what caused my crash?

[imran1042]

okay, i just wanted to know because the elevator and rudder servos are from my brothers extra 260.  maybe when he crashed something happened to the servos or  servo. 

[Gregor77]

It happened fast..

I suspect that something might have gotten binded somewhere are the plane pitched up.  I would check the servo a few times.  I think that simon H had an issue where the collar to the elevator slipped (not sure if the leader is the same with two rods to the elevator?

Also do a pressure test on the elevator and servo and see if it skips a tooth.  Sometimes you bang the elev and that breaks the servo.  I usually depending on the model put a metal one in rudder and elevator for this issue.

* Please fix the plane* its not that bad!

[Wingnutz]

I wasn't at the field so this is pretty much a shot in the dark ...are we sure the bottom motor mounts and standoffs were tight?

[Tom]

Hi Imran,

Many mysteries go unsolved - especially with electronics.  For example, there could have been a bad connection in the servo which only appeared with the vibration in flight. or it could have been in the receiver.  You may never find it.
I am sure you will repair the plane and you may want to re-use as many components as possible but if the cause was not obvious then the safe thing to do is not re-use anything in the elevator control path which can't be absolutely verified to be good.

[akabek]

I had a similar experience last Wednesday with my Apprentice.  When I flew to the South East corner of the field and started to turn right my elevator locked down causing the plane to go up and eventually loop.  It did it a few times but it was intermittent.  When I brought the plane in the elevator servo was fine.  I did have a capacitor plugged into my Rx that came lose so it may have caused binding with elevator linkage.  If it does it the next time out I will consider replacing the servo.

[Frank v B]

Thought:

I have had a problem once where a servo output arm skipped a position on the toothed output wheel that comes through the servo case.  This happens when there is a sudden input on a loaded surface (up elevator) and/or the servo arm is not 100% correct for the servo.  When this happens it is the equivalent of adding double max. up trim and it will never centre properly again.  When you test the servo, everything looks and acts fine.

Apparently the plane is on its way to my house as we speak.. for repairs.  Simon just called.

Will check it out and report back.

Frank

[Frank v B]

Here's what happened.

None of the above.

I have started rebuilding the model. This model has two aileron servos, one in each wing with a direct link to the aileron pushrod.

Noticed last night that the left wing had the servo arm facing forward (in line with the pushrod).  On both left and right aileron input the aileron would only go up.  That meant that on a left turn, the ailerons were working properly (left aileron up, right aileron down).  When a right aileron input was given, both ailerons would go up, acting as an elevator (elevon), sending the plane skyward.

The servo arm should be span-wise and 90 degrees to the pushrod.  The servo horn screw was still in and there were no stripped gears.

It will fly again.   

The new wing tube just arrived.

Frank

[Ededge2002]

I believe this plane flew fine previously. My thinking is that the AS3X was initialized incorrectly causing it to "think" that level flight was very nose high. 

[Frank v B]

Re-build update:
Picked up the new wing tube at GreatHobbies today (Sunday).  The wings are back together and the fuse is re-built.  The screw-in wing lugs are in place and aligned.  Am letting them dry overnight then I will take everything apart and re-enforce the entire structure*
Should be ready this weekend.

Frank

* I rebuild the entire structure first so it will hold together and be straight.  I then go around all joints and re-enforce them with plywood, balsa or fibreglass.  This way excess glue and wood does not get in the way of joints and pieces that need to come apart.

[Bobmic]

Imran, looks like instead of a "flimsy" ARF you will end up with a custom built Semi composite plane built by an expert. I am sure you didn't think about this when you first got it.   

[imran13]

How much weight do all these repairs and reinforcements add?

[Frank v B]

re: How much weight do all these repairs and reinforcements add?

About the weight of a piece of bubble gum.  Will not affect flight performance.  You will not notice it.  Guaranteed.

Frank

[piker]

I KNEW that was your secret repair technique.  Works for leaky drain pipes too 

[Frank v B]

Finished!  The plane is done and Simon picked it up this evening.  On its way back to you.

Regards,


Frank

[sihinch]

Thank you Frank. Another truly remarkable repair.