Chinook & other tandem rotors discussions
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I'm surprised that this is the first time you've seen us. The London heli-lanes are an easy way to get to the Stamford Training Area from Odiham and return. It is good training for the new guys as well because you really have to get on top of the radio calls, the nav (on the legs away from the river) and the required height changes. Thames Radar can get seriously p****d off if you f**k up. Of course the fact that the view is spectacular is merely coincidental.
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Through S**t to the Bar
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Through S**t to the Bar
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Very interesting thread. I can see I'll need to do some serious revision before my next standards check.
One minor point, the Chinook doesn't handle quite like a normal helicopter in roll. In a normal helicopter, once you have banked, the pendulum force of the cab tries to pull you wings level again, forcing you to keep some into-turn cyclic to maintain your angle of bank. For some unknown reason Boeing decided that the Chinook should fly like a fixed wing aircraft in roll. When you push the stick sideways the AFCS interprets this as a demand for a rate of roll proportional to the displacement. It will keep rolling the aircraft until you are upside down if you let it. You have to put the stick back in the middle to stop the roll, at which point the AFCS will automatically hold the angle of bank.
Lu: Your sideways stick stuff is not a problem in autorotation. As has been said, we can fly just like any other helicopter. It does play a major part in Vortex Ring or "settling with power" as the Americans would say. Although I know people who say that you can power out of Vortex Ring in the mighty wocca, and they have, the best solution is to accelerate, as it's impossible to maintain Vortex Ring above 30kts. Trying to pitch forward in the Chinook would only lead to an increase in collective pitch on the aft head which would go deeper into Vortex Ring and fail to pitch up. The way out of Vortex Ring in the Chinook is to accelerate sideways because, as you pointed out, this cyclically pitches both heads which gets round the problem.
Arm: All very good points and I wouldn't argue with any of them. The Chinook has a wind limit of 45kts from any direction and is very tolerant of downwind approaches/hover with very little increase in power demand. Even single engine, at training weights, the pilot would have plenty of power in hand, especially if he did a running landing (max speed 60kts). Into wind is better, but downwind at 10kts is not a problem.
Vfrpilotpb: Ever since the Wessex crash a few years ago, in which three ATC cadets died, the MOD have become EXTREMELY resrictive about carriage of civilians. It has to be approved from on high, and then only for a good reason. We would love to take you flying but, normally, they won't let us. I suggest you try to think of a cunning reason and write to the Station Commander at Odiham to ask. What have you got to lose?
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Through S**t to the Bar
One minor point, the Chinook doesn't handle quite like a normal helicopter in roll. In a normal helicopter, once you have banked, the pendulum force of the cab tries to pull you wings level again, forcing you to keep some into-turn cyclic to maintain your angle of bank. For some unknown reason Boeing decided that the Chinook should fly like a fixed wing aircraft in roll. When you push the stick sideways the AFCS interprets this as a demand for a rate of roll proportional to the displacement. It will keep rolling the aircraft until you are upside down if you let it. You have to put the stick back in the middle to stop the roll, at which point the AFCS will automatically hold the angle of bank.
Lu: Your sideways stick stuff is not a problem in autorotation. As has been said, we can fly just like any other helicopter. It does play a major part in Vortex Ring or "settling with power" as the Americans would say. Although I know people who say that you can power out of Vortex Ring in the mighty wocca, and they have, the best solution is to accelerate, as it's impossible to maintain Vortex Ring above 30kts. Trying to pitch forward in the Chinook would only lead to an increase in collective pitch on the aft head which would go deeper into Vortex Ring and fail to pitch up. The way out of Vortex Ring in the Chinook is to accelerate sideways because, as you pointed out, this cyclically pitches both heads which gets round the problem.
Arm: All very good points and I wouldn't argue with any of them. The Chinook has a wind limit of 45kts from any direction and is very tolerant of downwind approaches/hover with very little increase in power demand. Even single engine, at training weights, the pilot would have plenty of power in hand, especially if he did a running landing (max speed 60kts). Into wind is better, but downwind at 10kts is not a problem.
