Blended-wing Airliner

Tina wrote in
oups.com:

Bertie, the issue isn't the degree of bank, but rather how fast you
roll the airplane into the bank, that would make a px well off center
feel the gs Dave mentioned. For example, if you had Mx sitting on a
wing tip and you wanted to drop the wing out from under him, you'd
bank into that wing quickly. If you banked slowly he'd not feel
himself grow lighter, but if you did it sharply you near the center
line wouldn't feel much but you could yank that tip down at better
than 1 G even when going to a bank limit of 20 degrees. That was the
issue Dave addressed.

The question was, when you start to bank into a turn, how quickly do
you establish the bank angle? I'm guessing you go from wings level to
20 degrees in a slow count of 3 or 4 -- not too much acceleration --
but would appreciate a guesstimate from some who does it for a living.


Well, even in a conventional airplane you try to do it as smoothly as
you can Actually, you try to do that in any kind of flying no matter how
outwardly frantic it may appear! But I can't see it being significant to
pax comfort unless they were out at the wingtips. In any case the
aircraft would almost certainly be fly by wire anyway so the
opportunities we'd have to raise your red wine out of your glass!


Given a cabin width of fifty feet and a rate of rotation of, say, ten
degrees a second, you'd be moving, you'd move about four or five feet in
a second. You'd hardly feel it at all if the rate was introduced
smoothly.
In fact, you'd be closer to the CG than you would be if you sat in the
nose or tail of any other modern jet whilst it was making a pitch
change.


Bertie

Bertie, I'm not too good at explaining this. It isn't the angle of
banking that matters but how fast you roll the airplane on its axis to
to get to the back angle that matters. We've gone thru the arguement
that one can rotate an airplane around its roll axis 360 degrees and
not have someone on that axis feel anything but 1 G into the seat.
This is different -- someone else ran the numbers to show what happens
to the local G sense as a function of how fast the airplane
accelerated into the roll -- we'd have called that alpha with two dots
above it back in the long hand calculus days. Accelerate into the bank
angle too quickly and if I was sitting far from the roll axis you'd
lift the wine from my glass. You would, I promise, need a locked
cockpit door if you did that.

I'd be at whining over spilt wine.

OK, put the stun gun away, or aim it over there at the other widebody
and frequent poster here.



On Oct 19, 2:58 pm, Bertie the Bunyip wrote:
Tina wrote groups.com:

Bertie, the issue isn't the degree of bank, but rather how fast you
roll the airplane into the bank, that would make a px well off center
feel the gs Dave mentioned. For example, if you had Mx sitting on a
wing tip and you wanted to drop the wing out from under him, you'd
bank into that wing quickly. If you banked slowly he'd not feel
himself grow lighter, but if you did it sharply you near the center
line wouldn't feel much but you could yank that tip down at better
than 1 G even when going to a bank limit of 20 degrees. That was the
issue Dave addressed.

The question was, when you start to bank into a turn, how quickly do
you establish the bank angle? I'm guessing you go from wings level to
20 degrees in a slow count of 3 or 4 -- not too much acceleration --
but would appreciate a guesstimate from some who does it for a living.

Well, even in a conventional airplane you try to do it as smoothly as
you can Actually, you try to do that in any kind of flying no matter how
outwardly frantic it may appear! But I can't see it being significant to
pax comfort unless they were out at the wingtips. In any case the
aircraft would almost certainly be fly by wire anyway so the
opportunities we'd have to raise your red wine out of your glass!

Given a cabin width of fifty feet and a rate of rotation of, say, ten
degrees a second, you'd be moving, you'd move about four or five feet in
a second. You'd hardly feel it at all if the rate was introduced
smoothly.
In fact, you'd be closer to the CG than you would be if you sat in the
nose or tail of any other modern jet whilst it was making a pitch
change.

Bertie

Tina wrote in
oups.com:

Bertie, I'm not too good at explaining this. It isn't the angle of
banking that matters but how fast you roll the airplane on its axis to
to get to the back angle that matters.


Yes, I understood that and that was what I was adressing. If you were 25
feet from the roll axis ant the rol rate of 10 deg per second was
introduced smooothly, you'd rotate a bit under five feet in that second,
less than you would if the airplane was rotated on it's pitch axis at
even a third that rate if you were parked in the front or rear of the
airplane.




We've gone thru the arguement
that one can rotate an airplane around its roll axis 360 degrees and
not have someone on that axis feel anything but 1 G into the seat.
This is different -- someone else ran the numbers to show what happens
to the local G sense as a function of how fast the airplane
accelerated into the roll -- we'd have called that alpha with two dots
above it back in the long hand calculus days. Accelerate into the bank
angle too quickly and if I was sitting far from the roll axis you'd
lift the wine from my glass. You would, I promise, need a locked
cockpit door if you did that.

I'd be at whining over spilt wine.

OK, put the stun gun away, or aim it over there at the other widebody
and frequent poster here.


