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Prop Strike due to partial gear collapse


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On Saturday my M20C was involved in an accident at LSZH airport. The aircraft was on an ILS approach for Runway 14. The pilot reports that on touch down he felt the gear give way and immediately added full power to go around. During this, the aircraft touched the runway with the prop tips as well as some antennas on the belly. After the go around, the aircraft performed a turn at low altitude and landed without further problems on runway 28.

The airplane itself did not get damaged but the prop is ruined and the engine will at least require a sudden stoppage inspection up to possibly a full rebuild. The other damage is relatively minor.

By the looks of it, the landing gear lever was not put into the downlock properly, which still can cause the green light to appear but the locking pin not to engage properly. Not the first time I hear of these kind of accidents.

While the go around action did prevent further damage to the airplane, it was probably a split second reaction rather than deliberation. I think the pilot and pax were very lucky that the engine and prop continued functioning until landing.

WhatsApp Image 2021-09-05 at 15.20.26(1).jpeg

WhatsApp Image 2021-09-05 at 15.20.26.jpeg

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pilot and passenger where more than lucky! remind them that their lives are far more valuable than the airplane that the insurance company likely bought when the prop hit the runway anyway. Nobody gets hurt landing gear up, but many have perished trying to save the plane.
Hope you’re all back in the air soonest.


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Terrifying - sorry for the damage and expense but glad everyone is ok.  IMHO the gear position indicator lights in the J bar planes are not just useless but actually detract from safety relative to having no lights at all.  Early in my ownership of my C, I too was fooled once by a green light despite the gear handle being incompletely seated in the down lock block - luckily I caught it on short final and went around before contacting the ground.  Now I completely ignore the lights, which add zero info beyond merely looking at the position of the J bar handle.  Tugging down on the handle and trying to a unseat it from the lock block a couple times is an important ritual before landing these planes.

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While it’s not good to have it happen, assuming your insured a prop strike really isn’t a bad thing,I wouldn’t consider it “damage history”

You most likely end up with a new prop, and I almost guarantee that your engine will be fine, and if they follow the Lycoming mandatory SB for parts replacement which I’m sure any good shop would, you could literally be adding years and hundreds of hours to the life of the engine as pretty much everything in the bottom end that wears is replaced with new.

We had a Bonanza in my neighborhood with an MT prop that apparently hit a runway light, took off a few inches of the prop and he flew it for a few hours coming home, said he never knew anything was wrong.

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51 minutes ago, DXB said:

Terrifying - sorry for the damage and expense but glad everyone is ok.  IMHO the gear position indicator lights in the J bar planes are not just useless but actually detract from safety relative to having no lights at all.  Early in my ownership of my C, I too was fooled once by a green light despite the gear handle being incompletely seated in the down lock block - luckily I caught it on short final and went around before contacting the ground.  Now I completely ignore the lights, which add zero info beyond merely looking at the position of the J bar handle.  Tugging down on the handle and trying to a unseat it from the lock block a couple times is an important ritual before landing these planes.

It’s a simple microswitch with a lever that protrudes through the down lock where it is actuated by the j-bar.. it should be almost infinitely adjustable in relation to the J-bar’s travel within the down lock.  If yours is giving a false reading, It should be inspected the next time it’s on jacks.

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54 minutes ago, steingar said:

How did the gear horn not sound if the gear wasn't fully locked?

The lever inside the lock block that turns on the green light also silences the gear warning horn circuit.That lever is depressed by the top of the handle a tad bit before the the locking pin actually engages. That leaves room for the green light to be on and the horn to be silenced but the gear not to be fully locked down.    I’m sure that’s how it is on my setup - There should be room for adjustment internal to that switch.

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On 9/7/2021 at 1:58 AM, kortopates said:

Nobody gets hurt landing gear up, but many have perished trying to save the plane.

Paul is absolutely correct.

Sometime during the late 80's a J I used to fly had crashed following a botched landing attempt resulting in a prop strike and gear damage. A go-around was initiated resulting in a downwind stall/spin from the underperforming aircraft and the death of the the pilot and passenger.

