Pitch control emergency

[Sam Judd 17]

I took my '78 J out last Friday night to do a short night cross country and get my night currency back. After my first uneventful flight/landing, I ended up declaring an emergency doing pattern work. On short final I felt/heard a bang and the nose dropped about 5 degrees. I initially thought I might have done something silly with the flaps or trim and went around. Shortly after starting the go around, I realized my pitch control felt all wrong. I declared an emergency and landed uneventfully.

In retrospect I realized that, among other things, I'd been pulling up with full nose up trim to maintain the proper go around attitude and airspeed. Usually this requires lots of forward pressure prior to trimming. I'd also had to pull back on the yoke to slow below 80 knots on final even with full nose up trim. In the flare I was able to keep the nose off the ground with half flaps, but only barely. It felt like I was landing a 182 with full flaps, not an M20J with half flaps.

On the ground I didn't see anything visibly broken or damaged. The manual and electric trim both felt normal. The flaps and trim indicated their normal range and the empennage and flaps appeared visually to move the normal range. However, the elevator remained in a significantly nose down position, even with full nose up trim. Normally it ends up pretty close to level with the stabilizer, but in my case it still showed nose down. Here's a comparison of my airplane post incident with full nose up trim and a regular M20J with full nose up trim: https://photos.app.goo.gl/N6zpThBSttuuXP2R6.

My mechanic took a look today and found the elevator assist tube attach point broken: https://photos.app.goo.gl/KWZDTawRLRJBxLv99. 

There's definitely some things I could improve on during the flight. I should have used no flaps on the landing. Get-home-itis was much stronger than it should have been. I'm glad I had a group of Mooney pilots to talk things through with in real time. 

[Hank 8,011]

That photo of the broken tab is bad . . . Good job on getting back on the ground safely with no additional damage!

[flyer338 111]

God job handling the emergency. How many hours on the airframe? I have never heard of that part breaking.

[carusoam 12,058]

Congrats Sam!

I figure... if I can understand the challenge, and come up with a solution... as fast as I can read what you wrote...

I would agree that going around would be a good idea...

I had no other idea than something broke with the elevator, and the trim was the final solution...

 

In one other case around MS... the pilot ran out of arm strength before landing... in that case changing flap position is a good idea...

Without knowing what broke, it is only a guess on what to experiment with next...

You did really well with what you had... call it a success...

Now let’s figure out how that part failed...

Lets get the pics to Mooney if able...
 

That is not a normal failure point... it’s not even related to where the wear would occur...

During the free and correct test /boxing out the controls... anything odd almost get noticed in the feel of the yoke?

Being on the ground to be able to discuss a control failure, is a giant success...

Thanks a ton, for posting the details!

Inviting the good doc to stop by for a visit... @M20Doc (Broken elevator control hardware, occurred inflight, during landing phase...)

There is probably a proper maintenance report that goes with that... Something your mechanic is probably familiar with...

PP thoughts only, not a mechanic...

Best regards,

-a-

[N201MKTurbo 5,362]

Well, at least now I know if that thing breaks, I can still land the plane. good to know!

[ragedracer1977 1,504]

Just FYI, I’m pretty sure that is a mandatory reportable event.  If you haven’t already, you need to.  https://www.law.cornell.edu/cfr/text/49/830.5

[MooneyMitch 2,225]

So very interesting!  Congratulations to your flight success.

Diagnosis will be so helpful to us all.

I’ll be inspecting mine tomorrow!

[tmo 527]

One question - is the elevator hanging down like that while parked not right? A lot of parked Mooneys look like that, including mine. I'd be more concerned with the one that doesn't "droop" and consider it too sticky. Or am I missing something?

[Hank 8,011]

2 hours ago, tmo said:

One question - is the elevator hanging down like that while parked not right? A lot of parked Mooneys look like that, including mine. I'd be more concerned with the one that doesn't "droop" and consider it too sticky. Or am I missing something?

My understanfing is that long body tails droop, short- and mid-body elevators should be straight out on the ground.

Edited September 25, 2020 by Hank

[M20Doc 8,538]

That is a really odd failure, I’ve never seen this type of failure before.  Please post pictures of it when it’s removed.

Clarence

[Freemasm 168]

Without further details/evidence, the odds are probably on intergranular corrosion of the part. Is it possible for you to get some close-up photos? Details of the fracture surface would be best.

Two quick observations:

- The smooth appearance of the fracture surface would suggest a high cycle fatigue crack. Is there slop in the related linkages?

- There are some "non-typical" witness marks above the bolts head. IMO. One could almost surmise there was relative movement there; obviously there shouldn't be. The (beginnings of this related) crack could have been there for a while now.

I have access to a world class metallurgical lab with some stud engineers and technicians (though mostly super-alloy, gas turbine stuff). Want me to see if they'd like an unofficial swing at this?

