Are all three gear really down?

[Vance Harral]

27 minutes ago, Mooneymite said:

That would be about as effective as the present green light/stripe.  As you are aware, the gear can appear down, but if the over-center brace is not over-center, the gear is being held down by the push rod.....

A micro switch on the over-center brace like other aircraft manufacturers use would be best.

Maybe.  Such a system requires three microswitches and three lights, which is 6 components that could fail and give false indications.  That's at least a 3x greater probability of indicator failure than the current one switch/one light system.  That doesn't even take into account the fact the over-center microswitches and wiring to them would necessarily be exposed to the elements in open gear wells, as opposed to being tucked in the belly.  That makes them more likely to fail or become mal-adjusted.  There's a reason instructors train students transitioning to complex airplanes not to trust the squat switch that's supposed to prevent retracting the gear on the ground.

With due respect, I think you're over-weighting an unlikely failure mode in the linkages, and under-weighting the much more likely failure modes of your proposed indicator fix.  Think about how many threads we've had here discussing microswitch problems (squat switches, stall warning switches, flap limit switches), vs. the number of threads about failures in the mechanical gear linkages.

As for the camera, sure, there's a pathological case where the gear can extend so far as to appear to be down, but just barely not be over center, and you wouldn't see that on the camera.  But now you're really at the corner of the corner case, man.  The microswitch you propose wouldn't have to be mal-adjusted very much at all, to have the exact same problem of falsely indicating down and locked.

Edited April 26, 2017 by Vance Harral

[Yetti]

For your entertainment value.

 

[201er]

1 hour ago, Yetti said:

For your entertainment value.

 

Why do the nose wheel doors pop out extra? It looks like the wheel should clear them in the normal extended position?

[MB65E]

Just the geometry of the system I guess. Mine actually scuffs the left cowl flap if it's full opened. 

Wow multi camera views!!! Nice!!

-Matt

[gsxrpilot]

Sorry, this all seems like a solution in search of a problem. 

[carusoam]

Adding together some observations regarding tubes and failed landing gear...

 

A:  A common landing gear system issue that manual Mooneys get... (much more common than a bent gear push Rod)

1) MS has had a few landing gear collapses.  One guy had two nose gear collapses probably within a year of ownership...

2) there has been a rash of replacement gear down locking blocks. Procedures on how to inspect for the oval hole.

3) Somebody invented and named the thumbnail test to verify the gear is down and locked.

4) No AD has ever been generated for this common wear challenge.

5) No Service bulletin has been written or re-written explaining the procedure to measure and identify the egg shaped hole.

6) Users and well known service organizations have defined a way to handle this situation.

 

B: A more important situation where a control tube could was determined to be a weak design and could cause an issue in flight was the aerleron control tubes.

1) Push / pull control tubes that were not straight.  They were cut and welded to make the part.  The design did not include the needed welded bits to fill the corners (gussets)

2) An AD was published and everyone got new control tubes.

3) no proper service could keep this system working properly.

4) the probability of something deadly happening if this fails is significant.  Hence the AD.

 

C: Somebody mentioned FMEAs above.  Failure Mode effect analysis.  This is a common method of using proper group thinking to gather data and rank the different things that are going on when something like a push rod bends. Part of the analysis may include...

1) People: pilot, maintenance, linemen...

2) Product: Tube, tube materials, manufacturing, design....

3) Process: pilot operations, installation and maintenance operations, linemen operations...

4) It would be important to determine what caused the push tube to bend.  

5) Is it a One off issue?  

6) Does normal use, maintenance and wear cause this to happen? (Speak loudly if this is it)

7) Does normal use, maintenance and wear limits avoid this? (Discuss openly because even normal maintenance gets missed)

 

D: There are other uncommon challenges that can lead to disaster worthy of discussion.

1) Somebody had brought up an in-op alt air system over the North Atlantic Ocean.

2) Another person mentioned a failed trim system that made it difficult to fly/land.

3) my Friend Patrick lost the battle with WnB vs. density altitude.

4) there is an App that can find a coffee shop, order the coffee the way I like it, and pay for it using a cell phone.

5) why isn't there an app that would have saved Patrick from his simple botched decision?

 

Keep discussing this openly.  There is no simple answer. Avoid blaming anybody for this. The challenge is ultimately ours. 

PP thoughts only, i don't build planes.  I may have seen the inside of a few factories along the way....