Well, I have only Anthony's frequent postings to weight loss froups as
evidnce of his widebodiedness, but..


Bertie

"Tina" wrote ...
Bertie, I'm not too good at explaining this. It isn't the angle of
banking that matters but how fast you roll the airplane on its axis to
to get to the back angle that matters. We've gone thru the arguement
that one can rotate an airplane around its roll axis 360 degrees and
not have someone on that axis feel anything but 1 G into the seat.
This is different -- someone else ran the numbers to show what happens
to the local G sense as a function of how fast the airplane
accelerated into the roll -- we'd have called that alpha with two dots
above it back in the long hand calculus days. Accelerate into the bank
angle too quickly and if I was sitting far from the roll axis you'd
lift the wine from my glass. You would, I promise, need a locked
cockpit door if you did that.

I'd be at whining over spilt wine.


Just my two cents. I'd agree that any pilot would fly smoothly and avoid
jerking the controls. The issue is, as far as I can see, more about
turbulence-induced roll motion such as in windshear and wake turbulence. In
those situations there might occur large roll accelerations, both when the
gust hits and when the pilot has to correct quickly with large control
deflections.
I found a B767 pilot report which stated:

" We entered an arbitrary working area into the Honeywell Pegasus FMC and
set up for some flight maneuvers. The first was a check of roll rate in
bank-to-bank rolls from 30 degrees to 30 degrees at ½ wheel deflection.
Flying the clean airplane at 350 knots, bank-to-bank took 4 seconds, for a
roll rate of 15 degrees per second. Here is where a sharp control input
initiated an aeroelastic response from the airframe. A later check of this
same maneuver with flaps 30 at Vref=136 gave a bank-to-bank time of 6
seconds, or a roll rate of 10 degrees per second. This excellent response at
slow speed in the landing configuration is another indication of the
exceptional handling qualities of this airplane."

So in the first case the average roll rate was 15 degrees / sec. I guess
someone with fresher math / physics knowledge can estimate the instantaneous
start/stop g-forces from those numbers. To me this looks like your wine
might stay in the glass, but Mx at the wingtip may have a hard time hanging
on.

"Snowbird" wrote in
i.fi:


"Tina" wrote ...
To me this looks
like your wine might stay in the glass, but Mx at the wingtip may have
a hard time hanging on.




That would be a good thing.

Bertie

Larry Dighera wrote:
In the late 40s, when Northrop was building the YB-49 jet powered flying
wings, they put together a mock up of a civilian airliner version. I
remember seeing a promo film about it, which can probably be found floating
around the web somewhere.

Would that be this one?: http://www.youtube.com/watch?v=bR7gepoAf4E
or http://www.youtube.com/watch?v=jSBjiFtfkFg

Photographs:
http://commons.wikimedia.org/wiki/No...-49?uselang=de

Those are the military versions. The one I'm talking about is a ~10 min.
promotional film put together by Northrop, using the civilian airliner mockup
and showing off the "advantages" of the flying wing airliner of the future.

I might have it somewhere in my archives. If I locate it, maybe Jay can
host it on his site.

John Galban=====N4BQ (PA28-180)

--
Message posted via AviationKB.com
http://www.aviationkb.com/Uwe/Forums...ation/200710/1

Here's an interesting proposal from 1929 :

http://home.att.net/~dannysoar/BelGeddes.htm

John Galban=====N4BQ (PA28-180)

--
Message posted via AviationKB.com
http://www.aviationkb.com/Uwe/Forums...ation/200710/1

"JGalban via AviationKB.com" u32749@uwe wrote in news:79f137ded6b56@uwe:

Here's an interesting proposal from 1929 :

http://home.att.net/~dannysoar/BelGeddes.htm

John Galban=====N4BQ (PA28-180)


And, appropriately, it was on the cover of popular mechanix or one of those
around the time it was designed.

I'd love to have flown it..

Bertie

"Jim Stewart" wrote in message
...
Phil wrote:
Thirty Five percent more fuel efficient. That would translate into
less expensive tickets. And just a fraction of the noise. But will
Boeing ever build something like this? Or will they wait until Airbus
or Embraer or the Chinese or the Russians build one?


http://www.popsci.com/popsci/aviatio...cbccdrcrd.html

Well, you can bet that all the Boeing
engineers would give their collective
left nuts for a 35% increase in fuel
efficiency.



Gee - it should be easy to get a 35% improvement.

Just get congress to pass a law requiring it - That's supposed to be how it
works for the auto industry - right?

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

A back of the envelope scribble says a smooth sinusoidal quatercycle
from 0 to 20 degrees bank if done in something like a half a second
would make a px sitting about 20 feet from the centerline experience a
third of a g max. I think a half second is doable -- but very
unlikely.

Sounds like mountains and molehills, or, more likely, I really don't
remember how to scribble meaningful stuff on the back of an envelope.