Stall Warning

[kpaul]

The stall warning in my 75 M20F seems to activate early.  By early, I mean at 90 mph indicated going down hill.  On final it is on continuously. This was in very smooth air. It squawks quite a bit on take off as well.  Is there a way to adjust the angle or is it a replacement only item?

[Marauder]

The stall warning in my 75 M20F seems to activate early.  By early, I mean at 90 mph indicated going down hill.  On final it is on continuously. This was in very smooth air. It squawks quite a bit on take off as well.  Is there a way to adjust the angle or is it a replacement only item?

I believe the vanes are adjustable. I thought there was a thread on the topic somewhere on the site.

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[takair]

The vane likely got bent up.  Did this start recently?  if you take photo of the vane we can provide some feedback or compare to another Mooney.

[DonMuncy]

These vanes are a very stiff stainless steel. They don't ben easily. And definitely do not try to adjust it by bending. They are adjustable by loosening the fasteners and moving the switch/vane. It is my understanding they are tough to get to.

[kpaul]

 

29 minutes ago, takair said:

 Did this start recently?

Well recently is all the experience I have with the plane.  I have only had the plane since right before Christmas and have only put about 6 hours on it.  I will need to get a photo of it the next trip to the hanger.

 

41 minutes ago, Marauder said:

I thought there was a thread on the topic somewhere on the site

I did a search before I posted, but did not come up with anything.

[Marauder]

 

29 minutes ago, takair said:  Did this start recently?

Well recently is all the experience I have with the plane.  I have only had the plane since right before Christmas and have only put about 6 hours on it.  I will need to get a photo of it the next trip to the hanger.

 

41 minutes ago, Marauder said: I thought there was a thread on the topic somewhere on the site

I did a search before I posted, but did not come up with anything.

Post the picture when you get a chance. I have a 1975 F as well. Should look similar.

[Yetti]

It's adjustable.  It could be pretty easy to wack it with a fuel hose.  Or your cut your hand while cleaning bugs off the wing.  I have not found it in the Service Manual or the Parts manual. Hmmm

[MyNameIsNobody]

You probably bumped with your calf when you were walking buy

[Bob - S50]

In addition to your stall warning being out of adjustment, your airspeed indicator could be out of calibration too.  Ours was off by as much as 8 knots at some speeds.  I'd recommend taking your plane up and do a couple stalls making note of the stall speed.  Then go home and see how it compares with the calculated stall speed for your calculated weight.

You should be able to calculate the stall speed for any weight using: (Vactual)^2 = (Vgross)^2 x Wactual/Wgross

That is, actual stall speed is the square root of (the gross weight stall speed squared times your actual weight divided by gross weight)

If it's off by more than a couple knots you might want to have it re-calibrated.

[MyNameIsNobody]

Seriously, I would get that sorted/repaired ASAP.  Another experienced CFI and fellow pilot in training died for lack of a functioning stall warning.  Be safe.  Or, as others say "wear your helmet"...which in essence means be proactive to address the sudden undesired event that may result in personal injury and or property damage...Or just scare the hell out of you.

Somebody cares.  I know Nobody does.

[carusoam]

Until you know it is the stall indicator that is out of calibration...

Bob-S50 is bringing up a good point.

It would be bad form to fall out of the sky thinking the stall indicator was bad.

a pretty hard landing can occur by being slower than expected.

Thinking out loud,

-a-

[Marauder]

Here are a couple of mine on a 1975 F

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[kpaul]

I did some stalls in it during my transition training a couple of weeks ago.  While I will admit I was not focusing on the ASI, I know I saw it was in the low 60s IMPH, I don't remember the horn being so active either, but I was wearing a different headset because of an issue I had with my A20s at the time.  Now wearing the A20s, the horn is very clear.

Based on GPS speed and the fact the plane is floating on landing, I don't think it's the ASI however I will still get it calibrated and rehack my aircrafts IFR cert rather than take the risk.

[Yetti]

Sure you are not hearing the gear warning?

[kpaul]

2 hours ago, Yetti said:

Sure you are not hearing the gear warning?

No, that is a warbling tone for the gear and seems to come on at about 12 MP with the gear up. 

