Strange stall switch behavior

[Bartman]

Went up with the instructor for Instrument competency check instead of the usual 6 approaches yesterday, and we also worked on some manouvers.  While doing slow flight in the no flap configuration the stall horn came on at 70 knots and stayed on all the way down to just below 60 knots where we did minimum controllable airspeed.  This strange thing is my stall horn rarely works on landing. I always hold her off nose high about 1 foot off the runway and continue to use electric trim until she stalls with trim nearly full up and the yoke in my chest.  Usual landings are full flaps and occasionally partial flaps if really gusty, but I rarely if ever hear the stall warning on landing, but I do hear it chirp on takeoff especially if gusty.  The A+P and I recently adjusted the switch a couple of times and it is basically full up on the adjustment travel limits.

What gives ?

[peevee]

Ours basically did about the same thing and then stayed on permanently one day, maybe your switch is just getting flaky?

If you have the old safe flight design, I can't find a replacement switch and it's riveted together (not necessarily a problem but...)

If you have the newer retrofit design, it's a $15 micro switch and a little fiddling. Held on with 2 screws.

if you want to buy the safe flight design new, it's $1800

if you want the safe flight design overhauled by safe flight, it's $1200

if you want a new retrofit kit from lasar, it's about $550

That's what I've learned over the past 48 hours re: stall switches.

Oh, and used either retrofit or safe flight I only see one of each for sale right now and they're $325. I went with new from LASAR. I would definitely flood yours as best you can with contact cleaner and see if you can degunk it.

[RobertGary1]

Stall horn blaring the entire time in the flare for me.  One time it did not and turned out the cheap sonalert was dead  fortunately they are in expanse non-aviation part Same part number as the oil pressure warning horn on my boat  

 

-Robert

[Bartman]

3 minutes ago, Hyett6420 said:

The stall vane has to be adjusted in situ to make sure that it flips at the correct speed.  If yours is blaring continually in the flare, take the aircraft upto 4-5k or so and bring her back to a stall, note at what speed the horn goes off, is it at the correct speed or is it too high.  Go to your a and p with the results.  He will look and make sure your vane is set correctly.  Do hwe is before you start pulling vanes apart etc.

This is exactly what we did.  The stall horn is on continuously at 70kts and below at altitude, but not in the flare even when she is in full stall landing.

Why ?

[peevee]

14 minutes ago, Hyett6420 said:

Sounds like it is badly adjusted. Mine does not go off till below 70 and very very rarely in the flare unless im doing 65 or less.

How can adjustment make the horn stay on at 70kias and not a peep at 65 in the flare? 

[Bartman]

6 minutes ago, peevee said:

How can adjustment make the horn stay on at 70kias and not a peep at 65 in the flare? 

Exactly !

Sounds like there are other Mooneys with stall switches that behave like mine.

[peevee]

9 minutes ago, Bartman said:

Exactly !

Sounds like there are other Mooneys with stall switches that behave like mine.

Ours did for awhile. Couldn't get it to chirp on landing but takeoff would tickle it. Then as I said it just stuck on. We'll see if the new one is better 

[John Mininger]

My stall horn seems to work at the proper speeds and attitudes, but I usually can't hear it. Even on the ground, it's not very loud. Does the "horn" itself go bad? This is also the case for the gear up warning.

Now my hearing isn't what it used to be, and I am wearing Zulu ANR headsets. But I have no problem hearing ATC and I have no problems hearing the stall warning in other airplanes.

Are there any electronic devices that will pipe the gear up and stall warnings into the audio system?

Thanks

[peevee]

That could be the sonalert going out yeah

[Vance Harral]

Probably not the issue, but to scientifically complete the experiment, you'd need to perform stalls at altitude in your normal landing configuration (which you said is usually full flaps, occasionally partial).  In your original post, you said the stall warning came on at 70 KIAS in the "no flaps" configuration while airborne.  The indicated airspeed at which the stall warning horn will come on with flaps extended is slower.  But only by a few knots.  I did read where you said you make full-stall landings and agree it's odd you're not hearing the sonalert on landing.

