jthocker
Well Known Member
Vic,
This is exactly what I do!
Maybe I missed it, but was the locknut missing from the AN3 bolt or the jam nut and safety wire missing and the tube rotated and unscrewed from the rod end?
Van's Air Force
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RV-10 Landing Accident
- Thread starter PerfTech
- Start date
Vic,
This is exactly what I do!
Maybe I missed it, but was the locknut missing from the AN3 bolt or the jam nut and safety wire missing and the tube rotated and unscrewed from the rod end?
ScottSchmidt
Well Known Member
My guess is it was just forgotten or put on hand tight during a re-installation. I have checked that bolt for 6 annuals now and have never seen it get loose.
I did replace all the nyloc nuts that hold the ailerons, flaps and horizontal stab with castle nuts and cotter pins.
Mistakes do happen by everyone (even A&P's). In the last 15 years I have heard of many cases where people forgot to torque a nut, left cotter pins out, forgot a hole section of rivets, screws or bolts. Luckily these were caught on the ground during a pre or post first flight inspection or after an annual. I am guessing this would have been caught on the ground of it would have held together for 60 seconds longer.
Glad everyone is OK. I met Bob at the Nellis Air Show in 2007, he is a great guy.
JonJay
Well Known Member
Pat - all due respect, put a wrench on it. There has been more than one torque sealed nut that was never torqued to start with. It should not be a short cut to making your CI go faster IMO. I put a wrench on EVERY nut and bolt in the control system at every CI. To your point, I have never had one loose, but I still do it. Sometimes I knock off the torque seal and have to put a little back on it.
Walt
Well Known Member
Amen to that, I put a wrench on every critical fastener (this includes FWF) on every RV inspection I do. Torque seal is great but when the builder is the one applying it rather than an "inspector", it means nothing to me. The same person that is applying the seal is the same person that "thought" he torqued it.
Pat Stewart
Well Known Member
That's why it is important to put the seal on immediately after you torque the nut.
JonJay
Well Known Member
I do the exact same thing. So, how was it that I had a B nut leak on the fuel system. Torque seal was there. I always torque seal as you do, just after finishing torquing it. However, the nut had never been torqued and was only finger tight.
Simple, human error. There is a scientific explanation for the human behaviour of believing you did something to the point of swearing it was done, but you didn't. Same thing why people can read a check list and not take the action but in their mind, they did.
Hence, my tag line (see below)....
I made sure my push tube is in such length that if both jam nut became lose and the tube started unwinding, it will hit the end of one side and does not come off the other side. In another word, if your rod bearings are more than 50% in on both sides, it cannot come off completely unless it also gets disconnected from the attach point.
Mike S
Senior Curmudgeon
But, the 10 setup is not the same as your 7.
Lock nut vers Caslte nut and Cotter pin
Well being an old US AF mechanic, on fighters to B-52 the C-5, and a A&P with over 5 years in Alaska and almost 35 years turning wrenches on airplanes, where one sees just about every thing one can do wrong or done badly.
I have made a decision on final assembly all moving parts in the flight control system will have castle nuts and cotter pins. It is moves or changes direction or can cause a major failure then it will have a mechanical locking device on the nut no matter what.
This is a shame this has happened. And I glad no one got hurt, and looks like only damage to the plane that i am sure is repairable.
We all need to keep this in our memory banks to change habit patterns to insure this does not happen again, and that we build the safest planes possible.
Well being an old US AF mechanic, on fighters to B-52 the C-5, and a A&P with over 5 years in Alaska and almost 35 years turning wrenches on airplanes, where one sees just about every thing one can do wrong or done badly.
I have made a decision on final assembly all moving parts in the flight control system will have castle nuts and cotter pins. It is moves or changes direction or can cause a major failure then it will have a mechanical locking device on the nut no matter what.
This is a shame this has happened. And I glad no one got hurt, and looks like only damage to the plane that i am sure is repairable.
