False Gear Alarm, 68 M20F J Bar Gear

[Huckster79]

How does our gear alarm system work?  I'm assuming it's based off throttle position and airspeed maybe? I guess I need to understand the system of it better.

So I brought home my bird from a full tank strip and reseal, after a long day of flying where the only thing that went well was nothing got bent, and the tanks didn't leak,  I was finally on final to home airport and was ready to be done for the day, when on on short final an ear piercing beep started coming through my headset.  I quick looked, light was green, J bar was in the gear down position.  I elected to go-around, I unlocked and relocked the gear and made an attempt again, same results, did another go around, went a bit further out this time and fully recycled the gear a couple times.  I briefed myself that after a long day of flying I had done all I could do to troubleshoot it, all was indicating a sensor issue of sorts and that repeated go arounds was probably not the wisest thing to keep doing, so go back, land as gentle as possible, take my headset off if need be on short final to avoid the distracting ear piercing sound.  All went well.

Coming in the first time to to land at home, the first time I'v done this but the J bar slipped out of my hand as I was putting it in the lock block and it slammed to the floor when it slipped out of my hand, so I'm half assuming that when it bounced closed that it maybe "whacked" a sensor/switch whatnot.  She's headed right into annual, but thought I might see if I could get some "on the street" insight I could pass on... And also so I can start understanding each system on the bird.

Thanks

Ray

 

 

 

 

[N201MKTurbo]

First off, with the J bar, if it is locked in the down lock block, you can ignore any gear warnings. 

The gear warning is very simple, there is a microswitch in the down lock block and a microswitch on the throttle cable.

If the green light was on and the gear warning was sounding, there is something wrong with the warning horn wiring.

You can test the gear warning in the air by throttling back to idle and sticking your finger into the uplock block and pushing on the switch. If you bring the throttle up, the warning should quit. Or pushing on the switch should make it quit. The switch in the up lock block should make the red and green lights toggle.

If you have jacks, you can do all this on the ground.

[N204TA]

Ray,

It looks like my F came out of the factory not long before yours.  Rest assured, the J-bar slamming to the floor probably made a lot of noise but you didn't damage any switches/sensors.

As Rich said above, the gear indicator/warning switch is located in the downlock block under the instrument panel.  When the gear is unlocked/up, you can stick you finger under there and feel the little flapper.  When the gear is anything but down and locked, you should have a red "unlock" light and the horn will be triggered by the throttle position.  When the gear is down and locked, the green light will illuminate and, if you still have the ram air "Power Boost" open, the little amber light next to that control will light up, reminding you to close the ram air door.

Many years ago, I had a situation where the gear appeared down and the green light was on but, as soon as I pulled the throttle to idle, the horn went off.  I tugged on the J-bar and it came unlocked.  Apparently, the gear was down just enough to trigger the light but not fully locked in place.  Consequently, I always give the J-bar a little tug on short final just in case.

Tom

 

[Ragsf15e]

4 hours ago, Huckster79 said:

How does our gear alarm system work?  I'm assuming it's based off throttle position and airspeed maybe? I guess I need to understand the system of it better.

So I brought home my bird from a full tank strip and reseal, after a long day of flying where the only thing that went well was nothing got bent, and the tanks didn't leak,  I was finally on final to home airport and was ready to be done for the day, when on on short final an ear piercing beep started coming through my headset.  I quick looked, light was green, J bar was in the gear down position.  I elected to go-around, I unlocked and relocked the gear and made an attempt again, same results, did another go around, went a bit further out this time and fully recycled the gear a couple times.  I briefed myself that after a long day of flying I had done all I could do to troubleshoot it, all was indicating a sensor issue of sorts and that repeated go arounds was probably not the wisest thing to keep doing, so go back, land as gentle as possible, take my headset off if need be on short final to avoid the distracting ear piercing sound.  All went well.

Coming in the first time to to land at home, the first time I'v done this but the J bar slipped out of my hand as I was putting it in the lock block and it slammed to the floor when it slipped out of my hand, so I'm half assuming that when it bounced closed that it maybe "whacked" a sensor/switch whatnot.  She's headed right into annual, but thought I might see if I could get some "on the street" insight I could pass on... And also so I can start understanding each system on the bird.

