About doing a barrel roll at night with relationship to passengers;
it is possible, and could be done. The passengers, within a closed
environment, would feel the onset of whatever positive g was used by the
pilot to initiate the roll. If the pilot was very good, and kept perfect
control coordination all through the roll, all the passengers would feel
would be the positive g and no side g loads would be felt.
In short, a barrel roll under the conditions you have stated although
possible, would have to be executed perfectly not to alarm passengers
subjected to it at night in a closed cabin. :-)
Dudley Henriques
International Fighter Pilots Fellowship
Flight Instructor/Aerobatics/Retired

"LordAvalon" wrote in message
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"Dudley Henriques" wrote in message
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"Rob Stokes" wrote in message
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I have no proof, but looping an airliner without the passengers
being
aware
is not possible. Perhaps visually the passengers wouldn't notice,
but
balance wise / spatially they certainly would. I have heard from
many
sources that the last airliner to be taken for a loop was a B-707
after
which many of the A/C components shifted up to an inch, the pilot
was
immediately disciplined! other similar instances have occurred on
Russian
airliners by Ex-military pilots shortly after the war. At the
Goodwood
Festival Of Speed (England) this year, there was a 'semi'
aerobatic
display
by a south African jumbo (consisting of very low steep turns)

Thanks for your input.
I am not an expert in flying terms so maybe it is not exactly
"looping" i heard of. The plane would drop to the left for exemple
with his longitudinal axis straight and acquire vertical speed.
Then
the pilot would shift the stick right very slowly to convert this
vertical speed in a centrifugal vector. This is supposed to
recreate
the same phenomemom as a pail full of water tied to a rope you turn
fast. So, as this theory goes, after the initial banking the figure
would make the passengers feel only a moderate or no increase in
their
weight, the force being directed towards the floor of the plane.
Since
the long axis of the plane is not disturbed no other noticeable
effects should appear...

But if it is unheard of, it may well be purely theorical or simply
an
urban legend!

No. It's possible, but I haven't heard of it being done successfully
in
the pure vertical plane as in a straight positive g loop. More likely
in
a three dimensional maneuver like a barrel roll. The energy or Ps
bleed
for a big jet is tremendous in the vertical plane, and an entry
airspeed
required to get everything up and around the topside apex would be
considerable to say the least. Considering the huge drag index
against
what would have to be at least a 4 positive g pull to even have a
chance
at an inverted apex, the entry speed would be prohibitive for safety
I
think; considering the aerodynamic factors and the requirement for
positive g at the top for the scavenger pumps. In other words,
floating
it through the top unloaded is eliminated from the equation because
of
the pumps if nothing else. The engines oil system requires positive g
to
operate. Unloading would deny the engines oil and the result at a
high
percent RPM or EPR could lose you the engines. The result of that
would
be a negative nose rate and developing vertical descent while
inverted
that could really spoil your afternoon :-)
In a normal loop, you ease off the positive g at the top to round it
off
and keep the AOA in limits. In a big jet, this could really be a
problem.
A three dimensional roll (barrel roll) is possible for a big jet, and
has been done, even in the prototype 707. You are right about keeping
the g positive all the way around. Both myself and several other
demonstration pilots at one time or another have barreled airplanes
with
a glass of water on the instrument glare shield. I have done it in a
D18
Twin Beech several times and Bob Hoover has done it in a Shrike
Commander......many times. :-)
In barrel rolling a large airplane, you can keep the stress at a
minimum
and perform the maneuver in a wide low positive g profile that is
kept
positive all the way around. Because it's FLOWN around the circle
rather
than a pure roll on the longitudinal axis, the deep dishout on the
back
side that would be the result of an aileron roll can be eliminated by
the trade off in altitude on the upside against the backside
recovery.
Basically, even though I'm sure a pure loop has been done by heavy
jets
at one time or another, I would classify the maneuver as extremely
risky
at best, and totally unwise to attempt. But as I said....I'm sure
somebody managed to get the entry speed necessary to do it regardless
of
the risk, and somehow managed to pull it around without shedding all
the
critical parts in the process. But I wouldn't want to be the next
pilot
to fly that airplane :-)
Dudley Henriques
International Fighter Pilots Fellowship
Flight Instructor/Aerobatics/Retired

Thanks a lot for your learned answer. What I have heard of is
certainly what you call "barrel rolling". According to the unreliable
"sources", the pilot of a commercial flight would have done this
barrel rolling at night. Nobody in the plane would have noticed it but
an "Aviation Board Inspector(?)" is supposed to have been present and
reported the deed. Which would have led to sanctions against the
author... To be confirmed!