Best regards,

-a-

 

Edited April 27, 2017 by carusoam

[MBDiagMan]

18 hours ago, Vance Harral said:

I guess my question is to what extent Mooneys have suffered more, or more injurious/fatal accidents as a result of this "flaw" in the indicator system, vs. GA retractables with per-wheel indicators?  We have 50+ years of data on this, what does it say?

You're certainly correct that there are failure modes which are not caught by the current indicator system.  But it's not clear a different system would save more lives or dollars.  Don't forget that a more complex indicating system would have more complex indicator failures, potentially leading to bad outcomes that would not have happened with the simpler system.  In my 25+ year career in engineering, I can't tell you how many times I've seen systems that were (re)designed to catch some corner-case failure, actually wind up causing more trouble than the original corner case.

My gut instinct is that when each wheel is an independent system (e.g. hydraulic), independent indicators are a good solution.  With the mechanical linkages in our Mooneys, the combination of an electric (switches) and mechanical (floor line) indicator seem quite adequate.

Yep!  I am retired from a career in Automation Engineering and the cure can often cause more trouble than the original problem!  KISS!  Keep It Simple, Stupid!  The simplicity of the early Mooney gear and flaps is one of the things that drew me to a Mooney.

[goterminal120]

8 hours ago, gsxrpilot said:

Sorry, this all seems like a solution in search of a problem. 

Exactly! Sounds to me like a lawyer looking for an angle on a non issue.......again

[N201MKTurbo]

11 hours ago, Yetti said:

For your entertainment value.

 

The nut on your actuator is loose.

[Mooneymite]

9 hours ago, gsxrpilot said:

Sorry, this all seems like a solution in search of a problem. 

Solution?

In search of a problem?

My original post just brought out a fact about The Mooney gear that is often overlooked:  that there is no way for the pilot to know if all three over-center locks are in place when he puts the gear down.

I offered no solution, but did mention that usually aircraft have micros switches on the downlocks.

I speculate that some gear collapses are the result of bent push-rods not pushing the down-locks over center.

When a Mooney pilot gets a green light/stripe he really only has verification of the position of the left push-rod.

Is that a problem?

You tell me.

Does it need a solution?

 

[gsxrpilot]

I'll agree with the general consensus on this thread that a solution such as a plethora of micro switches at all the various joints in the gear linkage, would cause more of a problem than it would solve.  The design of the Mooney gear is such that all three wheels work together from a single actuation point. And therefore the situation where a single wheel hangs up while the other two extend, is exceedingly rare.  It's of course a possibility, as you've demonstrated that it happened to you. But since we're not relying on three separate gear actuators, pumps, motors, etc, there isn't really any reason for three indicators.  

I'm just saying, I don't think this is enough of a problem to warrant the additional points of failure, maintenance, expense, and likely false positives by adding such indicators.

As an example, the FAA was satisfied enough with the design of the manual gear, not to require any sort of backup extension/retraction system. 

Of course, shit happens, but I'd much rather keep the gear mechanism as it is today.

Sorry... edited to add one additional point.  In other airplanes such as the F33A I used to fly, individual gear motors/actuators/pumps eventually fail just from age and fatigue. And therefore all such planes could be expected to experience such a failure at some point in their lives.  The type of failure you're describing with the bent rod, doesn't seem to be from normal wear & tear but rather from a mistake by maintenance at some point. Therefore this is not a situation that we all should expect as our planes age. Therefore there isn't the need for an additional system requiring maintenance to keep tabs on the maintenance of the other system.

[N201MKTurbo]

I used to maintain a friends Rockwell 112TC (giant pile of crap) It was my borrow a plane when the Mooney was down for maintenance. It had switches everywhere and I was working on them constantly. The backup ended up being primary extension system. It was a maintenance nightmare. The biggest flaw with that system was the wires were held down with double sided sticky tape ty-rap anchors. There was no other way to hold the wires. They were constantly falling off and the wiring would get eaten by the gear leg!

Thank God for the simple Mooney system!

[MBDiagMan]

1 hour ago, N201MKTurbo said:

The nut on your actuator is loose.

Reminds me of what my Dad would say when, as a teenager, I would describe a problem with my car.  His response often was "sounds like a loose nut on the steering wheel."

