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Aircraft with specific icing vulnerabilities

There is a number of these around. Sometimes the POH mentions it, sometimes not.

The TB20 engine will stop at -15C in IMC – evidenced here. Alternate air (definitely) and propeller TKS running (very probably) protect against it.

The DA42 gets a dual engine failure also at -15C. I know a pilot who got this, and I believe he posted it here, but I can’t find it right now. Probably the same cause as above, and alternate air protects from it, per the POH.

The Aztec gets strange engine failures at low temperatures. Here one owner reports a reliable single engine failure at -20C. Here is another report of a reliable right engine failure at -20C. These pilots use a fuel additive to guard against this. I don’t know if the POH mentions this vulnerability. It is very strange because it is not related to IMC, and avgas freezes at -58C.

The SR22 has had strange failures, probably fuel servo icing again, e.g. here. That incident was inconclusive; the aircraft was sold immediately afterwards.

I met a pilot of a Baron who got a dual engine failure at FL250, in VMC, which he was sure was fuel icing. Both engines restarted at 2000ft. He sold it immediately.

Any others?

We all hear about carb icing in PPL training but fuel injection is not a complete solution. And alternate air reduces power quite a bit; the operating ceiling goes down maybe 2000ft so if e.g. climbing over the Alps one may need to do the whole climb in VMC.

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

The Aztec gets strange engine failures at low temperatures. Here one owner reports a reliable single engine failure at -20C. Here is another report of a reliable right engine failure at -20C. These pilots use a fuel additive to guard against this. I don’t know if the POH mentions this vulnerability. It is very strange because it is not related to IMC, and avgas freezes at -58C.

I spent years trying to beat this one. I think that it’s the positioning of the gascolator and associated filters on the right cowling in the airflow, but I really don’t know.

As IPA from eBay costs the same as Avgas, it seemed harmless just ro add 1% all year round and be done with it.

EGKB Biggin Hill

I think for the DA42 (at least) the problem is one in IMC, or do you mean in the clear too?

I’ve flown 3 of the same flavour (the old one unfortunately, not the NG or the VI, which I had never the pleasure to fly), and can’t recall having issues in the clear. At some point, I started turning on alternate air every time flying on very low temperatures just so I didn’t forget in case of entering IMC, but I think there might have been a couple trips where that wasn’t the case, and never had an issue.

The DA42 issue is in IMC, like the TB20 which I have had down to -37C in VMC with no issues.

Re the Aztec issues, I cannot understand how avgas can freeze at -20C. There must be water in it; maybe water accumulated somewhere. Or the issue is elsewhere and not related to the fuel itself – like the TB20 one which is not related to fuel at all.

Administrator
Shoreham EGKA, United Kingdom

I suspect @Pilot_DAR may have something to say on this subject.

LKBU (near Prague), Czech Republic

Not GA but the whole Fokker 28 series (including the -70 and -100) as well as all the CL600 series Challengers without wing slats are very dangerous with regards to icing on the ground. De-Icing there is absolutely necessary at the slightest onset of contamination on the wing. There are several well known accidents to prove this unfortunate tendency, the worst I recall was the total loss of a Fokker 100 belonging to Palair Makedonia in the 1990ties. That particular one hit very close as I knew all three cockpit crew from interacting with them on previous and the actual job. That plane was flown by the chief pilot and instructor F100 from AFT themselves who was training a very experienced Makedonian captain and they had a Swissair Mechanic as backup. The Fokker instructor and the Swissair Mechanic prepared the flight and the captain only arrived at the last minute out of reserve (all of them were in training at the time) and were told de-icing had been performed/was not necessary. Unfortunately he took their word for it, killing all 83 on board when the plane failed to get airborne and crashed. Another example of a top shot pilot failing miserably in what should have been very unambigous conditions.

The Fokker has had some other notables in similar conditions, one at Dryden, Canada and one at Pau, France which I remember off hand.

Challengers have come to grief at Birmingham and somewhere in Russia which I remember just now, but there were others too.

A plane which is very dangerous in icing during flight due to inadequate de-icing equipment on the airframe together with aerodynamics of the wing is the ATR series. There were at least 3 accidents which were caused by in flight icing and sudden loss of control, one at Roselawn USA, one near Como IT and one in the Carribbean. I flatly refuse flying on ATRs in anything but VMC conditions. I knew one of the Italian crew who had transitioned from the DC9 to the ATR shortly before the crash.

LSZH(work) LSZF (GA base), Switzerland

I think you are referring to engine limitations at very low/high temperatures these will probably less documented in POH unlike air-frame or propeller icing which probably have a very through certification testing?

Last Edited by Ibra at 31 Oct 15:21
Paris/Essex, France/UK, United Kingdom

What I don’t get is why there are any issues with avgas fuel systems, well below the freezing point of avgas.

There simply should not be any at all.

Do fuel servos contain poorly toleranced components which seize up at -20C? I don’t think so.

And if adding IPA protects from some issue, it must be that there was water in the fuel.

Administrator
Shoreham EGKA, United Kingdom

Extra 400. I once had the engine stop (actually windmilling) at FL180 in clear blue skies. Minus 15 degrees.
I had previously flown through very wet clouds in the climb, but this happened at least 15 minutes after I had exited into VMC.
I made an emergency landing, spent one miserable day trying to figure out what had happened and concluded that it was air filter icing and I should have pulled alternate air.
The reason for not doing it was that I made the wrong diagnostics:
I had previously had an engine stoppage due to a disconnect of the turbo to intercooler duct ( a common issue in this type) and the symptoms were identical.

So I am maybe 90% sure that it was air filter icing, but not 100%.
As Peter says: most people wait until they’ve sold the plane to disclose its issues. Not my mindset. This can save lives.
Since then I always stay on alternate air for a long time after exiting icing conditions…

LSGG, LFEY, Switzerland

Peter wrote:

What I don’t get is why there are any issues with avgas fuel systems, well below the freezing point of avgas.

Because water is in the fuel and can come out of solution and freeze well above the freezing point of the fuel itself.

EGTK Oxford
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