Chinook & other tandem rotors discussions
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Someone linked to the site about the 347. In one photo, it looks like there is a large tandom rotor heli in the background, much bigger than a Chinook. Anyone know what it is?
Soup,
The aircraft you mention was a mockup of the Boeing-Vertol Heavy Lift Helicopter (HLH). Alas, Sikorsky convinced Congress that the CH-53E Sea Stallion should be the "heavy lifter" for the military.
This link discusses the "final" end of the mockup.
http://www.aero-news.net/index.cfm?C...1-93e7f7b4c58f
The aircraft you mention was a mockup of the Boeing-Vertol Heavy Lift Helicopter (HLH). Alas, Sikorsky convinced Congress that the CH-53E Sea Stallion should be the "heavy lifter" for the military.
* While the Chinook is a big brute of a helicopter by American standards, it is dwarfed by the huge Soviet-Russian heavy-lift helicopters designed by the Mil organization, and for a long time Boeing and the US military had an urge to match or top the Mil heavy lifters.
In the late 1960s, Boeing came up with designs for machines with broad similarities to the Sea Knight and Chinook, but about twice the size of the Chinook in terms of linear dimensions. Proposed machines included the "Model 227" transport and the "Model 237" flying crane.
Following award of an Army contract for a prototype of a "Heavy Lift Helicopter (HLH)" in 1973, Boeing did move forward on building an oversized flying crane machine, the "XCH-62". Rotor diameter was to be 28 meters (92 feet), fuselage length 27.2 meters (89 feet 3 inches), and footprint length 49.5 meters (162 feet 3 inches). Its widely spaced landing gear would allow it to straddle heavy cargoes such as armored vehicles, and still carry twelve troops in its slender fuselage. Boeing also considered selling a commercial version, the "Model 301".
The XCH-62 prototype was in an advanced state of assembly in 1975, being readied for a planned initial flight the next year, when the US Congress cut funding for the program in August. The Sikorsky CH-53E Super Stallion was felt to give adequate heavy-lift capability for US forces.
The incomplete XCH-62 prototype was mothballed, to be pulled out of storage in the mid-1980s when the Army, the US National Aeronautics & Space Administration (NASA), and the Defense Advanced Research Projects Agency (DARPA) collaborated on a scheme to finish the XCH-62 for experimental flights. However, Congress put their foot down again and it didn't happen.
In the late 1960s, Boeing came up with designs for machines with broad similarities to the Sea Knight and Chinook, but about twice the size of the Chinook in terms of linear dimensions. Proposed machines included the "Model 227" transport and the "Model 237" flying crane.
Following award of an Army contract for a prototype of a "Heavy Lift Helicopter (HLH)" in 1973, Boeing did move forward on building an oversized flying crane machine, the "XCH-62". Rotor diameter was to be 28 meters (92 feet), fuselage length 27.2 meters (89 feet 3 inches), and footprint length 49.5 meters (162 feet 3 inches). Its widely spaced landing gear would allow it to straddle heavy cargoes such as armored vehicles, and still carry twelve troops in its slender fuselage. Boeing also considered selling a commercial version, the "Model 301".
The XCH-62 prototype was in an advanced state of assembly in 1975, being readied for a planned initial flight the next year, when the US Congress cut funding for the program in August. The Sikorsky CH-53E Super Stallion was felt to give adequate heavy-lift capability for US forces.
The incomplete XCH-62 prototype was mothballed, to be pulled out of storage in the mid-1980s when the Army, the US National Aeronautics & Space Administration (NASA), and the Defense Advanced Research Projects Agency (DARPA) collaborated on a scheme to finish the XCH-62 for experimental flights. However, Congress put their foot down again and it didn't happen.
http://www.aero-news.net/index.cfm?C...1-93e7f7b4c58f
Last edited by SASless; 6th Jun 2006 at 17:01.
Wobble cam
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The one thing I will say, looking at these pictures. It reminds me that this helicopter is a beast. A machine of war if ever there was one. Some great times, some absolutely desperate times, but glad to have had the experience.