We all need to keep this in our memory banks to change habit patterns to insure this does not happen again, and that we build the safest planes possible.
Walt
Well Known Member
Not a bad idea but there are some places where that will be very difficult/darn near impossible on the RV.
Geico266
Well Known Member
I find it hard to believe they can come loose. The new nyloc nut is tourqued. The bearing is doing the turning not the bolt. What am I not understanding?
dhammer
Well Known Member
Never enough
FWIW Personally I like cotter keys on flight controls. As a point of reference Dassault goes all the way. On Falcon Jets all flight control bolts have lock nuts that also require a cotter pin. On top of that the bolts are a pip pin device that requires pushing the release on the bolt head to rectract the little ball keeping you from extracting the bolt. The cotter pin keeps the nut in place and also locks the pip pin. Even with the nut off you can't take them out until the pip pin is depressed. Try buying one of them bolts. $$$
It's wonderfull to say that if the nut is tight it won't loosen, but I've seen rod ends that froze up and promply loosened the nut. Never seen one break a cotter key though.
Cheers
FWIW Personally I like cotter keys on flight controls. As a point of reference Dassault goes all the way. On Falcon Jets all flight control bolts have lock nuts that also require a cotter pin. On top of that the bolts are a pip pin device that requires pushing the release on the bolt head to rectract the little ball keeping you from extracting the bolt. The cotter pin keeps the nut in place and also locks the pip pin. Even with the nut off you can't take them out until the pip pin is depressed. Try buying one of them bolts. $$$
It's wonderfull to say that if the nut is tight it won't loosen, but I've seen rod ends that froze up and promply loosened the nut. Never seen one break a cotter key though.
Cheers
This is what worries me about using a lock nut on the inner race of a bearing/ball joint.
Thought this was an interesting read: http://aerospaceproducts.com/disconnect.html
I am not saying that is a bad idea, just pointing out that you shouldn't assume it is automatically better.
There are instances of accidents caused by cotter pin safetied fasteners that came apart. Depending on the technique and skill level applied by the installer, a cotter pin can be left vulnerable an many different ways. It is not unheard of for pins to become bent open because of catching on tall grass, rags while washing the airplane, etc.
The fact is, that pretty much every aircraft that flys, has many (sometimes hundreds) of critical system connections held together with self locking nuts.
If they are appropriately chosen for the location used (I.E., not using nylocks in high temp locations, etc.), and are installed properly, in most instances they are as reliable as a cotter pin safetied fastener would be. There are specific instances where a cotter pinned fastener is the only appropriate choice and then should be used.
I think this thread has taken a wrong turn and people are loosing site of the fact that you can just as easily forget to install a cotter pin, as you can forget to install a self locking nut (or install it properly).
I do not know if that is even for a fact the cause of this accident, but it is always a possibility that we as airplane builders need to be doing all we can to mitigate.
Since there is often more than one of us doing final assembly work in our shop, keeping track of what has and has not been final torqued can be even tougher than for someone working alone. For that reason we have a policy that parallels what has been mentioned by others already.
When we are at a point that final assembly has begun, we torque seal each fastener immediately after we torque it.
When the airplane is finished and ready for flight (other than all inspection panels open), we physically follow the complete control circuit of all critical systems and inspect every fastener along the way....
Stick grip attachment to control stick
Control stick attachment to rod end on push rod
Rod end attachment to pushrod end.
pushrod end attachment to push rod tube
and on and on.
If this thought process is used in the context of "the airplane is finished... I am no longer an airplane builder... I am now an airplane inspector, and you inspect without distraction (no one hanging around asking questions, etc), you will probably find everything that needs to be found. Then give a flashlight and mirror to someone else and ask them to do it all over again (again, without any distraction).
BTW, inspecting means just that, if you find something not right, make a note for resolving it later (when you switch back to airplane builder mode) and continue. If you jump back and forth between finding and fixing, you will always skip over things (this is the standard procedure used by aircraft mechanics... Inspect, then resolve any problems that were found).
