AoA is hardly a new innovation in GA. The Cessna 425 Conquest from the early 1980s had an AoA indicator.
Six years on, and l still regularly use my Jetprop installed Aspen derived AOA for landing on short runways.
It makes a significant difference to my approach speeds giving me the confidence to approach slower than l would otherwise. In practise the ASI becomes irrelevant when you use the AOA.
Infact l just used it on my previous landing at my home airport earlier today.
I am really surprised it is not standard equipment on high performance GA aircraft. It should be.
E
After the euphoria of some years ago (see this thread) the whole AoA indicator scene seems to have died. It was thus interesting to see this “advertorial” from US AOPA (see at 17:00 onwards)
Peter wrote:
Has anyone here installed an AOA sensor?
I have the Aspen one and it works well at high or low altitude. However, it indicates from an algorythm based on static&dynamic pressure (IAS) plus acceleration as measured in its AHRS and GS from the GPS , so it is rather theoretical (but so is attitude, at least partially, on the Aspen). It is probably just a derivation from the algorythm it uses for attitude. It still needs your pitot and static ports to be working, I think it might also work on an iced up wing but have not tested it.
The ones measuring pressure differential should work as well, but I would not worry so much about altitude as about different IAS (ie very wide weight ranges and accelerated stalls, on which the Aspen seems to do fine).
As you say the vane ones are the most accurate as they indicate either the relative wind angle (high-end version) or the position of the stagnation point on the wing (which is also a measure of the same). Were it not for the TKS panels, perhaps it would be possible for you to install a secondary advisory heated AOA vane on your leading edge as a minor mod, as long as you do not eliminate the OEM one.
Let’s look at these AOA sensors from a different angle.
The TB20 TKS system has an unheated stall warner. The certification route for replacing this with a heated one is likely to be complex. I wonder if a heated AOA sensor would work well enough? Taking the FAA (I am N-reg) concessions for AOA sensor installation, and assuming the heater wiring is a Minor Alteration (it should be), this ought to work.
One issue I see is that, as per my various previous posts, I was never able to establish whether any of these products actually work at high altitude. The AOA sensors on jets use a physical rotating vane (heated) which will obviously work, but all the “GA” sensors measure AOA indirectly by sensing the pressure difference between two holes. The manufacturers I contacted would not discuss this topic.
Has anyone here installed an AOA sensor?
As I posted here a long time ago, I looked at installing one of these to hopefully make it easier to climb to the operating ceiling, but none of the manufacturers were willing to discuss high altitude operation or indeed whether it works usefully at all.
The calibration is done at low levels and there seems to be no barometric input. The AoA is derived indirectly so I wonder whether this works.
The AoA sensor on a jet like Jason’s is normally a rotating vane which reads the airflow angle directly.
PetitCessnaVoyageur wrote:
Jason, while keeping AoA at .35, can you tell us how the pitch and the indicated speed move, during the climb up to the ceiling ?
Mine is probably not terribly relevant to lighter GA. But let’s say starting at 10,000 feet, would be a 20 degree nose up (it will go up fast like that) coming down to 5 degrees. My IAS will gradually drop from 220 to say 145 if I flew it all the way to the ceiling.
I googled different terms (added “using”) and found some better documents, e.g. here
Numbers seem to coincide with Jason’s post, pointer a 3 oclock (0.6) for approach. The advantage is that it’s intependent of weight / flaps configuration.
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Thanks Jason. I had planned to go flying and take some better pictures (and have a better looked at it) but the weather wasn’t good yesterday.
@JasonC wrote:
In the climb I can also now climb slower as the plane is faster to accelerate at the top so i can if I need best rate, fly the plane in pitch mode keeping a constant AoA of .35 on the dial.
Jason, while keeping AoA at .35, can you tell us how the pitch and the indicated speed move, during the climb up to the ceiling ?
