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Crunch !!!!

JohnF

Well Known Member
N29CX took off this morning for the initial flight. It lasted not more than two seconds. The plane accelerated smoothly and I noticed the RPM passing through 4950 when there was an uncommanded pitch of what I am guessing was 60-degrees, and full force forward on the stick didn't do anything and then there was a stall. Fortunately there was still forward momenten when the nose wheel hit the dirt at the side of the runway.

The nose wheel fork separated from the wheel. The nose leg severed at the point where it attaches to the bottom of the fuselage.

The exhaust pipe was a bit squeezed, and one exhaust pipe popped out of the muffler.

There were no oil, coolant, or fuel leaks. The ELT went off, and within perhaps 3 minutes I was out of the plane, stopped the ELT and disconnected the ELT antenna. The satellite still picked up the squawk.

The fuselage at the firewall is probably beyone repair, because of some rips in the skin. The firewall bottom is a bit curled up.
An aircraft mechanic helped me get the plane back into the hangar, and he found that the Ray Allen servo was damaged; the back of the servo box is broken out and there are broken gears showing. The linkage from the servo to the anti-servo tab, and to the point where it anchors to the tail cone area is in perfect condition - no scratches, no distortions, nothing broken, all in perfect shape, but the servo itself has its case broken at one side, and the part of the servo that screws out is jammed.

Was it an uncontrolled servo activation? The suspection right now is that it was, but that will be further investigated.

The prop broke away at the hub on one side, and broke off about 10-inches on the other side. NO damage to the pitot tube, nor the spinner. The oil cooler is perfectly OK, as is the muffler and the gascolator.

I know the engine will have to be removed, broken down, and I just hope that the crank is OK, but that will have to be determined.

The airworthiness inspection was on June 11th and I know the inspector took a lot of time looking at the anti-servo system (he had not seen an LSA or an RV-12 before) and he was satisfied.

I got as small scratch on my right index finger, but no other damage, nor even any shock.

My preliminary inspection makes me think that the entire 'fuselage' section will have to be replaced...wings are all OK, and tail section is fine, except where a plastic pipe that had reflective material on it to mark a taxi way edge poked a hole in the bottom of the fuselage...but that is an easy patch.

I will post more as I learn it. Only real damage is to my ego, and to a lesser extent, to the check book.

Does a 2-second lift off count as another RV-12 in the air? Darn, I took a lot of photos before the flight, and many more of the damage ... being an old FAA retiree and an attorney the back of my mind said take a LOT of photos of everything, including the Ray Allen servo...bad day at back rock, but at least I am OK, there was no property damage, and noone else was hurt.
 
Sorry to hear about your short flight. We had a servo lock but luckily we caught long before we ever flew. We were just playing with it on the ground. Glad you're alright!
 
Sorry to hear

For sure let us all know what you feel is the final estimate as to what may have happened. Glad you are OK !

John Bender
 
Wow...glad you are OK and sorry for the damage to your craft...

I am not familiar with the control system for pitch on the 12.

Why would a busted trim servo cause this? 60° pitch up with full down stick????

edit..

I just took a look at the plan revisions on Van's site that show this area and I now see how the mechanism works for the stabilator and anti-servo/trim tab....

Does anyone know if the 12 would even be stable enough to fly without the anti-servo tab? What is the expected result if it was disconnected and flapping in the breeze? How strong is it's influence changed by full range travel of the trim motor up and down?
 
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Sorry to hear about that, John, but glad you're ok. Things could have turned out much worse.
 
Sorry to hear about the problem. I cannot imagine the disappointment.

"An aircraft mechanic helped me get the plane back into the hangar"

Are you supposed to move the aircraft or leave it where it was for NTSB/FAA investigation? I'm sure there are alot of interested 12'ers that would like a report.

Good Luck
Tom RV-7A N175TJ Flying
 
NTSB

I doubt that there is a problem with having moved the aircraft, however I would contact the FAA and NTSB. As you will see in the attached, the first item they are interested in is flight control systems. The rules requiring a report are in NTSB 830:

Subpart B--Initial Notification of Aircraft Accidents, Incidents, and Overdue Aircraft

Sec. 830.5 Immediate notification
The operator of an aircraft shall immediately, and by the most expeditious means available, notify the nearest National Transportation Safety Board (Board), field office /1/ when:

(a) An aircraft accident or any of the following listed incidents occur:

(1) Flight control system malfunction or failure;

(2) Inability of any required flight crewmember to perform normal flight duties as a result of injury or illness

(3) Failure of structural components of a turbine engine excluding compressor and turbine blades and vanes;

(4) In-flight fire; or

(5) Aircraft collide in flight.

