Stall warning kits for 7/8/9

captain_john · Post by **captain_john** » Thu Dec 31, 2009 7:42 am

Spike, Yes... There is much more to it than meets the eye.

Pat summed it up very well stating that it is like comparing an idiot light to a gauge.

That .pdf linked by Thermos to the AFS site is VERY informative! If you buy the AFS "A" kit (for the AOA wing components), it comes with LOTS of information about how to use it.

CJ

Post by **Spike** » Thu Dec 31, 2009 9:17 am

Actually I have the "A" kit installed and have read all of the documentation. The .ppt is a good refresher as well. Though my original statement I hold to, at the end of the day the AOA and the stall horn both measure angle of attack, the only difference being that the AOA instruments do it over a wider range of operation. This is the gauge vs idiot light scenario which I agree is a great one.

I would think you could recalibrate the stall warning horn when you install it to tell you when you are at best glide instead of a stall.

Guys like ASF have done a good job of actually tracking the AOA and relating it to things such as Vx, Best Glide, and 1.4V (approach), but ultimately they are doing this by plotting it against the angle of attack. The instrument does not tell you how much "positive lift" you have.

Spike

captain_john · Post by **captain_john** » Thu Dec 31, 2009 9:39 am

Actually it does measure lift and compare it to drag.

That is it's primary function.

The L/D relationship.

Lift is what it measures.

CJ

Post by **Spike** » Thu Dec 31, 2009 10:30 am

This is becoming a good conversation, thanx for playing with me CJ. Nifty how we can debate without calling into question our heritage ...

So how does the AOA unit from AFS measure lift and drag? The way I read their documentation it sure sounds to me like they are applying an approximated modifier for PA/PF (1.5, 1.4) to the Stall angle using the curve that they map during the calibration process. From there it looks like you can slew it with the Pro units to dial it in though my version of the documentation doesn't go that far in the calibration instructions.

JOHN TIPTON · Post by **JOHN TIPTON** » Fri Jan 01, 2010 7:31 am

Hi Guys

Don't forget that VANS supply kits world wide, and some countrys require a 'stall warner' to be fitted, the UK requires a 'stall warner' with an 'audible alarm' we have fitted the 'Reddish stall warner' which from the look of the VANS photo is similar if not the same.

Best regards (and stall free flying) to all for 2010

John

captain_john · Post by **captain_john** » Fri Jan 01, 2010 8:05 am

Spike, I do enjoy an intellectual conversation that results in a better understanding of a subject. It is all part of being an educator. You never learn something better than when you discuss it with others.

I have no idea actually *how* the equipment does the actual L/D calculations. If one is interested in that, I am sure that Rob Hickman could provide them with the details. I only understand the concept of lift versus drag as explained in the literature. I am only a mere pilot. You know, the guy that makes the plane do the stupid things it does!

So Bruce, What are you going to do now? Are you going to install the stall horn or an AOA?

CJ

TomC · Post by **TomC** » Fri Jan 01, 2010 11:44 am

Don't forget that VANS supply kits world wide, and some countrys require a 'stall warner' to be fitted

I think someone hit the nail on the head?

Post by **Spike** » Fri Jan 01, 2010 12:08 pm

Now that information is truly interesting. If other countries mandate that functionality, and people here in the States are asking about it, it probably makes lots of sense to go ahead and just put it in the wing kits.

Thanx for that info!

As for how the devices are measuring L/D, I don't believe that they are. I think they get a curve from the two calibration points and then approximate the other points knowing that your average aircraft would have points at 1.4 & 1.5 Vso. This would be a decent question to ask Rob or someone.

Spike

bruceh · Post by **bruceh** » Fri Jan 01, 2010 6:08 pm

captain_john wrote: So Bruce, What are you going to do now? Are you going to install the stall horn or an AOA?

CJ

I am definitely sold on the value of AOA, and plan on using the Dynon pitot and EFIS. I think I'll defer on the stall warning for now. Doesn't look like it brings anything additional to the party.

captain_john · Post by **captain_john** » Fri Jan 01, 2010 6:24 pm

I agree... only weight!

Good call!

CJ

johnk · Post by **johnk** » Sat Jan 02, 2010 10:04 am

In addition to the gauge output, do the AOA systems also provide an "idiot light" warning of stall (either a horn or a blinking light)? (in case I'm not looking at the AOA gauge)

John

Post by **Spike** » Sat Jan 02, 2010 10:25 am

Depending on manufacturer many of them have audible output that you route through the intercom. You will get a verbal warning of the stall.

Spike

BSwayze · Post by **BSwayze** » Wed Jan 06, 2010 2:41 pm

I put AFS's AOA in my plane and I have no regrets. I wanted the extra margin of safety. Besides being cleaner and nicer looking, it will show you when you are approaching the critical angle of attack, whereas the stall horn goes off once you're already there.