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Aircraft Storage Lead to New Issues

Aircraft in storage in May. (Photo: AirlineGeeks | Ryan Ewing)

The COVID-19 pandemic has forced airlines around the globe to put thousands of aircraft into long-term storage. As demand slowly returns, these aircraft will be brought back into service. Both the process to store and return an aircraft to service is a laborious one. Through inspections are required of the stored aircraft, and with an unprecedented number of aircraft stored, issues are likely to arise. 

The FAA has issued an emergency airworthiness directive for inspections on Boeing 737 Classic and Next Generation aircraft. The issue may cause an engine to fail inflight and be unable to restart. The inspections will affect around 2,000 aircraft, mostly aircraft that have been in storage or recently returned from service. Boeing is providing support to aircraft operators that find the issue with their aircraft.

The emergency airworthiness directive was ordered after four incidents of a single-engine failure. Upon landing, the affected aircraft were found to have an aircheck valve stuck open due to corrosion. The valve would not close when the aircraft reduced power for the descent. This would then cause the engine to suffer from irrecoverable compressor stalls and render the pilots unable to restart the engine. 

Airlines need to inspect aircraft that have not flown within seven consecutive days. This effects aircraft that are returning to service after being stored for the ongoing COVID-19 pandemic. The valve becoming stuck due to corrosion is an issue to which stored aircraft are more susceptible.

Alaska Airlines Incident

It appears that one of the four cases of the engine failure was an Alaska Airline Boeing 737-800 descending into Austin on July 15. During the flight, the aircraft began its descent into Austin when the crew reported an engine failure. The crew made a successful landing at Austin after attempting to restart the engine. The aircraft had not flown for six days prior to the incident flight and required the engine to be replaced in Austin.

In rare instances, the corrosion issue can affect both engines. However, no incidents of dual engine failure due to the valve have been reported. The introduction of inspections of the valves will likely catch the corrosion before an incident can occur. The inspections have not been issued on the maligned Boeing 737 MAX aircraft, which is currently going through testing and certification to return to the skies. 

In the U.S., Southwest Airlines operates the largest fleet of Boeing 737 aircraft. For aircraft that have already been returned to service, they will only have to be inspected if they are within the first 10 flight cycles from returning to service. If corrosion is found in the stage check valve, it will need to be replaced before the aircraft is deemed airworthy again. 

Pandemic May Send Aircraft Back to Storage

Airlines had been slowly returning aircraft to service after the dramatic drop in passenger demand due to the COVID-19 pandemic. However, a dramatic increase in cases in the U.S. has caused travel demand to level off.  In the future, airlines may have to put aircraft back into storage if demand continues to remain low. American Airlines and Southwest have announced that they will be adjusting their flight schedules due to a drop in demand from the increase in COVID-19 cases. 

If aircraft are returned back to storage, airlines may see an increase in mechanical issues. Most commercial aircraft require multiple inspections per month to remain airworthy. They also require their systems to be used to ensure they are functioning properly. Aircraft maintenance may become the newest surprise of the COVID-19 pandemic as airlines and aircraft navigate never-before-seen situations. 

Daniel Morley


  • Daniel Morley

    Daniel has always had aviation in his life; from moving to the United States when he was two, to family vacations across the U.S., and back to his native England. He currently resides in South Florida and attends Nova Southeastern University, studying Human Factors in Aviation. Daniel has his Commercial Certificate for both land and sea, and hopes to one day join the major airlines.

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