On 2007-06-11 00:21:38 -0400, Bertie the Bunyip said:

"Maxwell" wrote in
:


"Bertie the Bunyip" wrote in message
.130...
"Maxwell" wrote in

A 1g barrel roll can be done, but the required trajectory of the
aircraft is not going to be one that is necessarily eye pleasing for
ground demonstration purposes.

Nope. the only thing you can do at 1 G is straight and level flight.

You can keep positive G around a barrel roll, but not 1 G


If you enter nose high (enough), and exit nose low (enough), you
should be able to maintain close to one g. But then would it still be
called a barrel roll.

mmm, nope. Not even close., If you fly it really accurately you might be
able to keep the entry end exit under two g, but I doubt it. If you fly
it very slack, you'll go, at best, Zero G over the top and probably
negative.
To keep positive G you need well over tow at entry and exit, to keep a
little over one as you pass 90deg, then you can probably keep a bit over
a half a G over the top and then pretty much the same down the other
side.



I'll have to admit, I've never specifically watched the g meter while
doing so, but if you are sloppy enough, it seems prettly close.

I have watched it. Quite a lot, in fact. I've been hearing this story
since I've been flying, It was wrong back then and it's wrong now. Even
if you dump the nose as you suggest on the way down, you're stil going
to have to pay for it eventually...... And on the way up, no way.




Bertie

Bertie is correct. Barrel Rolls are perhaps the most misquoted and
misunderstood maneuver done in an airplane.
Basically, you can do a barrel roll as loosely or as tight as the
airplane's flight envelope will allow. You can also enter a BR from
many different flight conditions involving many different g loadings.
The main thing to remember about barrel rolls is that they are a 3
dimensional maneuver through 3 dimensional space and that the common
denominator in a barrel roll regardless of the g used is that it will
remain POSITIVE all the way around. The one exception to this would be
after the pull and roll application, you can unload the airplane over
the top and drop the g to +1 if you like to loosen the roll rate, but
that g must be regained during the recovery.
Basically, you will be somewhere over +1g in the entry as you raise the
nose, then at some positive +g throughout the roll ranging from as
unloaded as you want to loosen up the airplane or as high a positive g
and tight a roll as the envelope will allow. As long as the airplane
transverses 3 dimensions through the roll, it's a barrel roll.
I've done them as loose as a 90 degree change of direction at the top
apex in a P51,the F8F, and several jets including the T38, and as
tight as a corkscrew in a Pitts S1Sl which was highly loaded with +g
and extremely tight.
Bob Hoover's rather famous Iced tea stunt in the Shrike is probably
responsible for much of the misconception about barrel rolls. He does
them fairly loose and with just enough positive g on the airplane to
keep the glass from spilling without stressing the airplane. The
"secret" to Bob's tea trick is simply his smoothness through the roll
as much as keeping positive g on the tea. It's really this smoothness
that makes this stunt possible, as although positive g will keep the
tea inside the glass. (You can actually POUR tea as you're rolling the
airplane but ONLY if you're as smooth as Hoover :-)
The reason smoothness is so necessary for the tea trick is that even
though you might have positive g on the airplane and in effect doing a
barrel roll, if you are not perfectly coordinated through the roll (any
excessive yaw for example) your tea will slide off the glare shield
laterally and you don't want that......not if you're Bob Hoover anyway
:-)
So it's positive g for the roll, and smoothness and perfect
coordination for the tea stunt.
Hope this helps a bit.
Dudley Henriques