Light Aircraft and Icing
The DA42 recently received its FIKI certification from FAA. FIKI ? Flight Into Known Icing conditions. Happy owners of DA42 equipped with the TKS system can now legally fly in clouds at temperatures below zero. Legally. But would that be a sound decision ?
Ice impact on performance is really strong. My experience of icing is very limited, as all light single engine planes I flew were not certified for flight in know incing conditions, so any ice encounter was unexpected, and quick escape was needed. If none was available, the only way would have been… down.
Jets and turboprops have much better anti-ice and de-ice systems, because their engines have all the extra.power required to melt the ice down, using hot air from the turbines, or pneumatic boots driven by the turbine compressor.
But the sole way to avoid icing problems is to not stay in icing layers. This is exactly what larger planes do. Icing can occur in any cloud when the temperature is below zero degrees Celsius. But if the temperature falls below -15, icing usually stops, except in Cumulonimbus. Jets simply climb high enough to be out of the icing layers.
Why don’t small planes do the same ? Because this requires much power, and the “ice-free” altitudes require turbo-engines and pressurization, or at least oxygen systems. The DA42 has turbo engines, but no pressurization nor oxygen…
I saw once ice forming on the leading edge of an Airbus 320, from Geneva to Zurich. Because this is a relatively short flight, we were flying at 15′000 feet only, the perfect altitude for icing. After a couple of minutes, the layer was so thick that the crew descended a few thousand feet to get out of it.
When I asked the Captain while un-boarding the plane, he confirmed that he descended because of ice, and that both anti-ice and de-ice systems were both running. Conclusion ? Even a plane with two powerful jet engines can’t sustain severe icing for long. So what about a DA42 with TKS ?
Only time will tell…
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2 Comments, Comment or Ping
Jess Sightler
I have no personal experience, but the FIKI piston pilots that I’ve heard from have all agreed that it isn’t powerful enough for prolonged flight into real icing conditions. Having said that, what it did do was to allow them to fly into “known icing” conditions long enough to (legally) break through a thin layer of light icing while climbing or descending to land.
And, of course, it buys you time to get out of a bad situation in some cases as well. My suspicion is that the DA-42s normal use will not tend to lend itself to the types of flights that some other FIKI piston aircraft have been prone to (cf. Cessna 210).
Apr 1st, 2008
PlasticPilot
I agree with you Jess. Climbing through an icing layer is usually not a problem. What can me more problematic however are approaches with long level segments.
Taking Geneva as an example (guess why), coming from the north-east to runway 05 requires to fly about 45 miles at 7′000ft. No way to get down, because of rocks. So if there is an icy layer from 7′000ft to 10′000ft, this would mean approximately 15 to 20 minutes in that. This is probably more than what it reasonably possible, even with a FIKI light aircraft.
Apr 1st, 2008
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