lejon
Senior Heliman
Location: Las Vegas Nevada
| It has been said that there are always signs and warnings about what is coming up and it is a matter of how attentive we are to those warnings as to our ability to avoid the occurrence or at least be prepared for it. Well a few days ago I landed and before going up again decided to check under the canopy. What I found was the ball link on the aileron servo was so loose that it was ready to come out. I cancelled the next flight and since I had a fancy purple carriage for the servo from another Xcell 60, decided to put it in. Looked it over and checked the bearings and all seemed good. Installed it and went to fly. After about 3 minutes it seem sloppy in left right cyclic so I landed and noticed that one of the bolts through the carriage and bearing had backed out. I thought dummy you should have taken it completely apart and rebuilt it. So did I? No I simply lock tited the bolts and last night went up for a few evening flights so that I could get the new engine broken in. Breaking in a new G260 from Toxic Marine so I did a 10 minute flight, mostly hovering with a few circuits. I checked the head and it is tight and all seems well, checked the bolts and they are staying put. I am on my 4th tank so I stop between flights, top off the RX and let it cool to ambient temperature, refuel then off for tank number 5. This is an Xcell 1005 gasser with the rubber isolators between the frame and the skids, a stator gator and revlock and an HC3A. I have the Revlock set at 10250 rpm which if I remember correctly is a 1670 or so head speed. Well it is getting late (read too dark to see well) and at 20:30 hrs (that's 8:30 pm) the temperature is down to 96 and there is a slight breeze. Oh did I forget to tell you that while charging the RX I looked at the TX and it was at 9.7 so I thought I would give it a little charge too and when I connected it the charger indicated there was no battery, I just assumed it was a bad charging lead and I would fix it later. Anyone other than me, not see (or in my case choose to ignore) all of the messages and hints I got last night?
Ok I will take it up and do just close to the ground hover so that I can get another tank burned. I lift off, am in a hover about 2 feet off the ground and then it happens.
The heli slams into the ground and starts doing a side to side dance, first on one skid then on the other and the collective seems to be in sink. It is going up (only slightly) then down again. I try to make adjustments and it does not respond. The engine is running at what appears to be wide open and the tail is not moving.
Snap, maybe the TX died and if I shut it off and then back on I will get enough signal to get it back to idle, no then again it might glitch when I turn it back on and cause it to tip over and self destruct. Ok just stand there and watch, WOW sure am glad it is dark and there is no one around (makes standing there looking and feeling stupid a lot easier). Hmmmm I notice that is sure is running smooth now that the side to side movement has stopped, engine is running pretty smooth with only a burble here and there, no apparent significant vibration and it does not have any tendency to move, but I hope I do not have to wait for 10 minute for it to run out of gas. I really am hoping it does not lean out and crispy yet another engine. If I had to choose would I prefer that it tip over and beat itself to death or lean out and burn up the motor? Can I choose option 3? I get back control and all is well? Nope. Didn't think so. Well after an eternity (actually about 3 minutes) it burbled a few times then decreased rpm and then shut down.
Post incident investigation:
The servo screw for the left right cyclic came loose. It appears that this allowed the pitch to bottom out (12 + degrees) which forces the heli to the ground where upon impact compresses the rubber skid standoff at the left rear (actually demolished it) which in turn allows the tail to impact the ground and break off one of the blades. The impact with the ground was strong enough to bend the lower left frame where the pull start is. I am not sure what or even if it hit anything but it has about a 1 to 2 inch bend in it. One tooth is missing from the main gear. The impact force the collet on the main shaft so that the gear lowered and disengaged from the tail rotor pinion and the on off switch for the RX turned off (yes it was installed so that that up is on and down is off) backwards? Not sure I can't remember but I think I will change it.
I have not had a chance to check for bent shafts but from the way the head was spinning that shaft is not bent. The tail shaft maybe. I took temperature readings on the engine and it was at 210 at the 3rd fin from the carb and when I took the muffler off there was a lot of lubricate and no scarring or burning. It would appear that the negative pitch is what kept it on the ground and provided enough load to keep the engine to self destructing.
Oh What A Night
Lejon |
