Reference
Modification no.
- 0 -
Page
58
Date
1997 02 01
Main
914 F
01476
9.5.3.3) Target pressure reduction by limiting the compressor pres-
sure ratio
The max. charging speed of approx. 165 000 rpm must not be exceeded to
prevent vibration resonances. Since the charger speed can be deduced
exactly enough from the pressure ratio, this ratio is limited to max. 2,6.
Example: e.g. at density altitude of 5500 m
atmospheric pressure approx. 500 hPa
max. permitted boost pressure (regarding deactivation) 500 x 2,6 = 1300 hPa
i.e. no reduction of the target pressure since this boost pressure cannot be
reached at all in this altitude.
Explanation:
The critical flight level for max. continuous power is reached at 4500 m.
Because of the low density in this altitude, the actual boost pressure is only
approx. 1140 hPa, even with the waste gate completely closed.
Deactivation would not start until airbox pressure of 1300 hPa is reached.
â—† NOTE: Deactivation happens very rarely and only under certain
climatic conditions and altitudes.
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