Stall alarm constantly on - Mooney Ovation 2 GX with TKS

[Yariv]

Hi all,

enclosed here is a link to a video I took of my Mooney on the ground when turning the master switch on - https://1drv.ms/v/s!Ajg51CbGb28qioNU40F4yOKtXrlIYQ

the problem started when it went for IFR certification last Wednesday. The technician called me and asked me if I had a trick to silence the stall alarm. He said all he did was to connect the aux power supply unit to the airplane and then when he turned the master switch on the stall alarm started sounding - high pitch continuous tone with “Stall Stall…” in between. They towed the airplane from my hangar to their shop for this IFR certification.

i checked a few things -

- the stall switch on the wing, it moved freely and came down on its own when releasing it from the up position 

- no circuit breakers popped out 

- there is no dedicated CB for the stall alarm 

i flew the airplane under IFR the previous week for a long cross-country flight with no issues at all. Every time I have landed this airplane I heard the stall alarm sounding during the flare but then it turned off after the landing.

i did exercise the TKS system during the last flight in altitude (warm temperatures though) and was told by the technician that the TKS pump was left on when he turned the master switch on. Not sure if it is relevant or if it was really on or not:-). The OFF position of the switch is kind of tricky to judge by sight as it is between the normal mode and “max” mode. I do remember turning it off and confirming that the light was off.

the shop tried a few things as well - cleaned the stall switch with a de-oxide spray but that did not help. Also, moving the stall switch tab did not help change anything.

i noticed a few postings here about the same issue and I am hoping to get more information on how some of these issues were fixed.

the nearest MSC to me is in Troutdale, OR (Advanced Aircraft Services) but i do not know how I can fly the airplane in this condition. The alternative is to let the local shop that did the IFR certification investigate the issue, but I’d prefer a Mooney Service Center do that.

thank you,

yariv

N33GX

[Yariv]

Mine looks simple to remove just that I am not sure I should mess with it as it is set at a certain position along the leading edge. Thank you for the information.  

[GeeBee]

That is the wrong stall switch for a FIKI Ovation 2 GX. It is not heated

 

 

[Yariv]

@GeeBeehow can you tell? totally sure?

[GeeBee]

Yes. I have an Ovation 2 GX as well. I learned what a good unit looks like in this thread. I had the correct unit, but the heating element was on its last hurrah.

Look at this thread.

If you notice the correct unit has a heating element on the tab and the pink heating element behind the plate. If you turn on your pitot heat, it will get hot. I'm betting yours does not. I really hate to tell you this because a new unit is crazy expensive, like 6 thousand expensive. If you go to the Mooney parts manual and you look in the electrical or flight controls section it gives you the unheated part number. The correct part number and diagram is in the " ice and rain section". Someone looked up the wrong part for your airplane. It fits, but it is not right. If you can find a used unit, SafeFlight can overhaul it for about 2200. Takes about a month. Beware, different connectors out there for these units, make sure you got the right one or have your mechanic rewire to the correct plug. CAV icing can provide technical help for you to get it right.

[carusoam]

That sure looks like a heated stall vane to me…

That thread regarding heated stall vanes should have a half dozen pics of vanes in different levels of dis-repair…

The black surface tatters and tries to escape…. Leaving a shiny ordinary stall vane behind…

Make sure there aren’t any bits and pieces that have escaped into the switch itself…

 

The unheated stall vane is typically mounted from inside the wing, making it really difficult to access…

The switch itself is an industrial switch (Honeywell) that should last forever…

Driving the water out of it may be key to getting it silenced properly…

 

There are a few threads around here for advice on stuck stall horns…

Get a really good close up pic of the stall vane’s surface and compare to a new one….  They don’t age well…. 
 

There may be an OH program for them… (?)

It is such an ugly installation on the beautiful Fiki wing!

PP thoughts only, not a mechanic…

Best regards,

-a-

[GeeBee]

You know, on further examination it may be a heated unit, but I don't see a heat pad on the mounting plate either. Someone really over tightened the screws and it looks like the heat pad on the base plate is missing, along with the tab heater. It may just be in bad need of overhaul. Overhaul is about 2200 now. 

 

[Yariv]

Thank you very much for the advice, this is really helpful. This is such a huge knowledge base. I will update the thread along the way. So far it doesn't look like I can fly it in this condition to a Mooney Service Center so I may need to have the local shop handle it.

[kortopates]

30 minutes ago, Yariv said:

Thank you very much for the advice, this is really helpful. This is such a huge knowledge base. I will update the thread along the way. So far it doesn't look like I can fly it in this condition to a Mooney Service Center so I may need to have the local shop handle it.

You could disable the stall horn by pulling 2 CB's if my memory is right, or even disconnecting it at the wing. But then you should have a Ferry permit to fly to the MSC, but then they or your local shop could get the Ferry permit for you. But in fairness the system is not that complicated and shouldn't need a MSC; but you probably do want someone that can repair the unit as opposed to just order a new one.

One thing I've seen happen is someone leaning directly against it while re-fueling the tank and bending the tab enough to do this.

