Backwards flight tail blowout

[simoncalver]

hi guys can i pick your brains.
have just started backwards flight on my 450 v2 and cant get the tail to hold its keeps blowing out, if i up the gyro gain it wags when going fast backwards and if i lower the tail wont hold. any ideas???
equipment is
450 v2. futaba 520 gyro and robbe fs61bb tail servo.curis tail blades align mains and runing +-10 pitch and 100% throttle in idle up

[Rotorhead]

Really you need something with more torque than that servo has, something like a 9257 or Align 520, there is no point in putting a decent gyro on a heli then putting a cheap low spec (for the job) servo on it.

You would also need a new servo mounting bracket for either of those, and I would also check the pushrod, if its too flexible it will make the gyros job extremely difficult when the servo is pushing.

[alioth]

A better servo may still not fix it if the basic setup's not right - my 500 was swapping ends when I was trying to do a tail slide with it (bizarrely, I thought at first, in the direction of rotor rotation, so the aerodynamic forces were not just overcoming the tail rotor but also the reactive torque). I just had too little negative pitch on the tail rotor available, once I increased the max negative pitch on the tail rotor the tail held.

[acwman]

Have to agree with 'alioth'.

You might have to check the setup. I'm not too familiar with the setup of the Futaba 520, but having had a small align 420 on a tail for quite some time on my sport, it holds extremely well in backwards flight, backwards hurricanes, and tail slides. This was when it was paired up with the align gp750 and it never blew out on me.. unless the setup was not right.

With the 750, in rate mode, the horn at 90deg, just ensure that you have a couple of degrees pitch on the tail blades to help counteract torque on the main blades. Either that, or hover in rate mode in idle up, and check that the heli is holding reasonably well. Switch over to hh mode and it should hold fine.

I have heard some good things on the robbe fs61bb servo on the tail, and have no reason for doubting that it should give you better performance than you are getting. REVIEW



Hope this may help.

[Rotorhead]

I wouldnt put a servo that small on a tail especially an align one, unless it had metal gears, a lad at our indoor had several plastic geared 420 output shafts snap, a 520 size servo would IMO be the best bet, more torque, more robust, and still very quick.

But yes like alioth said its got to be setup right no matter what servo you use.

I just really dont agree that such small servos are up to the job either in terms of torque or mechanical resilience, and since they seem to be at the limits of their torque on the tail they will effectively be slower than a larger servo even in some cases where the large one is rated at a lower speed.

[chugga-bug]

There's nothing wrong with the fs61's at all. My 450v2 had one coupled with a 401 and backward hurricanes, tailslides etc. were never a problem. When the servo finally packed up (after about 18mths use) I couldn't get hold of another one so put a DS520 on it. That was pants in comparison.

[simoncalver]

Thanks guys im pretty sure i set it up in rate mode as i do normaly. i will double check and then start looking else where for set up faults

[Rotorhead]

There's nothing wrong with the fs61's at all. My 450v2 had one coupled with a 401 and backward hurricanes, tailslides etc. were never a problem. When the servo finally packed up (after about 18mths use) I couldn't get hold of another one so put a DS520 on it. That was pants in comparison.

Each to their own I suppose, but I just dont think those fs61's have enough torque for the job, and I've had the opposite experience with align servos, the 410's, 510's, 520's and 610's (all in different applications, some cyclic, some tail) have been excellent, but a servo with less than 1kg of torque on a 450, that just seems too low, 2+ seems about right to me.