Odd crash, any ideas what happened?

This morning I stuffed my old F27B, and I don't know what happened:
Charged LiPo, topped off TX batteries. At the field, did the usual
pre-flight: Servo check, engine check, plugs all checked, linkages
checked, fuselage checked. It all checked out, nothing out of the
ordinary whatsoever.
Launched, plane climbed to altitude. Brought it around for a big circle
when I noticed the first oddity: The plane climbed rather steeply. I cut
back power and adjusted the trims, regaining control and deciding to
bring it down. Before I even got to lining up for approach the engine
revved up, the nose dropped into a straight down dive, from about 50-75
feet up. I cut throttle, flipped from low rates to high rates and tried
to pull up - but the engine was still screaming and the control input
had no effect whatsoever. The plane went straight into the ground, with
engine screaming all the way until impact.
The plane is pretty much a loss. I haven't looked at the mess yet but
I'm stunned as to what would cause such behavior? It doesn't feel like
radio interference, it just seems like an entirely odd loss of control.
Any ideas?
Jen
Reply to
Jennifer Smith
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Sorry for your loss, Jen. I know it stings.
I would check (analyze) both battery packs right off the bat.
A bad switch or a bad crystal could also be the problem.
IIRC, the F27 is an old radio?
Ed Cregger
Reply to
Ed Cregger
On Fri, 13 Jul 2007 11:10:10 -0600, I said, "Pick a card, any card" and Jennifer Smith instead replied:
Just a couple of questions for you, Jen. Were you alone at the field? Did you have the frequency pin (or whatever you use to ensure you have the only transmitter that is on)?
If you're certain it's not radio failure (did you test the radio after?) then it sounds very much like a second transmitter was on while you were flying. Even if you had the pin, a child who has no idea of the trouble that can ensue may have turned on a TX. -- Ray
Reply to
Ray Haddad
The planes power pack is destroyed. I dug it out of a 5" hole in the ground. I'll check the TX batteries as soon as I'm home from work.
Crystal might be an idea. I honestly don't even remember if that radio even has a removable one. If so, I certainly didn't check it.
Yes, the B model operates on the "Wallyworld" frequency: 27MHz. All my others use 72MHz until I can afford one of the newfangled spread spectrum ones. What surprises me about it is that I've had interference before, but that merely caused glitches. This was... odd. Just total loss of control.
Jen
Reply to
Jennifer Smith
I rarely fly at a field, this was in a park where I fly pretty often in the early morning. Could well be a child considering I was using a B model... which does operate on 27MHz. It'd be the first time their TX overpowered mine though.
Jen
Reply to
Jennifer Smith
Jen,
Sorry for your loss.
How many flights do you have on this unit? I don't have any rc experience, but at my job we diagnose all kinds of equipment problems.
If you are pretty sure there was no radio interference, then there was an electronic failure. Your batts were all up, so that should not be the problem. So it's either a bad TX or a bad receiver, which I assume is now destroyed. If it was the receiver, then a new complete plane will fix it. If it was the TX, then the new plane will do the same thing.
I would see if you can send the TX and whats left of the ESC/ Rx back to PZ for evaluation.
Larry
Reply to
Larry
I would move what ever it takes to check out your charger. A bad charger or having the power off most of the night can masquerade as a bad battery pack, which is what this sounds like. The TX side is the one you might want to test.
We used to have a guy in our club that was a great pilot but a little short on common sense. I was always crossways with because he insisted on pushing the safety envelope saying he was good enough that it did not matter. He lived about a mile from me. One night we had a massive power outage on our side of town. Since I was up building when the lights went out, I knew it. Then next morning I got up about sunrise and the power was still out. I loaded up and went to the flying field and put everything on fast charge. Around 10 or 11 our 'friend' shows up with his recently purchased pattern ship. I tell him that he probably needs a fast charge because we were without power the night before. We got along so famously that he checked the voltage on his battery packs only after I very loudly insisted because he had power at the house when he got up. His voltage check looked good so he went flying. He had the exact same kind of results you had. When we tested after the fact, the batteries were flat. Surface charges only last for a little while.
Jim Branaum AMA 1428
Reply to
Six_O'Clock_High
Jen,
I saw replies theorizing the problem might be with the the flight battery, but is it possible for the battery to have enough juice to run the motor full blast yet not run the RX properly?
Larry
Reply to
Larry
"Jennifer Smith" wrote
Could be a lot of things, but I vote for switch. A cheap one will not take the current and vibrations.
Reply to
Morgans
Hi Jennifer, I assume that you have the stock Parkzone Radio and RX that came with the Stryker B? The RX module is known to break down at least with some of your sympthoms. There is a component on the RX that is regulating the power to the motor (and perhaps to the servos) that tends to break down, this results in the motor running at full power no matter what you do with your TX, but usually there is still control over the servos.
If you are interested, you can read a lot about Parkzone electronics here:
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I have had two of those RX'es break down on my F27-B, but managed to keep flying until the battery was drained enough for the motor to stop. I have since switched to the DX6 and now to DX7, would never look back :-)
Helge
Reply to
Helge Opgård
Or it could have been a CB radio operator. With their power advantage over our R/C transmitters, they do not even have to be on the same frequency to do in your receiver (overload). It is quite possible that your system was functioning normally, but was not able to cope with a nearby much stronger signal near your system's frequency.
Ed Cregger
Reply to
Ed Cregger
Over the decades, I'll bet that I have seen four or five models crash because of a bad receiver pack switch.
Ed Cregger
Reply to
Ed Cregger
It's not unusual to lose complete control of a model due to BEC overheating/shutdown. However 99% of the time that results in a low throttle condition.
Its possible for a FET in a brushed setup to go short circuit, and give full throttle, but that does not normally result in loss of control of the control surfaces.
It may be that the ESC in question behaves differently under overload.
Or in the presence of total signal loss. However it would be a first for me if it did ..
Reply to
The Natural Philosopher

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