@Peter
Thank you! That’s exactly what would be interesting, a description of how they’re using it.
It really may be overkill for a Rallye, my money better spent on dual with a curmudgeon flying into one-way 300 meter strips at 8000 feet with century old conifers at one end and a cliff at the other.
The way I think I would use an AOA is cross checking it against various configurations, dirty, clean, light, at MTOW, slats in and out, and in various degrees of bank & then fly using it rather than airspeed. The idea of having a simple indicator that shows AOA at all weights, configurations and banks is appealing to me. But it might be just another gadget, and I would be better off just learning to fly the plane within its envelope.
It’s interesting how some gadgets you come to love (engine monitor and the magenta line) and others you can do without. AOA is which for those who have it?
WhiskeyPapa wrote:
Does EASA permit installation of these systems in legacy aircraft? For example, could I put a Bendix King or AlphaSystems AOA indicator in the Rallye without undue cost (in addition to cost of unit, labor and VAT)?
Yes. It is covered in CS-STAN.
Does that include ice protected AOA products?
As per discussion earlier in this or the other threads, AOA indicators have basically two uses: at low level (approaches and landings) and at/near the operating ceiling. Both are high-AOA regimes. The former needs ice protection in the winter and the latter needs ice protection virtually always.
WhiskeyPapa wrote:
The slats come out & that’s it? That’s as high as you want or should risk AOA?
Of course not, you use them in combination with the airspeed indicator: you check at what airspeed the slats come out (which depends on aircraft weight), and then you adjust your speed to X knots above/below that point. The value of X should be determined empirically, and researching it in a Rallye is a fairly simple but extremely edicational exercise. Prepare an empty table with columns corresponding to a number of different airspeed values across the range of your interest (say, 2 kt apart) and rows corresponding to different engine RPM from idle to full thrust. Make sure this airspeed range includes all of your characteristic speeds, including best glide. Then go high enough (say, 3000 ft AGL for safety’s sake) and fill the table: set a given RPM, trim to a given airspeed, and record your vertical speed in the corresponding cell of the table. Retrim to a different airspeed, record your vertical speed again, etc. Don’t forget to note the slats-out speed itself. Then set the next RPM value from the table and repeat the series of measurements at different airspeeds. If you are not confident enough, take a safety pilot with you. Once you are back on the ground, convert the absolute speeds in the table to differential speeds (positive or negative) from the respective slats-out speed. Now, if you fly at a different weight, your slats-out speed will change, but this differential table will still be valid! (Actually, it won’t be exactly the same but the deviations will be quite small). From this table, for each airspeed you can get the RPM at which your vertical speed / sink rate approaches zero. The zero-sink RPM will be the lowest at your best glide speed, and will increase as you go further above OR below the best glide.
If you wish, I can get to LOAN some time in June and we’ll do it together.
@ultranomad
I may take you up on that…
Probably late June-early July. Plane is getting its 50 hour, then to LHTL for avionics work (8.33 radio, audio panel, G5).
@WhiskeyPapa, sure, drop me a line once you get the work done.
@Peter,
I suspect that there’s not much point in having a heated AoA probe unless you also have an effective airframe de-icing system – because airframe ice may affect stall AoA.
P.S. I have an AoA indicator for my Maule, but haven’t fitted it yet. I probably will in the next 6-8 weeks.
I suspect that there’s not much point in having a heated AoA probe unless you also have an effective airframe de-icing system – because airframe ice may affect stall AoA.
That could be, although I suspect the AOA probe will need ice protection just as much as the standard pitot tube, which is universally protected on most certified planes, even ones not certified for IFR. And the vast majority of certified GA planes don’t have overall ice protection, but still “work” well enough.
The problem is that ice will accumulate on these protruding items even in light IMC or even in VMC, when you get none on the airframe.
But I am speculating; I have not read any real-life accounts which contained any detail.
Peter wrote:
The problem is that ice will accumulate on these protruding items even in light IMC or even in VMC, when you get none on the airframe.
So why you do not install a Heated AOA Pitot.
Look up “certified aircraft”, ACRO.
