PetitCessnaVoyageur wrote:
For the first time I hear about DA42 induction icing. Is there design prone to that ?
The DA42 manual calls for opening the alternate air for flight in icing conditions.
JasonC wrote:
That isn’t true at all.
My post isn’t clear. By aircraft design, I mean to include icing-conditions procedures, such as activating alt air when in below-zero air (there is CFI, Dick Rochefort I think, who is preaching for that around youtube).
In that way, the PA46 seems to be able to routinely cope with icing conditions, with no/few stories of engine shutting down due to icing conditions, if correctly managed.
On the contrary, Peter explained to us that using alt air all the time wasn’t for him a good solution, because induction icing could still happen, and he would then be hopeless.
So, including icing procedures, I wondered which types could be considered as generally immune from induction icing, which not.
Of course my examples can must be argued !! 
PetitCessnaVoyageur wrote:
- the PA46 seems to be rather immune from air induction icing.
That isn’t true at all. I always flew mine on alt air any time I would be flying with a below-zero OAT. The filter is well know for icing up.
Peter wrote:
In any practical non turbo installation there is bound to be a temp rise from the air inlet onwards.
@Peter, the informations you fed were actually hard to argue with :-), but Stephan is equipped with a turbocharger, so that may not apply directly.
This let us think again about the Aeroplus incident.
If I remind correctly, he had a high altitude loss of power (but not an engine shutdown) around FL210-230, while the wings were clean, and retrieve the power later on, around 5000ft. In between, the “ALT AIR OPEN” appeared on the PFD, but we don’t know if the power immediately came back after that. Maybe, in the end, was it an induction icing too ?
Apart from the presence of a turbocharger, the aircraft design seems to have an important role.
From examples/reports I have read here so far:
- the PA46 seems to be rather immune from air induction icing.
- SR22 really don’t like it
- AZTEC don’t much (Peter had a good story I think)
- I also remember about a Baron pilot, Peter knew about, would sold its aircraft after a double engine failure, related to induction icing, with a low-altitude-over-cold-water restart.
- For the first time I hear about DA42 induction icing. Is there design prone to that ?
- @achimha ‘s T182RG high flights, in icing condition, didn’t lead to any induction icing so far.. Could you confirm and tell us if it is a manual alternate induction you have, or an automatic gate ?
- TB20 may have a very very slight kind of little problem here, but it removes nothing to its excellent qualities , and more important, this could be cured by the use of prop TKS.
It seems that a lot of SEP/MEP types are prone to induction icing.
Of course, all these are case reports, so I don’t pretend to draw rules, but we are collecting quite much information here, about a remote problem barely known about !
I wanted to keep that out of the conversation for focus but now that you’ve asked:
Up to that flight I had not been really high. The highest so far was FL150. I was flying on cannula. There was an earlier need that brought me to FL190. I thought about going higher but was afraid of the O2 saturation on cannulas. Yes, I do have the monitor to measure O2 saturation on the finger and I do use it but still.
So my train of thought was to monitor the situation and climb out of it to probably FL210 or a bit higher, if needed. Sometimes the blue sky was visible through the thin layer. What held me back was the fact that I was on cannula without the real mask available. I did remember eg. Peter’s posts here about cruising FL200 on cannula.
As the descent was coming up the issue resolved itself.
The question for me is: why were you flying in IMC in the first place, if it was just a “thin cloud”?
Right, Flyer59. I’ve seen that door and it got checked also during the last maintenance action.
It appears that we all agree that the air filter was clogged up / iced up but because everything was already frozen / glaciated nothing stuck on the wings or the windshield.
It was a “get out of here” situation as well.
AStefan, from the SR22 Maintenance Manual (in case it interests you)
In the case of filter blockage, or induction ice, alternate air can enter the engine via the alternate air assem- bly. A tube from each air box leads to the alternate air assembly at the front of the engine. A blast tube con- nected to the heat exchanger provides heat to keep alternate air assembly flap from freezing. Under normal conditions, the alternate air assembly flap is held closed by a strip of magnets. When the air flow decreases, a vacuum is created that overcomes the pull of the magnets and allows the flap to open. After receiving a signal from a switch mounted to the alternate air assembly, the PFD will display “ALT AIR OPEN” in a yellow caution box.
Was that a diesel-engined DA42? Perhaps that’s a silly question, I’m not sure there’s any petrol-burning DA42’s around. But it seems obvious to me that a diesel will be less prone to icing – probably your customer got over-confident from thinking the same. Surely the only delicate point for a diesel can be the air filter? Or perhaps something in the turbo, I know nothing about those.
Since then I’m thinking about it. I tend to believe that the air filter did ice up. But why was there no other ice anywhere else?
At least in our PA46 that is typical. If the wing ices up in fact it is not even worth bothering with the alternate air. But then there is this very thin cloud which ices up the air filter but leaves no trace on the airframe.
But the details will depend on the aircraft. I just sold an ADL120 to a customer who though convective weather is harmless until both engines of his DA42 iced up badly so he was not able to maintain altitude. From now on he wants to fly around the weather. So the DA42 and the PA46 seem to behave quite differently when it comes to induction icing,