I get the steady stall warn even with the gear down at indicated speeds between 80 & 90 MPH.  So needless to say my landings yesterday were all too fast because I could not force myself to slow down with a constant stall warn.  I could tell they were fast and got nose bounce on a couple of them.

I was not able to get to the plane today, but plan on taking a good look at the stall vane tomorrow and if the weather cooperates I will take it out for a few stalls and see where the actual stall break occurs.  I couldn't do it yesterday since the wife and kids were in the plane and am pretty sure that intentional stalls would not bode well for getting them in the plane again.   If the IAS checks with the POH then I will talk with the local A&P about figuring out the calibration.

[Yetti]

Above 3000 AGL    If not 5000 AGL

[kpaul]

8 hours ago, Yetti said:

Above 3000 AGL    If not 5000 AGL

Thanks for the concern.  I was planning on 5000 AGL.  It was fairly docile when I did stalls with a CFI a couple of weeks ago with a slight right breaking tendency, but I will give myself plenty of altitude to work with.

[bonal]

Correct me if I'm wrong (likely) but shouldn't the stall warning be coming on before the stall I'll have to check my POH for my numbers but what's the point if it dosnt.

[kpaul]

 

17 minutes ago, bonal said:

Correct me if I'm wrong (likely) but shouldn't the stall warning be coming on before the stall I'll have to check my POH for my numbers but what's the point if it dosnt.

Correct,  the POH states that it "will sound when airspeed drops to near stall speed." I have no idea what Mooney defines as "near" however, 20 mph above seems a little ridiculous.  My POH states that at MGW, gear dn, flaps 15 (landing) the stall speed should be 64 mph.  The horn was steady at 80 mph and was intermittent from 90-80 mph.  I was not flying at MGW.  I was about 300 lbs below so really stall should be right about 60 mph.

 

[kpaul]

I took the plane out for a quick flight.  Gear down, flaps at takeoff, the stall warning comes on steady at 80mph, stall break was at approx. 62 mph.  I did multiple stalls and each time the horn sounded at 80 mph stalled around 62 mph and finally silenced passing back through 80 mph.  So 1.2 x would be 74.4 mph and 1.3 times would be 80.6, making the entire trip down final with the horn sounding.  Not only annoying but desensitizing as well, kind of like the boy who cried wolf. 

I couldn't see any damage or noticeable paint cracking where the stall vane may have been damaged.  I will attach the pics as soon as I get them downloaded.

[Shadrach]

On January 17, 2016 at 3:53 PM, kpaul said:

I did some stalls in it during my transition training a couple of weeks ago.  While I will admit I was not focusing on the ASI, I know I saw it was in the low 60s IMPH, I don't remember the horn being so active either, but I was wearing a different headset because of an issue I had with my A20s at the time.  Now wearing the A20s, the horn is very clear.

Based on GPS speed and the fact the plane is floating on landing, I don't think it's the ASI however I will still get it calibrated and rehack my aircrafts IFR cert rather than take the risk.

60s is actually high for an F under gross

[Bob - S50]

13 hours ago, kpaul said:

I took the plane out for a quick flight.  Gear down, flaps at takeoff, the stall warning comes on steady at 80mph, stall break was at approx. 62 mph.  I did multiple stalls and each time the horn sounded at 80 mph stalled around 62 mph and finally silenced passing back through 80 mph.  So 1.2 x would be 74.4 mph and 1.3 times would be 80.6, making the entire trip down final with the horn sounding.  Not only annoying but desensitizing as well, kind of like the boy who cried wolf. 

I couldn't see any damage or noticeable paint cracking where the stall vane may have been damaged.  I will attach the pics as soon as I get them downloaded.

Good on you.  Sounds like you just need to adjust the stall vane after all.

[kpaul]

On ‎1‎/‎17‎/‎2016 at 1:02 PM, Marauder said:

Here are a couple of mine on a 1975 F

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[kpaul]

Marauder,

It seems that my stall vane is set pretty much in the same position as yours....

Edited January 19, 2016 by kpaul

[Marauder]

Marauder,

It seems that my stall vane is set pretty much in the same position as yours....

I wish for your sake it wasn't. Now you have a different challenge to find the issue causing it. I think someone else mentioned the pitot static system or airspeed indicator being involved. Something isn't adding up.

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