Raptor 50 strange tail problem..

[Spanner]

Raptor 50 V2, OS 50SX, Futaba GY520, DS650. 35Mhz JR radio gear. 600mm TT blades and 85mm tail blades.

Heli hovers stable, with maybe a slight wag, but nothing to write home about.

In forward flight, during a turn to the left or the right, the tail sometimes loses itself and kicks quite rapidly about 20 degrees to the left or right and then centre's. (quite nerve wracking when your just learning to fly!)

The tail will then try to pirouette to the left (clockwise) I land the heli, and the light on the Gryo will be flashing purple. Flick the gear switch between rate and HH 3 times and the gyro resets itself and all is well, a couple of circuits later and the same happens. Initial thoughts were the belt was a little slack, but its now tighter than me and still the same. I got 70% travel on the gear switch. 2 large pads under the gryro. Does it sound like a gain problem? too much?

Your thoughts and musings appreciated,


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[Heliblerk]

Hi

With tail problems I always check engine tuning first. I'm not familiar with the 520 but my old 401 used to kick when the battery was getting low. I used 92mm blades - longest I could get away with. Hope this helps

[Spanner]

I had the same problem with the OS46, literally changed to the OS50 today. Tuning seems fairly good after bearing replacement, maybe 1 3/4 on the mixture, probaby go a few more clicks in but seemed plenty of power and plenty of smoke.

I tried 90mm carbon tail blades not so long ago with no noticable change. May put them back on with the new engine in.

[Heliblerk]

1 3/4 out seems a bit rich to me. Do you get it breaking into a four stroke around mid throttle?

[Spanner]

a little, I'll keep leaning I think, see if that sorts it. 1 1/2 turns about right?

[Heliblerk]

I think mine is about 1 1/4 with the idle needle level with the skids.
Just keep turning it in one click at a time with a couple of mins runtime in between adjustments to allow the engine to re-temp itself. You will notice if you go too lean by the sound. If it goes lean land straight away and turn it back 2 clicks and you should be somewhere in the ballpark.

Some run them with the idle at factory and around 2 turns out but I could never get mine to run like that. Just depends what your idle is set to.

[Spanner]

Yeah, I started at 2 turns out, but only had time for 2 tanks of fuel.

If I can, I'll get someone to film it this weekend.

[Si Goodchild]

Heliblerk sorted my Raptor twitching tail with engine tuning and bigger tail blades after I went up from 600 to 620mm mains. Whilst I had no real problems with the 85mm blades I used with the 600mm mains, I would advise using the larger ones if you have them to hand as the new engine will be able to generate more torque on the mainshaft.

What worries meis the purple flashing light on the gyro. I've not owned a 520 (just a 401) so i suggest you read the manual to decode that. You shouldn't have to reset the gyro in normal use. Unless this is a warning that the gyro tried it's best and failed to resist an uncommanded yaw (presumably due to engine tuning) then you may need to be looking at your power supply and servo integrity.

In sum: first thing, 90mm tail blades; second thing decode that purple flashing light!

[Spanner]

The purple flashing light also occurs if I adjust the rudder trim in rate mode, and flick to HH but don't flick the gear switch a couple of times to tell the gyro its new reference point. So it appears that the gyro has lost its point of reference?

According to the manual, the purple flashing light means "Offset from the Neutral Position"

[nevans]

I had a similar problem on my Raptor 50. Check the casing around the tail drive for cracks, as a common problem is that the locking pin, on the tail gear, slips out and grinds away at the casing. Everything seemed normal during a hover, but as soon as any load was put on the tail, the case would flex, and the gyro could not offer enough correction!

[Spanner]

Found this, http://www.rc-toy.de/cosmoshop/pix/a...21_1-F1244.pdf

Its a different manual to the one I've got sat in front of me.

It says

"We would like to point out that the automatic that the automatic storage
of the neutral point in AVCS-Modus, (3 x movement of the auxiliary
channel within one second), can sometimes lead, in unfavourable
interference conditions, can lead to an incorrect setting. The resulting
wrong setting of the tail rotor neutral point can lead to a poor or uncontrollable
control of the tail rotor
We therefore recommend that you only use a PCM or 2,4 GHz Rx to
avoid this effect.
Should a PPM (FM) - System nevertheless be used, it is very important
to ensure that the system has an excellent range.
This particularly important when in flight, where some manoevres,
which cause a dramatic change in the aerial position, such as the stall
turn, which will highlight a poorly aligned (particularly when mixers are
in operation) RC – System’s range limit.
A corrupt radio signal can, under these extreme conditions, lead to a
command being interpreted by the gyro to move the servo neutral
point."

Well I'm on 35Mhz gear, so maybe a little interference is causing the gyro reference to screw itself up?