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Chinook helicopter question
Do any commercial operators use Chinook helicopters or are they only used by the military?
If they are only used by the military, or only produced for the military, what would be the reason for this?
Thanks,
Dave
If they are only used by the military, or only produced for the military, what would be the reason for this?
Thanks,
Dave
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Dave:
The Chinook is primarily used by the military. It has had some commercial uses - as a passenger machine for British Helicopters and then an Alaskan operator. These were used for longer distance, large crew change operations. The UK operation had at least one accident which destroyed faith in the machine, and I think the long-range offshore work in Alaska dried up. Now the main use for civil Chinooks is either logging or heavy equipment moving.
Not a lot of call for a machine that can lift 12 tons with commensurate fuel burn in the civil world.
The militaries that operate the machine love it - a great example of evolution in terms of reliability and growth in transmission and engine capability, as well as the use of fiber-composite rotor blades.
The Chinook is primarily used by the military. It has had some commercial uses - as a passenger machine for British Helicopters and then an Alaskan operator. These were used for longer distance, large crew change operations. The UK operation had at least one accident which destroyed faith in the machine, and I think the long-range offshore work in Alaska dried up. Now the main use for civil Chinooks is either logging or heavy equipment moving.
Not a lot of call for a machine that can lift 12 tons with commensurate fuel burn in the civil world.
The militaries that operate the machine love it - a great example of evolution in terms of reliability and growth in transmission and engine capability, as well as the use of fiber-composite rotor blades.
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Chinook helicopter question
Dave
I flew the Civilian Chinook for British Airways Helicopters in the '80's. It was used for long range flights when the major off-shore installations needed large numbers of passengers moved. Our most distant destination from Aberdeen was the Magnus field, the most northerly platfom in UK waters. The Magnus was some 294 nautical miles from Aberdeen and a round trip without shutdown was about five hours. We almost always carried the full 44 passengers and the operation became very efficent. The BAH Chinooks had an excellent avionics fit with area navigation and ILS approaches could be flown with coupled Flight Director, a big step forward for those days for helicopters.
Sadly a serious accident saw the end of their service with BAH. They were undoubtedly expensive to operate and only succeeded because they fitted the oil companies requirements for specific routes and installations. It is difficult to see how they could be used profitably elsewhere in the UK but have found a role logging and heavy lifting in other countries - I once lifted ten tons on the hook and that was the absolute limit for the aircraft for that days ambient conditions
I flew the Civilian Chinook for British Airways Helicopters in the '80's. It was used for long range flights when the major off-shore installations needed large numbers of passengers moved. Our most distant destination from Aberdeen was the Magnus field, the most northerly platfom in UK waters. The Magnus was some 294 nautical miles from Aberdeen and a round trip without shutdown was about five hours. We almost always carried the full 44 passengers and the operation became very efficent. The BAH Chinooks had an excellent avionics fit with area navigation and ILS approaches could be flown with coupled Flight Director, a big step forward for those days for helicopters.
Sadly a serious accident saw the end of their service with BAH. They were undoubtedly expensive to operate and only succeeded because they fitted the oil companies requirements for specific routes and installations. It is difficult to see how they could be used profitably elsewhere in the UK but have found a role logging and heavy lifting in other countries - I once lifted ten tons on the hook and that was the absolute limit for the aircraft for that days ambient conditions
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A couple of Chinook tech questions, i never got around to asking before:
What sort of drive shafts does Chinook use? Clearly driveshaft failure would force an auto, but it is something i've never heard about failing. They must be some weight, despite the front gearbox.
Does the front rotor have a more forward inclination angle than the rear rotor? If so how does this affect handling? I don't know if there is fore/aft cyclic for each rotor, but imagine that negative longitudinal dihedral would reduce cyclic movement in forward flight.
Mart
What sort of drive shafts does Chinook use? Clearly driveshaft failure would force an auto, but it is something i've never heard about failing. They must be some weight, despite the front gearbox.
Does the front rotor have a more forward inclination angle than the rear rotor? If so how does this affect handling? I don't know if there is fore/aft cyclic for each rotor, but imagine that negative longitudinal dihedral would reduce cyclic movement in forward flight.
