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Blended Wing Bodies

Fluff

CLEARANCE: Secret
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The only one which makes any sense in the present context is moving the engines outboard. I look forward to your analysis of the all-engines-out-on-one-side flight condition.
Clearly your understanding of 'little' needs some calibration.

You mean one engine out, on one side, again, seems to work fine on a 757 etc.
May I suggest that your analysis needs to be a little more in-depth.
The 757 has a rudder with a long moment arm. That gives it high control authority. A BWB in the engine-out condition does not have that luxury. Precisely why I suggested you analyse the condition. Let me give you the general idea.

Say 40 M span, twin engines at 50%.
Conventional rudder; moment arm ca. 25 M in all conditions, thrust asymmetry 10 M. Rudder sideforce ca 40% single-engine thrust. Don't know the span of the 757 but very practicable.
BWB with drag rudders mean 90% span. One side out, drag rudder moment arm on the working side ca. 8 M. This has to counteract the drag of the whole of the rest of the airframe on the far side of the working engine, which has a mean moment arm from the engine ca. 15 M. So the drag rudder must exert twice the drag of the rest of the airframe - all to be overcome by one engine's worth of thrust! Even if sufficient emergency thrust is available to keep airspeed above the stall, the rudder force is 67% of emergency thrust and range is utterly knackered. Not so very practicable, especially on the trans-oceanic routes which are the main market.

Seriously, it is a well-known problem with all tailless multi-engine proposals; they have to keep the engines well inboard.

And sadly, flinging personal insults at either me or the rest of the world will not improve your numbers.
I'd be expecting the aircraft designer to be covering the control influence issues, thats his job.

I'm not sure where a personal insult was sent - perhaps your a little sensitive?

I suggested moving them a little out, to align with freight, now you feel they need to be well inboard? We both seem a little imprecise? And I didnt state tailless, you did.

Another suggestion, as this is clearly going to take a few years, is that these will end up as electric powered, so this seems to favour a large number of relatively small engines, so one out isnt going to be such an ordeal.
 

hesham

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From; Аэрокосмическое обозрение 2020-03.
 

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