Gmonnig
Pre-takeoff checklist
Anyone use the AV20S primarily as an angle of attack indicator? I’m curious how accurate it can interpolate the AoA by using just pitot/static inputs.
AV20S AoA function?
- Thread starter Gmonnig
- Start date
jbDC9
Pre-takeoff checklist
I installed an AV-20 as a backup attitude indicator for the dual G5s in my RV-8; it works well as an AI, but for AOA, I’m not impressed... perhaps I need to play with or study it some more, but for now it just doesn’t seem very useful.
What did you do to set the hi/lo range?
For me I flew at high cruise speed, reset the tell-tales, performed a power-off stall and then set the range to the tell-tales. The high range seemed a bit too high so I backed that one off a couple of clicks.
jbDC9
Pre-takeoff checklist
Ah man, it’s been 5-6 months since install, don’t remember that stuff. One of these days I’ll break out the book and try another calibration on it, see if it helps.
Gmonnig
Pre-takeoff checklist
I guess I'm just interested in how accurate it is. I don't "need" anything for my plane since it's loaded with avionics but trying to find myself a Christmas gift! The Comanche is very speed sensitive on landing, especially at different weights.
David Megginson
Pattern Altitude
I can't tell you from personal experience, but a basic limitation of any "probeless" AoA system (really, just a computer simulation of AoA) is that it will over-read in a downdraft or under-read in an updraft. In their FAQ, uAvionix estimates that in a 1,000 fpm downdraft (an extreme case) at typical light-piston speeds (they don't give an exact TAS or IAS), the AV-20 would indicate an angle of attack 5.6° higher than what it really is, so it would mistakenly claim that you were closer to the stall. Conversely, in an updraft, it would indicate an angle of attack lower than the actual one, so it would mistakenly claim that you were further from the stall than you really were. This same error should apply to the Aspen E5 or any other devices with so-called "probeless" AoA.
uAvionix's AV-20 FAQ downplays the operational importance of these errors, of course — you'll have to make up your own mind on that. I think it's important to remember that if there's not a physical probe, it's not real AoA but just an advisory/educational tool, and you probably shouldn't use it to fly close to the edge of the envelope the way a military, aerobatic, or STOL pilot would with real AoA. It will be right almost all the time, but when it's wrong, it could really hurt.
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