Pitting, General Information - Rotax 915 i A series Maintenance Manual

Pitting in the gearbox
Pitting in the gearbox can cause high-frequency vi-
brations. This vibration can cause several problems
as it is transferred via the engine to the connected
parts:
• Wear on the gearbox (gear profile and contact
faces)
• External accessories
• Wear on the exhaust system
• Leaking of the sealing surface of the crankcase
NOTE
This vibration can be detected with a dynamic
engine analysis; these are units which are also
used to balance propellers. If the propeller can-
not be balanced suspect pitting of the gear.

PITTING, GENERAL INFORMATION

NOTE
When pitting occurs it is necessary to distin-
guish between tolerable initial pitting and
flake pitting. To make the assessment easier
for you, see the following assessment tips.
Pitting is the breaking off of more or less small, flat
material particles from the active tooth flank. Where-
as tooth breakage results in failure of the gearbox,
this is not the case for pitting damage. There are in
this case different stages of damage.
Rate of development
The rate of development depends on the lubricant
and amount of stress. The pitting surface can be-
come so large that the remaining undamaged flank
can no longer transfer the load. During further opera-
tion the gear-tooth system is then completely
destroyed.
NOTE
Fine pitting or pitted areas hardly affect the run-
ning behavior of the gear-tooth system at all.
The rule is however pitting damage which increases
over time.
A distinction can be made according to the size, type
and number of pitting, as follows.
Effectivity: 915 i A Series
Edition 0/Rev. 0
BRP-Rotax
MAINTENANCE MANUAL HEAVY
• Slight pitting (initial pitting)
• Destructive pitting
• Flake pitting (large-area flank fractures)
72–10–00
Page 23
August 01 2018