dual stall warnings?

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The duchess I'm currently flying has 2 stall warning vanes - one on each wing. The right(?) wing's vane works for flap settings of 0-16 degrees. Above 16 degrees of flaps, the left wing's vane is used to activate the stall warning. Every single engine plane I've flown has only one stall warning vane.

Can someone explain why the duchess has two?

I'm told this is due to the difference in wing camber with and without flaps. But if that is true, why would a single engine plane not have one on each wing as well?

 

[poadeleted20]

The Grumman GA-7 Cougar has the same thing, as does the Cessna 421, and it is indeed because of the change of the wing camber with flap extension. However, it's not that way in all twins. My only guess is that there's something about those particular airplanes that they cannot meet the standards of 14 CFR 23.207 regarding stall warning without the separate vanes for the two configurations.

 

[Z06_Mir]

The Seneca has the dual stall warnings too.

 

[Sac Arrow]

I'm going to guess hearing only one stall horn on those planes is a big red flag.

 

[poadeleted20]

I'm going to guess hearing only one stall horn on those planes is a big red flag.

You hear the same horn either way, but you should hear it with each stall switch independently based on the position of the flaps, and that means with the appropriate switch activating the horn in and only in each position when you test it on the ground before flight.

 

[Sac Arrow]

You hear the same horn either way, but you should hear it with each stall switch independently based on the position of the flaps, and that means with the appropriate switch activating the horn in and only in each position when you test it on the ground before flight.

So then it's not for the purpose of spin warning?

 

[Cpt_Kirk]

So then it's not for the purpose of spin warning?

Would one go off louder than the other indicating the direction of the spin? No.

I flew the Duchess. You just treated it like a single stall warning horn, regardless of configuration.

 

[\__[Ô]__/]

The Grumman GA-7 Cougar has the same thing, as does the Cessna 421, and it is indeed because of the change of the wing camber with flap extension. However, it's not that way in all twins. My only guess is that there's something about those particular airplanes that they cannot meet the standards of 14 CFR 23.207 regarding stall warning without the separate vanes for the two configurations.

That sounds reasonable. I guess I probably won't get a better answer without talking to an aircraft designer.

 

[poadeleted20]

So then it's not for the purpose of spin warning?

Stall, not spin. Although the stall warning should be going off in a spin (since you're in a stalled condition when you're in a spin), it would have started when you approached the stall that led to the spin, and its purpose is warning of an impending stall.

 

[MyassisDragon]

The Grumman GA-7 Cougar has the same thing,

Sorry to hijack this thread, Ron do you have hours in a Cougar? I was wondering what they are like compared to a Twin Comanche? And how do they fly compared to their sibling the Tiger?

At times I see them reasonably priced, but with only 115 ever made it makes me nervous when looking at them as a contender for ownership.

 

[poadeleted20]

Sorry to hijack this thread, but do you have hours in a Cougar?

Maybe 750 or so.

I was wondering what they are like compared to a Twin Comanche?

I don't have any significant time in a Twin Comanche, so I couldn't say. But of the twins I have flown, it's very similar to an Aztec in terms of handling and flight characteristics.

And how do they fly compared to their sibling the Tiger?

Different plane entirely.

At times I see them reasonably priced, but with only 115 ever made it makes me nervous when looking at them as a contender for ownership.

I owned one for five years, and never had a problem with parts. Fletchair always had me covered. Not many twins will give you a big roomy cabin for four, more fuel than you could ever want, and 150 KTAS on 15 gph total fuel flow.

 

[Skip Miller]

The Seneca has the dual stall warnings too.

As does the Saratoga II PA-32-301. -Skip