Sunday, November 9, 2014 1:14:36 PM
HI HELOCOPTER MECHANIC HERE THIS WAS MOST LIKEY THE RESULT OF EITHER A POORLY DYNAMICALY BALANCED DRIVESHAFT OR A POORLY WEIGHTED ROTORHEAD/ROTOR BLADES WHICH GIVEN THE SPEED THAT DRIVE SHAFTS AND ROTOR HEADS SPIN COULD EASILY CAUSE THEASE PROBLEMS TRUST ME IVE SEEN IT IN PERSON LOOK HIGHLY SIMILAR TO THIS.
Sunday, June 8, 2014 6:34:46 AM
@Freddy: No harm mate. Just that response is wearing thin to us, you and me, Americans. I don't see it being resonance in the longer video. Resonance is not the issue that most give it. Yes there are frequencies in everything, especially fast spinning rotor blade, but this looks like an unbalance issue. As I am not trained in this type, I don`t know the ins and outs of them. I do remember the first time I landed on the back of a 378` cutter at sea and the resultant stain in my flight suit. Besides the 3 axis you are dealing with in the aircraft you have to add the speed of the ship and it`s pitch and roll in 3 dimensions. Just when you think you`ve got it, a wind vortice off the super structure will whip around the fantail and slide you around. Carrier landings are hard but they have nothing on a chopper landing on the back of a ship. This guy did good to survive. This could have had a real bad ending.
Sunday, June 8, 2014 4:03:07 AM
Here is a far longer video:
Sort of looks like ground resonance although I am not convinced. Maybe a trainee pilot getting a touch down wrong (it starts swinging just before that second touchdown) then bringing the collective up a little but not enough to lift again; it looks very light on the wheels compared to earlier in the video. When it is light on its wheels of course the resonant frequency changes, causing ground resonance.
However the instructor should then have lifted, solving the problem.
The alternative is that they had a control problem just before that second touchdown. Something broke causing imbalance in one of the rotors and that wild swing. When they managed to get it down the blade pitch could not be brought to zero and the imbalance caused vibration.