M20J Gear Retract Problem

[Costa Leite]

Dear All

 

On last weekend I had a problem retracing the gear of our 1998 M20J Allegro, S/N 24-3429.

 

After take-off on Saturday from home base with full tanks and wife+kids on board, I selected gear up and continued the initial climb… I felt something strange because we weren’t accelerating as usual, but as I was on MTOW I didn’t care too much, but few seconds after, when crossing runway threshold I noticed the Master Warning Light flashing, and then I looked at the Annunciator Panel and saw the red light for Gear Unsafe.

I was flying 85kts at the moment and the aircraft wasn’t accelerating too much. I selected flaps up and initiate the standard left turn at level flight. As soon as we accelerated, the gear retracted and all lights gone off.

Entering downwind and level flight at pattern altitude, I decided to check the system and cycle the gear (we were around +100kts on ASI), and the gear extended and retracted without any incident, and so I continued the flight.

Reaching destination, I lowered the gear and everything was normal and landed without any problem.

 

On the next day, we departure back to home base. On pre-flight I double check visually all 3 gears and everything looked normal.

But after take-off I selected gear-up and nothing happened… we were climbing at 80kts with poor acceleration.

This time I didn’t get any warning light but the gear was still down according to panel floor indication.

I decided to cycle again the gear selector, but nothing happened… and I left the handle at gear-up selection.

When I levelled off at pattern altitude, the aircraft accelerated and, around +90kts the gear started to retract normally and without any warning lights.

As everything seemed normal I decided to continue flying, and reaching home base, I selected gear-down and gear extended normally, all visual indications were good and I landed without any other issue.

 

I clarify that we have almost new rubber shock discs on all 3 gears.

I also clarify that the emergency gear lever was locked in place on both situations.

On both occasions I never tried to push the red button of Gear By-pass.

 

According to several topics here on MS related to Gear Retracing problems, this can be caused by:

-       Problem on the Gear Circuit Breakers (but none CB popped during the last two flights).

-       Problem on the Gear Relays.

-       Problem on the Gear Handle selector.

-       Problem on the Gear Electric Wiring from wheels to gear motor.

-       Problem on the Gear Limit / Up Switches.

-       Problem on the Gear Airspeed Safety Switch.

 

I believe this is a problem related to Gear Relay, or Gear Airspeed Safety Switch.

Thinking on Airspeed Switch, probably on Saturday I got the Warning Light  + Gear Unsafe Light because the Gear started to retract (maybe at a higher Airspeed than normal because of a faulty Gear Airspeed Switch), but somehow the airspeed reduced and the gear stopped retracing, activating the warning lights, and only after new consistent acceleration on downwind the gear continued to retract… is this possible?

If it is the Airspeed Switch, I read somewhere that there are two micro-switches on this part, one for the Gear and the other one for airborne flight timer avionics… and if this second microswitch isn’t used on any avionics it can be used to the Gear system to substitute the other faulty microswitch… Is this true?

 

Can anyone help with the troubleshooting?

 

Many thanks in advacne for sharing your knowledge.

Fredi

Edited May 6, 2021 by Costa Leite

[carusoam]

Nice problem solving logic and details Fredi!

Somewhere around here is the details regarding the airspeed safety switch and a possible resource for getting it OH’d...

It might just need a good cleaning too...

 

Best regards,

-a-

[A64Pilot]

If it’s the airspeed switch, the moment you push the red button the gear will start coming up, and if you release it they should stop? Not sure about the stop part, but it seems logical if the system works as I think it does.

‘If it’s the relay, then pressing the red button won’t do anything, because the purpose of the red button is to bypass the A/S safety switch?

I’m having the same problem, except mine is gear coming down, sometimes there is a delay in coming down, and once or twice that delay was several seconds and I recycled the switch and they came down.

‘According to LAZAR the relays aren’t available, there are two numbers of relays, the second can be had from junk yards at a crazy price for a junk part, and I found one new one for $800, there is also a retrofit kit in the parts manual that I think converts the original relays to the $800 one.

‘I pulled my belly panel yesterday and I have the old style, original I believe. Anyway that part number crosses fo readily available relays used on winches and apparently golf carts, it’s a continuous duty 100 amp relay, the landing gear actuator says 80 amps on it and 2000 lbs limit. I think without looking that the gear CB is 30 amps, so I assume the actuator is seriously derated if it’s has a CB that a little more than a 1/3 of the amps it can pull.

So with 30 amps being the theoretical limit, I also believe a continuous duty 100 amp solenoid is also serious overkill.

