Stall Horn May be Inop

[hnorber]

Yup - I adjusted the tab all the way up (up is early warning) per the instruction above before my BFR.   Still didn't work at all.

 

[PT20J]

This is going to be difficult for a shop to troubleshoot since it only happens in the air. If it works properly on the ground without any sticking noticeable friction then perhaps the vane is bent. They are supposed to be heat treated so they don’t bend, but it’s worth checking against another airplane. Here’s a picture of mine for comparison. 

 

[Shadrach]

On 5/9/2022 at 7:02 AM, A64Pilot said:

I was and bought a used one from a forum member for a decent price.

Then I figured out its MS number, and they are readily available for roughly $40, it’s a standard part.

My gear relays are the same, not available from Mooney, and junkyards wanted something like $1,000 for used, but all they are is a Golf cart relay, again a standard part.

The challenge is of course discovering the MS or other part number, used to be even if we knew the source part number we couldn’t use the part, but the FAA changed that with this AC in 09

https://www.faa.gov/documentlibrary/media/advisory_circular/ac_23-27.pdf

You wouldn't think of Amazon as an aircraft parts source, but IAW the above referenced AC it can be, the knob on the switch unscrews and you screw the plastic wheel on.

I dislike using used electronic and or electronic components as you can’t inspect them for wear.

On edit, I just need to figure out where limit switches come from.

 

 

If the old switch has a PMA mark and the new one doesn’t, I’m told that it’s not the same switch in the eyes of the FAA. If the switch being replaced doesn’t  have a PMA stamp, then you’re likely good to go.

[Shadrach]

On 7/6/2022 at 7:59 AM, hnorber said:

Well - it's been quite a while since I started this post - but bringing the thread back to the original issue...I did my BFR last week and took the plane into full stalls (yes-with abrubt wing drops) and the horn didn't come on at all.   It still checks fine on the ground.   Does anyone have any thoughts on or recommendations on where to have it serviced?  I'm in Chicago, and my regular mechanic (an extremely reputable shop - but doesn't specialize in Mooneys) is telling me that they can't do anything short of replacing the entire system.

 

 

If the switch comes on during a ground test when manually manipulated Than the issue is likely that the vane is not moving in spite of the airflow reversing direction over the leading edge. Does the vein move freely? And by freely I mean no discernible friction? I haven’t tried it but I’m almost positive that I could activate my stall horn simply by blowing on it from the correct angle.

It seems very unlikely to me that much has changed between working stall horn and not working in the air. The most likely culprit being dirt and debris causing it to hang up.

A second possibility is that there’s something electrical going on while the engine is running. Have you tested the horn on the ground with the engine  and all of the systems used in flight up and running?

[hnorber]

Thanks for the responses.   I suspect that the tab is somehow bent incorrectly (I'll need to PT20J's picture to mine when I get to the airport next) OR that there's dirt/friction (I actually don't think it moves very freely - it seems to move okay in the top third of its range, but gets stuck there).

I'm guessing WD40 is a bad idea- but happy to hear suggestions on cleaning it and getting it to move freely.

 

Thx!

 

[DonMuncy]

Just a crazy idea. I might glue a larger tab onto the stall warning tab temporarily, and fly it, with extreme variations in the tab angle. You might be able to figure out if the tab is very much out of place, and which direction.

[PT20J]

Another thought is that some models use a tone generator for both the gear and stall warning that emits the tone through an overhead speaker. I don't see how this could be the problem, but I'd try stalling it with the gear down just in case there is some weirdness with the generator assuming you have this setup.

[Shadrach]

3 hours ago, hnorber said:

Thanks for the responses.   I suspect that the tab is somehow bent incorrectly (I'll need to PT20J's picture to mine when I get to the airport next) OR that there's dirt/friction (I actually don't think it moves very freely - it seems to move okay in the top third of its range, but gets stuck there).

I'm guessing WD40 is a bad idea- but happy to hear suggestions on cleaning it and getting it to move freely.

 

Thx!

 

I would start CRC electronic cleaner and follow with LPS-1.

 

[PT20J]

There is one for sale on eBay if it comes to that. https://www.ebay.com/itm/334476502707?hash=item4de05a66b3:g:Sy0AAOSw7lRiq5to

Skip

[LANCECASPER]

@hnorber I would buy this one before someone else does:

 

[Shadrach]

On 7/8/2022 at 10:41 AM, PT20J said:

This is going to be difficult for a shop to troubleshoot since it only happens in the air. If it works properly on the ground without any sticking noticeable friction then perhaps the vane is bent. They are supposed to be heat treated so they don’t bend, but it’s worth checking against another airplane. Here’s a picture of mine for comparison. 

 

Am I missing something or is your left wing absent a stall strip?

[Shadrach]

31 minutes ago, LANCECASPER said:

@hnorber I would buy this one before someone else does:

 

It’s such a simple device. We’re talking about a thin SS strip by on a shaft that operates a micro switch. It seems unlikely that’s it’s not repairable. 

[Will.iam]

Goto this thread about stall vanes my plunger had dirt grime and even a blade of grass stuck in there. Once that was cleaned all out it worked like new. :

 

 

[PT20J]

1 hour ago, Shadrach said:

Am I missing something or is your left wing absent a stall strip?

No, It’s where I positioned the camera.