Chinook & other tandem rotors discussions
Senis Semper Fidelis
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I have finally watched the Vid via my desktop which was the most succesful download, the sound on my comp was accidently up at the max ( courtesy of my son) and because of this I heard the engines spooling down just about at the point where the R/H engine seems to go under strain( darker smoke) then you can hear the turbs whining down then the puffs of white smoke as Nick suggests they are giving up, the noise of the destruction is quite sureal, and seems less that what I would have expected.
Unbelievable to watch how quickly this giant piece of engineering "spits its dummy out" how quick for the little R22?
Peter R-B
Vfr
Unbelievable to watch how quickly this giant piece of engineering "spits its dummy out" how quick for the little R22?
Peter R-B
Vfr
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I asked some folks at Boeing Philadelphia about this.
Evidently it was a scrap fuselage and rotor blades that were being prepared for being shot at anyway.
The normal flight departments (production and experimental flight test) declined to be involved as it was not going to be inspected or subject to normal scrutiny.
It appears that the chains may have been tied down too tightly to prevent the oleos from working properly.
Impressive footage. Glad I wasn't in the machine.
Evidently it was a scrap fuselage and rotor blades that were being prepared for being shot at anyway.
The normal flight departments (production and experimental flight test) declined to be involved as it was not going to be inspected or subject to normal scrutiny.
It appears that the chains may have been tied down too tightly to prevent the oleos from working properly.
Impressive footage. Glad I wasn't in the machine.
quote from: Vfrpilotpb
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Unbelievable to watch how quickly this giant piece of engineering "spits its dummy out" how quick for the little R22?
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And how exactly do you want to wreck an R22? I heard they are very diffucult to destroy by ground resonance. Use a hammer instead.
Try a H300. Much easier.
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Unbelievable to watch how quickly this giant piece of engineering "spits its dummy out" how quick for the little R22?
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And how exactly do you want to wreck an R22? I heard they are very diffucult to destroy by ground resonance. Use a hammer instead.
Try a H300. Much easier.
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Queensland Rescue Pty Ltd
I believe a commercial operator is due to take over the Queensland Rescue operation Mid next year, for a 12 month trial. This, I believe, followed a confidential report outlining the extraordinary financial liability of Queensland Rescue on the Government. Not surprising considering the amount of staff they have at those bases.
No doubt a commercial or non-profit organisation could do it cheaper.
No doubt a commercial or non-profit organisation could do it cheaper.
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tandem rotor helicopter control
Here is a dead simple one...
Who out there can tell me how tandem rotor helicopters (eg chinook ch-47 etc) are yawed around the normal axis?? I realise there is some type of control input going on but what is it and what effect does that have on the aircraft in order for it to yaw left and right??
All I can dream up is that moving the pedals(they do have pedals right??) results in some type of opposing lateral rotor disc tilt/bias between the front and rear rotors
ie - to yaw left around normal axis,left pedal in causes left `tilt` of front rotor disc and associated total rotor thrust ...and right `tilt` of rear rotor disc and associated total rotor thrust.
...opposite of above for right pedal
While on the subject of counter-rotating helicopter designs how the hell do you yaw/control kamovs and k-maxs around the normal axis??? (ie- turn around the mast)
Please enlighten me on what really happens in these beasties!!
Who out there can tell me how tandem rotor helicopters (eg chinook ch-47 etc) are yawed around the normal axis?? I realise there is some type of control input going on but what is it and what effect does that have on the aircraft in order for it to yaw left and right??
All I can dream up is that moving the pedals(they do have pedals right??) results in some type of opposing lateral rotor disc tilt/bias between the front and rear rotors
ie - to yaw left around normal axis,left pedal in causes left `tilt` of front rotor disc and associated total rotor thrust ...and right `tilt` of rear rotor disc and associated total rotor thrust.
...opposite of above for right pedal
While on the subject of counter-rotating helicopter designs how the hell do you yaw/control kamovs and k-maxs around the normal axis??? (ie- turn around the mast)
Please enlighten me on what really happens in these beasties!!