Vfrpilotpb: Ever since the Wessex crash a few years ago, in which three ATC cadets died, the MOD have become EXTREMELY resrictive about carriage of civilians. It has to be approved from on high, and then only for a good reason. We would love to take you flying but, normally, they won't let us. I suggest you try to think of a cunning reason and write to the Station Commander at Odiham to ask. What have you got to lose?
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Through S**t to the Bar
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VFRpilot
You don't need any special software to insert these little pictures. You just need to make a reference to an image file held elsewhere on the web. Take a look at this message by editing it - you'll see what I mean (and how it works).
A good source of 'smilies' and other aviation related gifs like the one above can be found at
http://www.stopstart.fsnet.co.uk
It even shows you how you can insert them into your text
Regards
Balance!
Oh, and make that 3 please.... I'll get in the queue with FL
[This message has been edited by Balance! (edited 21 May 2001).]
You don't need any special software to insert these little pictures. You just need to make a reference to an image file held elsewhere on the web. Take a look at this message by editing it - you'll see what I mean (and how it works).
A good source of 'smilies' and other aviation related gifs like the one above can be found at
http://www.stopstart.fsnet.co.uk
It even shows you how you can insert them into your text
Regards
Balance!
Oh, and make that 3 please.... I'll get in the queue with FL
[This message has been edited by Balance! (edited 21 May 2001).]
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Down wind landings. The Chinook has a lot of flexibility in this area but every thing has a limit. I'll tell on myself a bit. This was back in my early Chinook days.
The aircraft was a "small C", L-7C engines, I believe, and metal blades. Landing at 8400'MSL and about 25deg C. Slight down wind. Not much down wind but when you’re too fast, which can happen very easy at that altitude, a little down wind is allot.
My last thought before touch down was that if I can keep the VSI at less than 492FPM at touch down then, according to the book, I shouldn't do any damage. The book is a bad bet when you are using it as a hedge against poor technique.
The aircraft was a "small C", L-7C engines, I believe, and metal blades. Landing at 8400'MSL and about 25deg C. Slight down wind. Not much down wind but when you’re too fast, which can happen very easy at that altitude, a little down wind is allot.
My last thought before touch down was that if I can keep the VSI at less than 492FPM at touch down then, according to the book, I shouldn't do any damage. The book is a bad bet when you are using it as a hedge against poor technique.
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Boeing Completes First CH-47F Chinook Flight
PHILADELPHIA, June 29, 2001
Press Release
Boeing has launched another chapter in the history of its longest-running continuous aircraft production program. The new CH-47F Chinook prototype heavy-lift helicopter, the sixth Chinook type designed for the U.S. Army, recently completed its first flight at the Boeing Philadelphia manufacturing facility. The June 25 flight, which involved hover and basic maneuvers, capped a series of comprehensive system checks leading to takeoff precisely as scheduled in the CH-47F program agreement completed three years ago.
"The first flight was flawless," said Roger A. Krone, vice president and general manager, Boeing Army Programs/Rotorcraft. "Our Chinook Team demonstrated not only technical excellence, but also a total commitment to our U.S. Army customer. The entire first- flight crew-pilots, engineers, technicians and support personnel-accomplished our program-schedule goals with consistently good performance and solid teamwork. They set a high standard for all our production programs." A Boeing Philadelphia flight crew consisting of Erik Kocher, Chinook program chief test pilot; Randy Wells, test pilot; Joe Schluck, flight test engineer; and John Rose, crew chief, lifted off shortly before 7 p.m., EDT, and remained airborne for about five minutes to validate aircraft handling qualities. "It was wonderful," Kocher said. "The aircraft performed right up to expectations while we completed rotor blade track and balance and crosswind hover as scheduled. The aircraft controlled nicely, and all systems functioned as advertised." The CH-47F modernization program will sustain the U.S. Army's Chinook fleet to provide rotary-wing heavy-lift capabilities well into the 21st century. Modernization will include aircraft remanufacturing, vibration reduction, improved avionics with integrated digital mission management systems and a digital map, and installation of more powerful Honeywell T55-GA-14A-714 engines. These core elements of the program will reduce operational and support costs to below those of the original CH-47D and provide at least another 20 years of economical and effective service. That means Chinooks will wind up serving in the Army's inventory for more than 70 years, an unprecedented record of service for military aircraft. The Boeing Company develops and produces military rotorcraft and provides support services worldwide from its production facilities in Philadelphia and Mesa, Ariz. Among its products are the AH-64D Apache Longbow attack helicopter, CH-47 Chinook, the RAH-66 Comanche armed reconnaissance helicopter and the V-22 Osprey tiltrotor aircraft.
