Kaman question
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Charles Kaman has his company, Kaman Aircraft, in Bloomfield, Connecticut USA. He developed the "syncromeshing" helicopter back in the 1940s which required no tail rotor. Called the "Husky" It was a popular helicopter used in fire suppression and as an air ambulance. Kaman also pioneered the very first radio controlled helicopter.
Today they make components, still make the "K-Max" single place lifting helicopter, as well as some parts for the space program. They also developed and made Ovation Guitars which were recently sold to Fender.
Hope that helps!
Rome
Today they make components, still make the "K-Max" single place lifting helicopter, as well as some parts for the space program. They also developed and made Ovation Guitars which were recently sold to Fender.
Hope that helps!
Rome
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They also make MD fuselages. The Seasprite was unusual in that it had servo flaps on the rotorblades and an automatic tracking system on the rotorhead.When the cyclic was opperated in flight with hydraulics off you could hardly tell the difference.
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Heli-kiwi,
I believe you are saying that the use of 'aerodynamic' servo-flaps require less control force than if the craft had been equipped with 'conventional mechanical' flight controls. This raises a question that you may be able to comment on.
Does the use of the 'aerodynamic' servo-flaps result in a slower response to a change in the cyclic control than would be obtained from 'conventional mechanical' flight controls?
Dave
I believe you are saying that the use of 'aerodynamic' servo-flaps require less control force than if the craft had been equipped with 'conventional mechanical' flight controls. This raises a question that you may be able to comment on.
Does the use of the 'aerodynamic' servo-flaps result in a slower response to a change in the cyclic control than would be obtained from 'conventional mechanical' flight controls?
Dave
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Dave, light fixed wing use a servo-flap as elevator trimmers. The fact that airspeed is so stable in gusty conditions says that response is fast. If there was a delay, for helo applications, some swashplate lead could be added. If response time was a concern the servos can be designed in as part of main controls for flight load relief.
To be honest it suprises me it is not more common, since it is simple light and effective...
To be honest it suprises me it is not more common, since it is simple light and effective...
Last edited by Graviman; 13th Apr 2008 at 09:10. Reason: To avoid misunderstanding with servos.
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Mart,
Preamble: It is assumed that we are talking about a servo-flap and not a servo mechanism
Trivia: Kaman's first full-scale rotor. Note the leading and trailing tabs.
The servo-flap (elevator trimmer) on an airplane is used to adjust for the location of the craft's center of gravity. It is used to eliminate any longitudinal force on the pilot's control 'stick'. It is normally only adjusted when the pilot changes the craft's attitude, such as climb, cruise, slow descent.
You are probably correct in that the servo-flap control of a helicopter may reduce perturbation induced vibrations; in the craft and in the cyclic stick.
The question in my previous posting relates to the relatively slow response time of helicopters. IMO, the servo-flap control adds an addition function (delay) in the chain of activities between the pilot's action and the aerodynamic response of the rotor.
Dave
Preamble: It is assumed that we are talking about a servo-flap and not a servo mechanism
Trivia: Kaman's first full-scale rotor. Note the leading and trailing tabs.
The servo-flap (elevator trimmer) on an airplane is used to adjust for the location of the craft's center of gravity. It is used to eliminate any longitudinal force on the pilot's control 'stick'. It is normally only adjusted when the pilot changes the craft's attitude, such as climb, cruise, slow descent.
You are probably correct in that the servo-flap control of a helicopter may reduce perturbation induced vibrations; in the craft and in the cyclic stick.
The question in my previous posting relates to the relatively slow response time of helicopters. IMO, the servo-flap control adds an addition function (delay) in the chain of activities between the pilot's action and the aerodynamic response of the rotor.
Dave
Dave and Gravy - a bit of light reading for you - TEF's
Saw this thing at ECD a few years back. Next trick will be to remove the Pitch links!
Saw this thing at ECD a few years back. Next trick will be to remove the Pitch links!
Just to clarify that comment that Kaman make MD fuselages - they do not.
They used to but caught a severe financial cold when MD plumetted into trouble. Lynn Tilton paid off the debts and took fuselage production to a 'car factory in Mexico'....
They used to but caught a severe financial cold when MD plumetted into trouble. Lynn Tilton paid off the debts and took fuselage production to a 'car factory in Mexico'....
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PANews - thanks for your correction. Dave - I believe the servo flap system results in the same cyclic control response, The Swashplate setup is the same but there are a series of Stainless steel 1/4"in rods throughout the system that run from the swashplate above the cabin roof all the way through the blades and to the servo flap. On the ground the blade will lead and lag, flap and change angle of attack of its own free will, Once the blade is flying the servo flap will dictate exactly how the blade will fly.
