ChopperAddict's Hints & Tips

CHOPPERADDICT SPECIALISES IN THE BUILDING, REPAIRING & 
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SAFETY - Checking out your new helicopter - things to look out for

This information arises thanks to another new pilot bringing his almost new Belt CP V2 down to me to look at after a (minor) crash while he was trying to learn to hover.

It illustrates very well the sort of problems that you could find in your brand new helicopter

The time available was limited as the owner had his small daughter with him and I also had another appointment later in the afternoon. The first thing I noticed was that the swash plate was not level fore and aft. This was duly corrected.

The next thing was that there was significant end float of the tail blades hub along on the tail rotor shaft itself, indicating that end float was present, which is a VERY BAD THING. On further checking, the cause of this was found to be that the grub screw that holds the tail blades hub to the drive shaft had been locked down (by the factory) without being on the flat that is provided. It must have been close to it as the hub was now able to slide in and out along the length of the flat.

Despite all efforts, the grub screw refused to loosen, and worse yet, would not even drill or cut out with diamond tipped Dremel bits, so I had to resort to cutting the drive shaft just inside the tail rotor.

One of the bolts holding the tail blade grips to the hub also would not budge, so I ended up putting together a new tail drive assembly from what could be salvaged from this tail, plus other parts, many of which have been KINDLY DONATED TO ME BY OTHER MEMBERS OF THE HELICOPTER FLYING FRATERNITY TO ENABLE ME TO DO JUST THIS.

MY THANKS GO TO ALL THOSE WHO HAVE ALREADY DONATED PARTS, 
AND TO ALL OF YOU WHO HOPEFULLY WILL DONATE PARTS IN THE FUTURE.

Having got the tail assembly sorted out, I checked the pitch, to find it set to +10 degrees at 50% throttle in idle up (we were using the stock Esky Transmitter).  So I sorted that out to give zero degrees at 50% throttle and +9 degrees at full throttle.

That done, I put it on the turntable and span it up to check the tracking.  The motor did not start to spool up until the throttle was at around 50%. NOT GOOD.  However, I went ahead and tracked the blades, and then started to check the Esky HH gyro.

Firstly, it was not really attached to the frame at all, it was just floating around, and worse yet it was strapped to the side of the helicopter, which meant it did not actually work at all. I repositioned it in the normal place on the top of the boom clamp, and then drilled through to add a tie wrap to make sure it would not move in the future.

Span the motor up again, and the tail went mad.  WHY - THE GYRO WAS SET TO NOR, AND NOT REV.

Switched it to REV, and got the tail servo positioned correctly so that it would hold the tail in RATE mode

I also removed the velcro strap that holds the LIPO as it had simply been slipped through the frame from one side to the other, making it almost useless as it would not go around the leads from the lipo.  These straps should be go around the battery from top to bottom (or vice versa).  Worst of all the supplier had the velcro going directly over the ESC's heat sink, which would certainly not help keeping it cool !

Finally, we were ready to try to test fly the helicopter although the weather was less than ideal, with a 20mph wind and strong gusts.

On the first spool up it took some time to get the heli airborne due to the binding on the motor we had noticed earlier, but at around 75% throttle she lifted off.   I adjusted the gain on the gyro to get the tail holding nicely, and we achieved quite a reasonable hover despite the wind.

Time had run out for us by this time (about 3 hours), so I could not investigate the cause of the terrible motor spool up.  I advised the owner to pull the motor out and spin it up separately to see if the cause of the problem is in the motor itself or else it must be in the ESC.

THE MORAL OF THIS STORY IS -

This was an almost brand new Belt CP v2, purchased from an unknown (to me at least) Internet heli supplier in the UK.  It had many problems straight out of the box, and had clearly never been test flown or even checked out by the supplier concerned.

The gyro was incorrectly fitted and did nothing at all, the pitch was so far out it would be a miracle if it ever got off the ground, the tail was incorrectly assembled at the factory, and either the motor or the ESC is clearly faulty.

SO EVERYONE - ALWAYS CHECK ANY NEW HELICOPTER YOU PURCHASE, OR YOU MIGHT ALSO GET ONE AS BAD AS THIS.

I feel sure the faults noted caused the new pilot to crash it trying to hover, as he knew no better at that time.

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