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  1. #1

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    Ground Resonance!!..watch this video for sure!!!

    ever wondered what ground resonance can do to ur helicopter? I could not believe it when i saw it......take a look at this....go to the following link & on the right side u will see two videos. download them & watch this amazing effect. http://www.starwoodmodels.com

  2. #2

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    RE: Ground Resonance!!..watch this video for sure!!!

    Such a waste of a good helicopter. If you're able to watch the slow motion footage you'll see one of the aft blades break its blade damper grip. That is the cause of the aft pylon seperating from the fuselage. Take a closer look though at how the engineers attached the helicopter to the pad. No one in their right mind would disable the oleo strut function of an articulated rotor system helicopter. So this is the end result. Helicopter goes into ground resonance, aft blade lead/lags beyond perameters, aft blade damper grip fails, aft blade goes out of rotation, aft blade contacts forward blade, and aft pylon fails from imbalance in centrifugal force.

    General info.

    Each blade is 350#
    Rotor 225 rpm
    60' rotor diameter
    (Blade tip rotating at appx 8 mpm or 480 mph or 704 fps)

    A Break down in repair.

    Blade $210,000 ea: need 6 ea
    Aft Transmisison $780,000 ea: 1 ea
    Enginge 1,000,000 ea: 2 ea
    Engine Transmission appx $280,000 ea: 2 ea
    Aft Vertical Shaft appx $160,000 ea: 1 ea
    Aft Pylon appx $????? expensive
    engine drive shafts, $???: 2 ea
    Hydraulics repairs, airframe repairs, drive shafts 1-9 replacements, I think they have to replace both heads, and the combining and forward transmissions as well. I would guess about 8-10 million easy in damage, and this is mostly the big stuff. But it doesn't take into effect the cost of pride and loss of major cool points.

    Happy Hookin'

  3. #3

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    RE: Ground Resonance!!..watch this video for sure!!!


    ORIGINAL: Hooker50

    Such a waste of a good helicopter. If you're able to watch the slow motion footage you'll see one of the aft blades break its blade damper grip. That is the cause of the aft pylon seperating from the fuselage. Take a closer look though at how the engineers attached the helicopter to the pad. No one in their right mind would disable the oleo strut function of an articulated rotor system helicopter. So this is the end result. Helicopter goes into ground resonance, aft blade lead/lags beyond perameters, aft blade damper grip fails, aft blade goes out of rotation, aft blade contacts forward blade, and aft pylon fails from imbalance in centrifugal force.

    General info.

    Each blade is 350#
    Rotor 225 rpm
    60' rotor diameter
    (Blade tip rotating at appx 8 mpm or 480 mph or 704 fps)

    A Break down in repair.

    Blade $210,000 ea: need 6 ea
    Aft Transmisison $780,000 ea: 1 ea
    Enginge 1,000,000 ea: 2 ea
    Engine Transmission appx $280,000 ea: 2 ea
    Aft Vertical Shaft appx $160,000 ea: 1 ea
    Aft Pylon appx $????? expensive
    engine drive shafts, $???: 2 ea
    Hydraulics repairs, airframe repairs, drive shafts 1-9 replacements, I think they have to replace both heads, and the combining and forward transmissions as well. I would guess about 8-10 million easy in damage, and this is mostly the big stuff. But it doesn't take into effect the cost of pride and loss of major cool points.

    Happy Hookin'
    Sweet Lord!..r u an aeronotical engineer with specialised in helicopters?...u know a lot about them

  4. #4

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    RE: Ground Resonance!!..watch this video for sure!!!

    I'm not an engineer, but that's what I'm going to school for. I just fly them for the WA National Guard. They're a lot of fun. In military circles, information regarding type specific aircraft accidents or mishaps spreads rather quickly. The Chinook units knew about this shortly after it happened. I suspect that this is similar in the Blackhawk, Apache, 58 D, and other interservice helicopter type communities. Supposedly, this is the Chinook that performed an uncommanded roll maneuver (read actually inverted) while on a ferry flight from Corpus Christi with a contractor crew on board. Don't know if that's really the case, but man is that video fun to watch. I'm sure if you scour the net you'll find the pictures of the british (maybe even Australian) Chinook crew who decided to remove the aft pylon the old fashioned way, but striking the aft blades on the ground by exceeding the 20 degree nose high restriction during roll-on landings.

    Happy Hookin'

  5. #5

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    RE: Ground Resonance!!..watch this video for sure!!!

    ORIGINAL: Hooker50

    The Chinook units knew about this shortly after it happened.
    Supposedly, this is the Chinook that performed an uncommanded roll maneuver (read actually inverted) while on a ferry flight from Corpus Christi with a contractor crew on board. Don't know if that's really the case, but man is that video fun to watch.
    Happy Hookin'

    ofcourse the Chinook units will know about it shortly after it happened.. man !! not knowing wts wrong in ur bird that can,t happen when ones life depends on these heli`s.
    This video does strike a sense of fear in us & not forgetting to mension , more fear in the hearts of Helicopter pilots like u....wish a safe flight!
    here are some Chinook navy crash pics!.. u can also find the video here .... http://www.youtube.com/watch?v=4Dl-IWAecgk
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  6. #6

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    RE: Ground Resonance!!..watch this video for sure!!!

