Reduction Of The Target Pressure; 1) Target Pressure Reduction At Overspeeding - Rotax 914 F Maintenance Manual

9.5.3)
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1997 02 01
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Reduction of the target pressure

Provision for target pressure reduction depending on various effects as
protective measure against overstressing the engine.

9.5.3.1) Target pressure reduction at overspeeding

See Pic. 30.
The pilot is responsible to prevent engine speed in excess of 5800 rpm and
has to reduce early enough engine performance at fast flight and descent
when using a fix pitch propeller.
Only in case of omission by the pilot, the TCU will lower the desired pressure
when engine speed exceeds 5900 rpm by opening the waste gate and thus
reducing boost pressure. See relevant diagram.
ATTENTION:The automatic opening of the waste gate by the TCU is an
emergency measure only in the event of a pilot error but is
not releasing the pilot to reduce the engine performance.
5900 6000
e.g. at take-off performance (throttle position 115 %)
target pressure 1350 hPa (without limitation)
at engine speed of 6100 rpm
by 265 hPa (according to diagram).
actual boost pressure now 1085 hPa
70 kW instead of 84,5 kW.
Main
914 F
6100 6200 6300
lowering of the target pressure approx.
Reference
Pic. 30
6400 6500
Motordrehzahl [1/min]
(engine speed)
corresponds to a performance of
Modification no.
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