Tail hunting problem

[BorisGarcia]

Dear all,

Background: I am an airplanes flyer for several years. Now I am beginner to helicopters, I have been flying a T-Rex 450S, I can hover (tail-in and about 80 grades sideways), Sideways & fw/bw translations, recently began flat figure of eight and FF, which made the T-Rex smaller for this type of flight, so I bought a Hurricane 550EP.

With the H550, I am facing something like a tail hunting (tail goes fast to both sides) while trying to lift off the ground (about 10 cms). I have done the following trying to solve the problem:

- Un-tight main and tail blades
- Un-tight the tail belt pulley
- Re-check that Gyro is not in DS mode (due to non-Digital servo)
- Change Gyro from AVCS to Normal and back again
- Reduce Gyro sensitivity (now up to 8)
- Increase Gyro delay up to 100%, but left it in 75%
- Change from 4-cell (4.8v) to 6-cell BUT installing the stock GAUI BEC (5.8v)
- Re-check belt tension

The helicopter is completely stock (including GAUI ESC and BEC), for electronics I am using: Futaba GY401 gyro, Hitec HS-322HD servo (x1), Futaba S3004 servos (x3), Futaba R146iP receiver and 2 x 2150 20C DN batteries in series (6s).

I will appreciate your help, because I do not know what can be originating the problem and I do not have an expert (near) that can check it.

Regards,

Boris.

[Mikej]

Boris,

It sounds like a bit of tail wag, which is usually resolved by setting the gyro a bit lower, other than that I'm short of suggestions I'm afraid.

Good luck,
Mike.

[Finless]

I have never seen anyone used a 322HD as a tail servo.. What is the speed of that thing? If it is slow or bad at centering it may not work well with a 401 on this size heli? You might have to fool with the delay on the 401 and gain settings to get it working. I dunno....

[BorisGarcia]

Dear Mike, Bob,

The specifications are:

Speed: 0.19 sec/60° at 4.8V
Speed: 0.15 sec/60° at 6.0V
Torque: 42.00 oz-in at 4.8V
Torque: 51.00 oz-in at 6.0V
Weight: 1.5oz (43g)

Thanks,

Boris.

[prollegbg]

Boris, that is likely to be the reason for tailwag.
The recomended servo with this setup is Futaba 9254.
9254 figures : 0.06 sec/60° @ 4.8V
Your servo is more than 3 times slower!

But, as Mike and Bob said, you may be able to solve it by turning up the delay and down with the gain. But one thing is sure - you will never be able to perform 3D flying with this servo on the tail!

[BorisGarcia]

Hi all, last night as a test, I replaced the HS-322HD servo with a Hitec HS-81 micro servo, (the faster I found on hand) which has the following specifications:

Transit Speed: 0.11 sec/60° @ 4.8V
0.09 sec/60° @ 6.0V
Output Torque: 36.10 oz-in @ 4.8V (2.6 kg-cm)
41.66 oz-in @ 6.0V (3 kg-cm)
Weight: 16.6g (0.58oz)

And the hunting problem was almost solved (just some eventual little wags), so finally, I could hover and feel it (I am happy), thank you all for your valuable suggestions.

As I though that this servo is not the appropriate for this application, I was looking for the recommended servo (Futaba S9254), but I think that I cannot afford its price: USD$ 110 (at least for this year), so, Do you know if there is a less expensive servo option to use with GY401 and Hurricane 550 EP ?

Thanks, Boris.