Question for Tiltrotor pilots,mechanics and engineers
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Question for Tiltrotor pilots,mechanics and engineers
I've been watching any and all video of the AB609 and Osprey....thanks Youtube!
Why do the engines have to be in the nacelles coupled directly to the proprotors? Can they not be mounted elsewhere with shafts along the wings to the proprotors?
The torque required for the jackscrew to rotate the nacelle would be less due to reduced weight of the nacelle? Help me out all you mech. and aero. engineers!
The tiltrotor concept is amazing, but looking at the design, my brain sees inefficiencies!
Am I out to lunch on this!
Appreciate feedback from an engineering perspective.....Nick et al.
DK
Why do the engines have to be in the nacelles coupled directly to the proprotors? Can they not be mounted elsewhere with shafts along the wings to the proprotors?
The torque required for the jackscrew to rotate the nacelle would be less due to reduced weight of the nacelle? Help me out all you mech. and aero. engineers!
The tiltrotor concept is amazing, but looking at the design, my brain sees inefficiencies!
Am I out to lunch on this!
Appreciate feedback from an engineering perspective.....Nick et al.
DK
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Common transmission?
I wondered the same thing, and as far as redundancy with OEI, would it not be easier to mount both engines in the center fuselage and use a combining gear box just like a standard twin engine helicopter rather then have to run drive shafts back and forth through each wing. If I understand correctly the V22 can power both prop rotors off of one engine, seems like a lot of extra work to run the drive shafts that way.. to me anyway..
Inquiring minds want to know!
Inquiring minds want to know!
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....and the passengers could be mounted....at the ends of the wings? 
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You loose monster amounts of power through drieveshafts and assosiated gearboxes...
Plus its more expensive to buy and maintain if you have lots of driveshafts and gearboxes...
There are IMHO no benefits to moving the engines anywhere else on the airframe so why overcomplicate things..
Plus its more expensive to buy and maintain if you have lots of driveshafts and gearboxes...
There are IMHO no benefits to moving the engines anywhere else on the airframe so why overcomplicate things..
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If the engines were mounted centrally, a substantial "propellor gearbox" would still be required on each wing, in addition to gearboxes to turn the drive through 90 degrees along the wings. A combining gearbox would also be required to couple both engines together. Would there be much weight saving at all?
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Don't forget tilt rotor is a category A machine. If one donkey quits, half of the 30 min/ 2 min / 30 sec power goes down that crossfeed shaft. It needs to be cat A for those marginal ops - like transition... 
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To use a driveshaft transmission instead of direct drive you cause yourself at least 3 headaches that direct drive saves you.
First: with the addition of driveshafts, and gearboxes/diffs you create a nasty weight issue which you wouldn't have otherwise, and with the added weight you give yourself more work when you calculate C.O.G.
Second: cost. More kit, more exspense through design/development/manufacture/shipping etc.
Third: reliabality and maintainance costs. With the addition of gearboxes and driveshafts you have more to worry about going wrong!
Another good reason, as mentioned by an earlier post, is power consumption. Direct drive is far more efficient transfer of power.
First: with the addition of driveshafts, and gearboxes/diffs you create a nasty weight issue which you wouldn't have otherwise, and with the added weight you give yourself more work when you calculate C.O.G.
Second: cost. More kit, more exspense through design/development/manufacture/shipping etc.
Third: reliabality and maintainance costs. With the addition of gearboxes and driveshafts you have more to worry about going wrong!
Another good reason, as mentioned by an earlier post, is power consumption. Direct drive is far more efficient transfer of power.
Last edited by teej5536; 10th Dec 2007 at 00:17. Reason: Post originally made using mobile resulting in too many spelling/grammar errors. (that is not to say they are all corrected :-P )
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Good input guys. There still has to be a driveshaft along the wing (in the present 609/Osprey a/c) because as stated, the loss of one engine still allows the good engine to turn the affected/relative proprotor on the other side of the machine. In my messed up mind....take a Chinook a/c and fly it sideways??? Engines in the "middle"...resultant lift at either end. I am speaking specifically about engine and drivetrain in this example.
