Crash-protected flight recorders

The crash of China Eastern Airlines Flight MU 5735 is deeply saddening. My thoughts are for the families, friends, and loved ones of those who were on board that ill-fated flight.

Watching video that has been circulated in social media the signs are that the China Eastern Airlines Boeing 737-800 dived and hit the ground at very high speed. The aircraft appears to have plummeted more than 20,000 feet in about a minute.

The aircraft crash site is in a difficult to get to location[1]. Authorities in China are searching the hillside looking for evidence as to what happened and recovery of the aircraft accident flight recorders[2]. Given what is suspected to have been a high-speed impact, damage to the accident flight recorders can’t be ruled out. They are made to withstand high impacts but are not invulnerable.

It’s most likely that the flight recorders will be of the solid-state type. This is where memory devices are enclosed in a strong crash protected metal box. So, much of the flight recorder could have severe damage but the recordings inside should be preserved.

On this type of public transport civil aircraft, there are usually two accident flight recorders fitted. One Cockpit Voice Recorder (CVR) and one Flight Data Recorder (FDR). To ensure that they meet rigorous technical requirements accident flight recorders are approved by aviation authorities. The technical requirements for approval are called: Technical Standard Orders (TSO)[3][4].

In both the US and European systems, TSO 123 is applicable to CVRs, and TSO 124 is applicable to FDRs. These two TSOs call up the applicable industry standards of EUROCAE ED-112A, MOPS for Crash Protected Airborne Recorder Systems[5]. This comprehensive technical document defines the minimum specification to be met for all aircraft required to carry flight recorders which may record flight data or cockpit audio in a crash survivable recording medium to be used for aircraft accident investigation.

One of the tests described in this long-standing international standard requires manufactures to shoot a crash protected module into a target at high speed. This test is often done by loading up a large pneumatic cannon, charging it and firing a module at a specially made target. To pass the test the module must survive sufficiently well to replay a recorded record.

So, there is a good chance that the on-board crash-protected recorders of MU 5735 might have survived. Let’s hope so.


[1] https://www.nytimes.com/2022/03/22/world/asia/china-eastern-crash-explained.html

[2] https://www.theglobeandmail.com/world/article-investigators-search-for-survivors-and-answers-after-china-eastern/

[3] https://www.faa.gov/aircraft/air_cert/design_approvals/tso/

[4] https://www.easa.europa.eu/domains/aircraft-products/etso

[5] https://eurocaeshop.azurewebsites.net/eurocae-documents-and-reports/ed-112a/#non-member

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