“Stall” warning on rollout, very annoying..

[Knuckledragger00]

Is this a common issue?  Very disconcerting for passengers!  I asked a mechanic to fix it and he charged me an hour to adjust the angle on the stall indicator with zero difference.  Guess I should point out that I am not stalling and just rolling down the runway taking off normally (even says “Stall” on takeoff up to a few hundred feet).

[David_H]

What airspeed are you climbing out at?

[LANCECASPER]

At what speed do you rotate?

[Knuckledragger00]

I have been pulling back the yoke around 45 to 50 to take pressure off the nose, then lifting off around 70’s.  Climb out in the 90’s for the first 400 or so then gradually increase speed to around 120.

I am still a very new Bravo owner and have less than a dozen takeoffs under my belt.  

 

Edited November 7, 2018 by Knuckledragger00

[carusoam]

No, it’s not normal or common...

There is some proper adjustment for the angle of the stall switch.

And does not include any bending, so if you see somebody approach with that in mind...

The vane is supposedly hardened and is expected to break if bent...

There are a few pictures around here if you need more details...

Best regards,

-a-

[LANCECASPER]

36 minutes ago, Knuckledragger00 said:

I have been pulling back the yoke around 45 to 50 to take pressure off the nose, then lifting off around 70’s.  Climb out in the 90’s for the first 400 or so then gradually increase speed to around 120.

I am still a very new Bravo owner and have less than a dozen takeoffs under my belt.  

 

The stall warning is a very simple system and I might tend to believe the horn quicker than I would your airspeed on the G1000. When was the last time you had a pitot static check done?

[FoxMike]

I have TKS and have had a problem with stall warning squaking on every takeoff since I bought the plane.  I tried to adjust the switch to no avail.  It seems the TKS panel changes the airflow slightly and the switch activates with higher margins before stall.  I have had nervous passengers who wonder if the plane is going to stall on takeoff.  

[David_H]

Is it possible to take a CFI up with you to do a few stalls to see where the airspeed is when the stall happens?

[David_H]

I’ll also agree that the stall warning system is fairly robust. The airspeed reading could very well be off.

[carusoam]

Without looking things up...

My dirty stall speed at max gross is 58kias...

The stall horn comes on about 5kias(?) prior/faster faster than the stall...

Hearing a stall horn at 400’ is scary. As it should be. Left tuned in this fashion, you will learn to ignore it. Ignoring a warning is Bad design... 

T/O is with T/O flaps deployed...

I hold the elevator neutral, until 65kias... raising the nose, she is above the usual stall horn activation speed. Accelerate to 75kias to begin the  lean-up activities...

nary a peep.

I don’t have a G1000 either... just a fancy electronic tone...

A whole bunch of things could be going on...

Give some detail to your T/O procedure, speeds and attitudes... it is quite possible you are raising the nose enough to get the attitude that the horn is sounding...

Soft field technique, or climbing over a 50’ object?

PP thinking out loud, not a CFI...

Best regards,

-a-

[Knuckledragger00]

Pitot static tests are current.  I do have TKS and have only ever flown in one other Bravo that also had TKS and the same issue!

Have had a checkout with a CFI and we stalled around 61 or 62 indicated dirty.

So now I am thinking maybe it is an issue only with TKS equipted Bravo’s?

[N201MKTurbo]

It may just be the attitude of the plane on the ground. Try pushing forward on the yoke on rollout to raise the tail some and see if it quits. 

[ilovecornfields]

16 hours ago, Knuckledragger00 said:

I have been pulling back the yoke around 45 to 50 to take pressure off the nose, then lifting off around 70’s.  Climb out in the 90’s for the first 400 or so then gradually increase speed to around 120.

I am still a very new Bravo owner and have less than a dozen takeoffs under my belt.  

 

You must be a fast learner. I just went back and looked at my transition training - 32 landings, 4 at night. Sounds like you have a good excuse to buy a GoPro...

