Chinook & other tandem rotors discussions
Stilton, look at a photo of a Chook - the blades intermesh and are very unlikely to bump into each other. There is fore-aft movement available.
SASless, there was an interesting accident in Oz back in 75 or 76, the right engine turbine blew out, went through the centre pylon and lodged in the left engine. Along the way it cut through hydraulic and electrical lines. The Chook was carrying 3 bladders of water on a training run, and the pilots tried to pickle the load, being under severe OEI conditions.
But with no electrics, could not pickle load. Loadmaster tried to move through the cabin to do manual release, but slipped over in the gushing hydraulic fluid. Machine could not hold height, and they did a running landing on a flat field - the squishing of the water bladders was a lot more convenient in cushioning the impact than landing on the big truck they normally used.
On rundown, with no electrics, they could not use the sped trim to level the rotors, so the back rotor started to slice through the transmission tunnel and fuselage as it slowed down.
SASless, there was an interesting accident in Oz back in 75 or 76, the right engine turbine blew out, went through the centre pylon and lodged in the left engine. Along the way it cut through hydraulic and electrical lines. The Chook was carrying 3 bladders of water on a training run, and the pilots tried to pickle the load, being under severe OEI conditions.
But with no electrics, could not pickle load. Loadmaster tried to move through the cabin to do manual release, but slipped over in the gushing hydraulic fluid. Machine could not hold height, and they did a running landing on a flat field - the squishing of the water bladders was a lot more convenient in cushioning the impact than landing on the big truck they normally used.
On rundown, with no electrics, they could not use the sped trim to level the rotors, so the back rotor started to slice through the transmission tunnel and fuselage as it slowed down.
That must have been an exciting few minutes!
Actually they were very...very...very lucky and not for the reasons One would immediately assume.
We had a rash of C Model's with the L-11 Engine without Shot Peened Power Turbine Wheels....that when the Turbines came apart tried to saw the aircraft in half and while doing so....severed the Main Fuel Lines which had (if memory serves me right) about 430 PSI shoving lots of Jet Fuel through some very big Lines. To say that creates a very large fire instantaneously is some understatement.
One aircraft was about 300 feet off the ground and burnt in half before it hit.
For a while we had what we called C- versions....that were retrofitted with L-7C engines which the upgraded A's and regular B's used. That was a very good engine.
Actually they were very...very...very lucky and not for the reasons One would immediately assume.
We had a rash of C Model's with the L-11 Engine without Shot Peened Power Turbine Wheels....that when the Turbines came apart tried to saw the aircraft in half and while doing so....severed the Main Fuel Lines which had (if memory serves me right) about 430 PSI shoving lots of Jet Fuel through some very big Lines. To say that creates a very large fire instantaneously is some understatement.
One aircraft was about 300 feet off the ground and burnt in half before it hit.
For a while we had what we called C- versions....that were retrofitted with L-7C engines which the upgraded A's and regular B's used. That was a very good engine.
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What do you think of this idea:
To have coaxial tandem rotor for the chinook.
The objective is to reduce the rotor diameter, and hence footprint of the helicopter.
With coaxial and the reduced rotor diameter, the vertical gap between the levels of rotors in an coaxial can also be reduced with reduced drag.
Is this worth exploring?
To have coaxial tandem rotor for the chinook.
The objective is to reduce the rotor diameter, and hence footprint of the helicopter.
With coaxial and the reduced rotor diameter, the vertical gap between the levels of rotors in an coaxial can also be reduced with reduced drag.
Is this worth exploring?
Stilton,
The first few pages of this pub show in pictures how the different control inputs are used:
http://www.chinook-helicopter.com/Pu...Operations.pdf
48mb, but worth a look if you're interested in the Chinook
The first few pages of this pub show in pictures how the different control inputs are used:
http://www.chinook-helicopter.com/Pu...Operations.pdf
48mb, but worth a look if you're interested in the Chinook
Last edited by Watson1963; 18th Nov 2018 at 12:52.
To have coaxial tandem rotor for the chinook.
Ok, understood then, correct me if i'm wrong but neither rotor can tilt forward and aft like a 'conventional' helicopter or it would risk having the blades hit each other ?
Interesting that isn't an issue with the rotors tilting left and right.
So when you input forward cyclic the desired affect is achieved by increasing the pitch on the rear rotor and decreasing on the front and vice versa on rearward cyclic ?
Interesting that isn't an issue with the rotors tilting left and right.
So when you input forward cyclic the desired affect is achieved by increasing the pitch on the rear rotor and decreasing on the front and vice versa on rearward cyclic ?
