Rotax 912 i Series Maintenance Manual page 151

CHECKING THE SPLINES
There are two essential splined shaft connec-
tions in the gearbox.
- Crankshaft to drive gear
- Propeller shaft to the clutch hub of the over-
load clutch
NOTE: To check the splines, determine the
tooth widths at the tip circle of the re-
spective inner or outer gear-tooth
system. The smallest value in each
case is significant.
Step
1 Inspect all the splines visually for damage
and wear. See section
72-10-00 Wear limits. (CS07,GB15,
GB14, GB16)
GEAR SET CHECK (GEARS)
The gear set is checked to identify any damage
to the gear-tooth system.
NOTICE
WARNUNG
Check all the tooth flanks for any damage or pit-
ting.
NOTE: If the gearbox is installed, it is also
possible to check the gear set using
an endoscope. This must be done in
such a manner that an exact assess-
ment of the tooth flanks is possible
and requires experience.
Pitting
Pitting is damage which is attributable to fatigue
of the material. As far as is known today, this is
caused when the Hertzian stress permissible for
the material in question is exceeded, the tangen-
tial stress on the surface (friction stress) and
temperature stress. As well as the material and
the heat treatment of it, the surface quality and
structure, surface treatment and lubricant (visco-
sity at operating temperature and additives) are
also important.
Effectivity: 912 i Series
Edition 1/Rev. 0
BRP-Powertrain
MAINTENANCE MANUAL
Procedure
NOTE: The likely location of pitting formation
is the dedendum flank of the driving
gear. Therefore, begin by checking
the drive gear.
Pitting in the gearbox
Pitting in the gearbox can cause high-frequency
vibrations. This vibration can cause several pro-
blems as it is transferred via the engine to the
connected parts:
- Wear on the gearbox (gear profile and
contact faces)
- External alternative 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 used to adjust propel-
lers. The normal vibration level for the
engine is approximately between
1.27 cm and 2.45 cm per second, or
the values specified by the aircraft
manufacturer for the respective instal-
lation apply.
PITTING, GENERAL INFORMATION
NOTE: When pitting occurs it is necessary to
distinguish 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.
Whereas 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.
72-10-00
Page 13
July 01/2012