All US operators of the Airbus A220 are required to update the software of the electronic engine control (EEC) system of the Pratt & Whitney PW1500G. The FAA has issued an Airworthiness Directive dated December 27 that prompts action after an A220 suffered a dual engine shutdown on landing. It is expected that the AD, which becomes effective on January 31, will be adopted by EASA and other regulators soon. PW1500 needs software update after dual engine shutdown.
The AD follows an FAA Notice of Proposed Rulemaking in October, shortly after the A220 of an unidentified operator was involved in the uncommanded dual engine shutdown upon landing. As engine power and power to the hydraulic systems were lost, braking capability was significantly compromised.
“A subsequent investigation determined that the sequence of the auto-throttle increasing throttle to maintain Mach number, immediately followed by pilot command to decrease throttle to idle, caused a transient disagreement between actual and commanded thrust. This disagreement triggered the thrust control malfunction (TCM) detection logic and resulted in dual engine shutdown once the weight on wheels signal was activated upon landing”, the FAA AD says.
It adds: “The installed EEC Full Authority Digital Engine Control (FADEC) software version latches the fault and allows the engine to continue operation as commanded but shuts down the engine upon landing.”
The FAA notes that P&W has identified the situation that could trigger a fault in the TCM logic and has come up with a software update. “This software update makes corrective improvements to the TCM logic, including revised criteria for triggering the TCM logic and establishing criteria that permit the TCM logic to unlatch during flight.”
The AD addresses the PW1519G, PW1521G, PW1524G, PW1525G, and various sub-versions. The software upgrade should take no longer than two hours to complete. The FAA says that there are 147 engines installed on US airplanes. On November 30, there were 238 Airbus A220-100s and -300s delivered to customers.
As reported before, the PW1500 has been suffering from reliability issues before, although of a completely different kind. Air Tanzania said in November that its flight schedule was severely disrupted because of engine checks and inspections required under ADs. These checks also affect the PW1900 that powers the Embraer E2 family. Dutch website Luchtvaartnieuws reported that KLM Cityhopper’s E195-E2s require more downtime for inspections too.
Active as a journalist since 1987, with a background in newspapers, magazines, and a regional news station, Richard has been covering commercial aviation on a freelance basis since late 2016.
Richard is contributing to AirInsight since December 2018. He also writes for Airliner World, Aviation News, Piloot & Vliegtuig, and Luchtvaartnieuws Magazine. Twitter: @rschuur_aero.