Propeller Gearbox; Checking The Friction Torque In Free Rotation - Rotax 912 Series Maintenance Manual

14) Propeller gearbox

General note NOTES:
Engine without
Engines without the overload clutch (slipper clutch) have no free rotation.
the overload
For this reason the friction torque method cannot be applied on engines
clutch
without overload clutch.

14.1) Checking the friction torque in free rotation

General note
See
Test procedure
The following steps are necessary for the testing procedure:
Step
1
2
3
4
5
6
Effectivity: 912 Series
Edition 3 / Rev. 0
BRP-Powertrain
MAINTENANCE MANUAL
The following "free rotation check" and "friction torque
check" are necessary only on engines with the overload
clutch as optional extra.
Fig. 32.
Risk of electric shock!
WARNING WARNUNG
Switch off ignition and remove key! Disconnect nega-
tive terminal of aircraft battery.
Fit the crankshaft locking pin. See chap. 12-20-00 section:
With the crankshaft locked, the propeller can be turned by hand 15 or 30 de-
grees depending on the profile of the dog gears installed.
This is the maximum amount of movement allowed by the dog gears in the tor-
sional shock absorption unit.
Turn the propeller by hand back and forth between ramps, taking into consid-
eration the friction torque. No odd noises or irregular resistance must be no-
ticeable during this moment.
Attach a calibrated spring scale to the propeller in distance (L) from the center
of the propeller. Measure the force required to pull the propeller through the 15
or 30 degree range of free rotation.
Calculate friction torque (Nm) by multiplying the force (N) obtained on the
spring scale by the distance the scale is attached from the center of the pro-
peller (L).
The friction torque must be between 30 Nm and max. 60 Nm (22 to 44.3 ft.lb).
See calculation example.
If the above mentioned friction torque is not achieved, in-
NOTICE
spect, repair or overhaul the gearbox in accordance with
the instructions for continued airworthiness.
Remove crankshaft locking pin. See chap. 12-20-00 section:
Procedure
12-20-00
September 01/2012
7).
7).
page 67