(6) Damage to property, other than the aircraft, estimated to exceed $25,000 for repair (including materials and labor) or fair market value in the event of total loss, whichever is less.


The usual procedure is for the NTSB to "appoint" the FAA to do the accident investigation when there are minor or no injuries.

John Clark ATP, CFI
FAA FAAST Team Member
EAA Flight Advisor
RV8 N18U "Sunshine"
KSBA
 
Moving the crunched rv-12

The A&E and the airport manager and I all thought the damage was just the prop and the nose gear leg. The tail was out over a narrow taxiway and the nose just in the dirt along side, so it was really blocking the taxi way. When we got the plane back in the hangar and removed the lower cowling we could see that the damage was major. The NTSB and the local FSDO were notified and reports filed over the internet. A lot of photos were sent to the FSDO and they are going to try to have an inspector here this coming week.

The linkage from the servo to the trim tab and back to the tail hard point are all in absolutely perfect condition...not a scratch, but the Ray Allen servo has its aft end busted out and you can see broken plastic gears inside. It is also mechanically jammed.

More as I learn it...but I wish now I had the mechanical trim tab control that my now-sold RV-6A had...heavy but fool-proof. I may try putting something like that in after we get the -12 fixed, since its experimental I could do that.

The plane will sit there in the hangar until the FAA looks at it. I hope they take the servo away and have it analyzed. It did meet the up/down time when it had proper battery voltage as I re-checked it just a few days ago.
 
Crunch

Ok Ill be the first to ask, not wanting to offend anyone. Where was the trim set for Takeoff?

John
RV12 N1212K
 
Does anyone know if the 12 would even be stable enough to fly without the anti-servo tab? What is the expected result if it was disconnected and flapping in the breeze? How strong is it's influence changed by full range travel of the trim motor up and down?

There's a procedure in the Pilot Operating Handbook for dealing with a runaway trim motor. Basically pull the trim fuse and then try to land safely. No indication of how flyable the plane would be with a full out-of-trim condition though. In level flight, you may have some chance of dealing with it, but near the ground on T/O or landing as JohnF was, I wouldn't be taking any bets. I wonder if Van's did any testing for controllability with this kind of malfunction during development?
rgmwa
 
Crunch

So sorry this happened and can't imagine your disappointment. But..... so glad you are physically OK. As to trim, none of the many light single engine planes I've flown was uncontrollable with full up or down trim, and in all it seems slowing down reduces to force to overcome the trim very much. Someone questioned whether the RV-12 had been checked for flyability at full up or down trim (e.g, following a runaway not caught in time). I wonder. Perhaps some experienced owners who have flown for awhile can sneak up gradually on out of trim conditions both up and down and report on forces required - are they reasonable? This also makes me wonder about my -8. Will await with great interest your report of final determination of cause. Thanks for reporting this.
 
Runaway trim?

Yes, I am familiar with the recommendations to pull the fuse if the trim motor runs away, but it you can do that when the nose is so high you cannot see anything but cowling and are about 20 feet (possibly less) above the ground and have about 2-seconds from the start of the emergency to the stall crash you are a bettery man than I am, Charlie Brown.

JohnF
 
N29CX took off this morning for the initial flight. It lasted not more than two seconds.
Ouch. I'm very sorry to read about your accident, but at the same time I am so happy that you are OK. This could have been much, much worse.

RV-12 flyers - Does the RV-12 have more nose up trim authority than it needs, or is there some part of the envelope where you will use all the available nose up trim?
 
RV-12 flyers - Does the RV-12 have more nose up trim authority than it needs, or is there some part of the envelope where you will use all the available nose up trim?

Personally, I have found the -12 to be pretty docile is every take off configuration imaginable. I think the trim "envelope" is no more "wide" than any other RV. Basically, you trim for take off, trim for cruise, and trim to land. Never been an issue.


John, Very sorry to hear about your incident today. Glad you are okay!
 
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John, very glad you are OK.

I'm sure your RV friends there around Salida, CO (googled your N-number) will go out of their way to help you get your plane back in shape. If you lived down the street I'd be over tomorrow....

