WIHIH?
Thread Starter
Joined: Apr 2001
Posts: 496
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From: Norfolk
WIHIH?
Anybody know the full story?...also caption competition... http://www.wimp.com/chopperproblems/
Joined: Jan 2002
Posts: 153
Likes: 5
From: Sydney, Oz.
http://www.pprune.org/forums/showthread.php?t=193151
Clearer videos:
http://www.chinook-helicopter.com/vi..._Side_View.mpg
http://www.chinook-helicopter.com/vi..._Rear_View.mpg
cheers,
Greg
Originally Posted by SASless
Shot at Aberdeen Proving Ground. Aircraft was to be used for ballistic testing....getting shot by various sized rounds in senstive places. During a pre-test ground run....encountered ground resonance due to being chained to the ground. There is also a side view video of the same event which is even better to watch.
http://www.chinook-helicopter.com/vi..._Side_View.mpg
http://www.chinook-helicopter.com/vi..._Rear_View.mpg
cheers,
Greg
Joined: Apr 2003
Posts: 3,012
Likes: 1
From: USA
That was an engineering test gone bad. The aircraft is run from a control blockhouse, without crew aboard. The Chinook was tied down too tightly, so the landing gear oleos were not able to absorb the ground resonance motions effectively. This meant that on shutdown the ground resonance became severe, and the aft transmission failed in its mounts. Part of the problem is that the US Army does not believe in rotor brakes, so when this Chinook started experiencing the GR, the crew shut it down, but there was no way to quickly stop the rotor, so the aircraft was lost during the shutdown sequence, anyway. If there had been a rotor brake, putting it on would have caused all blades to the forward damper stops, which would have stopped the GR instantly (as well as slowing the rotor very quickly to help stop the freak show.)
Joined: Oct 2004
Posts: 217
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From: USA
Taken from www.chinook-helicopter.com
One of the disadvantages of a fully articulated rotor system, such as that found on the CH-47 Chinook helicopter, is the susceptibility to ground resonance. Items to consider in limiting the chances of encountering ground resonance include ensuring that all tires are inflated to 88 psi and all landing gear struts and blade dampeners are properly serviced. The two videos below show the result of a Chinook helicopter falling victim to ground resonance. The tail number was 84-24156, and was the one that previously encountered uncommanded flight control inputs which resulted in the aircraft performing a barrel roll. After the roll incident, the aircraft was assigned to Aberdeen Proving Grounds in Maryland, and was utilized as a ground test device.
On a ferry flight from CCAD, 84-24156 rolled inverted in flight and was severely damaged. At some point, 84-24156 was assigned to Aberdeen Proving Grounds (APG), Maryland, and utilized as a ballistic evaluation device. Tied to the ground, projectiles were fired at 84-24156 while it was running. On an unknown date, 85-24156 experienced ground resonance and disintegrated while tied to the ground at Aberdeen. As of 1 January 2001, this aircraft was 35.9 years old. As of 27 February 2000, the last known location of 84-24156 is at Aberdeen, Maryland. Aircraft status: Ground evaluation test device.
One of the disadvantages of a fully articulated rotor system, such as that found on the CH-47 Chinook helicopter, is the susceptibility to ground resonance. Items to consider in limiting the chances of encountering ground resonance include ensuring that all tires are inflated to 88 psi and all landing gear struts and blade dampeners are properly serviced. The two videos below show the result of a Chinook helicopter falling victim to ground resonance. The tail number was 84-24156, and was the one that previously encountered uncommanded flight control inputs which resulted in the aircraft performing a barrel roll. After the roll incident, the aircraft was assigned to Aberdeen Proving Grounds in Maryland, and was utilized as a ground test device.
On a ferry flight from CCAD, 84-24156 rolled inverted in flight and was severely damaged. At some point, 84-24156 was assigned to Aberdeen Proving Grounds (APG), Maryland, and utilized as a ballistic evaluation device. Tied to the ground, projectiles were fired at 84-24156 while it was running. On an unknown date, 85-24156 experienced ground resonance and disintegrated while tied to the ground at Aberdeen. As of 1 January 2001, this aircraft was 35.9 years old. As of 27 February 2000, the last known location of 84-24156 is at Aberdeen, Maryland. Aircraft status: Ground evaluation test device.
Joined: Oct 2004
Posts: 217
Likes: 0
From: USA
For a good read, try this link:
http://www.chinook-helicopter.com/Fl...ax/ffmay98.pdf
Same aircraft.
http://www.chinook-helicopter.com/Fl...ax/ffmay98.pdf
Same aircraft.
Joined: May 2002
Aviation Qualifications: ATP+Mil
Posts: 18,633
Likes: 1,072
From: Downeast
Chinook Rotor Brakes
Bomber,
In the foggy recesses of my alcohol ravaged brain lurks a thought the Chinook originaly had rotor brakes but they had a very bad tendency to turn the disks into sickles suitable for harvesting grain and starting fires, thus they were removed very early on and were not used. That may be a prior to the latest models or the Spec Ops MH series however but I know they were not on the A,B,or C models.
The prototype aircraft in the fleet that we used at Fort Rucker for conversion training (serial numbers...1-10) as I recall had a wee On-Off toggle switch for the rotorbrake down on the center console. (no promise that is the case but that is my recollection). One of the first few Chinooks is now in the Fort Rucker Museum....reminds me of my own Sell by Date situation. They also had the small dual aft wheels vice the single large aft wheel configuration.
During shutdown, the APU powers the aircraft systems and upon shutting the APU off, a lot of additional drag is applied to the rotor system which assists in slowing the rotors to a stop.
