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Old May 24, 2015, 11:56 AM
Tyrotor is offline
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200SRX Trimming

New to helis after years of flying fixed wing and still learning the former. All micro collection at the moment and flying them with varying degrees of success. Fairly recently bought a 200 SRX to add to the MSR, MSRX, and 120SR. Oh, and my first rotary purchase, a Nano QX.

Not being a teenager, progress has been relatively slow! Have been flying mostly at home with occasional use of a sports hall. The 200SRX seemed to offer outdoor opportunity and the SAFE facility and three modes seemed ideally suited to my skill level.

First impressions were very good. Solid. Stable. Comfortable and relaxing to fly. After a few flights, however, there seemed to be a marked tendency for it to drift left, requiring full right trim plus significant right stick to maintain station. Cue web research in search of a cure.

Found Horizon's info on the subject and ran the servo set up procedure first. Despite adjusting the servos, which had been slightly out, the problem remained.

Then found some excellent info on this group including a suggested alternative procedure for setting up the trimming on the 200 SRX without the need to fly the model as Horizon recommend.

Sad to report that, for me, it didn't work and it has eventually left me questioning whether it could ever work on a Heli with stabilisation electronics on board.

Running the model on the bench with main blades removed and giving input to keep servos steady resulted in a swash, when re-initialised, that was level but went immediately FULL RIGHT as soon as main motor started, returning level only when main motor stopped. Funnily enough, this was apparently a problem that this procedure had supposedly cured, in another case!

Running the same trim "flight" procedure with no control input during running resulted in a swash, when re-initialised that sat left and aft. Applying throttle levelled the roll axis but not pitch .

It was also noted that, apart from a brief blip, the tail rotor did not run in either test. That was the first cue for me to start questioning the process. No main blades, therefore little or no torque reaction, therefore no tail rotor response, therefore no side thrust, therefore no cyclic response, perhaps?

As a nervous beginner with a now seemingly out of whack swash, I wondered how to remove the settings but it soon seemed clear that there was, and is, no simple fix for this.

Nope, I would have to decide which of the two swash conditions I would be less frightened of using during lift off into what seemed an inevitable and possibly unpredictable trimming flight!

I stayed with the second option and, in the event, whilst some quick correction was needed, the Heli came off and settled without too much drama, albeit with a reasonable amount of control stick initially being required.

Since then, I have carried out further trimming flights. These not only seem to have improved the trim immensely but my hovering skills seem to be improving as well, probably out of necessity! The electronics require a steady 30 seconds hover to gain and save accurate trim data!

Are my expressed concerns soundly based?

Is not our old and very influential friend, gyroscopic precession (and the effects) only present when a rotating mass is free to move in all three planes rather than just one?

It has been said that a Heli doesn't know when it is flying. In this case, can that really be true?

Can in flight stabilisation control systems really be set up when not in flight?

At least, fingers crossed, my 200SRX seems fine now. It probably just needs the pilot to catch up!

All comments welcome.
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