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On 9/6/2021 at 1:16 PM, DXB said:

Tugging down on the handle and trying to a unseat it from the lock block a couple times is an important ritual before landing these planes.

When I lower the gear, I move my right leg to the right and use my right knee as a fulcrum supporting my right forearm.  Pushing down with my right shoulder causes my hand that is gripping the j-bar handle to put quite a bit of upward force on it.  Then I move my leg back and pull down as hard on the handle as possible to make sure it is locked.  I only look for the green light on short final GUMPS check.

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Good luck with the next steps Urs.

Full power during the ground strike typically bends the prop tips forwards as it grabs the pavement…

This is often extra tough on the internal parts of the engine…

 

For historical reference… there are many down lock blocks that have caused this type of failure…. The holes become egg shaped, and some pilots don’t know to recognize the failure…

There is a test called the thumbnail test to know the gear is down and locked…

There are also replacement blocks for the worn out ones…

 

For future reference… for the next MSer to consider…

Once the prop has struck the ground… the accident has already occurred… the expenses are already high…

Going back into the air… the risks are unknown and increasing…  how much power is available… how long will the power last…  if something shakes loose, how fast can you shut the engine down..?

PP thoughts shared… not a mechanic…

Best regards,

-a-

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Sorry for OP, but glad nobody was hurt and there was no other damage aside from prop.

The irony is that with the electric gear J's, the POH still tells you in strong language not to pay attention to the gear indicator light and to look down at the floor indicator to verify the gear is down.

I still think the Mite's wigwag gear warning is still the best :)  Makes me smile every time I see a video with it

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4 hours ago, jaylw314 said:

The irony is that with the electric gear J's, the POH still tells you in strong language not to pay attention to the gear indicator light and to look down at the floor indicator to verify the gear is down.

I haven’t seen this before. I’ve been looking through my flight manual trying to find language that discourages use of the annunciator for gear position. Do you have a reference I could look at?

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2 hours ago, toto said:

I haven’t seen this before. I’ve been looking through my flight manual trying to find language that discourages use of the annunciator for gear position. Do you have a reference I could look at?

You have an 89, I think the POHs got a bit better by then. My 77 says something along the lines of "Gear down check: Gear down light on, floor indicator marks aligned" this is in the before landing checklist.

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Nothing personal to anyone that has commented, they should have just set it down, as I agree, but how many folks do we see criticizing a pilot that lands gear up? Or collapsed gear?... "there goes my insurance..."

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I haven’t seen this before. I’ve been looking through my flight manual trying to find language that discourages use of the annunciator for gear position. Do you have a reference I could look at?

you’ll find a service letter on Mooney’s website, in the form of a POH insert, to add to your POH.
transition training covers this as well.


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18 minutes ago, kortopates said:


you’ll find a service letter on Mooney’s website, in the form of a POH insert, to add to your POH.
transition training covers this as well.


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Any idea what service letter? Ballpark year? I’m looking through the website but haven’t found it yet. 

It’s a letter that just says you should look at the floorboard indicator and not at the annunciator panel?

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13 hours ago, toto said:

I haven’t seen this before. I’ve been looking through my flight manual trying to find language that discourages use of the annunciator for gear position. Do you have a reference I could look at?

I overstated it for dramatic effect.  It doesn't actually say don't look at the annunciator, it just beats you around the head to look at the floor indicator.  Here's the AFMS insert (it's the SB for the no back clutch spring replacement)

image.thumb.png.4852c19a0329d0401916e3920e675f24.png

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4 minutes ago, jaylw314 said:

I overstated it for dramatic effect.  It doesn't actually say don't look at the annunciator, it just beats you around the head to look at the floor indicator.  Here's the AFMS insert (it's the SB for the no back clutch spring replacement)

image.thumb.png.4852c19a0329d0401916e3920e675f24.png

Cool, thanks. That makes a lot more sense :)

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Thanks for all the reactions.