Thanks

Ray

 

 

 

 

It seems that the throttle switch is working, but the one on the downlock is not.  That’s where I’d start.

[Ragsf15e]

Also, there’s a circuit breaker for the gear warning on mine which will shut off the alarm if it gets stuck on.  I’ve had to use that once because the alarm is brutal.

[Shadrach]

2 hours ago, Ragsf15e said:

It seems that the throttle switch is working, but the one on the downlock is not.  That’s where I’d start.

The down lock is what drives the green/red annunciators.  He had a green light , so the down lock switch is working. 

[Huckster79]

We’ll get it on jacks tomorrow and be able to fiddle with it more… 

So I’m humble enough to know I’m above nothing- but man it made me wonder if it’s working how anyone could miss that beep!  I had to take my headset off on final to concentrate on landing.  

[Shadrach]

10 minutes ago, Huckster79 said:

We’ll get it on jacks tomorrow and be able to fiddle with it more… 

So I’m humble enough to know I’m above nothing- but man it made me wonder if it’s working how anyone could miss that beep!  I had to take my headset off on final to concentrate on landing.  

I’ve never had a gear up, but I came close enough once to understand how it happens. All it takes is the right distraction at the wrong time. It’s amazing what your brain can tune out.

[Shadrach]

@Huckster79 here is the gear system schematic. Might help to get your head around it ahead of disassembly. Something weird is going on with the down lock switch or the wiring. Try pulling the ram air on the ground to see if the warning light comes on.

[Huckster79]

On 7/1/2024 at 5:37 PM, Shadrach said:

I’ve never had a gear up, but I came close enough once to understand how it happens. All it takes is the right distraction at the wrong time. It’s amazing what your brain can tune out.

yea that makes all the sense in the world.  We all have a built in penchant to want to think we’re above “it” and “it” can be many things not even aviation related.  The stats simply prove there’s not one of us that’s guaranteed to be above anything. 

[Shadrach]

5 minutes ago, Huckster79 said:

yea that makes all the sense in the world.  We all have a built in penchant to want to think we’re above “it” and “it” can be many things not even aviation related.  The stats simply prove there’s not one of us that’s guaranteed to be above anything. 

I caught it with a short file final GUMPS check. I still shudder to think of the outcome had I not done that. My SOP is to do a final gear check on short final. I take my hand off the throttle and grab the Johnson bar tug the handle down to ensure it’s seated and locked. You can imagine my surprise when I found that the Johnson bar was not in the down lock.

The distraction was caused by tower incessantly, calling turbine traffic that really wasn’t a factor (it was a Malibu.)

Tower called me as I was approaching abeam the numbers on downwind. They continued to call traffic as I flew a pretty tight pattern. One thing they didn’t do was make any reference to the fact that my gear weren’t down which should’ve been obvious given the position of the tower.
 

The only thing that saved me was the rote procedure of grabbing the gear on short final. Had I also had a passenger in the left seat, asking questions and providing additional distractions, things could’ve gone worse. 

[PT20J]

On 7/1/2024 at 2:39 PM, Shadrach said:

@Huckster79 here is the gear system schematic. Might help to get your head around it ahead of disassembly. Something weird is going on with the down lock switch or the wiring. Try pulling the ram air on the ground to see if the warning light comes on.

How do those gear lights work? They have three wires each. One is tied to the bus, one is ground and the other is open or bus voltage depending on switch positions. I just don’t see what the extra bus voltage connection would be for.

[N201MKTurbo]

1 minute ago, PT20J said:

How do those gear lights work? They have three wires each. One is tied to the bus, one is ground and the other is open or bus voltage depending on switch positions. I just don’t see what the extra bus voltage connection would be for.

They are push to test lights. The third wire is power for the push to test.

 

[PT20J]

25 minutes ago, N201MKTurbo said:

They are push to test lights. The third wire is power for the push to test.

 

Ah, that explains it. Thanks!!