Rotax MMH-912 Series - 2) Systems description; 2.1) Propeller gearbox; 2.1.1) Gearbox version

BRP-Rotax
Maintenance Manual
Effectivity 912/914 Series
Edition 1 / Rev. 0
72-00-00
page 5
May 01/2007
d02622
2) Systems description
2.1) Propeller gearbox
See Fig. 72 -1
Transmission gear ratio crankshaft: propeller shaft 2.43 : 1
2), 3), 4)
; 2.27 : 1
1)
The propeller shaft is driven by the crankshaft via a straight toothed spur gear
(1).
The propeller gearbox incorporates a torsional shock absorbing device. This
consists of a torsional shock absorber with dogs (2) and axial springloading by
means of disc springs (3).
The design also includes a friction damped free rotation at the dogs to ensure
smooth engine idling. Due to this free rotation, a distinct torsional impact arises
at engine start and stop and in the event of sudden load changes, but due to the
integrated overload clutch it will remain harmless.
◆ NOTE: This overload clutch (4) will also prevent any undue load on the
crankshaft in the event of the propeller having ground contact.
◆ NOTE: The overload clutch is fitted in serial production on both certified
aircraft and uncertified aircraft engines of configuration 3.
2.1.1) Gearbox version
See Fig. 72 -1
There are 3 gearbox configurations for the 912/914 Series. See 71-00-00
sec. 2.2
1)
912 A, F, UL
2)
912 S, ULS, ULSFR
3)
914 F, UL
4)
912 A, F, UL - optional