Ground Operation Under High Ambient Temperature Conditions - Continental Motors O-470-B Operator's Manual

Another variable affecting this fuel vapor condition is the state of
the fuel itself. Fresh fuel contains a concentration of volatile
ingredients. The higher this concentration is, the more readily the
fuel will vaporize and the more severe will be the problems
associated with vapor in the fuel system. Time, heat or exposure to
altitude will "age" aviation gasoline; that is, these volatile ingredi-
ents tend to dissipate. This reduces the tendency of fuel to vaporize
and, up to a point, will result in reduced starting problems associ-
ated with fuel vapor. If the volatile condition reaches a low enough
leyel, starting may become difficult due to poor vaporization, since
the fuel must vaporize in order to combine with oxygen in the
combustion process.
The operator, by being cognizant of these cond"itions, can take
certain steps to cope with problems associated with hot weather! hot
engine starting. The primary objective should be that of permitting
the system to cool. Low power settings during the landing approach
will allow some cooling prior to the next start attempt. Ground
operation tends to heat up the engine, therefore minimizing this will
be beneficial. Cowl flaps should be opened fully while taxiing. The
aircraft should be parked so as to face into the wind to take
advantage of the cooling effect. Ifrestarting is attempted in less than
an hour following shutdown, vapor lock may be experienced.
Normal starting procedure should be used except that the throttle
should be opened more while cranking. Under extreme temperature
conditions, the "Hot Start Procedure" in Section III should be
employed.
Ground Operation Under High Ambient Temperature Conditions.
Oil and cylinder temperatures should be monitored closely during
taxiing and engine run-up. Operate with cowl flaps full open. Do
not operate the engines at high RPM except for necessary pre-flight
checks. If takeoff is not to be made immediately following engine
run-up, the aircraft should be faced into the wind and the engine
idled at 900-1000 RPM.
It
may be desirable to operate the fuel boost
pumps to assist in suppressing fuel vapor and provide more stable
fuel pressure during taxiing and engine run-up.
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