My first mechanical failure crash on the 700 :( Help....

[alex]

I'm gutted- went to the field this afternoon and things have been going really well lately, doing lots of rolls, inverted fly pasts, tic tocs and even started some piro flips.

It was all feeling fine and controlled and I had used about 3/4 of a tank doing stationary forward and back flips and tic tocs when the heli suddenly started pitching all over the place and was totally uncontrollable.

I managed to hit throttle hold and get it to the ground where it landed upright, but must have done a bit of bouncing as the canopy was smashed and the main blades broken, but not smashed.

I'm trying to work out the mechanics of what happened. The elevator arm plastic link had broken and the elevator servo DS610) buzzes a lot but would not move. The servo moves freely and smoothly with no power to it, but whichever postion it powers up in, it will not move from there with stick input but is held in that position. The servo was also pretty warm. All the receiver connections are fine and all the other servos work.

The flybar and head are fine with no damage, the feathering shaft is straight as is the main shaft. There is a slight upward bend in the tail shaft, but the torque tube is as good as straight. The tail gear is fine.

I do a full mechanical checkover at least once a week and preflight the servo movements before every flight.

My question is did I miss anything that could have been corrected before the flight, is there something else I should be doing to check servos and is it OK to expect the elevator servo to take the abuse of continuous tic tocks and flips in the forward aft plane?

THe bill- £230 which actually is not too bad considering that includes a new canopy.

Any feed back is much appreciated.

Thanks

Alex

[Neutrino]

Hey, sorry to hear about the crash! Im dieing to get a 700, but dreading any kind of repair bill for it, so good luck.

As far as the repairs/cause go, what servos are/were you using? Another thing you have to think about, is did the part you suspect, break during the flight to cause the accident, or did it break as a result of the impact. Its sometimes very difficult to tell.

EDIT: As far as a full mechanical check each week, and the normal preflight checks before each flight, i imagine you are doing an ample amount of precautions, and possibly this is something you definatly couldnt have forseen, if you didnt notice any thing unusual, or not quite rite during your checks.

[alex]

Hey, sorry to hear about the crash! Im dieing to get a 700, but dreading any kind of repair bill for it, so good luck.

As far as the repairs/cause go, what servos are/were you using? Another thing you have to think about, is did the part you suspect, break during the flight to cause the accident, or did it break as a result of the impact. Its sometimes very difficult to tell.

Yes - that is what I am trying to work out- the fact there is no other damage to the head shaft or swash makes me think it may be a failure.

[Neutrino]

Yeah i can agree on that, if you have a crashed heli, and there is just one vital flight part that is broken, and everything else is cosmetic damage, then its a good bet that was the culprit. So everything else was cosmetic, and it was the elevator control arm that was broken on your heli?

If not, some receiver problem? Although its unlikely, might have been a glitch that caused some random cyclic commands to be sent, and the elevator arm was broken on impact.

Just a thought: Im not expert by any long shot of the imagination, but if the elevator control breaks during flight, would that not just result in forward and backward pitch of the helicopter??? As the other two cyclic servos are still ok?? I could be/probably am wrong though

[alex]

Hehe- it all happened a bit quickly, so I am struggling to remember the exact movements though I think it was predominantly forward and back in random combinations. The other servos are working fine.

[chris jones2.4]

bring it tomorow dude, c if i can see anything

[Neutrino]

Haha i bet, i would have sh*t my pants in an instant im sure some more people may come in and give some advice. If i were you, repair, patch it up, and carry on as if nothing ever happened, and of course, keep up with the routine checks of the mechanics.

[machasm]

You said in your original post that the heli was totally uncontrollable. By this do you mean that none of the inputs responded at all or just that with the locked servo it felt like you had no control?
The reason I ask is that maybe you had a brown-out of sorts and the fault may lie in the battery or RX. The servo may have been damaged by the impact.
Were the lights flashing on the Rx when you went to pick it up after the crash?
Ade.

[alex]

You said in your original post that the heli was totally uncontrollable. By this do you mean that none of the inputs responded at all or just that with the locked servo it felt like you had no control?
The reason I ask is that maybe you had a brown-out of sorts and the fault may lie in the battery or RX. The servo may have been damaged by the impact.
Were the lights flashing on the Rx when you went to pick it up after the crash?
Ade.

That is a key question and I do not know the answer as I was in such a hurry to get it all turned off and stop the buzzing :P From what I remember, I don't think there was any control for a while as I can usually now recover from most orientations I get into and the loss of control was from a static hover after some moves, so nothing to recover from in that respect.

I'm going to do a servo post mortem tonight :P

The only other thing I can think of is if I weakened the plastic link- it was not bedded in properly in the elevator arm, so I snugged it down last week using an allen key to turn the link.

[pgkevet]

I'm wondering if the feedback pot failed on the elevator servo. that would cause erratic pitch movements and quite likely lead to death of that servo, power drains affecting the others and if it hit the deck and shocked the a-arm then it fractured then?

[moonmanflyer]

Have heard of the odd 610 frying in flight, is it the one in the plastic holder?, they can get hot

[alex]

Thanks- yes it is on the plastic holder and that servo was the one getting the most abuse from the moves I was doing.

I have just taken it apart and took all the gears out of that servo and reconnected- there was no gear damage at all, they are pristine. The motor just whined at me and stayed static when I put any stick inputs in. the motor also stinks and gets really hot ( too hot to touch) and drains lots of power. I think I have found the culprit.

I have a new DS 610 on order as they are good value- is there any mileage in getting the upgraded holder?

[millerman]

just got one for mine put it this way for a tenner you cant go wrong plus it look bling

[Martind]

Sorry to here about your crash but sounds like you got it down well
Dose soud like the servo died. I got the 55 in the velo in sunday and it has loads of power now

[chris jones2.4]

must be the tuning mart ;D