All B737 aircraft in storage in Nigeria to undergo FAA emergency corrosion checks
***NCAA lists danger of effects to airplanes
The Nigerian Civil Aviation Authority (NCAA) has asked all operators of B737 aircraft types to subject their airplanes which have been in storage for a long time to the Federal Aviation Administration (FAA) emergency corrosion checks.
This is contained in a letter dated July 24th, 2020 and addressed to all Boeing 737 aircraft operators and signed by General Manager, AOC & S, Engr. G.G. Balang for the Director General.
The letter with subject, “FAA Emergency Airworthiness Directive (AD) 202016-15,” was sent to owners and operators of the Boeing Company Model 737-300, -400, -500, -600, -700, -700C, -800, -900, and -900ER series planes.
According to Balang, the emergency AD was prompted by four recent reports of single-engine shutdowns due to engine bleed air 5th stage valves being stuck open.
He further stated that, “corrosion of the engine bleed air 5th stage check valve internal parts during airplane storage may cause the valve to stick in the open position”, stressing that if this valve opens normally at take-off power, it may become stuck in the open position during flight and fail to close when power is reduced at top of descent, resulting in an unrecoverable compressor stall and the inability to restart the engine.”
Corrosion of these valves on both engines, according to him could result in compressor stalls and dual-engine power loss without the ability to restart, which could result in forced off-airport landing.
He further explained that the authority had reviewed the FAA AD2020-16-15 vis a vis the COVID-19 pandemic lock-down that necessitated the storage of B737 aircraft and made a determination that compliance with the FAA emergency AD must be carried out by affected operators of Boeing 737 aircraft in Nigeria as required by the AD.
He equally directed that all affected operators should submit evidence of compliance with the FAA AD2020-16-15 to their Principal Maintenance Inspector (PMI) within two days following compliance.
The FAA, it would be recalled, issued the AD because the agency evaluated all the relevant information and determined the unsafe condition described previously is likely to exist or develop in other products of the same type design.
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