See inserts;


"Matt Whiting" wrote in message
...
Dudley Henriques wrote:


Don't mean to rankle anybody here, and I haven't seen any "condescending
tone" as yet, but how does any comment made by me about barrel rolls
violate the laws of physics?

I don't think I understood all of your descriptions of the variations of a
barrel roll well enough to make an assessment. Some of them didn't sound
like the traditional barrel roll description.

You were right. Some of them are not from the classic description. This is
what confuses this issue so often when discussing it. The "classic" barrel
roll description is absolutely correct. Its just possible to perform the
maneuver to tighter specifications that's all.

For example, do you
end up at the starting altitude in all of the cases you discussed related
to fighter evasive techniques?

In the classic BR, used for training purposes, you want to end up at the
starting altitude and the entry airspeed after meeting specific parameters
at different points through the roll. You do this by playing the g and the
various control pressures through the roll.
In the fighter role however, you are maneuvering the airplane in a 3
dimensional arena in relation to the true motion of another aircraft in that
arena. Your altitude and airspeed, and even the arc of a barrel roll is
referenced only to what you need in the way of positioning in relationship
to that other aircraft. These rolls are usually done quite fast and very
tightly as a corkscrew roll.


If you lose a lot of altitude
during the roll, then I can see being able to hold less than 1g through
most of the maneuver. I don't see how this is possible for any roll that
could be superimposed on a cylinder (the barrel) with the ending point
being at the same radial location as the starting point - that is if you
start at the bottom of the barrel you end at the bottom of the barrel. I
couldn't visualize all of your permutations on the roll to know if this
was the case or not.

If you didn't vary the g through the roll, you are right; you couldn't
maintain a steady position on the cylinder. The only way to do it is to ease
off the g on the way up to inverted, then re-apply the g on the back side.
If you held the same g through the roll, you would cork screw through the
roll. It would still be a barrel roll however. The cork screw shape of the
roll dosen't change the fact that the airplane is still traveling through 3
dimensions using a 3 dimensional maneuver. It just dosen't look as nice as
the big wide classic training barrel roll :-))