Gear warning switch

[DonMuncy]

The gear warning alert failed on my K model Saturday. 

I have a "Bitchin Betty" (warns of both stall and non-lowered gear) which is wired into the same system that activates the horns. The stall warning functions so, so I assume the device itself is working, and the horn is not the problem. I think it is most likely either the switch on the gear or the switch on the throttle.

I assume the switch on the gear mechanism is in the same location on all models. Can anyone tell me exactly where the one on the gear is located.

[carusoam]

The horns are called Sonalerts...

They are probably piezo electric devices...

You may have two or three...

Stall switch activates one.

Betty is on the other...

They are often mounted in the ceiling.

Their MTBF is in the middle between brand new and 60 years old....

Something to think about while waiting for a better reply...

Some ideas while you wait,

-a-

[Piloto]

I have a 1982 M20J and believe yours is like mine. There is actually no alarm switch on the gear but an airspeed switch behind the IAS. The switch is used to prevent gear retraction before achieving lift off speed. You by pass the switch by pressing the red button below to allow to retract the gear when on jacks. Check the wires on the gear switch and throttle switch. Verify that the throttle switch arm/roller click when the throttle is pulled. The throttle knob shaft may have rotated so the notch is not line up with the switch/arm roller.

 

José 

[laytonl]

What Jose says is absolutely correct for the J. However, I don't know if the K is the same. Lee

[GeorgePerry]

I just replaced a stall switch for the same reason.  It failed but failed in the "on" position making flying a noisy affair until I pulled the C/B.  Got it in the shop and I can report that is one very expensive heated micro switch. >$500 from Mooney plus labor.  While it was in they also checked the Gear Warning system as well.  On an eagle, there's another micro switch that gives gear warning based on throttled position (+/- about 13.5 in) as well as an airspeed warning.  So in an eagle, (don't know it it applies to a K) there are two way to activate the gear warning horn.

 

good luck with yours

[N201MKTurbo]

My schematics are out at the airport, but the gear warning runs through the limit switches. They are on the actuator in the belly.

[DonMuncy]

Piloto,

I'm not sure I understand. As I understand it, the sonalert is activated when the throttle is almost closed and the gear is still retracted. How  would an airspeed switch figure into that.

[RobertGary1]

I believe you have two round, black son-alerts in the ceiling. If you are not hearing the gear warning when you press the test button, the issue isn't with the gear down switch. In fact if you had an issue with that you'd have other issues. The horns themselves are not very reliable and you can expect to replace them every 5 years or so. First step is to lower the headliner enough to get a multi-meter in there and measure the voltage across the horn when pressing the test button. These horns are pretty inexpensive and used extensively in industrial applications (I the stall warning one on my boat that alarms for oil pressure, etc).

 

-Robert

[RobertGary1]

Piloto,

I'm not sure I understand. As I understand it, the sonalert is activated when the throttle is almost closed and the gear is still retracted. How  would an airspeed switch figure into that.

 

Its a different system that was used on older Mooneys. I don't believe air speed comes into play for you.

 

-Robert

[Piloto]

Piloto,

I'm not sure I understand. As I understand it, the sonalert is activated when the throttle is almost closed and the gear is still retracted. How  would an airspeed switch figure into that.

 

The airspeed switch keeps the gear from getting retracted on the ground if the gear knob is set up. However during a trip to Olathe KS at night at 10,000ft a horn started sounding off. At first I though it was the stall horn since the airspeed has dropped to almost zero and the plane started shaking. I just nose down a little bit but no speed increase. I realized that I was having ice on the pitot tube. Turned pitot heat on and the alarm went away as speed increased. The plane shaking was due to ice on the prop. The stall warning would have never come up since the leading edge was covered with ice. I am puzzle why the gear horn came on with full throttle. The only scenario I can think you would land with throttle in is during a dead engine landing. In this case the low airspeed and gear retracted will warn you. Maybe is a backup for the throttle switch. Since then I installed a gear voice alert device to differentiate a stall from a gear up warning

 

José 

[N201MKTurbo]

The gear warning system uses the limit switches on the actuator, the gear switch (the one that looks like a wheel) and the airspeed sensor or a micro switch on the throttle. The circuits used for the gear warning may or may not be the same circuits used for extending and retracting the gear.

 

If the green light is not on and you are below the airspeed limit, or the throttle is retarded on the planes with a micro switch, the warning horn will sound.

 

Why do you need a voice alert? The stall is a constant tone and the gear warning pulses. It is the same on every plane ever made.

[scottfromiowa]

That is like asking why do you need underwear. You don't, but they are nice to have and they may save embarrassment depending on your age.

[Piloto]

The gear warning system uses the limit switches on the actuator, the gear switch (the one that looks like a wheel) and the airspeed sensor or a micro switch on the throttle. The circuits used for the gear warning may or may not be the same circuits used for extending and retracting the gear.

 

If the green light is not on and you are below the airspeed limit, or the throttle is retarded on the planes with a micro switch, the warning horn will sound.

 

Why do you need a voice alert? The stall is a constant tone and the gear warning pulses. It is the same on every plane ever made.

 

I am not that smart. During gusty approaches the stall may sound intermittent just like the gear warning.

 

José

[KSMooniac]

The gear warning system uses the limit switches on the actuator, the gear switch (the one that looks like a wheel) and the airspeed sensor or a micro switch on the throttle. The circuits used for the gear warning may or may not be the same circuits used for extending and retracting the gear.

