Death of a Draganflyer, Watching a $1000+ helicopter crash from 200+ feet Options

[Old Man Mike]

One of my Draganflyer helicopters has fallen and can't get up:

Death of a Draganflyer

Here's a picture of the crumpled mess:



Actually, I don't think you can blame my flying. You can hear the motors drop once and then a second time just before it starts to go into freefall. I've seen this happen a few times before but it had always been for less than one second and then recovered.

The only good news here is that my homemade custom camera mount protected the video camera. It survived without a scratch.

Old Man Mike

[Clint]

ouch that looks painful.


here's a possible root cause analysis:
On that first glitch, it sounded like only one motor was cutting out. you can hear the rpms drop, and to
compensate, it started to pull too much current and a few seconds later fried one of the gyros/main esc
board. one possible reason for failure could be that the camera was a bit heavy and caused the motors to
pull more current than normal. Also high altitude summer air(thin air) also pulls more current/heat to the
motor. The brushes on 370's dont last too long under heavy load at 11.1v, they can overheat easily and
cause the situation above.

the only way to protect against this is a separate fuse for each motor. A benefit of this on a regular r/c heli
is, if the main motor/fuse dies, you can still autorotate the heli back down safely. if the tail rotor dies you can
hit throttle hold, and use the collective to lower the pitch of the blades to bring it down. Unfortunately with a 4
rotor, it's still going to crash if any single motor dies, but at least the electrics wont fry.

Using a single fuse on main v+ will not detect an overload on any single motor; ie 3 motors can be using 2
amps each and the failing 4th motor could be pulling 8 amps and still not cause a 15amp fuse to blow since
the whole system is using 8+2+2+2=14amps. whereas the Mosfets are most likely 5amp continuous/7amp
peak, so this situation would fry a gryo/esc. A single fuse setup only protects the Lipo from overdraw(which is
good too).

you may be able to salvage the main board if it's not physiclly broken from the crash(peizo gryos
can be damaged on impact.) If it's just some blown mosfets, then resoldering on some new mosfets isnt too
hard..and you can probably find replacement chips at newark.com or digikey for a buck or two each.
a few high res pics of the main board and i might be able to help.

The draganflyer is a really unique heli, sad to see it down.