Eagle ICA-D212-725, Instructions Manual

Page: 335 / 729

ICA-D212-725 (63)
Page 8 of 144
CHAPTER 63 – MAIN ROTOR DRIVE SYSTEM (63-00-00)
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COPYRIGHT

2007 BY DART AEROSPACE LTD.
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THIS DOCUMENT IS PRIVATE AND CONFIDENTIAL AND IS SUPPLIED ON THE EXPRESS CONDITION THAT IT IS NOT TO BE USED FOR ANY PURPOSE OR COPIED OR COMMUNICATED TO ANY
OTHER PERSON WITHOUT WRITTEN PERMISSION FROM DART AEROSPACE LTD.
Revision:
6
Date: 13.08.26
The information contained in this figure is provided
for the evaluation of contamination found on the
drive system chip detectors.
It is impossible to depict the shapes of all possible
particulate contamination, especially those
particles not generated within a gearbox, as a
result of component wear or failure. However, the
following basic assumptions will permit a rather
accurate assessment of any debris found, even
though the particles may be severely distorted as
a result of passing through gear meshes
63.1.2.2 Description:
63.1.2.2.1
Material, from the surfaces of gear
teeth or rolling element bearings is quite hard.
Particles broken from these surfaces may have
razor-sharp edges but rarely have sharp pointed
ends. With few exceptions, surfaces of such
particles will not appear smeared (as if cut by a
shear) under magnification; a grainy appearance
on the fracture surfaces is more common.
When damaged by passing through gear meshes,
these hard particles tend to breakup with relatively
little deformation.
63.1.2.2.2 Foreign ferrous material
introduced into gearboxes is often much softer
than the surfaces of gear teeth and bearings. The
same is true of most non-gear and nonbearing
components within gearboxes. The softer
materials are usually quite ductile and malleable,
i.e., particles from such materials can be readily
bent or rolled into a wide range of shapes without
fracturing.
Fragments of the softer material are capable of
being torn or sheared from the parent component
without suffering brittle fracture (easily broken or
snapped). Instead, during separation the
fragments are distorted and stretched such that
they often exhibit surfaces that appear stretched.
Ends of soft material fragments are often sharp-
pointed; the ductile nature of the material permits
such a condition.
Each type of debris has been identified as
significant debris or insignificant debris at the
beginning of the explanation of significance to aid
in troubleshooting. Recurring accumulation of
insignificant debris will require overhaul/repair of
gearbox.