I didn’t read that very interesting document page by page in detail, pilot_dar, but I wonder what they could be doing that is different from the old “3 heading 120 deg apart and plug the three GPS GSs into the formula” method, which yields an accurate TAS, assuming the wind aloft has not changed during the three legs.
Operating the pitot heat in flight will deice, or at least slow accumulation of ice on the pitot tube. If the pitot tube is not obstructed by ice, the pitot heat will not make any difference in airspeed reading. (If it did, this would be a big problem). A pitot which is blocked by ice in flight may hold the airspeed indication for a while, while the airplane speeds or slows. It will also give a different airspeed reading if the altitude is changed. Though the pilot may suspect an airspeed indication error, as far as pitot heat goes, either the pitot tube is unobstructed, or it’s obstructed. Yes, pitot heat should remove an ice obstruction, but the end result should simply be an accurate airspeed indication, not a variation or error because pitot heat is selected on. Yes, if pitot heat is not working at all, and you ice over the pitot tube, you’re going to have an airspeed error. It is very unlikely that pitot heat is partly working, it’ll either work or not. If you have a faulty connector resulting in resistance in the pitot heat circuit, look out, ‘cause it’s probably getting pretty hot!
As for checking indicated airspeed vs GPS groundspeed, yeah, sort of, but you’re unlikely to detect a small ASI error directly with this means, there are too many variables. You mush also consider calibrated airspeed (position error), and depending upon temp and pressure extremes true airspeed as well. Instrument error is the final variable, though there may be an error correction card for the instrument (when we flight test, we have them done). For flight test following a change to a pitot tube or static port on both helicopters and airplanes, I use the GPS method described in this paper:
I am assuming you mean 60 degres to fly a closed triangles with respect to the ground? (I better speak to someone on the RT before trying that ;) )
Something along that should work for any closed curve that you fly with respect to the ground irrespective of the wind state (at least going A to B and back, should give GS=TAS+W on outbound leg and GS=TAS-W on return leg, so the average GS should be TAS)
The general resoning can hold even on variable wind as long as there are no “source of wind” inside the closed-loop (for the full formula you refer to this?
https://en.m.wikipedia.org/wiki/Stokes%27_theorem ;) )
I think even if you fly a random path, you should be able to derive TAS from poistion & GS only assuming you stay at the same hight or from position, GS & VSI (or total energy VSI) assuming you have some changes of hight
Sure; the standard ASI calibration procedure is flying three legs, 120 deg apart, and the average of the three GPS ground speeds gives you TAS, and then you back-correct to IAS using the altitude, temperature, QNH… The full formula is more complex but for light winds aloft it is just an average of the three.
Form 214 before flight and real time data to SD & windy (works up to 6000ft tough)?
If you can fly rate 1 turns while watching your GPS ground track there is a way to derive W/V from the number/direction of circles it takes you to get out of the first circle (for advanced stuff XCsoar have a code that derive wind from GPS track and GS only irrepective of the regularity of the turns, it is called ZigZag wind calculation as the name suggest you have to do random stuff for the algo to work…)
you can get you IAS from GPS ground speed
Would need nil wind also 
@Pilot_DAR assuming you fly level, you can get you IAS from GPS ground speed, wind and density altitude down to instrument calibration errors (+/-5% ?) or from power and density altitude given POH data and you know how far that aircraft is from those numbers (+/-30% ?)
Large deviations from those estimmates probably indicate issues with pitot tube (or airframe), in my case I was expecting 120kts ASI that did read 80kts with +/-10kts rapid fluctuations (there was no icing but few rain around), pitot heat was ON in the air but it was not working: on the ground it was just cold…
As mentioned, unless it is capable of getting very hot, it’s not going to be much use in anger.
If there was a poor connection that may affect performance.
If a battery is in good condition there should be zero risk of leaving the Pitot heat on to check it gets hot, not just warm.
When I check ours, it’s done in isolation to other checks. The switch goes on and I check it constantly, waiting to ensure it will get too hot to hold…… I dont actually wait to that point, but close to it.
It’s quite obvious by the rate of change toward the end of the check.
This will not damage it. If it would, that would be a really daft design.
It’s out of propwash and would be turned on before take off, any delay, extra check or ATC hold would not and should not require me to remember to lean down and turn it off.
Once I’m happy it works well, subsequent checks, over the next weeks/months will be the usual ‘is it getting warm’. Unless of course I’m definitely expecting to enter cloud, then it would be a ‘big’ check again.
In 18 years, I’ve never flattened a battery this way.
Ibra wrote:
How one does check the pitot heatIt’s part of the daily preflight check on our PA28s.
It warms up to really hot if you wait, but you usually don’t wait that much so as not to drain the battery…or fry the heating element. The pitot heat is set to be hot enough at cruising speed, one the ground it gets too hot to touch.
one method that would work … is comparing ammeterThat’s actually how we check the alternator is working. At idle on the ground the pitot heat is the single largest electric load you can easily turn on and off. The needle moves more than a little.
Ibra wrote:
Probably the only reliable alternatives are from aircraft attitude/power performance
??
On the other hand, on digital ones (e.g. on a G1000, which shows battery current with 0.1 A resolution) it’s very obvious.
Yes, provided you understand how the ammeter is wired into the electrical system, and interpret the indication in the context of how it’s wired. Pages 4 and 5 of the Electronics International manual below describe the different ways to wire a digital ammeter in, and how to operate it depending on its connection. Understanding this will assure that a “no indication” on a digital ammeter is not mistaken for a non functioning electrical consumer, because the observer is misunderstanding the wiring.