[LANCECASPER]

Pitot static tests are current.  I do have TKS and have only ever flown in one other Bravo that also had TKS and the same issue!
Have had a checkout with a CFI and we stalled around 61 or 62 indicated dirty.
So now I am thinking maybe it is an issue only with TKS equipted Bravo’s?

I think that’s part of your problem - your indicated should be a few knots less than the 61-62 that you’re indicating on a dirty stall. So if you are rotating at 70 indicated but it’s really 65 and the stall warning is supposed to come on 10 knots before the stall . . . your stall warning might be telling you the truth.


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[Knuckledragger00]

Had a Mooney M20J before.  This is a whole new level!  Glass and trying to learn the whole LOP procedures is making things interesting.  Not to mention engine management!  

[Knuckledragger00]

23 minutes ago, LANCECASPER said:

I think that’s part of your problem - your indicated should be a few knots less than the 61-62 that you’re indicating on a dirty stall. So if you are rotating at 70 indicated but it’s really 65 and the stall warning is supposed to come on 10 knots before the stall . . . your stall warning might be telling you the truth.


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Except I also hear the warning on climb out at 90ish?

[LANCECASPER]

Ah well that’s different - time for a trip to a competent Mooney Service Center


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[carusoam]

Wait...

Stop...

Things are not sounding very good...

Tell us more about your transition training?  Trainer?

 

A Mooney specific trainer would have pointed out a mismatch between stall horn and actual stall speed.... based on his experience.

not only do you get to learn the New to you Mooney... you get to know if anything isn’t working as expected...

Your GPS should be pointing out differences between air speed and ground speed.

airspeed on the G1000 is susceptible to calibration error.

you had somebody do something with your stall indicator...

 

From an engineer’s perspective you have lost any reliable indication of actual air speed.  Reason enough to stop flying it...

your passengers are telling you something.

Mrs. Garmin is telling you something.

The internet is telling you something.

Lance is telling you something.

Did anyone tell you this is normal? Keep going?

Did the STC for anti - ice system say this is OK?

A fiki system goes out of its way to have the stall vane operate properly in icing conditions.

Based on the description... your systems are at risk of not operating properly.

on final approach, the stall horn may peep. A reminder, if you have stopped scanning the ASI... lowering the nose should silence it properly. if it stays on, that is a hint to be adding power and going around..: you have lost this reliable safety feature.

continued flight under these conditions leaves me uneasy as a reader from very far away.

Thoughts of a private pilot, from the comfort of an EZ chair... not an Instrument guru, or CFI...

Briefly, find an instrument guru. ASAP.

See if @donkaye has some insight for you... Engineer, cfii, Bravo owner, loves instrumentation.

Best regards,

-a-

[Shadrach]

2 hours ago, Knuckledragger00 said:

Pitot static tests are current.  I do have TKS and have only ever flown in one other Bravo that also had TKS and the same issue!

Have had a checkout with a CFI and we stalled around 61 or 62 indicated dirty.

So now I am thinking maybe it is an issue only with TKS equipted Bravo’s?

Is your POH stall speed given as KIAS or KCAS?  If with just you and a CFI it is actually stalling 3-4kts above what stall speed should be at MGW then you have an indicator issue.  I'm inclined to believe the stall horn.  It is activated when airflow reverses direction over the vane.  It does not mean the wing has stalled, but it does indicate that the wing is near critical AOA.

If it stalls at 61-62, at what speed does the horn first sound?

My horse sense tells me there may be both indicator and technique issues at play.  I fly a much lighter medium body and I break ground around 70kts or more depending on weight. I use about 5lbs of back pressure and let the plane breaks ground when its ready.

[Knuckledragger00]

I really don’t think it is technique in this case.  Believe me I don’t have an issue with admitting when I am wrong but when my CFI first demonstrated his takeoff technique it did the same thing.  That plus the other Bravo with TKS I flew in did the same thing and the owner of that plane had many years experience.  Strongly think it may be more of a TKS issue than anything else at this point?

