Stall warning kits for 7/8/9

Post by **Spike** » Tue Dec 29, 2009 12:19 pm

Yipes, where was this stall warning kit when I was building my wings?

I would have probably gone with the AOA system anyway but I have to say that I am really happy to see that they someone has come out with this. Anyone have plans on installing it?

Spike

hydroguy2 · Post by **hydroguy2** » Tue Dec 29, 2009 1:01 pm

AOA for me.

Stall warning kit is one more thing I won't add.

Mike Balzer · Post by **Mike Balzer** » Tue Dec 29, 2009 2:08 pm

It looks ugly and DRAGGGG!!!!!!

Just my .02 worth,

Mike Balzer

Post by **Spike** » Tue Dec 29, 2009 2:18 pm

Hmm, I didn't think about drag. Though I would not imagine it adds that much.

captain_john · Post by **captain_john** » Tue Dec 29, 2009 5:52 pm

HA! I was just surfing their catalog today and never even saw it!

It is incredible the stuff they have in there now!

I see that it is "Included in RV-7/8/9A wing kits from 2010 onward."

Hmmmm, wasup widdat?

I am not a fan. Keep the initial cost low. Add the thing if you need/want it.

Ohhhh, the slippery slope!

CJ

airguy · Post by **airguy** » Tue Dec 29, 2009 10:37 pm

Agreed - not impressed with the automatic inclusion of this in the kit. It should be an option, not a standard. This is obviously a CYA moment in Vans history.

bruceh · Post by **bruceh** » Tue Dec 29, 2009 11:44 pm

I'm in the middle of building the wings, so I'm wondering if it is worth putting the stall warning vane in now.

I was planning on putting the Dynon AOA pitot on the wing. What does the stall warning buy you over the AOA data?

captain_john · Post by **captain_john** » Wed Dec 30, 2009 8:21 am

The stall indicator is Van's way of mitigating lawsuits, I think. With him being the largest provider of kits (far and away) he needs to be cautious.

We have seen this in the past by the Service Bulletin on the fuel pick ups and how he designed the removable wings in the -12 to have safety pins that automatically engage the control surface pins when installing the wings.

Really can't blame him, I suppose. If I were building a pair of wings today, I would not install the stall horn. I still do like the AOA though.

I like it because it gives lift information as well as stall indication. It is also a cleaner installation with all of today's modern EFIS's.

Bruce, I don't see the stall horn doing anything more than a good AOA does.

My two...

CJ

Post by **Spike** » Wed Dec 30, 2009 9:35 am

Well, it does do what an AOA does, at less than 1/10th the cost, dependent on which AOA you compare it against. That seems to me to be a good enough reason to offer one.

I also tend to think that we don't know anywhere near enough about the decision making process over there to infer that this is purely a CYA thing. For all we know there may have been enough business justification to warrant inclusion in the kit. I would be interested in how many of the upgrade kits are purchased for those who have yet to fly.

Spike

captain_john · Post by **captain_john** » Wed Dec 30, 2009 1:12 pm

Hmmm, I didn't know that a stall horn indicated how much positive lift an airfoil has!

Live and learn!

CJ

dons · Post by **dons** » Wed Dec 30, 2009 1:22 pm

oh CJ

When I was first looking for what kit I was going to buy, I noticed there was no stall waring option, it concerned me for quite a while before learning about AOA. Having flown nothing but rentals with that same gizmo, not having one gave me reason to pause before buying into Vans. Maybe they have had a lot of feedback from potential builders about this, and that was one of many reasons they decided to include it, but again, just a guess.

smithhb · Post by **smithhb** » Wed Dec 30, 2009 2:01 pm

Having flown my -9 for over 120 hours thus far, I can see no reason for a stall horn... or an AOA for that matter. These are extremely docile machines and if you don't try and violate the Laws of Physics you should never have a problem.

The stall buffet is very pronounced since the planes are so light- even in a bank.

Someone here might know the history of when/why stall warning devices were first introduced. I'd be interested to know.

Post by **Spike** » Wed Dec 30, 2009 2:29 pm

Yeah Bret, but then I can think of no reason that one really needs to build their own airplane

Some people I believe just want one because they feel that they want to know empirically when they are approaching an immanent stall.

As for a stall indicator telling you how much positive lift you have, obviously it doesn't. Though neither does an AOA. Besides that information would be fairly useless I think since everyone generally knows the answer (in straight and level flight anyway.) What people really want to know is where they are in relation to the critical angle of attack. The biggest difference between an AOA and the stall horn is that the AOA works over a larger range of angles.

My guess is that enough people have asked for them and enough people are buying AOA's that Van's decided to get a piece of that pie. As for why make it standard, dunno, we would have to ask them.

Spike

captain_john · Post by **captain_john** » Wed Dec 30, 2009 3:25 pm

An AOA does not tell you how much positive lift you have?

Well then we better eliminate all those green lights from them because they are useless! May as well take out the yellow ones too!

CJ

4kilo · Post by **4kilo** » Wed Dec 30, 2009 5:23 pm

captain_john wrote:An AOA does not tell you how much positive lift you have?

Sorry CJ, I have to get a little pedantic with you here.

A true AOA system indicates the angle of attack. This is NOT the positive lift being provided by the wing. At 120 kts and 5 degrees AOA you have twice as much lift as you do at 60 kts and 10 degrees AOA. This example does not include the effect of flaps, which depending on the installation may be compensated for or not.

The best thing an AOA indicator can tell you is how closely you are approaching the critical angle of attack. The stall warning device can only tell you that you have reached a certain angle of attack. It's sort of like the difference between a gage and an idot light. (I prefer gages).

Pat

Post by **Spike** » Wed Dec 30, 2009 5:29 pm

Uh, if you mean how much force the wing is generating, I don't believe it does, though I am more than willing to be educated on the matter. Seems to me that in order for it to tell you how much lift the wing is generating it would have to tell something relative to a measurable force (ie.lbs/newtons). In straight and level accelerated that would be the equivalent of the aircraft weight in the upwards direction. Seems to me that the AOA measures and reports what the relative wind is to the wing chord (angle of attack) with respect to what it would be when the wing stalls.

What am I missing John? What do all of those little green and yellow lights tell you other than how close you are to the critical AOA?

Spike

Bob Barrett · Post by **Bob Barrett** » Wed Dec 30, 2009 5:39 pm

I have Dynon's AOA on my airplane and one of the reasons I wanted it was to provide a system of stall warning. Like many others most of the rentals I have used had them. I think the extra cost of the AOA gives a lot more and offers a greater margin of safety. N784TB has 79.8 hours on it and I prefer the AOA. I think the extra money was well spent.

1:1_Scale · Post by **1:1_Scale** » Wed Dec 30, 2009 11:44 pm

Hasn't the -12 had the stall warning as a standard feature from the beginning? Am I naive to think that Vans decided to include the same device as a standard feature since they already had it in their inventory and to "add value" to their kits?

Thermos · Post by **Thermos** » Thu Dec 31, 2009 6:20 am

Spike wrote:Hmm, I didn't think about drag. Though I would not imagine it adds that much.

It's probably almost immeasurable...unless you're gmcjetpilot!

Thermos · Post by **Thermos** » Thu Dec 31, 2009 6:46 am

AFS has a great Powerpoint brief on their website that describes AOA and how you fly with an AOA indicator. Check out...

http://www.advanced-flight-systems.com/ ... slides.ppt

There's just enough math in there to show how flying with AOA allows you to fly more precisely at the edges of your airplane's performance limits.

HTH

ds

RivetBangers.com

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