Mart
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Chinook helicopter question
Mart
The Chinook transmission is very complicated. Each engine drives a nose gear-box which drives into central combining gearbox. From there shafts called synchronising shafts drive to the forward and aft main gearboxes. Synchronisation is considered to be even more important than power transmission because the two rotors overlap and it would be catastrophic if they were not in phase. Autorotation in training with both engines out of the governed range were standard and in the simulator, full engine-off landings were achievable with a little practice. One anomaly that the simulator threw up was achieving vortex ring on one head and not the other. The recovery was violent!!
The fore and aft gear-boxes are mounted at slightly different angles for technical reasons that escape me but that makes no difference to handling. Longitudinal aircraft pitch changes are made by increasing collective pitch on one head and reducing it on the other. Laterally both heads tilt in the required direction and yaw changes are made by tilting one head in one direction and the other in the opposite direction. Handling however is completely conventional and anyone who can fly a helicopter would have no problem in handling a Chinook. Understanding the systems is something else.
The Chinook transmission is very complicated. Each engine drives a nose gear-box which drives into central combining gearbox. From there shafts called synchronising shafts drive to the forward and aft main gearboxes. Synchronisation is considered to be even more important than power transmission because the two rotors overlap and it would be catastrophic if they were not in phase. Autorotation in training with both engines out of the governed range were standard and in the simulator, full engine-off landings were achievable with a little practice. One anomaly that the simulator threw up was achieving vortex ring on one head and not the other. The recovery was violent!!
The fore and aft gear-boxes are mounted at slightly different angles for technical reasons that escape me but that makes no difference to handling. Longitudinal aircraft pitch changes are made by increasing collective pitch on one head and reducing it on the other. Laterally both heads tilt in the required direction and yaw changes are made by tilting one head in one direction and the other in the opposite direction. Handling however is completely conventional and anyone who can fly a helicopter would have no problem in handling a Chinook. Understanding the systems is something else.
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A native tribe just hired Columbia Helicopters big Chinook to place logs in the local river for salmon pools.
Usually, the logs are flying one way out of the woods.
Usually, the logs are flying one way out of the woods.
Hi Mart,
I'm not a Chinook-jockey - but I think, it depends, from which drive shaft you are speaking.
Engine - the helicopter has two - so normally not that a problem, except in hover.
Drive shaft between the gearboxes? That's why the Banana is also called flying coffin...
It tends to tangle the blades from front and back, when die dirve shaft goes.....
Much less chance than surviving a tailrotordriveshaftfailure in a normal helicopter....
Greetings Flying Bull
A couple of Chinook tech questions, i never got around to asking before:
What sort of drive shafts does Chinook use? Clearly driveshaft failure would force an auto, but it is something i've never heard about failing. They must be some weight, despite the front gearbox.
Does the front rotor have a more forward inclination angle than the rear rotor? If so how does this affect handling? I don't know if there is fore/aft cyclic for each rotor, but imagine that negative longitudinal dihedral would reduce cyclic movement in forward flight.
Mart
What sort of drive shafts does Chinook use? Clearly driveshaft failure would force an auto, but it is something i've never heard about failing. They must be some weight, despite the front gearbox.
Does the front rotor have a more forward inclination angle than the rear rotor? If so how does this affect handling? I don't know if there is fore/aft cyclic for each rotor, but imagine that negative longitudinal dihedral would reduce cyclic movement in forward flight.
Mart
Engine - the helicopter has two - so normally not that a problem, except in hover.
Drive shaft between the gearboxes? That's why the Banana is also called flying coffin...
It tends to tangle the blades from front and back, when die dirve shaft goes.....
Much less chance than surviving a tailrotordriveshaftfailure in a normal helicopter....
Greetings Flying Bull
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HeliEng & Shawn, thanks for the replies.
The reason for asking has to do with vibration. The Chinook has a rotor-to-rotor interaction, plus it has a relatively large fuselage area under the two rotors. I was wondering if these features result in a high level of vibration. A vibration that might be acceptable for transporting armed services personnel but not acceptable for transporting commercial personnel.