Hang in there and wishing you the best,
Doug
 
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Glad to hear you are OK, John. A scary thought to imagine that a runaway trim cannot be overcome by stick force. Seems so unlikely that a Van's design would have incorporated such a possibility. Certainly something that needs to be resolved, and very quickly. All RV12 flyers will be thinking about this each time they go up until root cause is clearly determined abd a fix established.
Dick Seiders
 
A scary thought to imagine that a runaway trim cannot be overcome by stick force. Seems so unlikely that a Van's design would have incorporated such a possibility. Certainly something that needs to be resolved, and very quickly. All RV12 flyers will be thinking about this each time they go up until root cause is clearly determined abd a fix established.

With this accident being no different than any other, I think it would be sensible to not jump to conclusions about the cause until one is actually identified.

If it is irresistible to speculate on the cause, keep in mind that the construction documentation specifys that the trim rate be adjusted for a travel time of 25 - 30 seconds between full nose up trim and full nose down trim. So instead of a trim runaway and RV-12 is more likely to have a trim leisurely walk away.
I would be interested in seeing what the trim position indicator on the D-180 says now after the accident.

Glad to hear you are ok John.
 
N29CX took off this morning for the initial flight. It lasted not more than two seconds. The plane accelerated smoothly and I noticed the RPM passing through 4950 when there was an uncommanded pitch of what I am guessing was 60-degrees, and full force forward on the stick didn't do anything and then there was a stall. (snip).

Wow.

John, we are very glad you're OK, and appreciate your sharing what must be a painful experience so we can hopefully learn something.

Do you think it's possible something fouled the pitch control? Your description reminds me of a dh-4 accident where gust locks were left in place.

I'm not familiar at all with the pitch system in the -12 except that it seems to be a cable-actuated stabilator. is it possible to mis-rig the stabilator cables and reverse the stabilator? that would be almost impossible to figure out on a first takeoff.

Thank you for sharing--it may save someone's life some day.
 
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James,

It was also my first thought, as he pitched down the airplane continued to pitch up until it stalled on the rwy. However that doesn't explain the broken servo.
 
John, I've been dreading the first RV-12 incident/accident. Sorry you had to be first. Thank God you are OK and this is not a tragedy. Thank you for being courageous enough to post your story so soon. Of course now you will have a huge following on this thread until there is an explanation. I trust that a logical and deliberate investigation, by you and others, will provide us all good information that could save lives. Until a cause is determined, we should, as in all accidents, refrain from speculation.

I echo DR - if this community was only physically closer we would all be over to help you rebuild!
 
More on the Crunch

Just got back from the airport...went there to verify that all control surfaces, cables, linkages, and stops were OK. Stick full forward or full aft makes stabilator hit the stops. Action feel same as before the crash.Rudder deflection also normal. Flaperons worked fine in all three flap positions, but there must have been some inertia-induced flexing of the wing assemblies because there was a VERY minor bend at the inboard edge of the skin of one of the flaperons...straightened it out with my fingers. FAA is trying to get here tomorrow.
 
Glad you are ok.

I am very sorry to hear about your incident John. A great group of fellow RV builders all wish you well. I too would be there asap if I lived closer to help you with repair if needed. Get back in the saddle as soon as possible and don't be spooked by this. Best of luck to you during the investigation. If any of can be of service just ask/post and if available will respond. Keith
 
John, I just heard about your accident- I'm certainly glad you are OK.
My first flight is planned, now, for Saturday. I have been delayed a couple of months, because my wife and I moved from Denver to Macon, MO. The reason being our brand new grandson- we want to watch him grow up. We have been back in Denver all this week to finish the airplane, and get it ready for first flight. The radio was giving me fits all week, but it's ready to go now. Your situation has given me pause not to rush things, but to take it step by step. I am not implying that you didn't do just that, but it has made me slow down and be even more methodical. Again, I'm glad you're OK. Steve
 
Just a guess?

Could it be some sort of a tail stall? exacerbated by the runaway trim?:confused:
 
To soon to Know

John glad you are OK every thing else can be replaced.

My Thoughts

The force of the impact may have broken the servo, from the stabilator and counter weight inertia.

I think a safety switch on the servo to stop runaway is possible (off at take off and Landing)?

If rotation came to soon the wing has lift and the Stabilator could stall first.

? Cross wind Component

? Weight and Balance

Joe Dallas
 
Since the stabilator must push down to raise the nose 60?, which way is the nose gonna go if the tail stalls???
 