A unique result of such a dynamic is upon arriving in a high nose high attitude and gross weight approaching the limits of power.....as you try to lower the nose by applying forward cyclic...you are reducing lift in the forward head and demanding more from the aft head that might not be available.....and the aircraft "Falls Through"....which can result in an unscheduled landing.
The various techniques of flying a Tandem Rotor design, once learned, facilitate takeoffs and landings that in a single rotor helicopter would just not work.
In the Chinook an aggressive combat landing with good visual reference, includes a sideways flair which uses the huge flat belly of the aircraft and the rotor system as "speed brakes".
Rotating the Aft Head outside of the disturbed air of the forward head enhances performance....and if is done with a fair bit of boot at the right time will actually accelerate the aft head transition into translational lift.
The one thing that always caused me to smile was the way the Chinook felt like a Truck driving over a street curb when encountering Thermals....the forward head hits the uprising air and moves up...followed by the aft head which then does the same thing a moment later.
Water landings are the real hoot.....as was pulling water skiers....but the last is a story for another time.
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The guys that I know that fly the hook love em, otherwise forget about it. Back when I was at Ft Drum they were trying to give away transitions into the aircraft and the poor guy tasked with going around asking wouldn't even stick his head in the door because he knew books and whatever was nearby would come flying at him for doing so.
I have told this story before:
To convert a Huey/Cobra/Blackhawk Pilot to a Chinook Pilot is simple.
During the first flight for the newbie....one does the old Fort Rucker Instructor Pilot chat while demonstrating maneuvers....the boring kind....and using the most boring tone and cadence of speaking....until the aircraft is light on fuel and you see the Student's eyes glazed over with boredom.
When you know he is no longer listening to you and is day dreaming about being anywhere but where he is....you keep up the boring chat and mention Confined Area Operations....giving the Fort Rucker chat until the aircraft is setting on the ground in the confined area.
Then you begin the Fort Rucker explanation of how to do a Confined Area Takeoff....and at some point the Student gets to say "Clear Right and Up!" as part of the procedure....but he is by now....very...very...very bored.
Then you apply Maximum Takeoff Power....right to the limit....rapidly......and ascend vertically....with your Left Foot stuck well out into the Chin Bubble causing the aircraft to rotate about its vertical axis.....climbing like a Rocket....with some pretty impressive "G" forces due to the acceleration upwards.
As the Student tries to get his chin out of his lap....and finally gets to where he can see out of the Windscreen.....by the time you stop the climb and rotation at 3,000 feet AGL.....you have created a Chinook Pilot!
The sheer power and performance of an empty Chinook is mind boggling!
The rest of the demo is to descend vertically turning to the right....back into the Confined Area and let the new guy try that takeoff for himself.
They are then are properly "hooked".
To convert a Huey/Cobra/Blackhawk Pilot to a Chinook Pilot is simple.
During the first flight for the newbie....one does the old Fort Rucker Instructor Pilot chat while demonstrating maneuvers....the boring kind....and using the most boring tone and cadence of speaking....until the aircraft is light on fuel and you see the Student's eyes glazed over with boredom.
When you know he is no longer listening to you and is day dreaming about being anywhere but where he is....you keep up the boring chat and mention Confined Area Operations....giving the Fort Rucker chat until the aircraft is setting on the ground in the confined area.
Then you begin the Fort Rucker explanation of how to do a Confined Area Takeoff....and at some point the Student gets to say "Clear Right and Up!" as part of the procedure....but he is by now....very...very...very bored.
Then you apply Maximum Takeoff Power....right to the limit....rapidly......and ascend vertically....with your Left Foot stuck well out into the Chin Bubble causing the aircraft to rotate about its vertical axis.....climbing like a Rocket....with some pretty impressive "G" forces due to the acceleration upwards.
As the Student tries to get his chin out of his lap....and finally gets to where he can see out of the Windscreen.....by the time you stop the climb and rotation at 3,000 feet AGL.....you have created a Chinook Pilot!
The sheer power and performance of an empty Chinook is mind boggling!
The rest of the demo is to descend vertically turning to the right....back into the Confined Area and let the new guy try that takeoff for himself.
They are then are properly "hooked".
Correct me if I err, SAS, but a pilot gets signed off in a CH-47 after he/she can demonstrate credible taxi 360’s with four wheels on the ground, without using the left rear power steering ( just unlocking the swivel locks ) and without knocking the droop stops off. oops, now that I think about it, once the rear left power steering appeared, one had to use it.
Last edited by JohnDixson; 9th Feb 2019 at 12:56. Reason: add’l info