Press Release
Boeing has launched another chapter in the history of its longest-running continuous aircraft production program. The new CH-47F Chinook prototype heavy-lift helicopter, the sixth Chinook type designed for the U.S. Army, recently completed its first flight at the Boeing Philadelphia manufacturing facility. The June 25 flight, which involved hover and basic maneuvers, capped a series of comprehensive system checks leading to takeoff precisely as scheduled in the CH-47F program agreement completed three years ago.
"The first flight was flawless," said Roger A. Krone, vice president and general manager, Boeing Army Programs/Rotorcraft. "Our Chinook Team demonstrated not only technical excellence, but also a total commitment to our U.S. Army customer. The entire first- flight crew-pilots, engineers, technicians and support personnel-accomplished our program-schedule goals with consistently good performance and solid teamwork. They set a high standard for all our production programs." A Boeing Philadelphia flight crew consisting of Erik Kocher, Chinook program chief test pilot; Randy Wells, test pilot; Joe Schluck, flight test engineer; and John Rose, crew chief, lifted off shortly before 7 p.m., EDT, and remained airborne for about five minutes to validate aircraft handling qualities. "It was wonderful," Kocher said. "The aircraft performed right up to expectations while we completed rotor blade track and balance and crosswind hover as scheduled. The aircraft controlled nicely, and all systems functioned as advertised." The CH-47F modernization program will sustain the U.S. Army's Chinook fleet to provide rotary-wing heavy-lift capabilities well into the 21st century. Modernization will include aircraft remanufacturing, vibration reduction, improved avionics with integrated digital mission management systems and a digital map, and installation of more powerful Honeywell T55-GA-14A-714 engines. These core elements of the program will reduce operational and support costs to below those of the original CH-47D and provide at least another 20 years of economical and effective service. That means Chinooks will wind up serving in the Army's inventory for more than 70 years, an unprecedented record of service for military aircraft. The Boeing Company develops and produces military rotorcraft and provides support services worldwide from its production facilities in Philadelphia and Mesa, Ariz. Among its products are the AH-64D Apache Longbow attack helicopter, CH-47 Chinook, the RAH-66 Comanche armed reconnaissance helicopter and the V-22 Osprey tiltrotor aircraft.
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“Modernization will include aircraft remanufacturing, vibration reduction, improved avionics with integrated digital mission management systems and a digital map, and installation of more powerful Honeywell T55-GA-14A-714 engines. These core elements of the program will reduce operational and support costs to below those of the original CH-47D and provide at least another 20 years of economical and effective service. That means Chinooks will wind up serving in the Army's inventory”.
The article did not indicate if the new elastomeric rotor system was installed on this aircraft. If and when this new rotorhead design is incorporated the operational costs at least for the rotorhead will be higher than the existing design and that design is the highest maintenance cost driver on the CH-47. The elastomeric concept on paper reduces operational costs and maintenance by reducing parts count and eliminating the need to lubricate the rotorhead elements. However, what they can’t eliminate are the stresses and strains that exist in the rotorhead because a great deal of the flight time is in a hover or at speeds less than 60 Knots which is at hover pitch.
