THIS is apropos the Safety Investigation Board’s preliminary investigation report published in Dawn’s Jan 12 issue. The report investigating the possible reasons for the crash of PIA’s ATR 42-500 aircraft on Dec 7, 2016 which killed all 47 souls on board has found a serious lapse on the part of PIA and CAA.

The engine manufacturer had issued a service bulletin (SB) which required the engine’s power turbine blades to be replaced on completion of 10,000 hours of use. The engine was under maintenance on Nov 11, 2016 but the blades were not replaced although they had completed 10,004 hours.

Only 93 flying hours after the missed maintenance opportunity, a turbine blade of engine No.1 disintegrated due to metal fatigue and caused an in-flight engine shutdown which led to the crash.

The power turbine operates at a temperature of over 2000 degrees Centigrade and each blade is subjected to several tons of centrifugal force.

The manufacturer therefore notified all operators through an SB to replace them at the prescribed limit.

Such SBs are normally categorised as ‘mandatory’ by CAA and PIA. Crossing the limit renders the aircraft non-airworthy.

In case of an accident, insurance claims for an aircraft which was not airworthy are denied.

All airworthiness authorities, quality assurance and maintenance personnel are aware that ignoring such SBs can be disastrous.

Asif Jah

Karachi

Published in Dawn, February 3rd, 2019