February 2010 - Indian Airforce

The air warriors (including me)
were compelled to compromise on
set procedures and conditions of
work environment to a certain extent
in order to continue with production
and meet the task.
Repair and Overhaul (ROH) of an aero engine is
one of the most challenging fields in aviation industry
involving precision work of very high order and thorough
professionalism. Majority of the aero engine assembly
process and the Micrometry checks (it is the process
of taking measurement of aero engine internal parts/
subassemblies/components, etc using digital scientific
measuring instruments) are required to be undertaken in
a dust free and controlled environment of temperature,
airflow and relative humidity to achieve conformity of
product’s requirements. Universally, it is an accepted
norm that for any accurate and steady measurement of
a physical entity, a controlled temperature of 20 o C + 2 o
is ideal.
Importance of correct working conditions and
environment can never be undermined. I would like
to bring to light two interesting cases related to the
working conditions at a BRD wherein, minute dust
particles (foreign objects) contributed to the rejection
of aero engines during operation/testing. During my
tenure as the Squadron Commander of an aero engine
and Gear Box overhaul line at the BRD we had a chronic
problem in the air conditioning system of the building.
Despite best efforts put in by the MES and C Adm O, there
seemed no solution. To make matter worse, the summers
were approaching and non availability of a suitable
ventilation system with adequate air flow in the building
was to complicate the working conditions further. The
entrance doors to the assembly hall were partially kept
open to avoid suffocation and allow inflow of some fresh
air. The air warriors (including me) were compelled
to compromise on set procedures and conditions
of work environment to a certain extent in order to
continue with production and meet the task.
Case I An aero engine was received for DI with a
snag of overheating marks on the torsion shaft driving
the main gearbox from the aero engine. It appeared to be
a clear case of oil starvation, albeit in the initial stages. As
per SOP, the necessary checks on the oil pump assembly,
scavenge pump, oil filters, flow rate of oil jets, circulation
check of lubrication system etc. was undertaken. All
the parameters checked were found within permissible
limits. Subsequently, the bearing support assemblies
(fourth & fifth support) were also dismantled for signs
of malfunction/blockage and their micrometric checks
were undertaken, which were again within the specified
tolerance limits as given in the repair manual.
After spending close to six days on the Defect
Investigation (DI), I gave up and decided to approach
my boss, “The Chief of Engines” (Gp Capt Mr. Right,
always believed in doing the right things the right way
and, possessed immense knowledge on aero engines
overhauling procedures & processes). After patiently
listening to us and our approach in tackling the defect
investigation, we were questioned about the condition
of the oil jet spraying oil in the affected area. When told
that the jet was functioning normally (based on the
spray obtained from it) he asked us to get it cut open by
the Wire Cutting Machine. All of us were taken aback
as this was the first instance when somebody in the
engine division was asking for an oil jet to be cut open
to view its internal passage. Reluctantly, we took up the
cutting process of the oil jet as advised by Mr. Right. To
our dismay we found a very minute solid dust particle
sitting prettily at the curved portion of the oil passage in
the oil jet (seen using a high magnification microscope).
The dust particle must have entered the lubrication
system during the assembly process of the aero engine
INDIAN AIR FORCE 2 01 0 F e b r u a r y Flight Safety
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