Stall Horn May be Inop

[hnorber]

HI all.  I have a 1991 MSE and the stall horn appears to work just fine when I test it during my preflight.   However, I never hear the horn when I land (and I generally do fully stall prior to touch down).   Wondering if maybe the tab isn't properly aligned or maybe bent incorrectly.   Has anyone else ever dealt with this?  My shop isn't much help.

 

Thanks

 

[carusoam]

hn,

Now is the time to post a pic of your stall vane…

Its position is adjustable…

It should be easy to get it to sound during slow flight with an instructor…

Bending it is not usually a solution to its misbehavior…

It is made of a hardened metal that is more likely to break than to bend…

Its ridiculously expensive to replace…

By 1991… things got really modern…

A few steps to look forwards to…. 
 

While you have the CFI with you… Slow flight with the stall horn on… then landing by the numbers… the stall horn will chirp just prior to the gear touching…  

PP thoughts only, not a mechanic or CFI…

Best regards,

-a-

[PT20J]

Take it up to a safe altitude and do some stalls and see if it is set correctly. Adjustment procedure is in the Service Manual.

[hnorber]

Thanks.  I haven't tried slow flight yet since I've been breaking my engine in from an overhaul (trying to maintain higher power settings/internal pressures).    I'll try slow flight shortly and also send some pictures of the stall vane.

Thx

 

[rgpilot]

I had stall horn inop and was able to remove it and clean it with contact cleaner. Now its works.

[Will.iam]

3 minutes ago, rgpilot said:

I had stall horn inop and was able to remove it and clean it with contact cleaner. Now its works.

But the OP said he can test it fine on the ground so his switch is making good contact, just not in flight when he wants it too.  

[hnorber]

That's right - no issues when I test it on the ground.

 

[Hank]

7 hours ago, Will.iam said:

But the OP said he can test it fine on the ground so his switch is making good contact, just not in flight when he wants it too.  

I thought he wasn't hearing it when he landed.

Tests good on the ground. Does it sound when doing stalls in the air? If so, the he isn't doing full stall landings . . . .

[rotorman]

I thought my horn was not coming on when I was landing. So I pulled back the right ear of the headset and there was the horn. Hmmm, I said to myself. This may be an age related problem. I found a Sonalert with a higher DB level and changed it out. Now the horn comes on again. I posted the part numbers somewhere on this forum back a few years ago.

[A64Pilot]

In doing production test flights I had to adjust the horn to 5 to 10 mph with flaps full down and engine at idle, with airspeed decreasing at one MPH per second. (our airplane AS was in MPH)

The stall warning will come on at different points if the airplane is configured differently, and at different rates of deceleration, so most I believe choose to test in the landing configuration at a deceleration that’s close to what you will have during a landing.

Not to insult but if it’s been awhile since you have done full stalls, remember your feet are very important to keep that ball centered, and have lots of extra altitude.

I always land on the mains with the nose up and hold it up after landing, yet rarely hear the horn, so there may be nothing wrong.

Edited May 7, 2022 by A64Pilot

[A64Pilot]

2 hours ago, rotorman said:

I thought my horn was not coming on when I was landing. So I pulled back the right ear of the headset and there was the horn. Hmmm, I said to myself. This may be an age related problem. I found a Sonalert with a higher DB level and changed it out. Now the horn comes on again. I posted the part numbers somewhere on this forum back a few years ago.

Some of us like a light on the instrument panel, it’s easy to add too. The original Thrush had only a light, the 660 as it’s a FAR 23 airplane had a horn, I added a horn to the Car 3 airplanes so now all have both now, just made the drawings the same for all instrument panels.

I believe the gear warning horn is often confused for the stall warning horn, just a theory of mine that helps explain gear up landings. If the gear warning horn were a completely different kind of sound like maybe a European warbling cop siren I think it might help prevent some gear ups, maybe? 

if I heard this I wouldn’t think stall

 

Edited May 7, 2022 by A64Pilot

[Will.iam]

58 minutes ago, A64Pilot said:

Some of us like a light on the instrument panel, it’s easy to add too. The original Thrush had only a light, the 660 as it’s a FAR 23 airplane had a horn, I added a horn to the Car 3 airplanes so now all have both now, just made the drawings the same for all instrument panels.