My recall of the Chinook....
Each head has a pivoting actuator and a swiveling actuator to control the rotor inputs. Each head also has a trim actuator that tilts the heads to reduce form drag by leveling the fuselage in forward flight.
Pedals, known as Yaw control pedals vice anti-torque pedals, do just as you suggest. Pitch attitude control is done by varying the amount of pitch in the two rotor heads....forward stick decreases pitch in the forward head and increases pitch in the aft head.
Lateral control is very similar to regular helicopters....
Tandem helicopters do not like to take off in trim....in the Chinook one can depart with more weight by taking off with the nose offset so as to allow the aft head to operate in clean air vice disturbed air from the forward head.
Being able to get up....and take a short walk around helps on long flying days....try that in your Bell.
To Chinook pilots....there are Chinooks and slingloads....when it comes to helicopters anyway.
Each head has a pivoting actuator and a swiveling actuator to control the rotor inputs. Each head also has a trim actuator that tilts the heads to reduce form drag by leveling the fuselage in forward flight.
Pedals, known as Yaw control pedals vice anti-torque pedals, do just as you suggest. Pitch attitude control is done by varying the amount of pitch in the two rotor heads....forward stick decreases pitch in the forward head and increases pitch in the aft head.
Lateral control is very similar to regular helicopters....
Tandem helicopters do not like to take off in trim....in the Chinook one can depart with more weight by taking off with the nose offset so as to allow the aft head to operate in clean air vice disturbed air from the forward head.
Being able to get up....and take a short walk around helps on long flying days....try that in your Bell.
To Chinook pilots....there are Chinooks and slingloads....when it comes to helicopters anyway.
Anyone else here remember Lu's version of tandem rotor control from a couple of years ago? I laughed 'til I stopped....
Iconoclast
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Every time I sneeze I lose a few brain cells
To: Thud_and_Blunder
A couple of years ago? I can't remember what I had for breakfast yesterday. However, If I described the workings of the flight control system on the CH-47 I got the information from the factory-training manual. I didn’t see anything funny in that but then again I lost my sense of humor a long time ago.
I think SASless got it wrong. Each rotorhead has two servos, both of which can work in the same direction and effect collective pitch, or they can work in opposition and effect lateral control. The pilot cannot input forward cyclic. As SASless indicated there is an electric servo attached to an extension of the swashplate and when the helicopter reaches about 60-knots the servo actuates lowering the forward end of the swashplate introducing forward cyclic allowing the pilot to lower collective reducing the stress on the two rotors.
Because of the nature of operations the CH-47 spends a great deal of flight time at less than 60-knots causing the rotors to operate at very high stress levels. When the rotors are returned for overhaul more than 70% of the parts in the rotorhead are scrapped where most of the steel parts in a Sikorsky head can be reprocessed and returned to service.
A couple of years ago? I can't remember what I had for breakfast yesterday. However, If I described the workings of the flight control system on the CH-47 I got the information from the factory-training manual. I didn’t see anything funny in that but then again I lost my sense of humor a long time ago.
I think SASless got it wrong. Each rotorhead has two servos, both of which can work in the same direction and effect collective pitch, or they can work in opposition and effect lateral control. The pilot cannot input forward cyclic. As SASless indicated there is an electric servo attached to an extension of the swashplate and when the helicopter reaches about 60-knots the servo actuates lowering the forward end of the swashplate introducing forward cyclic allowing the pilot to lower collective reducing the stress on the two rotors.
Because of the nature of operations the CH-47 spends a great deal of flight time at less than 60-knots causing the rotors to operate at very high stress levels. When the rotors are returned for overhaul more than 70% of the parts in the rotorhead are scrapped where most of the steel parts in a Sikorsky head can be reprocessed and returned to service.
Lu,
Before Nick beats yer butt on this....what do you mean by your statement..."A Pilot cannot input forward cyclic."?
