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Reposition airliner engines

 Place airliner engines above the wing
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I understand that lift comes at least in part from the pressure differential between the top and bottom surface of an aircraft's wing. My understanding is that air above the wing is forced by the curved upper surface of the wing to travel further and faster thereby decreasing its pressure and setting up the differential with the slow moving dense air at the lower surface. My half-baked idea is to put an airliner's jet engines above and to the front of the wing. This would blow hot fast moving air over the top of the wing, thereby increasing the pressure differential between the upper and lower surfaces and giving more lift. Any thoughts?
—dave_dale, Aug 20 2004

called "upper surface blowing" http://www.globalse...8-AC80-0613-3_a.jpg
"The aircraft is a highly modified De Havilland C-8A Buffalo consisting of a new swept, supercritical wing and 4 YF-102 geared, high-bypass-ratio turbofan engines mounted in an "over-the-wing" installation. Upper surface blowing is used to generate high-lift coefficients to provide low approach speeds and steep approach path angles. [and smaller noise footprint]" [FarmerJohn, Oct 04 2004]

Distributor wing airplane http://www.razak.co...r/feasibility.shtml
Designed for cropdusting, a few were made by cessna. [destructionism, Oct 04 2004]

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       //giving more lift//
How do you land?
—Amos Kito, Aug 20 2004
   

       Unless you plan on using engines like those in [FarmerJohn]'s link, it would probably fly until the wings melt off. Or rupture gas tanks. Tests have been done with "blown flaps" on piston engines, see link.
—destructionism, Aug 20 2004
   

       I was wondering what that was in the foreground within provided link (I thought it was a pirates peg leg)
—skinflaps, Aug 20 2004
   

       [contracts] Did you notice anything else about the photo that might hint at why there could be a fire hose at the ready? (Not that that is what that thing is, for sure)
—bristolz, Aug 20 2004
   

       I see a helicopter, and people running toward what appears to be a port-o-john, which is near the lawn chair. Is this like one of those ink-blot tests?
—Worldgineer, Aug 20 2004
   

       If it is a firehose nozzle, that makes sense - they're always out on the flight deck of an aircraft carrier. Makes it easier to fight the fires caused when Tom Cruise tries to land.
—shapu, Aug 20 2004
   

       Or Mr. Bush. "What do you mean I can't drive? I'm the president! Plus, look at this flight outfit I'm wearing!" "um, yes sir" (tightens safty belt)
—Worldgineer, Aug 20 2004
   

       I've photo shopped it, and am now playing spot the difference between the two.I still say it's a pirates peg leg.
—skinflaps, Aug 20 2004
   

       Baked, as shown by [FarmerJohn]'s link. Aerodynamically, it works well at maintaining a high Cl at low speeds, but it introduces problems of its own. There's the obvious heat issues. There's the issue of turbulence and flow interference during cruise. There's the potential of sudden loss of lift accompanying a decrease or loss of power.   

       There's also the structural issue of holding a heavy vibrating mass up above the wing. With a conventional under-wing engine, the forward angled placement causes the overall loads in the strut during cruise to be roughly aligned with the structural elements, placing them mostly in tension. Tension elements can be made very light. Placing an engine forward and above the wing as in the C8-A requires a much beefier (and therefore heavier) engine support structure. Also, in the event of a catastrophic engine failure, the fuselage is no longer shielded by the wing. Putting an engine up that high also makes maintenance more difficult.   

       It's conceptually interesting, but it's just not practical. Bone.
—Freefall, Aug 20 2004
   

       I thought this idea would relocate the eingein even closer to the fusulage...
—my-nep, Aug 20 2004
   

       Wrong. The airplanes fly because of the propelas. Those things that go put-put-put, like in the helicop. (helicop = twisted cop). Even the jet aerolinas have propelas hidden inside the motors, I've seen. No propelas turning, no fly. But placing the propelas over the wings is better, look at the Osprey. All that air washes over the wing stubs and produce turbulence and magnetic remanence of the histeresys. Even Mary Poppings had a propela-umbrela. See?.
—finflazo, Aug 20 2004
   

       Good summaries by [FJ] and [Freefall]. At cruise speeds, the wing doesn't need the help, and the great majority of the lift is Newtonian anyway. The wing is designed for greatest efficiency at cruise (where it spends most of its flight time) and then adjusted as necessary for the realities of low speed departure and approach.   

       This idea has been played with for specialized applications (heavy lifting, short fields) but I think the disadvantages have so far won out.
—bpilot, Aug 20 2004
   

       Ideas intent on getting more lift out of an airliner kind of miss the point. Lift is easy. Efficiency is the more relevant problem. You go farther with more stuff if you can carry less fuel to get there.
—zigness, Aug 20 2004
   

       Thanks very much for your responses! This came out of an argument with a fluid dynamicist who didn't like my (admittedly random) idea without being able to really say why. I'll refer him here. I guess I really should have tried a pilot/engineer for these kind of sensible responses! Cheers, dave
—dave_dale, Aug 21 2004
   


 

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