[tmo 527]

Let me butt in @carusoam's place and say "go mooneyspace!" - what an awesome offer.

[ArtVandelay 2,478]

My understanfing is that long body tails droop, short- and mid-body elevators should be straight out on the ground.

So long bodies don’t have the springs?

[N201MKTurbo 5,362]

13 minutes ago, ArtVandelay said:

So long bodies don’t have the springs?

It is bungees, springs and bob weights. There are at least two arrangements, maybe 3. Most 231s also droop.

[M20S Driver 189]

Long body attachment looks different.

[WaynePierce 81]

How can you even inspect this part on my J? Is there a plate there? Not at the plane or I'd look, but I will be later today and I will.

[Freemasm 168]

Interesting. Failed part looks like machined aluminum. Equivalent S looks like formed steel. Relative sizes/geometries would support this.

[carusoam 12,058]

14 minutes ago, WaynePierce said:

How can you even inspect this part on my J? Is there a plate there? Not at the plane or I'd look, but I will be later today and I will.

This is the tail hinge area...

Take the sheet metal cover off, and have a look.
 

PP thoughts only, not a mechanic...

Best regards,

-a-

[tmo 527]

20 minutes ago, WaynePierce said:

How can you even inspect this part on my J? Is there a plate there? Not at the plane or I'd look, but I will be later today and I will.

There are 7 screws in a vertical line on a relatively small cover; see section 53-50-00 of the Parts Catalog - for my M20K it is item #7.

[Jim F 79]

11 hours ago, Sam Judd said:

I took my '78 J out last Friday night to do a short night cross country and get my night currency back. After my first uneventful flight/landing, I ended up declaring an emergency doing pattern work. On short final I felt/heard a bang and the nose dropped about 5 degrees. I initially thought I might have done something silly with the flaps or trim and went around. Shortly after starting the go around, I realized my pitch control felt all wrong. I declared an emergency and landed uneventfully.

In retrospect I realized that, among other things, I'd been pulling up with full nose up trim to maintain the proper go around attitude and airspeed. Usually this requires lots of forward pressure prior to trimming. I'd also had to pull back on the yoke to slow below 80 knots on final even with full nose up trim. In the flare I was able to keep the nose off the ground with half flaps, but only barely. It felt like I was landing a 182 with full flaps, not an M20J with half flaps.

On the ground I didn't see anything visibly broken or damaged. The manual and electric trim both felt normal. The flaps and trim indicated their normal range and the empennage and flaps appeared visually to move the normal range. However, the elevator remained in a significantly nose down position, even with full nose up trim. Normally it ends up pretty close to level with the stabilizer, but in my case it still showed nose down. Here's a comparison of my airplane post incident with full nose up trim and a regular M20J with full nose up trim: https://photos.app.goo.gl/N6zpThBSttuuXP2R6.

My mechanic took a look today and found the elevator assist tube attach point broken: https://photos.app.goo.gl/KWZDTawRLRJBxLv99. 

There's definitely some things I could improve on during the flight. I should have used no flaps on the landing. Get-home-itis was much stronger than it should have been. I'm glad I had a group of Mooney pilots to talk things through with in real time. 

Hi Sam, Great Job and thanks for posting.  I second M20Doc's request for additional pictures.  It would be good to see if the break started with a stress point. 

[takair 988]

11 hours ago, Sam Judd said:

I took my '78 J out last Friday night to do a short night cross country and get my night currency back. After my first uneventful flight/landing, I ended up declaring an emergency doing pattern work. On short final I felt/heard a bang and the nose dropped about 5 degrees. I initially thought I might have done something silly with the flaps or trim and went around. Shortly after starting the go around, I realized my pitch control felt all wrong. I declared an emergency and landed uneventfully.

In retrospect I realized that, among other things, I'd been pulling up with full nose up trim to maintain the proper go around attitude and airspeed. Usually this requires lots of forward pressure prior to trimming. I'd also had to pull back on the yoke to slow below 80 knots on final even with full nose up trim. In the flare I was able to keep the nose off the ground with half flaps, but only barely. It felt like I was landing a 182 with full flaps, not an M20J with half flaps.

On the ground I didn't see anything visibly broken or damaged. The manual and electric trim both felt normal. The flaps and trim indicated their normal range and the empennage and flaps appeared visually to move the normal range. However, the elevator remained in a significantly nose down position, even with full nose up trim. Normally it ends up pretty close to level with the stabilizer, but in my case it still showed nose down. Here's a comparison of my airplane post incident with full nose up trim and a regular M20J with full nose up trim: https://photos.app.goo.gl/N6zpThBSttuuXP2R6.

My mechanic took a look today and found the elevator assist tube attach point broken: https://photos.app.goo.gl/KWZDTawRLRJBxLv99. 

There's definitely some things I could improve on during the flight. I should have used no flaps on the landing. Get-home-itis was much stronger than it should have been. I'm glad I had a group of Mooney pilots to talk things through with in real time. 