The steel elements of the existing design are 70-80% scrapped when the rotorhead comes in for overhaul or refurbishment. With this high level of operational stresses the elastomeric elements will degrade at a much higher level than on similar designs using elastomeric bearings. Because of the nature of the elastomeric bearings they must be matched to within 5% of each other relative to durometer (stiffness). If these elements go outside of that range the offending bearing must be changed and the remaining two bearings removed and tested for stiffness which runs up the ground maintenance times on the aircraft. If the remaining two bearings can’t be matched to the new bearing two new bearings must be installed and the other two put into the supply room to be referenced against the next bearing failure. This runs up the maintenance costs.
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The Cat
[This message has been edited by Lu Zuckerman (edited 02 July 2001).]
The article did not indicate if the new elastomeric rotor system was installed on this aircraft. If and when this new rotorhead design is incorporated the operational costs at least for the rotorhead will be higher than the existing design and that design is the highest maintenance cost driver on the CH-47. The elastomeric concept on paper reduces operational costs and maintenance by reducing parts count and eliminating the need to lubricate the rotorhead elements. However, what they can’t eliminate are the stresses and strains that exist in the rotorhead because a great deal of the flight time is in a hover or at speeds less than 60 Knots which is at hover pitch.
The steel elements of the existing design are 70-80% scrapped when the rotorhead comes in for overhaul or refurbishment. With this high level of operational stresses the elastomeric elements will degrade at a much higher level than on similar designs using elastomeric bearings. Because of the nature of the elastomeric bearings they must be matched to within 5% of each other relative to durometer (stiffness). If these elements go outside of that range the offending bearing must be changed and the remaining two bearings removed and tested for stiffness which runs up the ground maintenance times on the aircraft. If the remaining two bearings can’t be matched to the new bearing two new bearings must be installed and the other two put into the supply room to be referenced against the next bearing failure. This runs up the maintenance costs.
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The Cat
[This message has been edited by Lu Zuckerman (edited 02 July 2001).]
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hun
Sorry, reply is probably too late. However:
At a basic weight (std crew/fuel) of 30k-32k lb you can plan on about 2400 lb/hr. Remains fairly steady until about 42k lb, where it climbs to around 2750 lb/hr at a 135 TAS cruise. At 50k lb it can exceed 3000 lb/hr in hover, or with large external loads, and probably drops back to around 2800 lb/hr in cruise. Endurance/holding - about 2100 lb/hr. Start/taxi uses about 600 lb for first start of day plus IFR checks.
All info is off the top of my head, and for a '47D with the -712 engines (nil FADEC). If you need grater accuracy I can get you a fuel flow chart.
Cheers BFSC
Sorry, reply is probably too late. However:
At a basic weight (std crew/fuel) of 30k-32k lb you can plan on about 2400 lb/hr. Remains fairly steady until about 42k lb, where it climbs to around 2750 lb/hr at a 135 TAS cruise. At 50k lb it can exceed 3000 lb/hr in hover, or with large external loads, and probably drops back to around 2800 lb/hr in cruise. Endurance/holding - about 2100 lb/hr. Start/taxi uses about 600 lb for first start of day plus IFR checks.
All info is off the top of my head, and for a '47D with the -712 engines (nil FADEC). If you need grater accuracy I can get you a fuel flow chart.
Cheers BFSC
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Hover FF on a cool day at 1000'PA with a 23,400 LB. F-4 on the end of 125' of rigging will be about 3200 PPH and the engines will be nice and warm.
Two kinds of helicopter, Cargo and external load.
Two kinds of helicopter, Cargo and external load.
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VRS in Tandem rotor air craft
Here is my question.
Is possible to get vrs in on tandem (ch46/47)rotor system (front or rear) independantly of the other. I would guess it wouold be the rear rotor.
Can this happen?
Can anyone explin it to me..
Thanks
RB
Is possible to get vrs in on tandem (ch46/47)rotor system (front or rear) independantly of the other. I would guess it wouold be the rear rotor.
Can this happen?
Can anyone explin it to me..
Thanks
RB