[Knuckledragger00]

21 hours ago, FoxMike said:

I have TKS and have had a problem with stall warning squaking on every takeoff since I bought the plane.  I tried to adjust the switch to no avail.  It seems the TKS panel changes the airflow slightly and the switch activates with higher margins before stall.  I have had nervous passengers who wonder if the plane is going to stall on takeoff.  

Fox,

Have you ever had anyone try to fix it?

[carusoam]

We have a TKS resource around here as well...

@CAV Ice Protection

https://www.caviceprotection.com/products-services/ice-protection-systems/mooney-m20-fiki

 

It would be nice to get some insight to the effects of TKS systems on the stall warning system...

It would be wise to contact CAV directly to better understand what you have and why it does what it is doing...

See if you can post a pic of your stall warning vane... the switch behind it may have been contaminated with TKS fluid...?  Either way, still not very normal... a pic should indicate where the vane is and how far away the Tks panels are from it...

PP thoughts only...

Best regards,

-a-

[exM20K]

Kevin Kammer from Mooney told me he test flies the new planes at 3100# and 45" CG.  I was curious about whether the G1000 stall warning alerted faster than the beeper, and he said they are tied to the same switch. I had incorrectly assumed "Bitchin' Betty" was hard coded to an airspeed level somewhere in the G1000.  My M20TN probably flies very similarly to your Bravo (just faster and using less fuel, LOL).

He asked me to duplicate his method, so, power off:

at 3100# and 45" i got the following:

 

Stall Warning clean: 73

Stall Buffet clean: 65

 

Stall Warning Landing configuration: 65

Stall Buffet Landing configuration: 57

 

Betty and stall beeper are at the same speed, as you said they should be.

 

Approx 8 KIAS between warning and buffet.

 

For your situation, I'd record the power-off warning and stall buffet speed in T/O and LDG configuration.  See if you have the 8 KIAS difference.

Then I'd ask: are you getting book cruise speeds?  If you are in a TKS bird, then your ASI is probably indicating incorrectly.  Most are 8ish KTAS slow.

 

Lastly, a perhaps obvious question:  Are you certain that the Alternate Static is closed and not leaking somewhere?

[Knuckledragger00]

13 hours ago, carusoam said:

We have a TKS resource around here as well...

@CAV Ice Protection

https://www.caviceprotection.com/products-services/ice-protection-systems/mooney-m20-fiki

 

It would be nice to get some insight to the effects of TKS systems on the stall warning system...

It would be wise to contact CAV directly to better understand what you have and why it does what it is doing...

See if you can post a pic of your stall warning vane... the switch behind it may have been contaminated with TKS fluid...?  Either way, still not very normal... a pic should indicate where the vane is and how far away the Tks panels are from it...

PP thoughts only...

Best regards,

-a-

Car,

Spoke with Jerry Jordon and CAV and he said up till yesterday he has never heard of any issues with his system and this issue.  He did also say that he had heard of this happening with the long body and recommended calling Mooney (waiting on a call back now).  He thought the problem could be fixed simply by adjusting the stall vane housing slightly.  

[N201MKTurbo]

Everybody keeps talking about airspeeds and such. The stall vane is an angle of attack sensor. if the relative wind is below the plane of the tab it blows it up. If the wind is above the plane of the tab it blows it down. 

With the wheels on the ground, the angle of attack and airspeed are decoupled. When you rotate the plane for takeoff, you are raising the angle of attack above the stall angle of attack as evidenced by the fact the plane isn't flying yet. So the stall warning should sound. If you did a no flaps takeoff and just flew the plane off without rotating it, it probably wouldn't sound. 

The switch may have a weak or broken spring. There is a spring that holds the switch down requiring a certain wind speed to blow it up from the normal down position. This is what keeps it from going off all the time.