My 3 cents...
Walt
Well Known Member
I find it hard to believe they can come loose. The new nyloc nut is tourqued. The bearing is doing the turning not the bolt. What am I not understanding?
I was not trying to imply that that this method (castle nuts & cotter keys) needs to be standard practice, only that it can't hurt if it makes you feel better. Personally I am perfectly comfortable with lock nuts used with rod ends with bearings. However I do use locktite on critical fasteners for a bit of added insurance.
7960 flying RVs
The method of securing a nut and bolt to connect a push rod to the control column has been successfully employed in 7960 RV's.
Since everyone is speculating on the cause of this failure I put my money on either, no nut was ever installed or nut was finger tight only.
It boggles my mind how so many people freak out about this and think we need re-engineering of the control system.
Just like the doors on the 10, if you forget to close them, even the "third mandatory service bulletin latch" won't do any good.
The method of securing a nut and bolt to connect a push rod to the control column has been successfully employed in 7960 RV's.
Since everyone is speculating on the cause of this failure I put my money on either, no nut was ever installed or nut was finger tight only.
It boggles my mind how so many people freak out about this and think we need re-engineering of the control system.
Just like the doors on the 10, if you forget to close them, even the "third mandatory service bulletin latch" won't do any good.
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Excellent!
On a homebuilt experimental aircraft, a builder does not have to follow the plans.
IMHO, the plans show a technique that works and was designed in by someone that has more experience than most builders. IF a builder does not follow the plans and makes changes, be prepared to SHOW the FAA / DAR what supporting document is used for the change.
Our EXPERIMENTAL aircraft are not required to meet MIL specs or part 23 requirements that were not designed in by the designer.
Is the "improvement" that the builder does really an improvement or is it just a more expensive way that takes more time to do?
rleffler
Well Known Member
Rick,
That's a quote worthy of putting on everyone's wall during the build process!
Bob
pierre smith
Well Known Member
Demonstrated reliability.
Guys, my Air Tractor is a 1989 model and now has 9500 hours of abuse! Yeah, we work them harder than you can imagine, with literally hundreds of turns, both left and right, per day. Those are coupled with huge rudder inputs because of incredible adverse yaw....we have to replace the rudder cables every year. They're attached just like my RV's..castellated nuts and cotter keys.
Our elevator and aileron pushrods look exactly like Van's RV's and use a nyloc nut for attachment and in all these years and hours, no nyloc nut has ever fallen off. They're certified airplanes with an FAA inspector on the assembly line and they come that way.
Best,
Guys, my Air Tractor is a 1989 model and now has 9500 hours of abuse! Yeah, we work them harder than you can imagine, with literally hundreds of turns, both left and right, per day. Those are coupled with huge rudder inputs because of incredible adverse yaw....we have to replace the rudder cables every year. They're attached just like my RV's..castellated nuts and cotter keys.
Our elevator and aileron pushrods look exactly like Van's RV's and use a nyloc nut for attachment and in all these years and hours, no nyloc nut has ever fallen off. They're certified airplanes with an FAA inspector on the assembly line and they come that way.
Best,
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Geico266
Well Known Member
JonJay
Well Known Member
az_gila
Well Known Member
Even certified German factories can screw up...
http://www.ntsb.gov/aviationquery/brief2.aspx?ev_id=20001211X10364&ntsbno=LAX98LA209&akey=1
Wayne Gillispie
Well Known Member
The use of elevator trim, autopilot and throttle would be my choices in this particular failure. Not something we practice for. Our -10 is tougher than I thought. I sure am glad they are alive. All of that oil on the bottom sure seems excessive for break-in.
Steel lock nuts
I will use steel lock nuts for final assembly on all control surfaces and pushrods. The nylon lock nut provides about 1 or 2 in/lbs of resistance and the steel lock nut provides about 7 or 8 in/lbs according to my testing. Just a little extra insurance.
