Advice please. 450X spins when I shut down

[Hummingbird]

Has anybody got any idea why my Blade 450X spins when I spool down? It is quite severe and nearly caused damage. It is new and all the 7200BX settings are at their defaults. It hovers fine and there is no wag that I can detect. If I pump the pitch up and down the tail stays solid. But when I land and shut the motor down it spins to the right (tail goes left). I've tried adjusting dial 3 on the 7200BX and increase/decrease the gyro on my DX8. The gyro is set at 45. I put it at 50 and 40 but didn't see any difference. It doesn't spin when I spool up, only on shut down as the rotors are slowing down.
Any ideas? Thanks.

[tomatwalden]

Throttle hold putting the gyro into rate mode maybe rather than heading hold ? (ie. gyro gain is specific to flight modes - and can be different for normal, IU1, IU2 and TH)

[450man]

Well no real insight but the first thing I would do is a full AR7200BX set up from scratch. My 450X flew OK out of the box but once I had done a full set up and reset things like servo centering, swash level, servo limits, zero pitch at stick centre and the 6 degrees etc it flew much better. I guess that each heli is checked that it flies OK with the default settings but it really benefits from more accurate setting up IMO.

It only took me about 30 mins and I had never done it before so it isn't difficult. You just need a pitch guage and a swash leveling tool. Be careful to disconnect the motor though or reduce all throttle curves (all of them just in case you accidentally flick the idleup switch) to zero just in case.

Just thought... I'd also check tail belt for damage and correct tension. Sounds like it might be slipping after flight when it might be warm but not slipping when spooling up when cold.

[SGD]

Could it be the one way bearing not running smoothly? The tail kicks the same way as the mains rotate so may have an impact.

[kroozing]

Brake function on esc?

[tomatwalden]

Brake function on esc?

I'm not sure the 450X stock ESC has a brake function - though that would certainly send the heli into a spin!

My vote is still on gain wrong in TH

Sounds like something that should be fairly easily to isolate. Curious to know now what the outcome is!

[dillwhacker]

Why would the brake make it spin if the OWB is working OK?

[tomatwalden]

Advice please. 450X spins when I shut down

Why would the brake make it spin if the OWB is working OK?

True.

[Hummingbird]

My gyro is the same gain on all modes. And I'm not sure what you mean about throttle hold (I know what TH is but not sure what you're suggesting). When I shut down I dont use TH. Just closing the throttle with the stick, that's when it spins. It doesn't actually spin all round, but if you imagine landing with the tail towards you (6.o'clock position), it moves hard round to the 9 o'clock position before the friction with the grass stops it!
But maybe I should do what 450man says (hello again!!) and run through the entire 7200BX setup, which I haven't done, simply to avoid getting something wrong. I am fully aware how to set up a flybar heli, this is my first FBL. Thanks also tomatwalden, I'll let you know.

[milly0812]

Advice please. 450X spins when I shut down

Could the tail have too much pitch one way ie not centered ? The HH will kick in and hold the tail regardless but on the deck the blade pitch overpower it

[450man]

I could be totally wrong here as I am still very much a beginner but just to help us understand what might be happening...

The way I see it is that for the body to spin there must be a mismatch between the torque of the rotating blades and the anti-torque force created by the tail rotor. This could be caused in a number of ways...

Physical causes might be: tail servo problem, sticky tail rotor, tail rotor or assembly damage, torque tube or TT gear damage (if TT) or damaged or slipping belt (if belt drive), faulty OWB

Electronic causes might be: gyro adjustment needed or FBL controller adjustment needed

Other causes might be that a sudden power up or down might generate so much immediate torque that the tail rotor system or gyro system does not have time to react... such as a very rapid power change.

Have I missed anything?

For it only to happen when powering down my guess would be electronic or the OWB otherwise wouldn't you see some effect in normal flight?

[tomatwalden]

Advice please. 450X spins when I shut down

450man. For the tail to go from 6 o'clock to 9 o'clock position implies the tail moves to the left. That means the tail is moving with the rotors, not against (ie not torque related).

Does that lead us towards to OWB????

[tomatwalden]

Advice please. 450X spins when I shut down

The more I think about it, for the body of the heli to move with the rotors can only be either the tail is pushing too hard with anti-torque or the body somehow gets locked to the main shaft.

Not sure what would cause the first, but maybe OWB or main shaft bearings might cause the latter ?

[450man]

450man. For the tail to go from 6 o'clock to 9 o'clock position implies the tail moves to the left. That means the tail is moving with the rotors, not against (ie not torque related).

Does that lead us towards to OWB????

But if the power is reducing then the blades would be slowing so the torque would be in the opposite direction wouldn't it?

My gut feel is OWB but my gut is often wrong!!!

[tomatwalden]

Advice please. 450X spins when I shut down

Hmm. Not sure. It's Newtonian physics here isn't it? Ie. Every action has an equal and opposite reaction. On spool down, there is no action as such - no force, just momentum.

So I'm inclined to conclude that there is no torque to counteract rather than its reversed?

OP : is the OWB running freely? Thats easy to check.