One must remember Lu....the hydraulic system drives the flight controls including cyclic pitch control.....the speed trim system is electrical and operates off air speed generated signals sensed by the pitot static system.
The trim system acutators work together on each head.
The point of major stress on the Chinook is the aft vertical shaft....that is why the speed trims exist actually more than as a trim for fuselage leveling. There is a lot of bending moment applied to the aft vertical shaft much the same as in Bell 206/204/205/212 aircraft.
The Chinook is quite speed limited without a functioning speed trim system.
Lu...you reckon Frank Robinson had anything to do with the design of the Boeing-Vertol rotor head?
Before Nick beats yer butt on this....what do you mean by your statement..."A Pilot cannot input forward cyclic."?
One must remember Lu....the hydraulic system drives the flight controls including cyclic pitch control.....the speed trim system is electrical and operates off air speed generated signals sensed by the pitot static system.
The trim system acutators work together on each head.
The point of major stress on the Chinook is the aft vertical shaft....that is why the speed trims exist actually more than as a trim for fuselage leveling. There is a lot of bending moment applied to the aft vertical shaft much the same as in Bell 206/204/205/212 aircraft.
The Chinook is quite speed limited without a functioning speed trim system.
Lu...you reckon Frank Robinson had anything to do with the design of the Boeing-Vertol rotor head?
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At the risk of piling on, let me pile on....
The Chinook has normal cyclic control on each rotor, both lateral and longitudinal. The Chinook data that I have specifies that each rotor has almost 50 degrees of longitudinal cyclic capability (as measured in blade pitch angle). Lu is wrong, Chinooks have longitudinal cyclic.
Furthermore, with the drivel about spending more time at low speed somehow adding to stresses, Lu is also dead wrong. Not only is low speed the LOW stress regime, but even the ill-founded rumor mill that Lu owns can't invent bad component lives for helicopters that have good lives.
Give it a rest, Lu.
The Chinook has normal cyclic control on each rotor, both lateral and longitudinal. The Chinook data that I have specifies that each rotor has almost 50 degrees of longitudinal cyclic capability (as measured in blade pitch angle). Lu is wrong, Chinooks have longitudinal cyclic.
Furthermore, with the drivel about spending more time at low speed somehow adding to stresses, Lu is also dead wrong. Not only is low speed the LOW stress regime, but even the ill-founded rumor mill that Lu owns can't invent bad component lives for helicopters that have good lives.
Give it a rest, Lu.
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In response:
To: SASless and Nick
To: Nick in response to your post above:
Fore and aft cyclic movement introduces differential collective not cyclic.
QUOTE: Before Nick beats yer butt on this....what do you mean by your statement..."A Pilot cannot input forward cyclic."?
RESPONSE: If the pilot moves the cyclic stick laterally he will introduce left or right cyclic causing both rotors to move in the same direction. However if the cyclic is moved along the longitudinal axis the pilot introduces differential collective. With forward cyclic movement the forward rotor will decrease in collective and the rear rotor will increase in collective causing forward movement.
QUOTE: One must remember Lu....the hydraulic system drives the flight controls including cyclic pitch control.....the speed trim system is electrical and operates off air speed generated signals sensed by the pitot static system.
RESPONSE: This is true. When the helicopter reaches around 60-knots a signal is sent to the speed trim servo and it retracts or, gets shorter. This causes the swashplate(s) to dip down and pivots around the two hydraulic servos. This introduces forward cyclic in both rotors and the pilot can lower the collective thus reducing the stresses on the rotor system and the masts.
QUOTE: The trim system actuators work together on each head.
RESPONSE: Again this is true. If you are addressing the electrical trim servo both will retract when commanded or, extend when the helicopter drops below 60-knots.
QUOTE: The point of major stress on the Chinook is the aft vertical shaft....that is why the speed trims exist actually more than as a trim for fuselage leveling. There is a lot of bending moment applied to the aft vertical shaft much the same as in Bell 206/204/205/212 aircraft.
