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Gentlemen:
<br>I can assure you that your discussions find more than a few very interested
ears.
<br>Thanks.
<br>Bill Glaze
<br>Capt. United Airlines, (ret'd.)
<p>Ron Van Putte wrote:
<blockquote TYPE=CITE>For a non- aeronautical engineer, Earl has a great
explanation about what happens during a snap roll. I tried to find
fault and couldn't. Nice job Earl.
<p>Ron Van Putte
<br>aeronautical engineer
<br>
<p><a href="mailto:EHaury@aol.com" class="moz-txt-link-abbreviated">EHaury@aol.com</a>
wrote:
<blockquote type="cite" cite="midb9.334f530f.2c2a131f@aol.com"><font face="Arial"><font size=-1>Ron</font></font>
<p><font face="Arial"><font size=-1>Very good points. The rotational rate
changes during snap initiation and stopping should not be downgraded. My
point is that major track changes during initiation should be downgraded,
as well as returning to an unstalled condition and rolling to finish. The
latter is not a zero, but a severe downgrade!</font></font>
<p><font face="Arial"><font size=-1>You're the AE, take a look at my view
of the snap. First the wing must be quickly (to maintain track) loaded
to stall or very near stall. The mechanism is pitch input in the positive
or negative direction. The pitch angle needed will vary with the stall
characteristics of the wing, the existing load (level, 45, vertical) and
speed. Fast pitch change is definitely better!</font></font>
<p><font face="Arial"><font size=-1>Just as the wing reaches stall a yaw
input In the desired direction of rotation retracts one wing and advances
the other. The retracting wing now has less relative airspeed and stalls
(or stalls more deeply) than the advancing (higher airspeed) wing and rotation
occurs as though a wing fell off. Again fast rudder input is good.</font></font>
<p><font face="Arial"><font size=-1>The accelerations and decels of the
rotation of snaps done this way will be very dependent upon the roll axis
inertial characteristics of the aircraft. The lighter the wings the better,
with heavy wings making the snap unmanageable.</font></font>
<p><font face="Arial"><font size=-1>Enter ailerons. The ailerons contribute
in a couple of ways. The upward traveling aileron on the retracting wing,
that we wish to stall more deeply, helps the stall while the downward traveling
aileron on the other lowers stall speed of this wing somewhat like a flap.
Therefore less pitch and yaw to stall / rotate. The big benefit is that
the aileron application helps overcome the roll inertia involved at the
start and stop, making both more controllable. (Yes, the full scale folks
use ailerons in snaps to help manage inertia also.)</font></font>
<p><font face="Arial"><font size=-1>Back to the elevator. The amount of
pitch needed to initiate a snap is more than required to maintain it (likewise
yaw). If maintained at high angles throughout the snap the aircraft will
retain some pitch and yaw upon snap exit. (General term is "buried snap.")
If the pitch and yaw inputs are reduced after snap initiation to levels
just sufficient to maintain the snap, the snap will be tighter and exits
cleaner. Unfortunately, some who have the skills to achieve this level
of control are mistakenly accused of performing an axial roll.</font></font>
<p><font face="Arial"><font size=-1>Another spin control that can be used
to advantage is the throttle, remember that the faster the wing is moving
the more pitch angle is needed to effect stall and the more likely the
track will change before stall occurs. While idle will get the quickest
stall, the drag created during the snap will render the airplane a dead
duck on exit. Some middle ground exists for each airplane design, be it
faster entry or powering up during the snap to offset drag.</font></font>
<p><font face="Arial"><font size=-1>I agree that the snap is probably more
difficult to judge than execute. However, it seems that it's here to stay
(and it's a fun maneuver). I started this discussion to stimulate thought
and encourage folks to think about appropriate judging of the maneuver.
"Sticks in the corner" doesn't necessarily result in a good snap and the
very skilled folks, who have developed techniques to make the snap a joy
to watch, haven't all figured out a way get something that isn't a snap
judged as such.</font></font>
<p><font face="Arial"><font size=-1>Earl</font></font></blockquote>
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