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Video: Helicopter falls apart on landing in Brazil
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. (www.telegraph.co.uk) More..."Ground resonance" is mathematically a "simple harmonic motion of increasing amplitude". It was most prevalent on helicopters where the lift/weight is slightly less that one (1/1) during rotor near full rpm when in the transition between start up before takeoff, or rotor shut down after landing. It can also be initiated during certain conditions while taxiing and hitting a chuck-hole or bump. It is caused by the compressive action of the landing gear system on the ground reacting to the non-linear transitional lift during this period. The gear (struts, oleo, cross-bar, tire pressure, etc.) acts like a spring that compresses, and then when the lift (wind factors included) is lessened or increased, this low frequency can increase in amplitude in just a few cycles to structurally fail the landing gear and other components. Past methods of recovery are 1. During rotor speed-up: Stop procedure immediately, with rotor brake if available. Wait for different conditions and/or check shocks. 2. During taxi, or at beginning of shutdown: Lift the aircraft into the air immediately and either burn some fuel or find a different-wind landing area, or both. Ground resonance is a function of many aircraft and environmental factors that are not standard for a particular aircraft or standard environmental condition. Hello to my friends at Embraer.
The video was shown on CNN news. The small screen playback in the video link above does not do justice to the amount problems. On my large screen TV, the violent shaking/vibration showed all parts breaking up. What ever the causes were, it was incredible to see it much clearer on the big TV screen.
http://www.youtube.com/watch?v=RihcJR0zvfM
Chinook
Chinook
Wow. I have a decent understanding of ground resonance and have seen photos of other incidents but this takes the cake.
It appears that something went wrong (just what is TBD) and vibration setup. The higher them amplitude of vibration, things will start to give. Fortunately no fatalities.
Brazil Helicopter Falls Apart During Landing (VIDEO)
Have you ever dreamt of soaring high above the ground on a helicopter flight? The video above might make you reconsider.
A rescue helicopter fell apart (luckily, shortly after landing) in the Brazilian state of Para. Footage shot by the Para Fire Department on Wednesday showed the copter heavily vibrating before completely disintegrating. According to the Telegraph, Brazil's Regional Service for the Investigation and Prevention of Aeronautical Accidents is looking into the accident. 4 people reportedly were injured in the crash.
Watch the helicopter come apart and the immediate aftermath in the video above.
http://www.huffingtonpost.com/2012/02/27/brazil-helicopter-falls-apart_n_1297748.html?icid=maing-grid7%7Caim%7Cdl11%7Csec3_lnk3%26pLid%3D138951