A345 - engine mounting
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A345 - engine mounting
Question from an enthusiast...
At LHR tonight, and seen the Arik A345 taxi by. It may have been an optical illusion, but the two inboard engines seem to be canted slightly forward in comparison to the outboard engines. Checked a few pics on the web, and the same effect appears to be present. Am I seeing thngs or is this correct? Does this correct in flight as the wing lifts?
Just curious...
At LHR tonight, and seen the Arik A345 taxi by. It may have been an optical illusion, but the two inboard engines seem to be canted slightly forward in comparison to the outboard engines. Checked a few pics on the web, and the same effect appears to be present. Am I seeing thngs or is this correct? Does this correct in flight as the wing lifts?
Just curious...
Last edited by NWSRG; 21st Mar 2013 at 09:07.
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At LHR tonight, and seen the Arik A345 taxi by. It may have been an optical illusion, but the two inboard engines seem to be canted slightly forward in comparison to the outboard engines. Checked a few pics on the web, and the same effect appears to be present. Am I seeing thngs or is this correct? Does this correct in flightbas the wing lifts?
Not sure exactly what you mean by 'canted forward' but the inboard engines are about 1.5 degrees nose down relative to the outboards when on the ground. In flight the wing twist (which goes with the bending) brings them into line.
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Thanks Owain,
Eyesight one of the few things still working!
Seems counter-intuitive that the inboard engines are the ones that 'drop' on the ground. I can see how the wing lifting might pull up the outer engines, but it seems strange that the inboards would lift while the outers don't...but that's maybe why I'm an electrical rather than structures engineer!
Eyesight one of the few things still working!
Seems counter-intuitive that the inboard engines are the ones that 'drop' on the ground. I can see how the wing lifting might pull up the outer engines, but it seems strange that the inboards would lift while the outers don't...but that's maybe why I'm an electrical rather than structures engineer!
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In flight the wing twist (which goes with the bending)
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but it seems strange that the inboards would lift while the outers don't
On a swept wing the lift of the outer bits lies aft of the flexural axis of the inboard bits. Consequently the outer wing exerts a torque on the inner bits tending to produce nose down twist. The inboard half (say) of the wing is so stiff that this twist is pretty small, but as you move outboard the bending and torsional stiffnesses of the wing get smaller and more liable to bending and twisting deflections. Adding winglets makes it worse.
In flight the wing twist (which goes with the bending)
Last edited by PJ2; 22nd Mar 2013 at 14:50.
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PJ2
Yes that's right. There would indeed be a minor difference depending on TOW or, for that matter, as fuel is burned off in cruise, but those are small differences.
Now I come to think of it, the downward bending on the ground due to fuel in the outboard tanks would presumably have the opposite effect ....
So the outboard engine's "angle of incidence", (so to speak!) reduces as the wing bends, to become approximately the same as the inboard engine's? Would there still be a minor difference between the two depending upon take-off weights?
Now I come to think of it, the downward bending on the ground due to fuel in the outboard tanks would presumably have the opposite effect ....