Model Forum / Radio Controlled / Helicopters / November 2008

Hi

My MCX arrived last Tuesday and I am very impressed with the way it
flies for such a small model.  But.............

It flew fine for the first few days with the number of "heavy
landings" being counted on the fingers of one hand - and only on the
first few flights until I got used to the model. The few times it did
"crash", it was from a few inches onto thick carpet and I was able to
knock the throttle back to zero before it hit; as far as I am aware
there have been no serious rotor blade strikes.  There was never any
visible damage and the heli always flew perfectly afterwards.

However, a couple of days ago and with no obvious cause, a minute or
so into a flight, the power to the rotors suddenly reduced without any
stick input - exactly as though the Low Voltage Cutoff had kicked in.
Thinking I had forgotten to charge the battery, I replaced it with a
battery fresh from the charger but with similar results, and it now
happens every flight.   The only difference between the above
throttling back and a normal LVC is that the LED does NOT blink (see
EFlite mCX thread).  Sometimes power is reduced for only a second,
returning to normal by itself with no stick input (the model will
briefly drop a foot or so then return to normal by itself). If I move
the throttle stick while power is down, then control usually returns
to normal but sooner or later into the flight it will happen again and
eventually yaw control is affected and becomes completely erratic.
This would indicate to me that there is a possible problem with the
ESC, firstly both rotor motors are affected together (yaw continues to
work) but later only one motor is affected (yaw is uncontrollable).  

Replacing the battery, a flight always starts OK then the same thing
happens after only a minute or so; obviously unplugging the battery
temporarily clears the fault.

I would make the following observations:-
1)  I have 3 batteries and it happens with all three (even fully
charged straight from the charger) - I think it unlikely that every
battery should fail at exactly the same time so the problem is
unlikely to be a duff battery.  In any case, after the problem has
occurred, if I try and recharge the battery, the flight has been so
short that it is obviously still nearly fully charged.
2)  It could possibly be the charger but charging appears to go
normally - the light goes out when it should.  The supplied charger
batteries have now been replaced with fresh alkaline but I cannot see
this causing any problems.
3)  It could be A Tx fault, but I have no means of checking this.
Personally I think it unlikely, as the heli always flies as it should
for the first a minute or so (i.e. after the flight battery has been
plugged in; and without the Tx having been switched off).  Had it been
a Tx problem I would have expected the fault to recur immed1ately the
flight was resumed.
4)  My layman's guess would be the ESC on the "5-in-1 control unit"
but, before contacting the supplier, wonder whether anybody else has
had similar problems.  I haven't contacted the (mail order) shop yet
but, being cynical, suspect they could try and wriggle out of it by
claiming crash damage.

Checking the WWW, there are one or two reports of mCXs giving problems
after a few days, but I wonder whether the model has basic reliability
issues.  Any help would be appreciated.

Regards (sorry about the long post, but I wanted to give all the
facts)

KGB