixture as
described under FUEL
SAVINGS
PROCEDURES FOR
FLIGHT TRAINING OPERATIONS.
4. Just prior to TAKEOFF, apply lull throttle, for approximately 10
seconds to verify smooth engine operation for takeoff.
4·28
NOTE
When the engine is operated above 1800 RPM, the
resulting increased fuel flow also makes for lower fuel
temperatures throughout the engine fuel system. This
increased flow purges the fuel vapor and the cooler fuel
minimizes vapor formation.
Oct 4/01