[Yariv]

Do you remember which 2 CBS? Enclosed below is a picture of the circuit breakers in my Mooney -

[GeeBee]

 

If I understand the wiring diagram correctly the stall warning is part of the G1000 interface so you don't have one C/B to pull. As Kortopates suggested, I would pull the plug in the wing, you're going to have to anyway to get the thing out.

One thing I learned in dealing with SafeFlight when you ship it back to them in NY is contact them by phone on the "AOG" line. If you just send it to them on a regular basis, it takes over a month to get the unit back. If you talk to them first and arrange an "AOG repair" you can get it back in about two weeks. Things seem a little crazy there due to Covid, so I highly recommend the AOG line. Also take a picture of the connector and wires before you send it to them. The Mooney installed connector is a 4 hole connecter. SafeFlight says that is "non-standard and snip it off and put on a 12 hole connector. They will return the old connecter to you and you will have to put it back on, or tell them not to remove it in the first place. Just went through this about a year ago.

[Dmax]

It’s pretty common. Grab the stall vane and pull very hard and it should stop. The arm is very long and linemen lean against it fueling the plane. It bows up in the middle and does not activate the switch 

[carusoam]

@Yariv check the note above from DMax!

Best regards,

-a-

[Yariv]

This is great to know. Thank you very much.

here are a few things I learned today:

• i can silence the stall alarm, both the high pitch continuous alarm and the voice alarm, by pulling the 5 amp Engine Inst circuit breaker. However, as expected, you would lose all engine instruments displays.
• i can silence the voice alarm only (“stall, stall…”) by pulling the Audio circuit breaker. At this point you can only communicate on radio #1 but the high pitch stall alarm is still in the background and could be heard by ATC even though you don’t hear that sound in your headset.
• the only way to get to the stall switch is through the inspection plate directly underneath it. This plate is riveted to the wing but should be straight forward to drill the rivets out.

the local shop is handling this now. The first step is to access the switch and check if it is the problem by disconnecting it and verifying the stall alarm stops sounding. 
 

i will continue to update with findings as I know more. Thanks again for all your help.

[Yariv]

5 hours ago, GeeBee said:

 

If I understand the wiring diagram correctly the stall warning is part of the G1000 interface so you don't have one C/B to pull. As Kortopates suggested, I would pull the plug in the wing, you're going to have to anyway to get the thing out.

One thing I learned in dealing with SafeFlight when you ship it back to them in NY is contact them by phone on the "AOG" line. If you just send it to them on a regular basis, it takes over a month to get the unit back. If you talk to them first and arrange an "AOG repair" you can get it back in about two weeks. Things seem a little crazy there due to Covid, so I highly recommend the AOG line. Also take a picture of the connector and wires before you send it to them. The Mooney installed connector is a 4 hole connecter. SafeFlight says that is "non-standard and snip it off and put on a 12 hole connector. They will return the old connecter to you and you will have to put it back on, or tell them not to remove it in the first place. Just went through this about a year ago.

Thank you @GeeBee! This is very helpful.

[Jeff_S]

I expect your problem is more complex, but on several occasions I've had the stall warning horn be on consistently just because the vane got bent a little bit, once during a refueling operation and once by myself during a wing cleaning.  The solution both times was to just nudge the vane back into its appropriate position with the master on (engine not running, of course) so you can hear when it stops screeching at you.

But this was a simple stall warning device in a non-FIKI plane, so again, probably not the same thing.  I put this out there for others who may find this thread in the future.

[Yariv]

Thanks @Jeff_S. I have tried this but there was no change. The tab moves freely and is not bent.

[Warren]

From the outside, it is very hard to tell if the arm is bent.  The total arm is about 2" long and if there is a bend, it will be bowed up in the middle enough to clear the switch and this will produce a very small change in the angle of the exterior part that is not noticeable (even 5 degrees is probably enough to cause the problem).  Careful with rebending the switch as it is a hardened steel material - do the minimum amount required to get it working again.  However, if it is bent, not too much to lose as it needs repair anyway.

[mike_elliott]

The guy that fixes a lot of them gave you the fix..grab that sucker and pull on it to unbend the arm. Failing that, send it to Don and he will fix it for you and a for a few bitcoin

[carusoam]

Great reminder…
 

Use caution when refueling….  

There is no visible warning where the vane is until after you whack it…

It makes a great conversation starter when talking to the lineman…

I usually have them leave the caps off, for fuel level review and sumping…

Best regards,

-a-

[Yariv]

Update:

good news - it was fixed exactly like many of you suggested, by pulling on the tab. The local shop did it, with a small plier being careful not to scratch the paint. They marked the position of the stall vane/tab and installed it using that mark. I flew it this afternoon, did many stalled in different configurations and the alarm came on before the stall:-), at the correct speed.

i am very happy that we did not end up needing to ship it for an overhaul.

thank you very much for all the good advice. Enclosed it the picture of the stall vane after the fix. It looks like it protrudes more than in the previous picture when it was stuck.

[carusoam]

Great follow-up Y!

That is great news.

 

Best regards,

-a-