Federal Aviation Administration (FAA) of the United States on Tuesday announced that it had issued an emergency airworthiness directive regarding certain Pratt & Whitney PW4000 engines.
Titanium Blades to be inspected
Following the United incident which resulted in someone’s Colorado-garden becoming a modern art installation (fortunately without any injuries), the FAA issued a directive which requires operators with airplanes equipped with these engines to inspect them before further flight.
The agency said that it had reviewed all the data from Saturday’s incident, where a United Boeing 777-200 suffered an engine failure shortly after take-off from Denver.
Combined with other safety factors, the agency has determined that airlines have to conduct a thermal acoustic image (TAI) inspection of the large titanium blades at the front of the engine.
Boeing had already recommended grounding of the 777s that are equipped with PW4000 engines almost immediately following the incident. The specific type of engine is fitted on 128 earlier generation Boeing 777s. Out of these, 52 are with United Airlines, with close to half already being parked due to the ongoing COVID-19 pandemic.
The rest of the affected aircrafts are with All Nippon Airways which has 22 out of which half are in storage, Korean Air which has 16, Japan Airlines which has 13, Asiana Airlines which has 9 and low cost Korean carrier Jin Air which has 4. All carriers except Jin Air has voluntarily grounded the aircraft in question.
Engines included in the emergency Airworthiness Directive are Pratt & Whitney Division PW4074, PW4074D, PW4077, PW4077D, PW4084D, PW4090, and PW4090-3 model turbofans with specific types of low-pressure compressor blades installed.
Results to be reviewed on a rolling basis
The Airworthiness Directive is effective immediately upon release and the FAA says that it will review the results on a rolling basis. The usual inspection interval for these engines is every 6,500 flight cycles, meaning one take-off and landing.
Thermal acoustic imagery can reveal cracks on the blades’ interior surfaces, which would not be detected during a visual inspection. It uses a short burst of high-power ultrasonic energy in the 20KHz range to excite a part and then monitor it with a thermal camera. The method ‘heats up’ potential cracks and makes them visible in the infrared range.
Featured image by InSapphoWeTrust via Flickr
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