RESPONSE: This is very true however I could only address the rotorheads as I did not see the gear boxes being overhauled so I can’t talk about parts rejection on the gear boxes during overhaul.
QUOTE: Lu...you reckon Frank Robinson had anything to do with the design of the Boeing-Vertol rotor head?
RESPONSE: Frank was a young man when the rotorheads on the CH-47 and its’ predecessors were designed. Actually another Frank developed the concept for this rotorhead. Frank Piaseki. I believe it has the same design concept as the Sikorsky S-51.
For what it’s worth, my first ride in a helicopter was in a Piaseki HRP-1 back in 1949. Hey Nick where were you in 1949?
Why would Nick beat my butt? Now I know.
To: Nick in response to your post above:
Fore and aft cyclic movement introduces differential collective not cyclic.
QUOTE: Before Nick beats yer butt on this....what do you mean by your statement..."A Pilot cannot input forward cyclic."?
RESPONSE: If the pilot moves the cyclic stick laterally he will introduce left or right cyclic causing both rotors to move in the same direction. However if the cyclic is moved along the longitudinal axis the pilot introduces differential collective. With forward cyclic movement the forward rotor will decrease in collective and the rear rotor will increase in collective causing forward movement.
QUOTE: One must remember Lu....the hydraulic system drives the flight controls including cyclic pitch control.....the speed trim system is electrical and operates off air speed generated signals sensed by the pitot static system.
RESPONSE: This is true. When the helicopter reaches around 60-knots a signal is sent to the speed trim servo and it retracts or, gets shorter. This causes the swashplate(s) to dip down and pivots around the two hydraulic servos. This introduces forward cyclic in both rotors and the pilot can lower the collective thus reducing the stresses on the rotor system and the masts.
QUOTE: The trim system actuators work together on each head.
RESPONSE: Again this is true. If you are addressing the electrical trim servo both will retract when commanded or, extend when the helicopter drops below 60-knots.
QUOTE: The point of major stress on the Chinook is the aft vertical shaft....that is why the speed trims exist actually more than as a trim for fuselage leveling. There is a lot of bending moment applied to the aft vertical shaft much the same as in Bell 206/204/205/212 aircraft.
RESPONSE: This is very true however I could only address the rotorheads as I did not see the gear boxes being overhauled so I can’t talk about parts rejection on the gear boxes during overhaul.
QUOTE: Lu...you reckon Frank Robinson had anything to do with the design of the Boeing-Vertol rotor head?
RESPONSE: Frank was a young man when the rotorheads on the CH-47 and its’ predecessors were designed. Actually another Frank developed the concept for this rotorhead. Frank Piaseki. I believe it has the same design concept as the Sikorsky S-51.
For what it’s worth, my first ride in a helicopter was in a Piaseki HRP-1 back in 1949. Hey Nick where were you in 1949?
Why would Nick beat my butt? Now I know.
Lu,
The correct term for the effect of fore and aft cyclic stick movement is DCP...differential collective pitch. I assure you...the pilot can input forward cyclic whilst commanding Sheba to dance. ...along with rear cyclic and left cyclic and right cyclic and all sorts of combinations of cyclic.
The aft vertical shaft is in actuality not a part of the aft tranny...but rather acts as a "mast" to raise the aft rotor head to a height well above the plane of rotation of the forward head.
My first tandem rotor experience was an Air Force H-21....at Langley AFB in the early 60's....and resulted in a forced landing....it should have told me something...but then I had already shed a set of blades off a Bensen gyrocopter that was loosely afixed to the back of a pickup truck. After that...the H-21 ride was kinda tame. The bladeshed was not tame!
You left out a few words Lu....your concept was good...but your implementation fell short of the mark.
The correct term for the effect of fore and aft cyclic stick movement is DCP...differential collective pitch. I assure you...the pilot can input forward cyclic whilst commanding Sheba to dance. ...along with rear cyclic and left cyclic and right cyclic and all sorts of combinations of cyclic.
