Rotax MMH-912 Series, Maintenance Manual

Page: 342 / 464

76-00-00
page 8
May 01/2007
Effectivity 912/914 Series
Edition 1 / Rev. 0
d02626
BRP-Rotax
Maintenance Manual
2.1.2) Target pressure reduction
Provision for target pressure reduction is made depending on various
effects as a protective measure against overstressing the engine.
2.1.2.1) Target pressure reduction at overspeeding
See Fig. 76-6
It is the responsibility of the pilot to prevent engine speeds in
excess of 5800 rpm, and during fast flight and descent when
using a fixed pitch propeller, the pilot must therefore reduce
the engine performance.
Only if the pilot fails to do this will the TCU lower the target
pressure when engine speed exceeds 5900 rpm and open the
wastegate, thus reducing boost pressure. See relevant dia-
gram.
■
CAUTION: The automatic opening of the wastegate by
the TCU is an emergency measure in the
event of a pilot error, but does not release the
pilot from responsibility to reduce the engine
performance.
-100
0
100
200
300
400
500
600
700
800
900
5000 5900 6000 6100 6200 6300 6400 6500
Motordrehzahl [1/min]
(engine speed)
D
ruckr
ed
u
kt
io
n [
h
P
a]
(pre
ss
u
re
re
du
ct
io
n)
e.g. at take-off performance (throttle valve position 115 %)
- target pressure
1370 hPa (without limitation)
- at an engine speed of 6100 rpm -
target pressure reduc-
tion
by approx. 265 hPa (according to diagram).
- current target pressure 1105 hPa - corresponds to 70 kW
power
instead of 84.5 kW
.
Fig. 76-6
00177