redgiki
04-28-2008, 11:30 PM
So I upgraded my venerable Raptor 30 v1 to a Raptor 46. It had some issues with the engine when I tried to fly it recently at the field, so I took it home and fixed a few things here and there. It turns out I'd lost the two screws holding in the carb on my OS .46FX-H; I pillaged another set from my similar aircraft motor. I bought a brand-new high-performance muffler, got it attached, and started running it up and checking things out.
I was just out in my back yard doing a few test hops, getting the mix just right so that I had good head speed, pitch-pumping to listen to the engine and hear where it bogged, you know the drill. I had it just about dialed in. Second tank of fuel, I landed, adjust my throttle curve to get my new motor running at the right RPM, stood back, and applied a little collective. It got about two feet above the ground, right where I wanted it, so I backed off just a tad... and it kept rising.
I jammed throttle hold. No response. Total radio lockout. Zero control. The helicopter looked like it wanted to fly to the moon. It described a gentle arc at probably forty to fifty miles an hour, sailed right over my house, then slammed upside-down into my front yard, ricocheted into the air on a bounce that went for fifty-four horizontal feet, landed on its skids, and proceeded to spin madly on until the motor quit.
Well, all in a day's work, right? Expensive lesson in radio lockout, but it could have been worse.
Much worse.
There were eight children playing near my front yard. Four of them were mine. This helicopter, luckily, missed all the kids and the four adults doing yard work to slam into my yard and flip end-over-end out into the cul-de-sac.
If it had struck any person on its way toward beating itself to death, I'd have been devastated. I really like my neighbors. I really love my children and my wife. This big beast could have killed any one of them a few minutes ago. Or done significant property damage if it had impacted on someone's vehicle or home.
Yet I was following AMA safety guidelines. I was over 100 feet from my house, downwind (like that matters for a heli, though,, and there was practically no wind) and over 200 feet from the eventual point of impact (250 feet from where it eventually bounced to, according to my Google Earth ruler). I had kicked my kids out of the acreage behind my house, counting on distance and objects to limit the possibility of damage to anybody other than me. I'd counted on a lot of things... but not a radio lockout sending the heli sailing in a rainbow arc toward unsuspecting family members and neighbors.
Upon further investigation, I think I found the cause of the lockout. I had a bad cell in my NiCD Rx pack, which seemed to hold a good surface charge, but dropped voltage under load. I believe the voltage hit the magic "don't run below 4.5v" mark for my Spektrum receiver, rendering the receiver and all servos inoperable while it spent five seconds reconnecting.
I should have cycled the pack.
I almost hit someone because I didn't cycle my pack. Sure, maybe it's a freak accident.
I still feel like crap.
On a side note, the only parts left intact and unbent on the heli were the frame, the servos, and the motor. Everything else is shattered or bent. Maybe it's time to upgrade to a T-Rex 600N... or stay away from large fuel helis entirely.
Lesson learned: cycle your NiCD packs thoroughly at the start of the season. Don't trust the green light on the onboard voltage monitor if it shows anything less than full green. In my case, since I'm so familiar with LiPos, I think I'll probably convert all my NiCD/NiMH stuff to LiPos with voltage regulators. And only test motors out at the field, as much as I hate futzing rather than flying when I'm near my club-mates.
I went to Spektrum because flying over the pastures near my house, I'd had glitches on 72MHz due to the high-tension electrical wires nearby. Several hundred dollars of ruined heli later, I'm not entirely sure it was the right decision.
I was just out in my back yard doing a few test hops, getting the mix just right so that I had good head speed, pitch-pumping to listen to the engine and hear where it bogged, you know the drill. I had it just about dialed in. Second tank of fuel, I landed, adjust my throttle curve to get my new motor running at the right RPM, stood back, and applied a little collective. It got about two feet above the ground, right where I wanted it, so I backed off just a tad... and it kept rising.
I jammed throttle hold. No response. Total radio lockout. Zero control. The helicopter looked like it wanted to fly to the moon. It described a gentle arc at probably forty to fifty miles an hour, sailed right over my house, then slammed upside-down into my front yard, ricocheted into the air on a bounce that went for fifty-four horizontal feet, landed on its skids, and proceeded to spin madly on until the motor quit.
Well, all in a day's work, right? Expensive lesson in radio lockout, but it could have been worse.
Much worse.
There were eight children playing near my front yard. Four of them were mine. This helicopter, luckily, missed all the kids and the four adults doing yard work to slam into my yard and flip end-over-end out into the cul-de-sac.
If it had struck any person on its way toward beating itself to death, I'd have been devastated. I really like my neighbors. I really love my children and my wife. This big beast could have killed any one of them a few minutes ago. Or done significant property damage if it had impacted on someone's vehicle or home.
Yet I was following AMA safety guidelines. I was over 100 feet from my house, downwind (like that matters for a heli, though,, and there was practically no wind) and over 200 feet from the eventual point of impact (250 feet from where it eventually bounced to, according to my Google Earth ruler). I had kicked my kids out of the acreage behind my house, counting on distance and objects to limit the possibility of damage to anybody other than me. I'd counted on a lot of things... but not a radio lockout sending the heli sailing in a rainbow arc toward unsuspecting family members and neighbors.
Upon further investigation, I think I found the cause of the lockout. I had a bad cell in my NiCD Rx pack, which seemed to hold a good surface charge, but dropped voltage under load. I believe the voltage hit the magic "don't run below 4.5v" mark for my Spektrum receiver, rendering the receiver and all servos inoperable while it spent five seconds reconnecting.
I should have cycled the pack.
I almost hit someone because I didn't cycle my pack. Sure, maybe it's a freak accident.
I still feel like crap.
On a side note, the only parts left intact and unbent on the heli were the frame, the servos, and the motor. Everything else is shattered or bent. Maybe it's time to upgrade to a T-Rex 600N... or stay away from large fuel helis entirely.
Lesson learned: cycle your NiCD packs thoroughly at the start of the season. Don't trust the green light on the onboard voltage monitor if it shows anything less than full green. In my case, since I'm so familiar with LiPos, I think I'll probably convert all my NiCD/NiMH stuff to LiPos with voltage regulators. And only test motors out at the field, as much as I hate futzing rather than flying when I'm near my club-mates.
I went to Spektrum because flying over the pastures near my house, I'd had glitches on 72MHz due to the high-tension electrical wires nearby. Several hundred dollars of ruined heli later, I'm not entirely sure it was the right decision.