 

If the green light is not on and you are below the airspeed limit, or the throttle is retarded on the planes with a micro switch, the warning horn will sound.

 

Why do you need a voice alert? The stall is a constant tone and the gear warning pulses. It is the same on every plane ever made.

 

This is correct.  I just got done tracing the schematics for my gear system ('77) which is the last year of the squat switch on the gear itself.  '78+ use the airspeed switch plumbed behind the ASI.  Anyway, the system is fairly tortuous in my opinion as a non-electrical engineer.  The path for the gear system goes through the selector switch, annunciator panel, up- and down-limit switches on the actuator, the sonalert horn, and either the squat switch or airspeed switch to make everything work.  Wires go from the console to the panel to the ceiling and to the belly.

 

I believe failure of the airspeed switch would prevent the gear from going up without using the override button.  The throttle microswitch is installed on the cable, just forward of the knob/behind the center console.  It is mechanically mounted on the cable, and could have been bumped out of position so that should be checked first IMO.  If the switch itself went bad, I think it can be removed from the mounting plate and replaced easily enough.  The sonalert can fail as well.

 

I'd start with the switch on the throttle with a visual inspection, and maybe a function test on jacks to swing the gear.

[Piloto]

That is like asking why do you need underwear. You don't, but they are nice to have and they may save embarrassment depending on your age.

 

Ok, what disposables do you use for long trips. I use the bottle but have to admit is embarrassing at times.

 

José

[RobertGary1]

This is correct.  I just got done tracing the schematics for my gear system ('77) which is the last year of the squat switch on the gear itself.  '78+ use the airspeed switch plumbed behind the ASI.  Anyway, the system is fairly tortuous in my opinion as a non-electrical engineer.  The path for the gear system goes through the selector switch, annunciator panel, up- and down-limit switches on the actuator, the sonalert horn, and either the squat switch or airspeed switch to make everything work.  Wires go from the console to the panel to the ceiling and to the belly.

 

I believe failure of the airspeed switch would prevent the gear from going up without using the override button.  The throttle microswitch is installed on the cable, just forward of the knob/behind the center console.  It is mechanically mounted on the cable, and could have been bumped out of position so that should be checked first IMO.  If the switch itself went bad, I think it can be removed from the mounting plate and replaced easily enough.  The sonalert can fail as well.

 

I'd start with the switch on the throttle with a visual inspection, and maybe a function test on jacks to swing the gear.

 

 

Unless you are having issues with the gear retracting I'd not jump there. Again, 90% chance its just normal Son-Alert wear. They're good for about 5 years. If you don't get the horn with the test button pressed its not related to the airspeed or the squat switch; that's all bypassed. the horns are around  $30.

 

-Robert

[manlewt]

Assistance requested. I fly a 1970 M20E that for the first time decided to refuse my command to raise the gear after takeoff. I selected gear up and nothing happened. The light remained green and no other actions taken by the plane to heal itself of the landing configuration setup. I landed, placed it on jacks, checked the weight on wheels switch to no avail. I am not certain if the switch is working or not however before I replaced it, I wanted to make sure I checked all other possible areas that could have also caused the gear to remain down and locked. I have reset the breakers for the gear however, I am not sure I fully understand what other switches may also need to be checked. Any suggestions? I don't think it is the gear switch however, I am not even sure about that.

I will take guidance from anyone who has any suggestions that don't require me to drop the belly pan!

Thanks,

Bill

[carusoam]

Welcome aboard Bill.

Do you have a copy of your ships wiring diagram handy?

The POH usually has this type of information.

What year is your plane?

Stand by for somebody with more knowledge than I...

Best regards,

-a-

[KSMooniac]

Gear limit switches might be the next culprit, or old rubber donuts that don't expand when unloaded are another likely source of your problem.

[ArtVandelay]

If you can get behind the panel, can't you just short the switch and see if they raise then, eliminating it as a possible problem

[Marauder]

It sounds like a limit switch or gear switch issue. If it were the squat switch, you should have gotten the gear unsafe light.

[manlewt]

It 's a 1970 model. The donuts are new however I didn't drop thr belly pan to check the limit switches. This will by my next area of focus. If the throttle switch was out of tolerance I wouldn't think that they would engineer it to not allow the gear to deploy. Thank all of you for the quick response on this! What a great group of folks.

Bill

[Marauder]

It 's a 1970 model. The donuts are new however I didn't drop thr belly pan to check the limit switches. This will by my next area of focus. If the throttle switch was out of tolerance I wouldn't think that they would engineer it to not allow the gear to deploy. Thank all of you for the quick response on this! What a great group of folks.

Bill

The gear will deploy or retract if the throttle switch is not working. Let us know what you find out.

[RobertGary1]

The limit switches can get stuck and its good to get some triflow on them and exercise them. 

 

-Robert

[manlewt]

Thank you for the input. I drove up to Denton Tx to meet with a certified Mooney AP this afternoon. I described the situation to him as well as the actions I had taken. After very little thought, he said that if I flew it up to their shop he would put it on jacks, drop the belly pan and check the two switches for freedom of movement and electrical current. He felt that it is more than likely a bad switch or broke wire. So, I will purchase a can of triflow and put it back on the jacks to get a look at them this weekend. I will update my findings as soon as possible.

Many thanks

Bill