Piper stall warning works on ground but not in an actual stall.

cowman

cowman

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This is on a PA-32R-300 Lance.

Went up for a flight review the other day and practiced stalls. We stalled the airplane but never got the warning horn. On the ground the stall switch on the wing moves freely and the horn does sound. The only thing I can think of is it felt like it took a little more force than usual to move it like it was a little stuck initially but we're talking something one can barely notice using one finger to move it.

I'm adding it to the squawk list for the upcoming annual, just wondering if there any known common causes of this.
 
Some PA-32's have two stall horn switches, one for flaps up and one for flaps down. They look like this, approximately:

upload_2020-3-16_12-45-48.jpeg

If you have two installed, check them both independently....

-Skip
 
The stall warning indicator does not directly determine an imminent stall. It switches at a certain angle of attack. By adjusting it up and down the switching or warning AOA is adjusted. If it has slotted mounting holes loosen screws and slide up and down to get the pre-stall warning you want.
 
They're usually adjustable up/down which allows it to change the AoA at which point it goes off. Try bringing it up towards the top of the wing to see if that has an affect.
 
It should require a feather-light touch only on the ground. Mine was intermittent on the ground. Removed the switch, soaked it overnight in some corrosion-X, placed it back on, back to BWEEP for stalls now.

I'm a "throw new parts at the problem" sort of dude, but the price for stall warning switches is beyond stupid.
 
Mine was intermittently working even in the ground, I got tired of that chit and got a new PMA-Ed one
 
cowman said:
This is on a PA-32R-300 Lance. Went up for a flight review the other day and practiced stalls. We stalled the airplane but never got the warning horn. On the ground the stall switch on the wing moves freely and the horn does sound. The only thing I can think of is it felt like it took a little more force than usual to move it like it was a little stuck initially but we're talking something one can barely notice using one finger to move it. I'm adding it to the squawk list for the upcoming annual, just wondering if there any known common causes of this.
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Exact same problem. Mine has never seemed to work properly in the air. My mechanic and I decided to take a peek. On a 172 you remove the tie down ring, let down the cuff, and open the inspection plate for access. Get a wrench in there and loosen the 4 screws. Move the unit toward the top of the wing and retighten.

In my case, it was already full up in the slot. So we disconnected the wire and the screws and nuts and removed it. Cleaned it up and filed the slots about 1/8" to allow the unit to slide just a smidge higher. We also slightly increased the curve of the slotted bracket to match the inside of the wing. Reinstalled and got a chirp during a nose-high landing for the first time in awhile. Wish I had taken a pic of the device while it was out of the wing. Probably 30 minutes and the second easiest R&R after installing new seat rollers on my brand new rails.

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Glad I have the old reed horn in my 150f. I give it a good suck each preflight and it fills my lungs with a familiar dusty honk each time.
 
Matthew Rogers said:
Glad I have the old reed horn in my 150f. I give it a good suck each preflight and it fills my lungs with a familiar dusty honk each time.
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And dead bugs.

During an annual inspection I went to test the stall warning by sucking on it, and saw a big red lipstick imprint on it. A stark reminder to wipe that area first.
 
I put my handkerchief over it before sucking, so the bugs get caught. There was a wasp in there once.
 
WannFly said:
Yah I don’t how how special the OEM one is, but they are certainly proud of it
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I'd seen the price of what they wanted which is why I asked. I don't need one, it was just one of those things to keep in mind if I ever do.
 
Moral of the story .... all Cessna high wing drivers suck every time they fly .... lol lol lol
 
Those stall horn switches are just industrial microswitches mounted on a bracket with a lever to actuate them. The big cost would be in the bracket and lever, if they're not currently in production. The switch is cheap and is usually what fails, but a new switch might not be available from the OEM without the hardware, and a locally-sourced industrial switch wouldn't have the right paperwork to make it work:rolleyes:

I fixed a couple of those switches by cleaning them in non-chlorinated brake cleaner and working them a few times and blowing the cleaner out. They get dust in them and water can get in when flying in rain. Just got to get the trash out.
 
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