‘OK long story, but I guess I’m talking myself into that a new non aircraft, but identical solenoid is a better choice than an aircraft solenoid bought from a junkyard that doesn’t have an 8130, and how do you determine it’s airworthiness?

So if you determine it’s the relay, then you may be in the same boat

 

On edit talking to others, it’s not been the gear switch, something else thst LASAR says they don’t have and Mooney says special order, 5 week wait.

‘Apparently LASAR used to sell a switch for less than a third of what the one with the wheel cost, you just had to put the wheel on it,but it’s no longer available.

I’m a new Mooney owner, but with this parts situation, I’m starting to wish I had bought an older Bonanza, they seem to have parts availability

 

Edited May 6, 2021 by A64Pilot

[LANCECASPER]

2 hours ago, Costa Leite said:

Dear All

 

On last weekend I had a problem retracing the gear of our 1998 M20J Allegro, S/N 24-3429.

 

After take-off on Saturday from home base with full tanks and wife+kids on board, I selected gear up and continued the initial climb… I felt something strange because we weren’t accelerating as usual, but as I was on MTOW I didn’t care too much, but few seconds after, when crossing runway threshold I noticed the Master Warning Light flashing, and then I looked at the Annunciator Panel and saw the red light for Gear Unsafe.

I was flying 85kts at the moment and the aircraft wasn’t accelerating too much. I selected flaps up and initiate the standard left turn at level flight. As soon as we accelerated, the gear retracted and all lights gone off.

Entering downwind and level flight at pattern altitude, I decided to check the system and cycle the gear (we were around +100kts on ASI), and the gear extended and retracted without any incident, and so I continued the flight.

Reaching destination, I lowered the gear and everything was normal and landed without any problem.

 

On the next day, we departure back to home base. On pre-flight I double check visually all 3 gears and everything looked normal.

But after take-off I selected gear-up and nothing happened… we were climbing at 80kts with poor acceleration.

This time I didn’t get any warning light but the gear was still down according to panel floor indication.

I decided to cycle again the gear selector, but nothing happened… and I left the handle at gear-up selection.

When I levelled off at pattern altitude, the aircraft accelerated and, around +90kts the gear started to retract normally and without any warning lights.

As everything seemed normal I decided to continue flying, and reaching home base, I selected gear-down and gear extended normally, all visual indications were good and I landed without any other issue.

 

I clarify that we have almost new rubber shock discs on all 3 gears.

I also clarify that the emergency gear lever was locked in place on both situations.

On both occasions I never tried to push the red button of Gear By-pass.

 

According to several topics here on MS related to Gear Retracing problems, this can be caused by:

-       Problem on the Gear Circuit Breakers (but none CB popped during the last two flights).

-       Problem on the Gear Relays.

-       Problem on the Gear Handle selector.

-       Problem on the Gear Electric Wiring from wheels to gear motor.

-       Problem on the Gear Limit / Up Switches.

-       Problem on the Gear Airspeed Safety Switch.

 

I believe this is a problem related to Gear Relay, or Gear Airspeed Safety Switch.

Thinking on Airspeed Switch, probably on Saturday I got the Warning Light  + Gear Unsafe Light because the Gear started to retract (maybe at a higher Airspeed than normal because of a faulty Gear Airspeed Switch), but somehow the airspeed reduced and the gear stopped retracing, activating the warning lights, and only after new consistent acceleration on downwind the gear continued to retract… is this possible?

If it is the Airspeed Switch, I read somewhere that there are two micro-switches on this part, one for the Gear and the other one for airborne flight timer avionics… and if this second microswitch isn’t used on any avionics it can be used to the Gear system to substitute the other faulty microswitch… Is this true?

 

Can anyone help with the troubleshooting?

 

Many thanks in advacne for sharing your knowledge.

Fredi

Have you  checked the emergency gear extension latch ?

Back seat passengers tend to kick that open and it prevents the gear from retracting until re-latched. Ask me how I know this.

[Rmag]

8 minutes ago, LANCECASPER said:

Ask me how I know this.

How do you know this?

[LANCECASPER]

Just now, Rmag said:

How do you know this?

22 years ago I flew a friend from San Antonio to Fort Worth so he could pick up a car. Another friend came along for the ride. No problem on the way there. On the way back after a long day and nice dinner we take off and I pull up the gear switch after take-off and I notice soon after that our climb rate is not good. I look down on the floor and the gear is still down. I try everything I know how to do and nothing, so we fly back at Cessna 172 speeds. I'm envisioning a huge bill, gear motor, etc. The next day I taxi over to Lone Star Mooney (no longer around). I explain the situation to Dennis Bernhard and I see him getting a big smile on his face. He reaches in and closes the latch and tells me that it happens to everyone at least once. He was right. I now always include that in my briefing to passengers on entry and exit.