I believe the gear warning horn is often confused for the stall warning horn, just a theory of mine that helps explain gear up landings. If the gear warning horn were a completely different kind of sound like maybe a European warbling cop siren I think it might help prevent some gear ups, maybe? 

if I heard this I wouldn’t think stall

 

Or this:

 

[A64Pilot]

I was actually thinking an inexpensive IR laser which is an accurate distance measurer, set to alarm at 100ft but disabled when the gear are down.

But that’s more complex than I think many would want to go through, but you know electronics are so easy and inexpensive now, why not?

You could even have it disabled for 30 sec upon retracting the gear to prevent if from going off on takeoff.

Things that used to be hard are now easy and relatively inexpensive

 

[Hank]

11 hours ago, A64Pilot said:

I was actually thinking an inexpensive IR laser which is an accurate distance measurer, set to alarm at 100ft but disabled when the gear are down.

But that’s more complex than I think many would want to go through, but you know electronics are so easy and inexpensive now, why not?

You could even have it disabled for 30 sec upon retracting the gear to prevent if from going off on takeoff.

Things that used to be hard are now easy and relatively inexpensive

 

That's available now, the Landing Height System, and is approved for installation in your Mooney.

[Fly Boomer]

7 hours ago, Hank said:

That's available now, the Landing Height System

I just walked through their website, but couldn't see where their system disables the gear warning if the gear is down.  Do you have a reference?

[PT20J]

2 hours ago, Fly Boomer said:

I just walked through their website, but couldn't see where their system disables the gear warning if the gear is down.  Do you have a reference?

I'm pretty sure that any system that connected to the certified gear warning system would have certification hurdles. A more reasonable approach is to have the system just remind you to check that the gear is down similar to the ATC "Check Wheels Down" call to Navy pilots (7110.65 2-1-25).

[Fly Boomer]

1 hour ago, PT20J said:

more reasonable approach is to have the system just remind you to check that the gear is down

Makes sense.

[A64Pilot]

As it’s not interfering with the system I don’t think so, now if it made the gear warning system change it’s behavior then yes it may be problematic, or there was a failure mode that could interfere with the stock system

The problem with always being alerted is you learn to ignore it, but an alert that you never hear, when you do hear it, it gets your attention.

It would be child’s play to install a completely separate microswitch if it became an issue.

Also the gear switch is a dual pole dual throw switch, but on my J model only one side is used, use the other side for gear warning disable

Edited May 9, 2022 by A64Pilot

[PT20J]

59 minutes ago, A64Pilot said:

As it’s not interfering with the system I don’t think so, now if it made the gear warning system change it’s behavior then yes it may be problematic, or there was a failure mode that could interfere with the stock system

The problem with always being alerted is you learn to ignore it, but an alert that you never hear, when you do hear it, it gets your attention.

It would be child’s play to install a completely separate microswitch if it became an issue.

Also the gear switch is a dual pole dual throw switch, but on my J model only one side is used, use the other side for gear warning disable

But, you would have to do this for every make and model.

BTW, weren't you looking for a gear switch a while back? If so, there is one on eBay: $247.50

[A64Pilot]

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.

 

 

Edited May 9, 2022 by A64Pilot

[Stan]

After reading all the "mission creep," responses, I did what rgpilot did, except I didn't remove it.

Just sprayed it down, two or three times, and now do so every annual.

Just make sure the contact cleaner is safe for plastics.

 

 

 

[A64Pilot]

2 hours ago, Stan said:

After reading all the "mission creep," responses, I did what rgpilot did, except I didn't remove it.

Just sprayed it down, two or three times, and now do so every annual.

Just make sure the contact cleaner is safe for plastics.

 

 

 

His works when manually operated, he doesn’t have an electrical issue.

If you don’t remove it, you may not be getting contact cleaner into the electrical portion of the switch.

If you use contact cleaner, use Deoxit, it’s plastic safe and more importantly it does seem to deoxidize the contacts in the switch, only cleaner I know that does, but I’m no electrician either.

[OR75]

The stall warning is an airworthiness item. Make sure the repair is well documented 

[hnorber]

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.

 

 

[PT20J]

Have you tried adjusting it per the service manual?