I think the go around was not a concious decision but a gut reaction. I am not at all sure that they had already touched the runway when they went around. The PIC said he saw the bar jumping out of the uplock and immediately added max power and pulled, during which the ground contact occurred. I agree it was definitly not the safest thing to do and I am more than glad that it worked out. We don't know yet how high they really got but it was not that high and the turn to landing was over a populated area. We will maybe learn something when the TSB is done with their analysis. It appears that the post by @carusoam would confirm this sequence of events:

On 9/9/2021 at 8:16 AM, carusoam said:

Full power during the ground strike typically bends the prop tips forwards as it grabs the pavement…

Thanks for that. We were totally baffled with the figure we have seen from the prop blades. I agree, this gives a distinct possibility that the engine may well be toast.

Damage to the fusellage is minimal, a couple of antennas and a bent attachment point for the left flap. Still, we have to check everything properly.

There also was damage to the runway. I have not seen pictures yet however.

I am darn glad that nothing more severe happened. If the plane had been wrecked, well tough, but it can be replaced (or I would have been paid out the hull value and probably retired from flying). People can not.

 

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I know all the Johnson bar folks think it’s bullet proof ;), but years ago I instructed in a club with a 1964 Ranger and pilots managed to land it and have the gear collapse two — maybe three, I forget — times. When checking people out, I’d always train them to tug on the handle to be certain it was locked in the socket. Mooneys are tough: N78888 is still flying.

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On 9/12/2021 at 2:24 AM, PT20J said:

When checking people out, I’d always train them to tug on the handle to be certain it was locked in the socket.

We are doing this as well with everyone who flies it, including the pilot in question. He had quite a few hours on it prior to the accident and he is totally baffled how it could have happened. I am sure it won't happen to him again!

Actually, tuging on it may not be enough. What I do is to press it forward and try to slide the handle downwards, as if to unlock it, without pressing the locking pin of course. If the pin is engaged, it won't move, if it is not, it will come out. I had that happen twice on my final checks.

I also found that engaging the pin is helped sometimes with a small left/right movement with the handle, motorcycle grip like if you get my gist. And ever since I know what to look for, it is beyond me how anyone can not notice the "click" of the pin, even if you can not hear it, you can feel it. If you don't, it is not in.

We are actually thinking of removing the gear lights altogether. The red light does exactly nothing (and it should not be on during the whole flight anyway as it redlights a normal condition) and the green light gives a false sense of security. We have had this switch adjusted 3 times in the last annuals when we found that it showed green too early in the gear swing, post accident it was found again out of adjustment by 4 mm, so it came up way too early. The TSB inspector who came to check it said the same thing: Better no light at all than this and just manual verification.

We will do a massive refresher with everyone, if possible on jacks. I recall myself looking at this mechanism the first time on jacks and it was only then I fully understood it.

No, the Johnson Bar is not at all bullet proof, but sometimes we have to forget political correctness and remind people why it is called a Johnson Bar and what to do with it in terms not usually used amongst civilized people. Works every time though. I had the TSB guys grasp for air and go red on me because of it, but after a short demonstration they fully got it.

 

One of my mechanics suggested to modify the gear to electric. I am not even sure if it's possible and even less so if it makes sense. Generally I am happy with the maintenance cost and ease of use of the JB, but well, maybe the electrical system is better after all. Opinions are welcome.

 

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Urs,

While researching next steps…

One of the big problems found with the down lock block is unusual wear over the decades…

When you put the plane up on jacks, or in flight… take a picture looking up into the hole…

The original shape of the hole is a perfect circle…

Over the decades, it gets reshaped into an egg shape, with a ledge, that can get in the way of a good insertion…

Unknowing pilots can put the JB all the way in, and bump into the ledge…not knowing the ledge isn’t really all the way in…

 

Recently, there was a round of owner produced parts around here for building a bunch of both up and down lock blocks…

 

Cause of the wear… probably related to hard chrome on steel vs. the softer aluminum… with no lubrication… leading to tiny rubbing movements while on the ground…

If unable to take a pic… reach up with a finger to find the ridge…  it shouldn’t be there.

+1 on the click of the locking mechanism functional test each time… it either locks, or it doesn’t. Kind of a digital outcome…

Going electric is possible, but has as many failure points in its operation…  PIC has to do more than operate the switch or JB…

 

Go JB!

 

PP thoughts only, not a mechanic…

Best regards,

-a-

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