This happened a couple of weeks ago, I watched the video, should have a copy
in a few days.
A well respected local builder and pilot, been in the hobby a LONG time
buys a 104" P-38. Installs two G-26's, JR 10X, PCM, flys the plane for a
year without incident.
This year he decides to replace the battery pack with a new unit to insure
he has no problems.
He buys a new pack, charges it for fifteen hours and installs it. At a giant
scale meet, he is now flying the plane for the first time with the new pack.
During the take off roll, he feels that something is rotten in Denmark so he
attempts to abort the take off. When he throttles back, the plane instead
takes off on its own. Banks OVER the spectator area and proceeds to fly
around for eight minutes, doing various loops and circles, totally ignoring
any input from the transmitter. Plane finally drifts out about a half mile
from the field, goes into a death spiral and hits a concrete pad, destroying
pretty much everything. The one thing that did survive was the new battery
pack. Complete with shorted cell. (6 Volt, around 2000MAH).
My perception of mistakes made:
1) He installed the pack without cycling it a couple of times.
2) He didn't check it with some sort of loaded ESV before the first flight
3) He used a single pack and switch assembly on a $2500.00 plane when he
should have been using some sort of battery redundancy.
The only good thing to come out of this, besides the fact that no one was
hurt, is that now he, and all of his friends will be paying much closer
attention to their battery packs from now on.
The only question I have is if he had two packs and switches, would a dead
shorted cell have dragged down the second pack and insuring the same
A shorted cell on a 6 volt pack would have left him with what 90% of the
rest of the modelers fly on. 4.8 volts. It was not the shorted cell that
caused the crash.
No battery ESV check before first flight? Inexcusable!
Red's R/C Battery Clinic
The battery pack had about 3.8 volts in it when tested after it was removed
from the what was left of the plane. They charged it on a known good charger
and voltage once again dropped below 4 volts. I guess we all assumed that
there was a short. ???
The plane flew fine for over a year, the only thing changed was the battery
pack. He flew another plane without incident with the same transmitter (JR
10X) The battery pack was intact, still in its undamaged padding. The only
other thing would have been the receiver. I didn't ask him about that.
Someone told me that he had fail safe set up for control hold. The guys who
were there at the time said it appeared the plane went into and out of fail
safe at least once before it was destroyed. ???
I had a similar type of incident recently and got similar results with my
ESV. Localized it to the battery pack and called it a day. I was lucky in
that the failure occured just after engine start but before plane was
released. Chilling thoughts!
'scuse me? Every-repeat every- large plane, from 1/4 scale Extra's up,
that i have see droop the surfaces when power goes off. that means that
whatever aerodynamic forces are acting on the surfaces will move them at
will...there is no way a servo stays locked in position with no power
to it...unless you buy some sort of special, custom servo...
Paul Mc> If it went in and out of failsafe, it had sufficient power to do so. In
Any chance someone was on his frequency? I ask, because I just saw a
similar event. Turns out this pilot had two planes with two
transmitters, both on the same freq. He then precedes to shoot himself
down by leaving the other radio on. I guess you figure if your card's
in the slot, you must be good to go. : - )