 

16 minutes ago, John Mininger said:

Are there any electronic devices that will pipe the gear up and stall warnings into the audio system?

Absolutely.  One of the best and least expensive upgrades we made is the addition of an EI AV-17 Voice Annunciator to our airplane.  In addition to the factory sonalert tone (which I agree is easily missed), we now get a "check airspeed" warning through an always-on feed into the audio panel.  It also generates voice alerts for the landing gear warning, engine monitor alarm, low bus voltage, and low vacuum.  My mechanic was willing to sign it off as a minor modification.

[peevee]

Av17 install on our old k  was 5k in labor 

[RobertGary1]

Probably more important to be adjusted now that the faa does not want slow flight to be slow enough to trip the stall horn anymore. 

-Robert

[Vance Harral]

Just now, peevee said:

Av17 install on our old k  was 5k in labor 

Something about that doesn't seem right.  Assuming $100/hour labor, that's 50 hours - more than a full week.

I try not to cry "inflated mechanics charges!" without understanding details.  Was there something complicated about your installation?  Other work done in addition to the AV-17, or maybe a bunch of old wiring removed?

By way of comparison, I did the wiring myself and had the mechanic inspect it.  Total cost, about $350 for the hardware, plus one hour of labor for inspection and sign-off.  The work is mostly just adding wires to existing connections via screw-on ring terminals, no soldering involved.  It does help to have a firm understanding of electrical behavior, to understand where an AV-1 inverter or equivalent is needed.  As an amateur working very slowly, it took me a couple of days to do the wiring.  That doesn't include the time to study the Mooney system schematics and fully understand the AV-17 manual, though.  I'd like to think a decent shop would already have that knowledge or at least not charge you for their learning curve, but maybe that's debatable.

I completely understand that some folks don't enjoy the DIY approach.  But even turning the whole process over to the shop, I would have guessed $2K total cost at most.

[RobertGary1]

22 minutes ago, peevee said:

Av17 install on our old k  was 5k in labor 

I have the same but it doesn't change much. Still uses the same stall sensor n. Mine is wired to the stall horn 

-Robert

Edited May 11, 2017 by RobertGary1

[Vance Harral]

1 hour ago, RobertGary1 said:

Mine is wired to the stall horn 

I wired ours to the terminals of the sonalert, rather than the stall sensor itself.  Saves running a set of wires out into the wing.

[peevee]

2 hours ago, Vance Harral said:

Something about that doesn't seem right.  Assuming $100/hour labor, that's 50 hours - more than a full week.

I try not to cry "inflated mechanics charges!" without understanding details.  Was there something complicated about your installation?  Other work done in addition to the AV-17, or maybe a bunch of old wiring removed?

By way of comparison, I did the wiring myself and had the mechanic inspect it.  Total cost, about $350 for the hardware, plus one hour of labor for inspection and sign-off.  The work is mostly just adding wires to existing connections via screw-on ring terminals, no soldering involved.  It does help to have a firm understanding of electrical behavior, to understand where an AV-1 inverter or equivalent is needed.  As an amateur working very slowly, it took me a couple of days to do the wiring.  That doesn't include the time to study the Mooney system schematics and fully understand the AV-17 manual, though.  I'd like to think a decent shop would already have that knowledge or at least not charge you for their learning curve, but maybe that's debatable.

I completely understand that some folks don't enjoy the DIY approach.  But even turning the whole process over to the shop, I would have guessed $2K total cost at most.

Nope, nothing else. Just a lot of time. Then another 2k to troubleshoot problems

[Vance Harral]

Sorry you had a bad experience, we've had zero trouble with ours in the 7 years it's been installed.  That's just one data point, though.  There are certainly opportunities for things to go wrong with it.