Ouch! (Unexplained crash)

just had my first unexplained crash.

adjusted the aileron throw and went flying with the pl trainer.
first battery perfect flight, turns were spot on, loops aok, a little bit of inverted, then came in for a very nice landing.
swapped battery, took of fine.
climbed away from me and turned left.
i was flying level along the tree line and she suddenly dipped and recovered, wind i thought.
then it did it again, so i turned to bring it back for a landing and it went into a full dive at full power.
i shut the engine off and applied full up elevator and nothing, no response.
dived straight into the ground at full chat.
smashed the nose and broke the motor shaft clean off.
re connected the battery that had fallen off in the impact and every thing was working fine, did a range check. ok
so i dunno what happened there, could have been interference.

dont suppose i will ever know.
motor is fixed, nose is glueing.
will try again tomorrow once it has all set.

weird.

35 meg futaba.
i have flown over this area many times as i use all the field when flying, never had any problems at all till tonight.
so its a weird one this.

problem solved.
the tx crystal was moving in the holder and causing intermediate loss of control.

on full power if i pull the crystal out it takes 4 secs for the engine to shut down couple that with the down elevator i had on to bring it in for a landing caused the crash.

flew fine tonight with the new motor and esc fitted.
rolls, loops, inverted, vertical s's all ok.

phew.

blooper wrote: problem solved.

on full power if i pull the crystal out it takes 4 secs for the engine to shut down

That doesn't sound right for a "Fail safe" Blooper.
A model can do a lot in 4 seconds.
I'd suggest testing it by simply turning off the Tx & looking for the response .... it should be instantaneous.

You need it to shut down the motor & put the model into a glide path.

Pol.

last night i got the plane up to a good height and turned off the tx.
gentle left turn and a nice glide.
turned it back on and carried on with my flying.