ATSB (Australian Transport Safety Bureau) report into a M20J in-flight fire resulting in a subsequent fatality

[Mooney in Oz]

Although the below accident resulted in a fatality in Australia, I thought I should post the details here for the information of all Mooney owners, particularly J or M owners to check with your mechanic as to the condition of the O-ring seal of the engine driven fuel pump outlet fitting.

Particularly those whose engines and fuel systems that have not been overhauled for many years or aircraft that have lived outside for many years resulting in O-ring deterioration. 

Yes, this humble O-ring can cause an in-flight catastrophe if allowed to deteriorate to the point of leakage.

Today, I received an email Safety Advisory Notice link from the ATSB regarding the crash of a M20J on 17 October 2022 at Luskintyre NSW. During flight, a fire started in the engine compartment resulting in the pilot attempting to land at the airfield. He could not make the airfield and landed in a field just 300 metres from the runway, colliding with trees resulting in a catastrophic fire. Sadly the pilot died from his injuries 10 weeks later.

Upon receipt of the email, I immediately called my mechanic who advised that he checks this O-ring for condition and leaks using pressure from the electric fuel pump at every annual.

Please ensure your mechanic does the same. 

The Safety Advisory Notice link - https://www.atsb.gov.au/publications/safety-advisory-notice/2024/condition-replacing-o-ring-seals-age-catches

The full ATSB report - https://www.atsb.gov.au/publications/investigation_reports/2022/aair/ao-2022-049

Both are well worth the read.

[exM20K]

Some owners are unconcerned with burn test tags on interior materials. I used to be, too, until I had a chafed line drop burning insulation on the Pep Boys floor mats I had in my 231. Never again.  I’m glad the ATSB noted the interior renovation and lack of burn tags, and I’m of course saddened by the loss of life in what must have been a terrifying final few minutes.

-dan

[GeeBee]

I've always said if armageddon ever happens it will be causes by a failed o-ring or a bad micro-switch. The two nemesis of the mechanical world.

 

[PT20J]

There are other possibilities besides the o-ring being old. That fitting is used on Lycoming fuel pumps to allow clocking the connections. It uses a jam nut against a washer to compress the o-ring to make a seal. According to the Parker o-ring ehandbook, the o-ring is permanently deformed in this type of application and should not be reused. So, if the fitting was ever loosened or removed and reinstalled, the o-ring should have been replaced. According to Lycoming SSP-1776, a straight thread 0-ring boss fitting size 9/16-18 should have the jam nut torqued 23-24 foot-lbs. That's a lot of torque and it's possible that someone didn't tighten it enough.

[N201MKTurbo]

I agree. All the o-rings from those fittings look like the pictures from the report. If you put a brand new o-ring in and torque it down it will look like that. If the leak was coming from that fitting, it was because it was loose, not from an old o-ring.

The report said the engine was installed on that plane recently. If it was leaking from that fitting, I suspect it was an installation error.

Why anybody would install an 1800 hour engine in a plane seems strange to me BTW.