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An AS 9100C and

ISO 14001-2004 Company

xnix Bx]C ]bHINDUSTAN AERONAUTICS LIMITED

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As a way forward Russian side has proposed 20 recommendations (11 for

Manufacturing and 9 for Exploitation) after Joint Investigation was carried out

along with Indian side. Recommendation is given for modification of Inter Rotor

bearing (Part No: 5-272822P2Y) with improved cooling of the Bearing byintroduction of additional Lubrication oil supply holes.

Indian side is of the opinion that this recommendation is a short term solution

to the Bearing failure problem. Other critical design aspects such as Material

characteristics of the Bearing races and Rollers, Micro-structural changes leading to

plastic deformation during operation, Material erosion and Load characteristics need

to be introspected and validated.

Preliminary findings/Analysis of the Cat-A Bearings vis a vis failed Engine

Bearing reveal the following:1. Inter-shaft bearing (55-2672919P5):

a. Abrasive wear and moisture corrosion observed on raceway withdiscoloration of outer ring.

b. Plastic deformation of inner ring with discoloration and abrasive andadhesive wear on raceway.

c. Crack initiation on almost all cage pockets.d. Spalling observed in cage pockets at roller contact.e. High ovality noticed on inner and outer rings.f. Signs of overheating seen with micro-structural changes leading to

deformation.

g. Hardness profiles of outer ring showed low hardness values fromraceway to core rather than from outer diameter to core which

confirms heat generation is high on raceway compared to outer

diameter.

2. Inter-rotor bearing (5-272822P2Y):a. Outer ring and inner ring raceways shows false brinelling marks, spalling

and plastic deformation. Also fretting and micro cracks were observed

on one side of face end of outer ring.

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