I will use steel lock nuts for final assembly on all control surfaces and pushrods. The nylon lock nut provides about 1 or 2 in/lbs of resistance and the steel lock nut provides about 7 or 8 in/lbs according to my testing. Just a little extra insurance.
pierre smith
Well Known Member
Maybe
Wayne, I just had a gentleman here for some transition training on Friday and I demoed elevator trim use, and he evaluated it too. You run out of trim during the flair and still need elevator pressure to hold the nose up. As you well know, the -10's are very trim dependant.
These guys may well have started the flair when the elevator let go, and instantly pitched nose over and smacked the pavement with no opportunity to react in the one or two seconds in this episode.
Best,
Wayne, I just had a gentleman here for some transition training on Friday and I demoed elevator trim use, and he evaluated it too. You run out of trim during the flair and still need elevator pressure to hold the nose up. As you well know, the -10's are very trim dependant.
These guys may well have started the flair when the elevator let go, and instantly pitched nose over and smacked the pavement with no opportunity to react in the one or two seconds in this episode.
Best,
Wayne Gillispie
Well Known Member
I have 25 extra lbs of aux battery/hot bus/wiring aft of baggage bulkhead. I flew solo Thur with 40 lbs of baggage. I left trim set after landing and it was still a great amount of nose up trim. I had not trimmed off all of the stick force either or it would have been close to being at max deflection. When I have the whole family on board and do the same thing, there is very little nose up trim needed on landing.
Wonder if we could also use our autopilot if we knew far enough out and high enough? I think I have my "Min Aspd" set at 90 kts, so that would need to be set down around 65 kts in order to keep it from nosing us over. Set up for a 200-300 fpm descent at the longest runway available. The flare would be the tricky part...dialing in a level off or slight climb at just the right moment while not taking out so much power that the nose drops.
This accident pilot did a fantastic job getting down, so not questioning his piloting skills. Just thinking of our options.
Wonder if we could also use our autopilot if we knew far enough out and high enough? I think I have my "Min Aspd" set at 90 kts, so that would need to be set down around 65 kts in order to keep it from nosing us over. Set up for a 200-300 fpm descent at the longest runway available. The flare would be the tricky part...dialing in a level off or slight climb at just the right moment while not taking out so much power that the nose drops.
This accident pilot did a fantastic job getting down, so not questioning his piloting skills. Just thinking of our options.
Wayne Gillispie
Well Known Member
In this case here AP may be another option. Anything aft of pitch servo and one is left with trim, power and weight shifting(which works, we have already tried that up high).
Kyle Boatright
Well Known Member
Don't forget the flaps. They create quite a nose down pitching moment on my -6. I'd bet the -10 is similar.
NovaBandit
Well Known Member
If the connection failure was at the control horn of the elevators itself, yeah... the trim wouldn't even help you as that bolt is also keeping the two elevator halves together. With the 10's asymmetrical trim system, you'd be out of luck.
BUT, that's not where this disconnect happened (according to an earlier post). The nut was supposedly missing from the WD1010 control column. In this situation, the AP servo (which connects near the F-635 Bellcrank) would have still been connected and useful, as long as the F1089 pushrod didn't jam up somewhere. and when you're on short final at 75' above the runway, there isn't much time for anything other than realizing something is wrong.
Weight Shift
On the first Cassutt Racer, Tom Cassutt had the bolt between the pushrod and elevator come loose. He landed the airplane by shifting his weight. No damage to the airplane.
Elastic nut, the nut had been used for holding something during welding and the elastic was burned.
On the first Cassutt Racer, Tom Cassutt had the bolt between the pushrod and elevator come loose. He landed the airplane by shifting his weight. No damage to the airplane.
Elastic nut, the nut had been used for holding something during welding and the elastic was burned.
