Severe Icing in Mountainous Terrain

5 Apr 13 One Comment

This ATC recording with an MU-2 in severe icing is not new but it is new to me and it is incredible. I was on the edge of my seat.

The MU-2 is made by Mitsubishi. It is a Japanese high-wing, twin-engine turboprop. In the US they were assembled and sold by Mooney but they fell out of production in the mid-1980s.

The captain of the plane, Moray Isaac, posted details about the incident in the YouTube comments:

I was the Captain of that flight and would like to add some facts and clear up some misconceptions posted by some. Firstly, I am an ATR rated commercial pilot with 13000 PIC hours in turboprop, turbojet and turbofan aircraft not an owner/operator and had extensive training in the operation of the MU2.

The flight route had reported cloud tops at FL190 and we were cruising at FL230 that night, the aircraft did not have weather radar and we entered cloud, heavy ice and executed a 180 within two minutes of encountering. The anti-ice systems were on and operable according to cockpit indications. We had a tailwind of 70 plus kts and once the turn was initiated the A/C could not maintain altitude with full power, torque and temp limiters off.

We descended into the cloud layer we had been above which further exacerbated the icing problem. The critical problems occurred as the engines failed due to ice ingestion from the prop hubs as we descended into warmer air. The starboard engine failed and was feathered as per emergency checklist… while descending at 4000 feet per minute the port engine failed after and a restart was attempted, but unsuccessful due too severe first stage impeller damage from ice ingestion.

The starboard engine was them unfeathered and restarted, then I attempted a second time to restart the port engine, which was successful. Interestingly, post incident inspection showed cracked bleed lines running to the engine inlets, all cockpit indications showed green, valves open but bleed air was getting dumped overboard which resulted in ice build up on the engine inlets and reduced air intake performance.

Also and most importantly, this A/C did not have the optional pilot selectable ignition modification. It was the only A/C I have flown, and authorized by the MOT and the FAA at the time, to operate in icing conditions without it, if I had that option, the engines could have relit and the emergency would not have become so dire. The company retrofitted the A/C shortly after.

On another note, we descended to 3500 above SL, about 5 to 15 seconds from ground/lake impact and if not for the heroics of two IFR terminal controllers that night, Jim and his brother, who came over from a different sector and helped by transposing the radar image onto a topographical map and directing us over a valley, we would not be here, forever indebted, thanks guys. Also thanks to whoever posted this transcript, and all the encouraging posts from my fellow aviators.

Moray Isaac

My favourite moment is when the controller says they’re clear of terrain at 7 (thousand feet) and then just says “Wow.” He clearly can’t believe it.

Maybe I’m blind, but I can’t find any reference to the incident in the list of Transportation Safety Board of Canada – Aviation reports, despite the fact that it is a declared emergency. It would have been nice to see the details.

I tend to agree with the pilot, though, I think they might have had angels on board.

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