Rolling a 172 - or not

Big John wrote

Talk me through a loop doing a Barrel Roll. We must be using
different words or maneuvers?

John, have you looked at the barrel roll picture that I e-mailed
you and posted on alt.binaries.pictures.aviation?
If not, further discussion will be of no use.

Have you checked the "Willian Kershner" web site and read the
author's credentials?
If not, you just leave us wondering "who-the-hell" is Big John,
and what credence should we give to his unsupported assertions?
Mr. Kershner owns and operates an Aerobatic Flight School and
has authored the book, "The Basic Aerobatic Manual" which as he
points out, was an offshoot (with permission) of the manual he
helped write for Cessna Aircraft in 1969.

First let me try a different set of words for a GA barrel roll.

Here are William Kershner's words that accompanied the diagram of
the barrel roll in his The Flight Instructor's Manual in which he
devotes all of chapter 5 (66 pages) to aerobatic instruction.

Quote..............or should I say OCR'ed

THE BARREL ROLL
• Preparation. It's almost impossible to draw a barrel roll
on the chalkboard, but a model will give the desired results.
Have the trainee study the references.

•Explanation. The barrel roll is a precise maneuver in which
the airplane is rolled around an imaginary point 45° to
the original flight path. A positive-g level is maintained
throughout the maneuver, and the ball in the turn indicator
should stay in the middle.

You may wonder why the barrel roll is taught this late,
since it appears to be so simple. Well, it is a precise maneuver
requiring particular airplane attitudes at particular reference
points, which is difficult for the average trainee to do properly
at first.

This maneuver might be considered an exaggeration of the
wingover, but instead of starting to shallow the bank at the 90°
position, the pilot must steepen it continually until the airplane
has rolled 360° and is back on the original heading. The rate of
roll must be much greater than that used for the wingover
because the airplane must be in a vertical bank at 45° of turn,
and it must be inverted at 90° of turn. The roll and turn is
continued until the airplane is headed in the original direction with
the wings level. Compare the barrel roll in Fig. 23-12 with the same
view of the wingover in Fig. 20-7.

From behind the maneuver looks as though the airplane is being
flown around the outside of a barrel. This is a very good maneuver
for gaining confidence and keeping oriented while flying inverted in
balanced flight.
Good coordination is required to do the barrel roll properly and
the trainee will show an improvement in that area after a session of
barrel rolls.

The barrel roll is generally more difficult and precise than the
aileron roll, and he may have to work on this one awhile.

Why-
The barrel roll is one of the best maneuvers for improving
orientation.

Unlike the other acrobatic maneuvers covered thus far, the barrel
roll requires a constantly changing bank and pitch (with attendant
changing airspeed) and a radical change in heading (90°) while the
airplane is rolling. The average trainee probably will be looking at
the wing tip at a time when he should be checking the nose, or vice
versa.
When he is able to stay well oriented in the barrel roll, he is ready
to move on to the reverse Cuban eight or reverse cloverleaf.

How-
You might use the following explanation, or develop your own:
(1) Make sure the area is clear, then pick a reference on the
horizon off the wing tip as in the wingover and lazy eight.
(2) Set the throttle to low cruise rpm and ease the nose over to
pick-up about 10 K more than used for the wingover or set up
the airspeed used for a loop, whichever is higher. Power
adjustment should not be necessary during the maneuver. You
might have some of your sharper trainees apply full power as
the airplane approaches inverted and then remind them to
throttle back as the airspeed picks up in the last part of the
maneuver.
(3) Smoothly pull the nose up and start a coordinated climbing turn
(note that it will have to be at a much faster rate than was
used for the wingover) toward the reference point. (Assume that
at first the roll will be to the left.)
(4) When the nose is 45° from the original heading, it should be
at its highest pitch attitude and the left bank should be
vertical.
(5) When the nose is at 90° from the original heading, you should
be looking directly at the reference point that was originally
off the wing tipfrom a completely inverted position
(momentarily).
(6) When the airplane heading is again 45° from the original, the
bank is vertical but you will be in a right bank as far as the
ground is concerned; that is, the right wing is pointing
straight down at this instant of roll. The nose will be at its
lowest pitch attitude at this point.
(7) The roll is continued to wings-level flight as the nose is
raised back to the cruise attitude.

The maneuver must be symmetrical; the nose must go as far above the
horizon as below. The barrel roll requires definite checkpoints to
ensure that the airplane is at the correct attitude throughout. It is
interesting to note that if the barrel roll is to the left, all of
the airplane's path is to the left of the original line of flight and
the airplane's nose is always pointed to the left of the original
flight line (until it merges again at the completion of the
maneuver). The opposite occurs, naturally, for the barrel roll to the
right.

Another method of doing a barrel roll is to pick a reference on the
horizon, turn the airplane 45° to the reference point, and proceed to
make a wide roll around this real point. One disadvantage of this
method for the newcomer is that it depends on the pilot's own
judgment of how large the orbit around the point should be. For an
introduction to the maneuver, the first method is usually better, but
you may prefer the second and work out your own techniques of
instructing it.

Demonstration.
Try not to lose the reference point yourself while demonstrating
this one. You may find your explanation is not keeping up with the
airplane, which usually results in sputtering and stuttering while
the maneuver proceeds to its foregone conclusion -and then you have
to do a new demonstration. Don't worry, this will happen plenty of
times during your career of instructing aerobatics -when your mouth
can't keep up with your brain or the maneuver-and it can ease tension
if you react to it with humor.

Usually the trainee is surprised to see the same wing tip back on the
reference point and may confess that, like the first snap roll, the
earth and sky were blurred and he had no idea where the reference was
during the maneuver.

Practice.
You may rest assured the trainee will "lose" the reference point
during the first couple of barrel rolls. He'll usually stare over the
nose, seeingnothing but blue sky or ground and not really seeing the
point at all.

Common errors during barrel rolls include these:
1. Not pulling the nose high enough in the first 45° of the
maneuver, which means that the highest and lowest nose positions
are not symmetrical to the horizon.
2. Not maintaining a constant rate of roll. Usually things are fine
at the 45° position; the nose is at its highest pitch and the
bank is vertical.
As you approach the position of 90° of turn you will probably
find that he is not going to be completely inverted at that
point and will have to rush things a bit to make it. The usual
reason is that he did not maintain a constant rate of roll.
Remember that the nose is up and the airspeed is slower in this
segment of the maneuver, so the controls must be deflected more
to get the same rate. This is where coordination comes in. Watch
for it in particular.
3. Letting the nose drop after passing the 90° point; losing too
much altitude and gaining excess airspeed.
4. Failure to roll out on the original heading; having the wing tip
well ahead, or well behind, the reference when the maneuver is
completed.

Evaluation and Review.
Review each barrel roll briefly in the air, and have the trainee
use the model on the ground. This one can be hard to "see," so go
over it again as necessary after getting on the ground.

By the time a half-dozen barrel rolls have been practiced, the
average trainee should be oriented throughout the maneuver even
though he may still have minor problems of heading and symmetry.
After a dozen rolls he should be starting to work on a constant roll
rate and starting to ease his heading problems. After several
hundred, he may begin to be satisfied with his barrel rolls but will
realize that constant practice is required.

Unquote.................

But John...you really should look at that picture.

Bob