Scary failure.  Nice save. Is the helm bearing free to move or is it frozen?  

[Sam Judd 17]

13 hours ago, flyer338 said:

God job handling the emergency. How many hours on the airframe? I have never heard of that part breaking.

Thanks! About 5200 hours. 

 

13 hours ago, carusoam said:

During the free and correct test /boxing out the controls... anything odd almost get noticed in the feel of the yoke?

 

I always do a control test during my runup. I noticed nothing abnormal until after the incident. Then the pitch force felt quite heavy when pulling nose up, even on the ground

 

12 hours ago, ragedracer1977 said:

Just FYI, I’m pretty sure that is a mandatory reportable event.  If you haven’t already, you need to.  https://www.law.cornell.edu/cfr/text/49/830.5

I reported it to the NTSB via phone the night of the incident. I had one follow up call. Both times they basically said they'd only be interested if I discovered substantial damage. I've sent them the picture and haven't heard anything yet. 

 

4 hours ago, Freemasm said:

I have access to a world class metallurgical lab with some stud engineers and technicians (though mostly super-alloy, gas turbine stuff). Want me to see if they'd like an unofficial swing at this?

I'd be totally happy to work with you on this. I can make sure my mechanic preserves the part. It won't get replaced until next week. I'll pass along your other observations to my mechanic, thank you!

 

6 hours ago, M20Doc said:

That is a really odd failure, I’ve never seen this type of failure before.  Please post pictures of it when it’s removed.

 

Will do, I'll make make sure I get hold of the old part. 

 

2 hours ago, takair said:

Scary failure.  Nice save. Is the helm bearing free to move or is it frozen?  

I'm not sure what the helm bearing is? I could ask my mechanic? 

[PT20J 2,306]

A few points:

First, great job handling a true emergency. Loud noises followed by controllability problems are scary -- especially at night. It's common to second guess your actions afterward when the adrenalin has dissipated. Just remember that no one handles an emergency perfectly unless it's been repeatedly practiced. This isn't something we can easily practice.

The broken part looks like a casting that may have failed due to corrosion. The inspection panels between the tailcone and empennage should be removed at each annual inspection to inspect this area and lubricate the trim jackscrew inside the boot.

This might be considered a "Flight control system malfunction or failure" reportable to the NTSB per 830.5 (a). It would not hurt anything to file a report. Also, I would make sure that your mechanic files a Service Difficulty Report and I would contact Mooney as they may want to inspect the part and perform analysis on it to determine the root cause.

Mooney has used a couple of trim assist systems. All the models through the J had up springs and down springs and the balance point is dependent on the tail incidence angle, the latter being controlled by the trim system. On the ground in these models, the elevator sits in trail with the stabilizer when the trim is set to neutral. You can feel the springs when you move the elevator up and down during preflight. You can see the effect of the springs on the elevator position if you watch the elevator as you adjust the trim up and down on the ground. The part that broke is the attachment point for the up springs. When it let loose, it left you with only the downs springs which is why you had to pull so hard and the elevator now droops.

The K and later models have a different system with a variable down spring and they sit on the ground with the elevator full down.

Skip

 

[Freemasm 168]

@Sam JuddPM me when the parts are available and I'll get you an address.  If it's going to be a while before the major surgery, send the part from the rod end. That will probably be enough.

You're going to need two tall saw horses (or equivalent) as the tail is coming off. Try and find a riveter with two elbows in each arm for the repair.

A couple of observations. Solvent wash that area at every inspection. It collects dirt and thus retains moisture; a great catalyst for both surface and IG corrosion. Keep that area well treated with preservative. It is more vulnerable that most areas, IMO.  

The good thing is, that linkage is there to help manage elevator forces as the emp is trimmed up and down.  Those old guys were some thorough, f'ing stud designers.

Edited September 25, 2020 by Freemasm

[Sam Judd 17]

@Freemasm I'll let you know. For what it's worth, my mechanic hasn't mentioned any substantial repair beyond replacing the part that broke. What's prompting you to think the tail needs to come off? 

31 minutes ago, PT20J said:

Mooney has used a couple of trim assist systems. All the models through the J had up springs and down springs and the balance point is dependent on the tail incidence angle, the latter being controlled by the trim system. On the ground in these models, the elevator sits in trail with the stabilizer when the trim is set to neutral. You can feel the springs when you move the elevator up and down during preflight. You can see the effect of the springs on the elevator position if you watch the elevator as you adjust the trim up and down on the ground. The part that broke is the attachment point for the up springs. When it let loose, it left you with only the downs springs which is why you had to pull so hard and the elevator now droops.

 

Thanks! I hadn't even heard of this system before, so I appreciate the clear explanation of how it works and why it felt the way it did. 

Edited September 25, 2020 by Sam Judd