posted on Jul, 27 2006 @ 03:35 AM
Modern passenger jets seem to have two options for engine placement: tail mounted below a T-tail, or hung in nacels below the main wings. The two
alternative designs offer tradeoffs, with wing-mounted engines beeing the universal choice for larger aircraft, while tail-mounted engines are favored
by smaller business jets.
As I understand it, Tail mounted engines require additional plumbing (fuel lines) and increased structure to support the weight and thrust they
generate. And they require T-tails, which are heavier and more complex to build. However smaller craft need to mount their engines high enough fo
avoid sucking up runway debreis (FOD). And the high tail helps with pitch control, which is needed with shorter aircraft.
Larger commercial planes can keep their engines higher above runway, and mounting the engines to the wings reduces the structural requirements - it's
near the fuel supply and wings/landing gear that support it's weight. And you can use a low-mounted horizontal stabalizer (lighter, less
The trade-off seems to occur at the ~100 passenger limit; anything significantly below mounts the engines in the tail, anything bigger will mount the
engines to the wings (with some exceptions, of course).
The new Hondajet offers an interesting alternative: mounting the engines over the main wing. This isn't the first jet to do so, but it's interesting
as it offers wing-mounted engines in a jet that would normally be too close to the ground to use them. Honda claims the design offers a 5% fuel
efficieny increase. It seems like an ideal solution, which makes me wonder if there aren't other tradeoffs involved that make the design less
favorable(i.e. why we haven't seen it used more often).
So... I think thats the end of my ramblings. I guess this is where I say, "what does everyone els think?"
Link to the Hondajet: Link
P.S. Of particular note, both Boeing and Airbus are working on their 737/A320 replacements. They're both (reportedly) waiting for a high-bipass (high
efficiency, low noise) engine that can fit below the wings of a smaller jet. Mounting the engines over the wings seems like one possible solution to
(or short-cut around) the problem...