1) the photo at the beginning of this thread: first I also thought about cold fuel in the tank. but the frost is far away at the end of the wing, where I would not expect any fuel; I sometimes saw similar frost on the wings of a glider when flying in the mountain waves (and low temperature). Why this position – could it have something to do with the lower pressure above the wing? I certainly would not consider it dangerous, because in my experience it has never grown beyond a mere temporary esthetic issue.
2) we have heated prop and heated shield and boots on the wings. If an STC was available to change the prop to TKS on our aircraft, we would have gone for it, because in case of one alternator failure, the other alternator may not be enough to support all of the de-icing and other loads – and with TKS, you get the free & full screen de-icing
3) anybody has experience with how much of the de-icing fluid must be sprayed (on average) over a normal GA aircraft (say 182 or 210) to get rid of the ice, which has accummulated on the wings & tail during parking? I am planning some skiing with several overnights parking outside and don’t want to carry the full 20 ltr tank if I would only need…. how much??? for one de-frosting..
thanks for your feedback
JasonC wrote:
No, one should use pitot heat whenever airborne. I have no idea why people would do anything else.
I agree and disagree. I have concluded for myself / and my students / that pitot heating should be ON whenever there is more moisture in the air (i.e. not only IFR flights or VFR with some risk of icing). However, when the air is dry and there is clearly no risk of icing, I prefer to keep all unnecessary bus loads OFF, to keep the batterry drain down in case of unnoticed electrical failure. But I am always looking for improving in-flight risk management and will be happy to hear other suggestions / considerations.
That’s a personal preference, really.
I will only switch it on if it’s cold and if there’s moisture in the air, and of course for every IFR flight that will lead me into the clouds. In dry air that’s not too cold and when I fly VFR, i don’t use pitot heat.
Centurion_Flyer wrote:
I agree and disagree. I have concluded for myself / and my students / that pitot heating should be ON whenever there is more moisture in the air (i.e. not only IFR flights or VFR with some risk of icing). However, when the air is dry and there is clearly no risk of icing, I prefer to keep all unnecessary bus loads OFF, to keep the batterry drain down in case of unnoticed electrical failure. But I am always looking for improving in-flight risk management and will be happy to hear other suggestions / considerations.
I think the risk you are looking to address with this procedure is far less likely than a failure to turn on pitot heat when it was needed or becomes needed during the course of a flight. Hence you are ignoring a serious risk and addressing a very low risk.
That’s a personal preference, really.
I will only switch it on if it’s cold and if there’s moisture in the air, and of course for every IFR flight that will lead me into the clouds. In dry air that’s not too cold and when I fly VFR, i don’t use pitot heat.
I believe it is more fundamental than that. Why not turn it on every flight and then never have to worry about pitot icing?
JasonC wrote:
Why not turn it on every flight and then never have to worry about pitot icing?
What if OAT is +20°? Don’t you risk overheating?
What if OAT is +20°? Don’t you risk overheating?
Does your POH have any restriction on use when airborne based on OAT?
Mine is restricted to two minutes on the ground regardless of OAT. Has anyone here had pitot overheating when airborne?
AeroPlus wrote:
Seemingly the pitot tube had frosted up and the system did not get any airspeed data in anymore from there and thus the indicated airspeed was gone and the DFC90 pitched all the way down to protect me.
I assume your pitot was not blocked immediately but flow restricted so the AP saw a decline in airspeed. My guess is that it would do that if it lost airspeed altogether but instead go into some “unreliable airspeed” mode.
If you block the front of a pitot tube in flight, it will not show a change in airspeed.
To get it to read “low” you would need to divert the airflow from the hole in the front of it while keeping the hole in it open. I guess that is possible with ice.
To get it to read “low” you would need to divert the airflow from the hole in the front of it while keeping the hole in it open. I guess that is possible with ice.
Not only possible but common. Decaying airspeed is the classic sign of pitot icing.
I am yet to see an airplane where the pitot tube is in the propeller slipstream! What would that be good for?
The DFC90’s envelope protection DOES use attitude data. That and the speed.
@ AeroPlus: if i take off for a VFR flight i don’t end up in clouds, right? And in a SEP and in VMC there will never be ice on the pitot tube outside of rain and visible moisture.
I wonder if the heater element will wear out sooner if it’s always on?