[MB65E]

6 minutes ago, N201MKTurbo said:

I used to maintain a friends Rockwell 112TC (giant pile of crap) It was my borrow a plane when the Mooney was down for maintenance. It had switches everywhere and I was working on them constantly. The backup ended up being primary extension system. It was a maintenance nightmare. The biggest flaw with that system was the wires were held down with double sided sticky tape ty-rap anchors. There was no other way to hold the wires. They were constantly falling off and the wiring would get eaten by the gear leg!

Thank God for the simple Mooney system!

I worked on a 112TC and a 114 before. The 114 had gear issues. One of the castings broke on the mains and it didn't collapse. I think I had the exhaust off the 112TC 3 times. It exited on the top of the engine. It was a Hot smoking nightmare.

They looked cool, and were fairly stout, but I was glad I didn't have one. 

Just spent 3 days troubleshooting a caution light on a citation. All of the inputs were in the correct location, monitoring devices were good, turns out the annunciator panel itself was bad. The "safer" the airplanes become, the more systems they get, the more those systems will fail. I'm glad the Mooney is so simple. 

-Matt

[N201MKTurbo]

37 minutes ago, MB65E said:

I worked on a 112TC and a 114 before. The 114 had gear issues. One of the castings broke on the mains and it didn't collapse. I think I had the exhaust off the 112TC 3 times. It exited on the top of the engine. It was a Hot smoking nightmare.

They looked cool, and were fairly stout, but I was glad I didn't have one. 

Just spent 3 days troubleshooting a caution light on a citation. All of the inputs were in the correct location, monitoring devices were good, turns out the annunciator panel itself was bad. The "safer" the airplanes become, the more systems they get, the more those systems will fail. I'm glad the Mooney is so simple. 

-Matt

Wow,

I fixed the master caution on a Citation 500 once that had been broken and bypassed for 10 years because no one could fix it. It turned out to be this little relay that was impossible to get to behind the panel behind a 2" bundle of wires. The wires had almost all cracked inside the heat shrink on the relay. They looked perfect but none of them were making contact. I cut them all off and re-soldered them and everything worked as designed. The owner was ecstatic.

[Guitarmaster]

Is it possible for the mechanical indicator window on the floor to show down (the green box) if the gear is not fully down?  Question - not a statement.

Yes, although it would be rare.

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[Mooneymite]

2 hours ago, gsxrpilot said:

I'm just saying, I don't think this is enough of a problem to warrant the additional points of failure, maintenance, expense, and likely false positives by adding such indicators.

You and others have built a straw-man and are beating it.  I never made a suggestion that any modifications should be made to the Mooney gear indicating system.  Not once.

I actually like the simplicity as is.  I am certainly not advocating an AD to add micro switches; I merely point out that's what most aircraft use.

If you will read the original post, I am making the point that on a Mooney, a green light/stripe does not assure one that the gear is down.  That's an important point to consider when maintaining your Mooney's gear system.  Those over-center locks are very important.  The pre-load tension has to be maintained.  Push rods should be inspected for any bowing/bending.  The gear indicating system can lie to you.  (As a point of fact, micro-switches on the down-locks can lie to you, too.)

No solution looking for a problem.  Not even a suggestion for a change to the Mooney.

 

[Yetti]

9 hours ago, N201MKTurbo said:

The nut on your actuator is loose.

Not anymore... at least one thread showing.   Before I buttoned everything up I wanted to make sure things were copisetic and not hitting. So I took this video and reviewed it.   Then tightened everything up.

Good catch. You can work on my plane.

 

[cnoe]

I speculate that some gear collapses are the result of bent push-rods not pushing the down-locks over center.

 

I can't back it up with evidence at the moment but I'd speculate that 99% of Mooney gear-ups are caused by the "loose nut on the (yoke)" as Larry so eloquently stated. My mentors suggested "if it ain't broke don't fix it".

 

 

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[cnoe]

This Navion delayed my departure last week by 45 minutes at my home field. He landed with 3 green and still ended up with his nose on the pavement. Sucks.



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[MBDiagMan]

I am not seeing MKTurbo's video link.  I am only seeing a big white square.

[gsxrpilot]

6 hours ago, MBDiagMan said:

I am not seeing MKTurbo's video link.  I am only seeing a big white square.

Works for me, try a different browser?

[Yetti]

his video is a copy of my video

[MBDiagMan]

Yeah, I have my IPad while on vacation.  The video doesn't like Safari.

[Yetti]

It shows on my android...