    My apologies, I seem to have misspoken and not communicated my intended response. I was inferring that each respective aircraft community hears about mishaps and/or accidents before official information is dissiminated down from higher HQ’s, and substantually quicker then when the general public hears about it. Also, the un-commanded roll maneuver is believed (due to pilot report) to be due to a hydraulics gremlin and was not to be reproduced.

    Everyone fears something. For us, we accept that helicopters can be dangerous. To this point emergency procedures are continually discussed, studied and trained to the point of being instinctual. You get nervous at times when first starting out, and then with experience you gain more confidence with your ability, aircraft and operating environment. There is always the knowledge that something could happen. But pilots can’t function as pilots being afraid of this. The best analogy to describe this is driving a car. There are risks associated with driving that could kill or seriously injure you. Though the specific risks are different, there is still risk. Does this stop you from driving? Do you drive with the constant fear that someone will run into you? Most people accept the risk associate with driving and with experience you gain confidence in your ability, automobile and conditions. Pilots do the same thing.

    I have the video of that CH-46 crashing in the water. It is pretty interesting to see how fast the pilot was coming in. He just missed the deck.

    Anyway the CH-46 Sea Knight (civilian designation BV-107) (the Marines nicknamed it the Phrog) was manufactured in I think the early 60’s. So they pre-date the CH-47 Chinook (civilian designation BV-234) by a few years. The Navy had different requirements, so they are smaller, more ground crew friendly, and have a lower load hauling capability. Both have similar flight characteristics, controls, handling and shape.

    Happy Landings

  7. #7

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    RE: Ground Resonance!!..watch this video for sure!!!

    Actually this can't happen in helicopters with a skid type system!
    OH-58 pilot!

  8. #8

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    RE: Ground Resonance!!..watch this video for sure!!!


    ORIGINAL: Hooker5

    Everyone fears something. For us, we accept that helicopters can be dangerous. To this point emergency procedures are continually discussed, studied and trained to the point of being instinctual. You get nervous at times when first starting out, and then with experience you gain more confidence with your ability, aircraft and operating environment. There is always the knowledge that something could happen. But pilots can’t function as pilots being afraid of this.
    I might have said that because I am not a pilot & hence thought helicopters strike fear in to the hearts of pilots. but i understand that over a period of time u guys get easy with all the aspects of heli`s & the risk involved with it..& I respect u guys for that

    apart from all this, seeing the earth from above & those beautiful seneries ...wow! u guys enjoy life to the fullest.

    cheers!

  9. #9

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    RE: Ground Resonance!!..watch this video for sure!!!


    ORIGINAL: AAVN60

    Actually this can't happen in helicopters with a skid type system!
    OH-58 pilot!
    why is that so ? what difference does a skid type system in a helicopter make to omit ground resonance ?

  10. #10

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    RE: Ground Resonance!!..watch this video for sure!!!

    I'm not so sure it can't happen, but it's a lot less likely. The 'give' in the suspension and tires of a heli with wheels contributes to the scenario by allowing an oscillation to begin. A heli with skids doesn't have that 'give', so the oscillation is much less likely to happen.

  11. #11

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    RE: Ground Resonance!!..watch this video for sure!!!

    It has to do with the m/r system, not the skid system. If you took a fully articulated head and had a solid skid system, it would likely rollover before getting to idle. A Bell Jetranger (2-bladed, semi-rigid, underslung m/r head) doesnt shake the fuselage like a Hughes 500 can on the ground, and doesnt require more than a simple skid landing gear. A pilot also has to be very smooth on landings with that system, it has NO give. The landing gear on a Hughes 500 has a lot of play, very absorbing, and a HUGE pain in the ass to work on!
    Cub Brother #10
    Waco Brother #221

  12. #12

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    RE: Ground Resonance!!..watch this video for sure!!!

    As stated above this is dependent on the M/R design. Anything with a fully articulated rotor head can get into ground resonance. Your OH-58D has 4 blades spaced out at 90 Degree intervals. Change just one blade to about a 80 degree/100 degree interval and you have an off balanced head. You would know your system better then I but I'm sure you'd feel it and have a problem. Most times, ground resonance is encountered when you set your aircraft down on the ground and the impact of the wheel/skid can cause a blade rotation independent of the main rotor.

    They tell you to come to a hover to get out of ground resonance. Good plan, but impossible when your 47 is chained down to the pad with now where to go.

    Happy Hooking

  13. #13

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    RE: Ground Resonance!!..watch this video for sure!!!

    Hi guys
    You really need to see this video.
    It is a vario MD 500 E turbine which suffers ground resonance after touching down from its first "hop".
    It was repaired and the second flight was much better

    http://www.youtube.com/watch?v=fln6I2bhk6I


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