[AH-1 Cobra Pilot]

48 minutes ago, LANCECASPER said:

22 years ago I flew a friend from San Antonio to Fort Worth so he could pick up a car. Another friend came along for the ride. No problem on the way there. On the way back after a long day and nice dinner we take off and I pull up the gear switch after take-off and I notice soon after that our climb rate is not good. I look down on the floor and the gear is still down. I try everything I know how to do and nothing, so we fly back at Cessna 172 speeds. I'm envisioning a huge bill, gear motor, etc. The next day I taxi over to Lone Star Mooney (no longer around). I explain the situation to Dennis Bernhard and I see him getting a big smile on his face. He reaches in and closes the latch and tells me that it happens to everyone at least once. He was right. I now always include that in my briefing to passengers on entry and exit.

I presume it also popped the applicable circuit breaker?

That is how many of us "know this".

Edited May 6, 2021 by AH-1 Cobra Pilot

[Costa Leite]

Lancecasper, Thanks for the tip, but I clarified on my initial post that the problem wasn't with the emergency latch mechanism, because I dobled checked it in flight when I had this gear problem. I was aware of this situation, and with kids on board it was likely that someone could kick the latch. But that didnt happen. The latch was secure and in place on both occurences.

[PT20J]

From the description it sounds like an airspeed safety switch problem. However, if the airspeed safety switch fails, you should get a gear warning horn and the red safety bypass button should illuminate when you put the gear handle in the up position (check the emergency procedures in the POH). Since you didn't mention this, there may be more going on here.

The way to troubleshoot this is to put the airplane on jacks and follow the procedures in the Service Manual.

A few points about the airspeed safety switch:

1. It is connected to the pitot and static systems so any plumbing issues can affect it.

2. The second microswitch is only a solution if the problem is a failed microswitch -- it won't help if there is a leak in the diaphragm.

3. The switch is adjustable, but that's really only for initial calibration -- it shouldn't change unless there is a leak or some other problem with the system.

Skip

 

[Costa Leite]

Thanks PT20J

does anyone have the service manual instructions for this gear problem that can share it here? I am trying to get ahead of the problem and study a bit this situation before the maintenance shop gets in

[LANCECASPER]

1 hour ago, Costa Leite said:

Lancecasper, Thanks for the tip, but I clarified on my initial post that the problem wasn't with the emergency latch mechanism, because I dobled checked it in flight when I had this gear problem. I was aware of this situation, and with kids on board it was likely that someone could kick the latch. But that didnt happen. The latch was secure and in place on both occurences.

True, but there's a switch also associated with that latch.

[PT20J]

22 minutes ago, LANCECASPER said:

True, but there's a switch also associated with that latch.

What switch?

[LANCECASPER]

26 minutes ago, PT20J said:

What switch?

You may be right. I always thought there must be a micro switch that the latch triggers, but maybe it's mechanical.

[Phil EF]

Had the same issue two years ago on the 79 231. 
Liberal spraying and working the up and down limit switches fixed it and has not recurred since. 
Easy to get to, easy to fix. 

[Costa Leite]

Does anyone have a picture of the limit switches?

[A64Pilot]

Testing it on jacks means your bypassing the airspeed safety switch, so I don’t understand how that will test the switch?

Secondly as has been said, you didn’t get the other warnings you should have for it to be an airspeed safety switch, especially the horn, hard to miss that.

I believe your going to have to trouble shoot this in the air, unless of course you have access to a pitot static system tester and an rankin some kts that way and test on jacks, I woudnt just blow on the pitot tube as that’s tough to get a steady airspeed and not be too much etc.

‘I think your going to have to wait for it to not work again, then push the airspeed safety bypass button and see if the gear starts up them, I’m betting it won’t, andI base thwt in you not getting the horn in flight when it didn’t work.

‘I think it’s going to be the relay myself, but as I’m trying unsuccessfully to find out which is which, I don’t even know which one to change.

‘The problem with intermittent as I used to tell people who wanted me to fix something is, I can’t fix what isn’t broken, because it’s working for me.

[A64Pilot]

56 minutes ago, Costa Leite said:

Does anyone have a picture of the limit switches?