All the Facts are not in

Since the stabilator must push down to raise the nose 60°, which way is the nose gonna go if the tail stalls???

? Cross wind Component

? Weight and Balance

And at what angle did it Stall

At 60° At 40° At 30° ?

And at 60° the Thrust is at 60°

And is there a Trim Runaway

Joe Dallas
 
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Glad you're OK!

Glad you're OK John! My heart goes out to you ... I don't know what to say ... but no one was hurt ... and I'm sure the plane can be repaired. Better days ahead, my friend.
 
Crunch

Sorry to hear about your incident. Glad your OK!

I hoped it would be some time before someone bent some metal, but I guess not. We'll just have to wait it out and see what the outcome will be.

It's interesting that someone asked me awhile ago if there would be a problem with run-away trim in this aircraft? My answer was no. Now I'm not so sure.

I'm also interested in that I am presently working on that area of the aircraft. I ran the trim to both limits to check the clearances of the AST and Stab as well as the push rod and the rudder. There were no problems and the servo motor shut down at each limit.

I did find that when I lined up the AST with the Stab, the right side was perfect. The two halves were even at the center where the push rod attaches, but on the left side the outboard edge was even with the stab and the aft outboard corner was 1/4" low. This suggests a twist in the left AST. It could also indicate the outboard trailing edge of the stab is twisted upward. Though I have recieved new parts for a left AST, I'm going to give this a little more thought.

I'm not suggesting this had anything to do with you incident, but may give those investigating something to think about.

Best of luck! Hope your flying soon and that your flight is a lot longer.

Art Pennanen
 
RUN / WALKAWAY TRIM

Weather or not this incident WAS a trim problem, I am going to modify my take off check list. There is plenty of time for the trim to continue to run to the limit after setting take off trim and taxiing onto the runway. I intend to add a last look at both the trim indicator on the EFIS AND a look over my shoulder at the stabilator in the full nose up position (and I will learn where the antiservo tab should be in that position at take off trim setting before the next flight).
So happy there was nothing more than damage to the plane!
Larry
 
Could the control have been reversed hard to believe this could be missed but the scenario fits. I had this same thing happen when I first started flying radio control.
 
Best Wishes

Everything that we know about this event has been passed on to us by John. The one positive we can all be glad about is that John is physically safe. Speculation about the cause is not where we excel. There are investigators who do that for a living. To make unjustified decisions about your own servo or about the design is not clear thinking. Best wishes to John and his future headaches trying to put things back together.
 
I hate to bring it up ,but there is the possibility that the stab cables may be routed incorrectly, making the stab work in reverse. It did it! I caught it on inspection, thank goodness.
 
Elevator Trim

Years ago my instructor made me cycle the elevator trim tab in both directions through the full range of travel during the pre-flight check. It was all mechanical and I had to turn a little wheel many revolutions. I thought it was a waste of time and effort back then.
We have been taught not to trust electrical fuel gauges. Perhaps the Dynon trim position indicator should not be trusted either. Potentiometers can fail as can electronics.
I appreciate John sharing his experience with us and am glad that he was not injured.
Joe
 
Hard forward on the sick and she goes up and stalls, well. I?m glad we have forums like this that we can discuss things like this and work them out. That's what forums are for.
 
More on the crunch

I spent the day waiting for the FAA inspector who didn't make it. But I used the time to make a detailed list of what I need to repair the fuselage. it involves only the bottom part of the firewall...that was lucky, plus the lower curved pieces just behind the firewall, and the belly forward that attaches to the firewall. Because of buckling and rather severe damage right behind the firewall the two large side skins will have to be replaced..not hard..just a lot of rivets to remove. The tail section needs a patch over a hole that was a puncture made by a taxiway marker pipe (rather easy fix)

No engine components were harmed, not even the gascolator, the oil cooler, the water radiator, etc. Lucky ! Engine crank shaft and the gear box are still unknowns.

The servo needs replacement but all the linkage is still perfect.

I no longer have any suspicion that the servo 'ran away" - too improbable, but if the unit jammed that might explain why it was trashed by maximum force on the stabilizer when I tried to recover from the strange and sudden severe upward pitch.

I have gone over this incident hjundreds of times in my mind, and can't put an action or event on every milliscond of the 2 or 3 seconds the entire incident took, but I now feel that if I had another 5 feet of altitude at the peak of the pitch up I might have save the situation. The plane did not hit the taxiway in a nose straight down attitude but the damage marks on the plane show that it was in a shallow down attitude, the result of my instinctive efforts to nose down the plane.