Tracking is detected via a fuselage mounted sensor which tells one of the 3 electric motors on the head to adjust a cam for whichever blade requires a change in AoA.
I found the Seasprite to be a pretty complex type of machine to work on but overall reliability was pretty good considering.
Those GE T700s can not be beaten for reliability either.
Tracking is detected via a fuselage mounted sensor which tells one of the 3 electric motors on the head to adjust a cam for whichever blade requires a change in AoA.
I found the Seasprite to be a pretty complex type of machine to work on but overall reliability was pretty good considering.
Those GE T700s can not be beaten for reliability either.
Last edited by Heli-kiwi; 13th Apr 2008 at 13:21.
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RVDT, that does look very interesting. This approach has a lot of potential.
Dave, what i mean is that the response is very quick. Then again the longitudinal response of any elevator last fixed wing is not fast (I've wondered about altering main wing AOA or camber (flaps), like a canard).
If response was an issue you could keep a standard blade pitch control mech. The tip servo-flaps would be connected to the mech to compensate for varying pitch moments, like a reflex aerofoil section. This would allow the aerofoil good Cl/Cd characteristics but without the need for hydraulics. The system could be active, using pitch link forces for feedback (although getting power/signal across rotating/static interface would be a challenge).
Heli-Kiwi, that system sounds pretty good with its automatic track. I wonder why it is not more popular? There could be some flap angle feedback in the mech which would explain why the servos appear to have a mind of there own on the ground.
Originally Posted by Dave Jackson
You are probably correct in that the servo-flap control of a helicopter may reduce perturbation induced vibrations; in the craft and in the cyclic stick.
If response was an issue you could keep a standard blade pitch control mech. The tip servo-flaps would be connected to the mech to compensate for varying pitch moments, like a reflex aerofoil section. This would allow the aerofoil good Cl/Cd characteristics but without the need for hydraulics. The system could be active, using pitch link forces for feedback (although getting power/signal across rotating/static interface would be a challenge).
Heli-Kiwi, that system sounds pretty good with its automatic track. I wonder why it is not more popular? There could be some flap angle feedback in the mech which would explain why the servos appear to have a mind of there own on the ground.
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RVTD and Hei-Kiwi;
Thanks for the information.
Mart,
The Kaman helicopters (at least the intermeshing ones) have very soft rotors, and this is necessary for a servo-flap to act as a primary flight-control. The increasing rigidity of modern rotors may preclude the use of servo-flaps for primary control.
To my knowledge, current R&D in servo-flap technology is only for reduced noise and vibration.
Now if some company with deep pockets would like to fund this......
Dave
Thanks for the information.
Mart,
The Kaman helicopters (at least the intermeshing ones) have very soft rotors, and this is necessary for a servo-flap to act as a primary flight-control. The increasing rigidity of modern rotors may preclude the use of servo-flaps for primary control.
To my knowledge, current R&D in servo-flap technology is only for reduced noise and vibration.
Now if some company with deep pockets would like to fund this......
Dave
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Dave, having given the design of servo-flaps a small amount of thought:
I would say that the response lag will depend on the blade inertia about the pitch axis, the distance of flap behind this axis, and the linkage gearing for flap_pitch/blade_pitch. The other way to think about it is that the servo-flap/blade/linkage system will have a natural resonance, albeit likely to be well damped. If the servoflap/blade/linkage system natural frequency is sufficiently high above the rotor rotation frequency then the response will not be an issue. It should be possible to determine how much swash plate lead is required to correct for the servo-flap lag.
I think this system could be made to work with modern rigid rotors. I suspect that it works better with softer rotors because the servo-flap has an immediate effect on the tip, without the inertia of the rest of the blade causing lag. The vibration suppresion systems should also benefit a reduction in hydraulic dependancy too.
Now if this tip control system was used in combination with root pitch links...
I would say that the response lag will depend on the blade inertia about the pitch axis, the distance of flap behind this axis, and the linkage gearing for flap_pitch/blade_pitch. The other way to think about it is that the servo-flap/blade/linkage system will have a natural resonance, albeit likely to be well damped. If the servoflap/blade/linkage system natural frequency is sufficiently high above the rotor rotation frequency then the response will not be an issue. It should be possible to determine how much swash plate lead is required to correct for the servo-flap lag.
I think this system could be made to work with modern rigid rotors. I suspect that it works better with softer rotors because the servo-flap has an immediate effect on the tip, without the inertia of the rest of the blade causing lag. The vibration suppresion systems should also benefit a reduction in hydraulic dependancy too.
Now if this tip control system was used in combination with root pitch links...