I just put my panels back on, but they are easy to find, they are under the big panel, the second one back from the nose. they are simply large button looking momentary switches that are actuated by a flap piece of metal that’s clamped to gear actuating rods, hard to miss.

‘This same panel covers both the actuator and the relays

Edited May 6, 2021 by A64Pilot

[PT20J]

1 hour ago, A64Pilot said:

Testing it on jacks means your bypassing the airspeed safety switch, so I don’t understand how that will test the switch?

If you read the manual, you will find the test for the airspeed switch. 

[A64Pilot]

1 hour ago, PT20J said:

If you read the manual, you will find the test for the airspeed switch. 

I haven’t but does it involve blowing in it? besides his problem is like mine, intermittent, and they are hard to trouble shoot

To test the AS switch, I’d want a pitot static tester, put the handle up. then slowly increase airspeed until the horn stopped and the gear came up, that gives you the airspeed at which it activates as well as function check it. If I understand the system. But I don’t have a pitot static tester available anymore.

But I bet lunch the safety switch is a red herring, only because he didn’t get the horn, and the few times a  have seen videos of gear swings, the horn is always there when the switch is placed in retract.

‘Now I’m new to Mooney’s so I will bow if you will to those with experience, but if the switch is bad, you will get the horn won’t you? 

[A64Pilot]

Just read it, it seems to involve a water manometer which are easy to home make, and I guess any Mooney owner with wet tanks ought to have one anyway to test wing leak repairs.

 But I bet a pressure bulb used in a sphygmanometer if you were careful would work well too, just go slow and watch the AS indicator.

Be sure to tape the drain holes in the pitot before you start or you can’t build pressure of course, if you look you’ll see them, I think they may be there to let water out, but that’s a guess.

[PT20J]

22 minutes ago, A64Pilot said:

Just read it, it seems to involve a water manometer which are easy to home make, and I guess any Mooney owner with wet tanks ought to have one anyway to test wing leak repairs.

 But I bet a pressure bulb used in a sphygmanometer if you were careful would work well too, just go slow and watch the AS indicator.

Be sure to tape the drain holes in the pitot before you start or you can’t build pressure of course, if you look you’ll see them, I think they may be there to let water out, but that’s a guess.

There is a hole on the bottom of the pitot tube near the tip that is a drain hole to let water out. There is a second hole on the back that is for versions of the tube that use that hole as a static port and this is unused on the Mooney. You are correct that the bottom hole needs to be covered. The back hole can be left open. I used a syringe (approx 5/8" diameter) and length of plastic tubing between the syringe and the pitot carefully taped to be leak proof. You can test the gear safety switch and also test for pitot leaks this way. The Manual also has a test procedure and specs for pitot leaks.

[Ragsf15e]

4 hours ago, Phil EF said:

Had the same issue two years ago on the 79 231. 
Liberal spraying and working the up and down limit switches fixed it and has not recurred since. 
Easy to get to, easy to fix. 

I have had exactly the same “delayed” retraction issue and resolved it the same way with the limit switches.  DMax also told me they are available and not terribly hard to replace.  However, my original switch is working more than a year after cleaning and lubing it.  It was an intermittent problem too with no other indication except that the gear didn’t move when I put the handle up.

[Costa Leite]

Hi Ragsd15e,
Many thanks for your comment. I hope my problem will be that simple.
Just to understand a bit more your experience (which seems to be the same of Phill EF comment above) with delayed retracing issues, in any of the ocurrances does the MasterWarningLight iluminated and the GearUnsafe light on AnunciatorPanel iluminated?... ti happened to me on first time, perhaps indicating that the gear stopped at the middle of the retracting process...!? 

[Ragsf15e]

33 minutes ago, Costa Leite said:

Hi Ragsd15e,
Many thanks for your comment. I hope my problem will be that simple.
Just to understand a bit more your experience (which seems to be the same of Phill EF comment above) with delayed retracing issues, in any of the ocurrances does the MasterWarningLight iluminated and the GearUnsafe light on AnunciatorPanel iluminated?... ti happened to me on first time, perhaps indicating that the gear stopped at the middle of the retracting process...!? 

Unfortunately my airplane is older than yours and more simple (68F).  It’s got the limit switches, airspeed switch, and up/down lights.  I don’t have an unsafe or master caution.

Id say this, 45 minutes to remove belly panels and 5 minutes to lube/exercise the switches with lps2 is well worth it.

[Costa Leite]

Thanks Ragsd15e,

Can you confirm that the switch is the one highlighted in red in the pic in attach?
 

Edited May 7, 2021 by Costa Leite