The aft vertical shaft is in actuality not a part of the aft tranny...but rather acts as a "mast" to raise the aft rotor head to a height well above the plane of rotation of the forward head.
My first tandem rotor experience was an Air Force H-21....at Langley AFB in the early 60's....and resulted in a forced landing....it should have told me something...but then I had already shed a set of blades off a Bensen gyrocopter that was loosely afixed to the back of a pickup truck. After that...the H-21 ride was kinda tame. The bladeshed was not tame!
You left out a few words Lu....your concept was good...but your implementation fell short of the mark.
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Lu, in 1949 I was doing what I still do, and what you forgot to do, LEARN.
The Chinook has BOTH DCP and cyclic to control longitudinal, and it uses both. It has cyclic Lu. Cyclic, Lu. Read that and say it slowly, you might then learn it. I doubt it, actually. Your next post should prove it, I think.
The Chinook has BOTH DCP and cyclic to control longitudinal, and it uses both. It has cyclic Lu. Cyclic, Lu. Read that and say it slowly, you might then learn it. I doubt it, actually. Your next post should prove it, I think.
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tandems tilt rotors etc...
Thanks folks for the feedback...was also wondering who of you out there have flown tilt rotors v-22, ba609 (test pilots/military) how different are they from conventional helicopters and how complex will the training transition process be for pilots when they are eventually used in the civilian world?
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ground effect
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I warn you that the more you think about the Chinook's levers and pulleys, the less confidence you will have to execute a given manoeuvre.
The Boeing TP who did my conversion lifted to the hover for me, then put his snake-skin boots up onto the dash and commanded: "spot turn around the aft head". Seeing my face, he said "don't even think about it, just do it". He appeared to go to sleep after that while I explored the incredible abilities of this machine. Gently does it at first though, and still wind until you know what to expect!
I don't doubt they're even more complicated now than they were then; but no, they're not much like a conventional helicopter to fly. But the training process was very pleasant (ground school excepted); as for civilian use, they aren't very passenger-friendly and accidents are nearly always BIG accidents. They are however brilliant load-lifters, nothing can touch them. Columbia are the absolute masters of this.
On the North Sea (1980's) they certainly scared the accountants and sometimes they scared the passengers; I loved them but usually tried not to think about the mechanical complexities too much, especially when airborne. Hope that's some help to you...
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I warn you that the more you think about the Chinook's levers and pulleys, the less confidence you will have to execute a given manoeuvre.
The Boeing TP who did my conversion lifted to the hover for me, then put his snake-skin boots up onto the dash and commanded: "spot turn around the aft head". Seeing my face, he said "don't even think about it, just do it". He appeared to go to sleep after that while I explored the incredible abilities of this machine. Gently does it at first though, and still wind until you know what to expect!
I don't doubt they're even more complicated now than they were then; but no, they're not much like a conventional helicopter to fly. But the training process was very pleasant (ground school excepted); as for civilian use, they aren't very passenger-friendly and accidents are nearly always BIG accidents. They are however brilliant load-lifters, nothing can touch them. Columbia are the absolute masters of this.
On the North Sea (1980's) they certainly scared the accountants and sometimes they scared the passengers; I loved them but usually tried not to think about the mechanical complexities too much, especially when airborne. Hope that's some help to you...
Senis Semper Fidelis
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Hi GE,
some time during 2001/02 I posed a similar question, the replies from the current flyers then, really did explain how these giants worked, and how to do most of the tasks in the book with them.
I stand in awe of such Helicopters and would dearly like to snitch a ride one day, even by clandestine means if needed, and then rewarding the crew afterwards !
Vfr
some time during 2001/02 I posed a similar question, the replies from the current flyers then, really did explain how these giants worked, and how to do most of the tasks in the book with them.
I stand in awe of such Helicopters and would dearly like to snitch a ride one day, even by clandestine means if needed, and then rewarding the crew afterwards !
Vfr