2. During the development process, engineers will design the helicopter in such a way as to avoid having the fuselage and rotor system vibrate in sympathy with each other. Otherwise, the helicopter would be difficult to control. Instability can occur when the lead-lag frequency of the rotor couples with one of the natural frequencies of the fuselage, usually due to a shock to the airframe.
1. Ground Resonance is an aerodynamic phenomenon associated with fully-articulated rotor systems. "Ground" implies the airframe must be in contact with the ground. "Resonance" refers to the natural vibration frequency of the airframe resulting from the design and manufacturing process. Each part of the airframe, including the rotor system, vibrates at a certain frequency.
actually if you actually paid attention to the sound you would notice that engine speed has nothing to do with this test as they started shutting down one of the engines and thats when it started bouncing around. if you actually knew anything about Chinooks then you would also noticed that the aircraft is chained down and has no landing gears. i wasn't there but when i went to my training this video was shown as an example of the importance of the landing gear and what would happen with out it.
Everything that has mass has a natural frequency. When it is shaken at that frequency it begins to shake more and more and more. Eventually the object shakes so hard that it falls apart. It is safe to shake the object a little faster or a little slower.
For this test they adjusted the speed of the engine until the helicopter really began to shake. Basically they just left it spin at that speed until it fell apart. The will then take the speed that made the helicopter fall apart and mark it on
@Calcx, close but maybe misleading. A mass alone can't give you a natural frequency. You need a system of at least two masses and something elastic or flexible that connects them. In this case, the masses are the different parts of the helicopter, including the blades, engines, and other parts of the body. The elastic is provided by the parts of the helicopter body, which are not absolutely rigid (nothing is).
What happens is when multi-blade rotors get a vibration or shock from landing or something, the shock moves up to the lag-lead hinges -- which are supposed to keep the blades equally spaced -- and basically makes the distribution of centrifugal force unequal, causing the helicopter to bounce around with a lot of stress, sometimes tearing the craft.
@JebusJames That was such a brilliant explanation of what is actually being done here. Now @safesax85 fully understands what they are trying to accomplish here. They know, because of your detailed post that they are testing for a dangerous imbalance that could result in the total destruction of an aircraft of this kind.
sometimes you need to destroy a helecopter to make changes to save a thousand
nibbler125 7 months ago
2. During the development process, engineers will design the helicopter in such a way as to avoid having the fuselage and rotor system vibrate in sympathy with each other. Otherwise, the helicopter would be difficult to control. Instability can occur when the lead-lag frequency of the rotor couples with one of the natural frequencies of the fuselage, usually due to a shock to the airframe.
SteveTech83 8 months ago 3
1. Ground Resonance is an aerodynamic phenomenon associated with fully-articulated rotor systems. "Ground" implies the airframe must be in contact with the ground. "Resonance" refers to the natural vibration frequency of the airframe resulting from the design and manufacturing process. Each part of the airframe, including the rotor system, vibrates at a certain frequency.
SteveTech83 8 months ago 2
Did Ford build this thing?
noshadowmaster 8 months ago
Der gute heli :(
TheShorty1500 10 months ago
actually if you actually paid attention to the sound you would notice that engine speed has nothing to do with this test as they started shutting down one of the engines and thats when it started bouncing around. if you actually knew anything about Chinooks then you would also noticed that the aircraft is chained down and has no landing gears. i wasn't there but when i went to my training this video was shown as an example of the importance of the landing gear and what would happen with out it.
kmcnish320 11 months ago
Everything that has mass has a natural frequency. When it is shaken at that frequency it begins to shake more and more and more. Eventually the object shakes so hard that it falls apart. It is safe to shake the object a little faster or a little slower.
For this test they adjusted the speed of the engine until the helicopter really began to shake. Basically they just left it spin at that speed until it fell apart. The will then take the speed that made the helicopter fall apart and mark it on
Calcx 1 year ago
@Calcx, close but maybe misleading. A mass alone can't give you a natural frequency. You need a system of at least two masses and something elastic or flexible that connects them. In this case, the masses are the different parts of the helicopter, including the blades, engines, and other parts of the body. The elastic is provided by the parts of the helicopter body, which are not absolutely rigid (nothing is).
marzolian 8 months ago
well that sucks :)
YoungEagle08 1 year ago
Think 'Tacoma Narrows Bridge'. Same thing, resonance causing structural failure.
wolfeh89 1 year ago
If you go to school for engineering you will learn about it in dynamics
vampov 1 year ago
hoolly shit hahaha
vatolocovarato 3 years ago
What happens is when multi-blade rotors get a vibration or shock from landing or something, the shock moves up to the lag-lead hinges -- which are supposed to keep the blades equally spaced -- and basically makes the distribution of centrifugal force unequal, causing the helicopter to bounce around with a lot of stress, sometimes tearing the craft.
cmdr2005 3 years ago
I can't tell what test they're running, what are they trying to do?
safesax85 4 years ago
Ground Resonance Test
JebusJames 4 years ago 8
@JebusJames but what is a Ground Resonance Test?, What are they testing?, The engine vibration?, what originates that then
Colt357B 1 year ago
@JebusJames That was such a brilliant explanation of what is actually being done here. Now @safesax85 fully understands what they are trying to accomplish here. They know, because of your detailed post that they are testing for a dangerous imbalance that could result in the total destruction of an aircraft of this kind.
jediclone 8 months ago 11
Comment removed
gabilanconor 5 months ago
oooopppppppppppppppppppppsssssssssssss
cmutch2007 4 years ago