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analyzing a crash

Old 07-20-2006, 12:27 PM
  #1  
mountainflyer
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Default analyzing a crash

Flying my 4*40 yesterday, 1st flight deadstick, no problem brought it down adjusted the needle, back up.. I was a bit far out and after review i believe tx was pointed directly @ rx.. lost all control and lawn darted. One of our clubs instructors witnessed it and thought it looked like my rx failed, after picking up the pieces in a shopping bag, we looked it over. All the control horns, rudder,elevator, airlerons etc still seemed to function.. he suggested i send in the receiver to futuba to have them look at it. I had a few 'hard landings' with my trainer with this rec before i transfered to the 4*, also not sure if this could have been a battery issue. I charged the night before, unfortunately i don't have a voldmeter (mistake #1). I checked it on my field charger and ran a quick charge before heading out to the field. I'm curious if anyone has any suggestions about how i can diagnose the problem before sending off to service.. My wing survived, thinking i'll order another fuse kit and rebuild, i just don't want to run into this problem again. Any advise is appreciated.. I'll submit a pic of the wreckaga later.. unfortunately Yoda my jedi master pilot did not use the force!!!
Old 07-20-2006, 12:57 PM
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Flyboy Dave
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Default RE: analyzing a crash

It may have been that the switch on the airplane lost contact, and the
airborne system failed to respond. This is not uncommon. It is more
likely than a receiver failure, although this can happen too.

You can check the receiver for glitches by tapping on it with the eraser
end of a pencil. Charge up the battery. It should read 5.55 volts, or close
fully charged. Hook up the complete radio system on the bench. Get the
system working with the transmitter, then start tapping on the receiver
with the pencil. If the servos start glitching, the receiver is bad.

While this is not the "super factory test", most times it will show the bad
receiver. If the switch doesn't have a crisp "snap" to the on and off position,
throw in in the trash, and get a good switch. Cermark sells good switches
for little money.

Keep in mind, the receiver may or may not have been bad before the crash.

FBD.
Old 07-20-2006, 01:11 PM
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RaceCity
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Default RE: analyzing a crash

Dave is SO spot on with his "faulty switch" concern. An intermittent switch can wipe you out, and then appear to work perfectly during the post mortem. Why trust hundreds of dollars in equipment to a $0.39 switch? Aftermarket switches such as those from Cermark (MPI is my favorite) can be purchased for $10-$12 and are good insurance against similar problems in the future. I replace switch harnesses every few years regardless of how well they appear to be working.

For now...I'd advise sending your radio in for service to verify that there are no hidden problems. Doing so, you'll feel better too.

Old 07-20-2006, 02:00 PM
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Edwin
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Default RE: analyzing a crash

I would also suggest you buy an ESV right now. That would help in diagnosing at the field. And you should use it before the first flight and then occasionallly after that. I've never had a switch fail but that doesnt mean I dont take the previous 2 suggestions to heart. I HAVE had two battery failures in the last 15 years that were just bad timing. The first was a weld joint that broke during flight and the second was an older battery that just decided to retire at the most inopertune moment. I had cycled that battery 2 months earlier and it tested to 95% capacity. After the crash it only tested to 50% and didnt hold the charge very long. I'm starting to use those led battery monitors built into my planes now. I have used an orbital sander (transformer type?) with no sandpaper in it held up against the fuse to test switches. If you see any voltage jumps while its on its time to replace the switch.
Edwin
Old 07-20-2006, 05:34 PM
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RC MANIAC119
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Default RE: analyzing a crash


ORIGINAL: mountainflyer

I was a bit far out and after review i believe tx was pointed directly @ rx.. lost all control and lawn darted.
I would agree that you may have been flying "a bit far out"......that happens to almost everyone at some time or another, and if you do have some faulty equiptment on board it will bite you......BUT.....pointing that TX directly at the RX while flying is truely one of those old wives tales that for some reason never goes away!!!
In this age of narrowband technology and LIPO batteries...it just aint true!!!

So here's your chance all you radio guru's......prove me wrong!!!!
Old 07-20-2006, 06:35 PM
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RaceCity
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Default RE: analyzing a crash

No, it is time for YOU to prove dipolar wave propogation theory wrong.

Narrowband, and LiPos have no effect whatsoever on the propogation characteristics of our transmitters.

Hurry! The world is waiting.
Old 07-20-2006, 08:20 PM
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RC MANIAC119
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Default RE: analyzing a crash

See what I mean......you guys take this stuff...wayyyyyyyy to seriously!!
Old 08-14-2006, 08:46 PM
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Default RE: analyzing a crash

Hey RaceCity,

Dude do you even know what the H@LL "dipolar wave propogation theory" is?? [sm=confused.gif] Its OK man we know, you can say it!! Rubber side down Boys!! (Unless the Magnotometerspectrographpsychosymaticionizerblende rphaseconverter says you can't!! Say that 10 times fast!!)

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