I do not know of any cases of ground resonance with the Chinook although I can imagine it did happen. I do remember what we call Thrust Bounce which resulted from a weak Magnetic Brake on the Thrust (Collective for you single rotor guys) Lever. That could give every resemblence to Bronco Busting rides if not corrected in a timely fashion. Broncs can give a fun ride but get 45,000 pounds of Chinook hopping about could prove entertaining to bystanders trying to figure out what kind of stunt you were trying to pull off.
In the foggy recesses of my alcohol ravaged brain lurks a thought the Chinook originaly had rotor brakes but they had a very bad tendency to turn the disks into sickles suitable for harvesting grain and starting fires, thus they were removed very early on and were not used. That may be a prior to the latest models or the Spec Ops MH series however but I know they were not on the A,B,or C models.
The prototype aircraft in the fleet that we used at Fort Rucker for conversion training (serial numbers...1-10) as I recall had a wee On-Off toggle switch for the rotorbrake down on the center console. (no promise that is the case but that is my recollection). One of the first few Chinooks is now in the Fort Rucker Museum....reminds me of my own Sell by Date situation. They also had the small dual aft wheels vice the single large aft wheel configuration.
During shutdown, the APU powers the aircraft systems and upon shutting the APU off, a lot of additional drag is applied to the rotor system which assists in slowing the rotors to a stop.
I do not know of any cases of ground resonance with the Chinook although I can imagine it did happen. I do remember what we call Thrust Bounce which resulted from a weak Magnetic Brake on the Thrust (Collective for you single rotor guys) Lever. That could give every resemblence to Bronco Busting rides if not corrected in a timely fashion. Broncs can give a fun ride but get 45,000 pounds of Chinook hopping about could prove entertaining to bystanders trying to figure out what kind of stunt you were trying to pull off.
Joined: May 2002
Aviation Qualifications: ATP+Mil
Posts: 18,633
Likes: 1,072
From: Downeast
Dear Boy,
Rotorbrakes are extra weight, require additional maintenance, require a modicum of intelligence to use correctly (how the Marines use them must be interesting at best), and are way...way...way.. too high tech for the Army.
Rotorbrakes are extra weight, require additional maintenance, require a modicum of intelligence to use correctly (how the Marines use them must be interesting at best), and are way...way...way.. too high tech for the Army.
Joined: Jul 2004
Posts: 376
Likes: 4
From: Durham, NC USA
Big Helicopter Rotor Brakes
Most Marine and Navy helicopters have rotor brakes. SASless is correct. Weight and complexity are issues. Both services have lost aircraft due to in flight rotor brake activations. These mishaps are due in part to the complexity of their systems. I believe that EH-Industries lost at least one prototype EH-101 due to an in flight rotor brake activation. Service life also enters into the equation. Rotor brakes are short lived at best. Large helicopter shipboard operations would be difficult without rotor brakes. As an example the H-53E rotor (2 tonnes) may coast for a very extended period of time without the help of a rotor brake to stop it.
Joined: Feb 2005
Posts: 1,957
Likes: 0
From: Australia
Jack Carson
How long?
trivia time.
bell 47G3B1 with polished blades, T/r neutral, Coll right down, M/r rigging spot-on, nil wind,
9 mins 30 secs
bell 47 G5 same except lighweight blades (less 10 pounds each tip) and fitted with no-bar kit (less 30 lbs stab bar)
just over 5 mins.
trivia time.
bell 47G3B1 with polished blades, T/r neutral, Coll right down, M/r rigging spot-on, nil wind,
9 mins 30 secs
bell 47 G5 same except lighweight blades (less 10 pounds each tip) and fitted with no-bar kit (less 30 lbs stab bar)
just over 5 mins.
Joined: Apr 2003
Posts: 3,012
Likes: 1
From: USA
In general, the US Army does not believe in rotor brakes, and does not equip its helos with them. I know personally that for several models they set the reliability requirement so far above the state of the art that no brake could be fitted without losing points in the competition - specifically the UTTAS (Black Hawk) and the LHX (Comanche).
The special operations Hawks have them, due to shipboard operations, and the Apache has one (I learned from above!)
The special operations Hawks have them, due to shipboard operations, and the Apache has one (I learned from above!)
Joined: Feb 2006
Posts: 102
Likes: 0
From: Australia
Nick,
For information, all Australian S-70A-9 Black Hawks have rotor brakes as standard and in fact we were required to use them for all starts. From memory we didn't seem to have many problems with them.
No idea whether our D model Chinooks have them.
P68
For information, all Australian S-70A-9 Black Hawks have rotor brakes as standard and in fact we were required to use them for all starts. From memory we didn't seem to have many problems with them.
No idea whether our D model Chinooks have them.
P68
Joined: Jul 1999
Posts: 195
Likes: 0
From: UK
Its strange how nothing seems to be learned over time. The UK version of the S58 (Wessex) had a hydraulically operated, manually pumped rotor brake which worked perfectly. A little sight glass to tell you it had fluid in it. If it got spongy, you bled it. It held the rotors quite happily against the torque of one engine when starting on board ship.
Far too simple, so to save the pilot the effort, people much brainier than I started taking pressure from high pressure hydraulic systems, with electric activation. So now you can rip your transmission out or set fire to yourself with the flick of a switch. Nice!
If it ain't broke don't fix it!
And while not having a brake at all certainly follows the KISS principle, there are so many circumstances where it is important/ useful that I think all types military and civil should have one as standard. IMHO.
Far too simple, so to save the pilot the effort, people much brainier than I started taking pressure from high pressure hydraulic systems, with electric activation. So now you can rip your transmission out or set fire to yourself with the flick of a switch. Nice!
If it ain't broke don't fix it!
And while not having a brake at all certainly follows the KISS principle, there are so many circumstances where it is important/ useful that I think all types military and civil should have one as standard. IMHO.
