J

JohnF

Well Known Member
I am still trying to resolve the RV-12 accident. I am trying to eliminate every possibility, no matter how remote.

I wonder if someone with a flying RV-12 could take two photos of the stabilator front edge right where is almost meets the tail side skin.

I would like a photo of the stabilator full up, and full down. If you have a digital level, perhaps even the degrees of difference from full up to full down would be a help

I want to gauge the stabilator's deflection in relation to the line of rivets on the tail cone skin, to eliminate any possibility of some remote chance something isn't right on the construction...I am sure it isn't but nothing is being overlooked.

Thanks for any help.

JohnF
 
Close up comparison?

One of us builders that have a flying RV12 might want to consider flight to visit with John so he can see and compare construction first hand. Just a suggestion. I know sometimes if I can see the actual finished product it helps me visualize better. Keith
 
Page 11-08 Check AST Clearance

One thing to check is to be sure the stabilator travel is limited by the stops and not by the anti-servo tab bottoming out against the stabilator. Page 11-08 shows a detail drawing of the clearance between the stabilator and anti-servo tab. That clearance needs to be checked with the trim full up and then again with the trim full down while also positioning the stabilator to its maximum up and down stops. A piece of thin cardboard can be used as a feeler gauge to make sure there is clearance. The damage to the Pitch Trim Servo could have been caused by an internal failure. Or it could have been caused by excessive external force. But there should not be excessive external force applied as long as the above mentioned clearance is met. All of the stress from control stick force should have occurred at the stabilator stops, not at the pitch trim servo. Now I am not saying that this is the cause of the accident. But since every possibility is being checked, it would not hurt to double check to be sure that everything is adjusted properly. If the anti-servo tab hit the ground during the accident, that could have damaged the pitch trim servo too. I am not trying to point fingers either, just trying to be helpful.
Joe
 
Dynon Trim Indicator

John,

Are you settings your Dynon trim indicator in the correct position for take-off on the panel? Does the trim button that says "down" push your nose down and vice-versa? The Dynon readings are the best way to know you're in the clear before leaving the ground.
 
Van's prototype

Hi John,

I took this shot last week during checkout to compare it to my airplane. This is the stab position at full NOSE DOWN stick position. Hope it helps.

Wayne

Stab.jpg
 
Trim Indicator

Pete, the Ray Allen servo is trashed so I can't do anything right now about checking...have just sent an order to Vans for all the stuff I need to restore the plane...FAA has not come yet so I can't do much except get ready to start repairing the damage...

I have to say that all the speculation by my local A&E, me, and others about the servo being a cause/involment/factor in the crash is not valid. I think the servo was damaged/destroyed as a result of the accident, and in no way a causal factor...there was no tail area damage whatever but kenetic factors could be the cause of the servo being trashed. There is no physical damage beyond about 6-inches back from the fire wall...absolutely none because he plane was ALMOST recovered from the pitch up and if I had only about 5-feet more altitude at the top of the pitch up I think I would have recovered, but I was not quite level when the front wheel/prop, etc contacted the blacktop, so the tail and the servo just were not involved or a cause it is my considered opinion.
 
John

Understand. Good luck with all your efforts. Use any of us if you need to. Some of these guys are on here are pretty smart...as I'm sure you can tell.
 
John, do you have any recall of moving the stick back to any degree just prior to pitch up? The stabilator has considerable pitch power. During a taxi test at 30 knots I moved stick back approx. half way and the nose came right up at that speed. The point is stick back pressure is not required. I did my first flight today after calibrating my trim on the Dynon. On takeoff with the trim set at takeoff value I did not move the stick at all and the 12 simply started flying at about 60 knots and executed a perfect rate of climb with no stick action on my part. I am not suggesting anything, but wanted to run one possible contributing cause for your consideration. Good luck.
Dick Seiders
 
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JohnF said:
Pete, the Ray Allen servo is trashed so I can't do anything right now about checking...have just sent an order to Vans for all the stuff I need to restore the plane...FAA has not come yet so I can't do much except get ready to start repairing the damage...

I have to say that all the speculation by my local A&E, me, and others about the servo being a cause/involment/factor in the crash is not valid..
Click to expand...

John,

Pete asked the same question. Where did you position the trim as indicated on the Dynon prior to take-off? After calibrating the trim indicator per the Dynon installation manual, just a bit below the centerline (about 40% of full scale) works very well for me.

Let us know...
 
Takeoff stick position

The procedure taught by Mike Seager during my -12 checkout was to use back stick force until the nosewheel comes off the ground and then FORWARD to hold the nose just high enough to keep the wheel off. I was VERT surprised at the amount of pitch trim change needed when flaps are lowered and raised. Apparently those full-span flapperons combine with the airfoil used to produce quite a bit of pitching moment.

Wayne 120241/143WM
 
yankee-flyer said:
The procedure taught by Mike Seager during my -12 checkout was to use back stick force until the nosewheel comes off the ground and then FORWARD to hold the nose just high enough to keep the wheel off. I was VERT surprised at the amount of pitch trim change needed when flaps are lowered and raised. Apparently those full-span flapperons combine with the airfoil used to produce quite a bit of pitching moment.

Wayne 120241/143WM
Click to expand...

That is the technique I use. Keeps the nose gear from bobbing. A VERY GOOD thing to try if you have not given it a try. That Seager guy is something else.
 
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