Friday, February 24, 2012

'Ground Resonance' destroys a helicopter


Readers may be familiar with the phenomenon known as 'ground resonance'. Wikipedia has an article about it, but briefly, the dynamic balance of a helicopter's rotor system may become disturbed, leading to distortion between its axis of rotation and the system's center of gravity. This places excessive strain on the helicopter, which can lead to serious damage or even total destruction of the aircraft.

That's what happened to a rescue helicopter this week during a landing in Brazil. The Telegraph reports:

Brazil's Regional Service for the Investigation and Prevention of Aeronautical Accidents is looking into the reasons why a rescue helicopter disintegrated shortly after landing in the northern state of Para on Wednesday.

. . .

Officials believe the helicopter experienced what is known as ground resonance, a condition that happens when the aircraft's rotor is working while the helicopter is on the ground.

Four people that were travelling aboard the helicopter were injured.


Here's how it looked to a nearby cameraman.







I'm glad I wasn't aboard at the time! You can see more videos of ground resonance on YouTube.





Peter

5 comments:

Anonymous said...

Peter,
When I first saw that a couple of days ago, my first thought was GR. But on further viewing, it appeared more a badly out-of-balance dynamic system--most likely the main rotor. I don't know for sure though.

Leatherneck

Don said...

It may have been GR, but the emergency procedure for that is to pull pitch and get back into the air. It sounded as if he shut down when the beat started. Bit hard to tell from this video though.

Tim said...

At the 0:05 mark, it appears to me that the rotor actually stops, then the shaking starts and it starts spinning again completely out of balance. How very odd.

Don said...

Peter, I saw an update at the YouTube link you have.

Apparently, they experienced a serious beat in flight and landed. The aircraft then went into resonance and broke up.

A malfunctioning main rotor system would mean the pilot wouldn't want to pull back up. It also appears he had already shut down the engine prior to the start of the video.

Marisa said...

*grumble* and you all wonder why I keep my feet on the ground!