Horror Story

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
outcome?
Reply to
me
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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. Red's R/C Battery Clinic
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us out for "revolting" information.
Reply to
Red Scholefield
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. ???
Reply to
me
Even still, no one can say for certain that the battery was definately bad during the flight. The crash may have damaged the cells.
Reply to
Paul McIntosh
Don't know about the brand of pack. The owner of the plane is not known for cutting corners. Knowing the guy, I would guess that it was a name brand pack.
Reply to
me
Paul 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. ??? Bill
Reply to
me
How about the corner that says "thou shalt give your pack an ESV check before its first flight"?.
-- Red S. Red's R/C Battery Clinic
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us out for "revolting" information.
Reply to
Red Scholefield
Seems to me that that is on the order of "Breath in, breath out!" ;>)
Reply to
me
More like 2 cells. Was this a name brand pack?
Reply to
John Alt
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!
Reply to
Six_O'Clock_High
If it went in and out of failsafe, it had sufficient power to do so. In most PCM systems, if you lose power the servos all stay in the last position coded. They wouldn't be wandering around.
Reply to
Paul McIntosh
Hard to say what was really happening. Speculation was that the battery pack was supplying voltage at varying levels before it finally gave up the ghost.
Reply to
me
'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...
Roger
Paul Mc> If it went in and out of failsafe, it had sufficient power to do so. In
Reply to
Roger
And every other flight therafter!!!! I check my batteries every 2-3 flights. I put to much into my planes to let a low battery ruin my day. My planes don't like dirt naps. Eddie Fulmer AMA 63713
Reply to
Efulmer
Since I am new to the hobby and unfamiliar with some of the terms would someone define ESV please.
Thanks
Ray
Reply to
Kat3595
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. : - )
Alan Harriman
Reply to
Alan Harriman
Expanded Scale Voltmeter. I think what these guys are alluding to is a tester that applies some load to the pack, rather than just measuring the unloaded voltage.
MrBonk
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Reply to
MrBonk
Are you going to post the video to a web page when you get it? It would be interesting to take a look at it if you do.
MrBonk
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Reply to
MrBonk
That would be an expanded scale voltmeter. This simply reads the voltage in your batteries. Most of them put a simulated flight load on the batteries too. Eddie Fulmer AMA 63713
Reply to
Efulmer
Why not check them before every flight? That makes sense to me. You're taking a chance doing it every other flight. Joe L.
Reply to
JosLvng

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