Will post FAA results, but expect it to say, "Aircraft stalled due to failure of the pilot to maintain adequate airspeed." That ends it for them and gets rid of me, but answers little.

JohnF
 
John,

When you pull back on the stick, which way does the stabilator move?

I ask point blank because of this statement:

I hate to bring it up ,but there is the possibility that the stab cables may be routed incorrectly, making the stab work in reverse. I did it! I caught it on inspection, thank goodness.

EDIT....John stated in a PM that his stabilator/stick are correctly rigged...
 
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Really sorry, John

But REALLY glad to hear that you're OK and the bird is repairable. Sounds like you did everything possible in the exceptionally limited time you had. I'd just been going over all the emergency procedures in prepareation for my checkout with Mike Seager and agree 100% that there's no way you could have recognized the problem and pulled the fuse in the short time available. Also, I don't believe you could have had the controls reversed or you'd never have rotated for takeoff-- even with no flaps it takes a significant pull to lift the nose. REALLY worries me to hear there's part of the envelope where you can't overpower the trim system with the stick. If that's the case, I smell an FAA investigation coming.
Once again-- glad YOU are OK.

Wayne 120241/143WM
 
Jammed trim tab?

If the trim tab were jammed with the stabilator, then the control stick can not be moved fore and aft. Excessive pitch force on the control stick would stress the trim servo. I do not know if it is possible to break the servo like that, but people have extraordinary strength in an emergency. I am not saying that a jammed trim tab is the cause of this accident, but it is one of the possibilities.
Joe
 
John, Please take this post as it is intended, to try and figure out what happened, and not point fingers. Good pilots learn from every flight. Lets find out what happened and move forward to get you and your plane back in the air, this time longer than 3 seconds. ;)

Last night I decided to test fly -12 with trim fully deflected in "up and down" position. My speed was about 60-MPH (to simulate rotate speed) and I used no flaps, 1/2 flaps, and full flaps. While the -12 trim demonstrated good command over the stabilator I was able to maintain flight straight and level with one arm, and actually control the plane up and down as if to attempt to land. Granted, I was prepared and ready for the "heavy stick" and had this happened on my first flight it certainly would have been a surprise and I possible would have needed longer than 2-3 seconds to figure out what was happening. The stick does become heavy and pushing on it hard to counteract the force would seem very unnatural and unnerving, especially on the 1st flight.

The Dynon has a trim indicator gage on it that appears after calibration. What does it indicate now? Where was the trim set for take off?
 
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Larry..

That's very useful information. Good to know how the plane behaves with adverse trim deliberately dialled it. Thanks for doing the experiment.
rgmwa
120346
 
That is wonderful information from Larry as a runaway trim is a nightmare condition. I can only assume that Van's has flight demonstrated the same conditions, i.e. that the aircraft is controllable under both a full pitch up and pitch down trim condition. Hopefully, they can comment on this to put everyone's mind at ease.

I also wonder if Van's is becoming involved with John and the FAA/NTSB on the investigation as I see no mention of this.

John
S/N 120317
 
That suspected cause does not explain this.

full force forward on the stick didn't do anything and then there was a stall

I cannot imagine that if the trim caused the pitch-up, full down elevator could not overcome it. Something still does not add up. As Brian posted earlier, were the elevators rigged properly? If they were rigged backwards, forward movement of the stick would cause the plane to pitch up even more.

Just my $.02

Tom
RV-7A N175TJ Flying
 
Yep, more to this story I am afraid....Even more so since Larry tested his to full travel in both directions in different flight modes....

Maybe not. The SURPRISE factor may have a lot to do with the situation. Have to wait for the final report.
 
N29CX took off this morning for the initial flight. It lasted not more than two seconds. The plane accelerated smoothly and I noticed the RPM passing through 4950 when there was an uncommanded pitch of what I am guessing was 60-degrees, and full force forward on the stick didn't do anything and then there was a stall. Fortunately there was still forward momenten when the nose wheel hit the dirt at the side of the runway.

John, I can't imagine how you felt seeing your damaged -12 after the first flight. So glad you were not injured.

This may have been in an earlier post and I missed it but am curious and don't know how to ask this in a subtle way--did you receive transition training in an RV-12 prior to first flight?

Thanks,
 
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