If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#5
|
|||
|
|||
"Blair Maynard" wrote in message
... On Wed, 2 Jul 2003 09:16:51 +1000, "The Raven" wrote: "Blair Maynard" wrote in message .. . I haven't looked much into the future design of the quad tiltrotor, if anybody else has, please post any info you can. A variant of the Osprey has been proposed with two sets of rotors. Consider it a CH-46 Osprey....... But a quadtiltrotor seems to be a promising project. I presume the engines in front and rear would be standard forward-facing props and I guess they would be offset so that the rear props would be pulling "fresh" air (as opposed to air which was already pulled by the front props). My question is why not configure the rear engines as pusher engines? Because you'd potentially be swinging the prop arc towards the loading ramp. Yes, a good design would minimise the possibility of resultant danger but it would be easier to avoid it in the first place by sticking with the same method as the Osprey. Of course, you then simplify design and support by utilising interchangeable assemblies etc rather than having "pusher" and "puller" variants of the engine/pivot/prop assemblies. Did the German Arrow aircraft not show that this was an effective combination? Not really, it wasn't a tilt rotor and didn't have to contend with a loading ramp at the rear. Wouldn't that somewhat alleviate the need to offset the engines/props? It would certainly space the props further apart. Disadvantages: I would guess the main obstacle would be the ground configuration of the aircraft. Since the rear props would be pushers, they would have to be pointing down for VTOL. Why? You could have them pivot upwards. I am assuming the rear pusher engines are mounted on the tips of a second wing positioned behind the first, probably slightly heigher than the first wing. Basically a biplane, but with the top wing set a significant distance behind the bottom wing. The rear engines are pushers, so if they rotated up they would be pushing up. This might help the Quad Tiltrotor to arrive at the ground, but not in one piece. Oops, I realised my gaff regarding pusher props and rotating up after posting it. I see no real benefit in using pushers, the engine is there so why not stick on the front as a traditional "puller". Picture an Osprey with pusher props on it (I am not saying that is the way it should be, it is just to help visualize it), instead of the current puller ones. The engine would be pointing backwards and pushing air behind it. Try imagining what would happen if you rotated those engines upward. They would push the plane downwards. Yup, agreed. Anyway, I will work on a drawing in a month. Thanks for everybody's input. You should see if you can hunt up pics of the Osprey four rotor concept. Perhaps that will help. And yes the rear props would come close to the cargo ramp. That is one of the disadvantages. One wonders if jets could be used, thus eliminating the prop...........Of course, you'd need a lot of thrust to lift it. But I am sure there are a few disadvantages in the current design which, i believe, would put rear puller engines partially in the wake of the front puller engines. They must lose a lot of power if much of the air that is running thru them has just been pulled by the front engines. Stick a normal rotor on the back of an tilt rotor? Give you a hybrid setup. Hmmmm, sounds more like a Rotodyne every minute. The Raven |
Thread Tools | |
Display Modes | |
|
|