CH-47 Ground Resonance Test

Ground resonance test done by Boeing.

Category:

Autos & Vehicles

Tags:

• CH-47
• vibration
• test
• boeing
• helicopter
• grounded
• Chinook
• chopper
• smoke
• fire

[safesax85]

I can't tell what test they're running, what are they trying to do?

[JebusJames]

Ground Resonance Test

[jediclone]

@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.

[nibbler125]

sometimes you need to destroy a helecopter to make changes to save a thousand

[SteveTech83]

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]

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.

[noshadowmaster]

Did Ford build this thing?

[marzolian]

@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).

[TheShorty1500]

Der gute heli :(



[kmcnish320]

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.

[Calcx]

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