Is the vibration in the Chinook higher than that of other large helicopters?
Dave
The reason for asking has to do with vibration. The Chinook has a rotor-to-rotor interaction, plus it has a relatively large fuselage area under the two rotors. I was wondering if these features result in a high level of vibration. A vibration that might be acceptable for transporting armed services personnel but not acceptable for transporting commercial personnel.
Is the vibration in the Chinook higher than that of other large helicopters?
Dave
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Chinook Helicopter question
Dave
The vibration level in the Civilian Chinook was quite high, certainly higher than for example the S61 or S76. Because of that both pilot seats and the entire passenger cabin were mounted on dynamic vibration absorbers. When levelling into the cruise the rotor revs were reduced slightly and that change of rotor speed induced extra vibration that the seat absorbers might take as much as two minutes and more to absorb. When the first Chinooks were received we found that vibration was usually what determined the cruising speed regardless of what the book said. Typically on departure from Aberdeen the book cruise might be 120 knots. The aircraft was accelerated until the vibration level became uncomfortable and the speed was reduced a couple of knots which speed then became the cruise. On the inbound leg minus 10,000 lbs or more of fuel up to 135 - 140 knots was usually possible
The vibration level in the Civilian Chinook was quite high, certainly higher than for example the S61 or S76. Because of that both pilot seats and the entire passenger cabin were mounted on dynamic vibration absorbers. When levelling into the cruise the rotor revs were reduced slightly and that change of rotor speed induced extra vibration that the seat absorbers might take as much as two minutes and more to absorb. When the first Chinooks were received we found that vibration was usually what determined the cruising speed regardless of what the book said. Typically on departure from Aberdeen the book cruise might be 120 knots. The aircraft was accelerated until the vibration level became uncomfortable and the speed was reduced a couple of knots which speed then became the cruise. On the inbound leg minus 10,000 lbs or more of fuel up to 135 - 140 knots was usually possible
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Originally Posted by Flying Bull
It tends to tangle the blades from front and back, when die dirve shaft goes.....
Much less chance than surviving a tailrotordriveshaftfailure in a normal helicopter....
Much less chance than surviving a tailrotordriveshaftfailure in a normal helicopter....
I would imagine that shaft will be carbon composite, and very substantial. The other problem is that the surrounding structure has to be stiff enough to avoid torsional and flexural resonance problems. At high rpm any initial flexure in the shaft would soon lead to catastophic failure.
Hmmm, them Chinook boys must trust the ground crews.
Dave, have you ever heard a chook fly overhead? Vibration from ground level is pretty high. Every rotation each blade intersects the vortices from the opposite rotor set, so you get persistent blade slap. Great noise though.
Mart
Last edited by Graviman; 27th Oct 2006 at 18:12.
Does the front rotor have a more forward inclination angle than the rear rotor? If so how does this affect handling? I don't know if there is fore/aft cyclic for each rotor, but imagine that negative longitudinal dihedral would reduce cyclic movement in forward flight.
For Dave, they aren't any worse to me - if tracked & balanced properly of course. The older metal blades were a lot easier to get smooth back in my days but you could also get the composite ones just as good - just took longer! The minumum standard used to be .2 IPS, which isn't particularly smooth to me - this was 20 years ago, who knows what the story is now.
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Boslandew, brett s & Mart
Thanks for the remarks about vibration, particularly since it is related to a craft with twin-rotors.
Mart,
Nick has said that the noise is intentional. He mentioned an old documentary called 'Apocalypse Now'. Nick said that the noise caused the enemy to **** their pants. Then the helicopters could catch the enemy with their pants down.
Dave
Thanks for the remarks about vibration, particularly since it is related to a craft with twin-rotors.
Mart,
Nick has said that the noise is intentional. He mentioned an old documentary called 'Apocalypse Now'. Nick said that the noise caused the enemy to **** their pants. Then the helicopters could catch the enemy with their pants down.
Dave