Some Diagrams

[Ted Sander]

Very interesting Bob!  A few years ago I was messing around with a 3D
animation program (Bryce 3), and tried my hand at making a clip showing a
plane tracing out a basic loop while following a "ribbon in the sky" - ie,
the path looked like those shown in the maneuver descriptions in the AMA
rule book.  It allowed for perspective effects, placement of viewpoint and
all the other usual stuff a 3D program can do.  So, on to my point:  When I
mathematically made the loop perfectly round, it had a distinct egg shape to
it when the view point was moved from the same level as the center of the
radius, to a more typical 5 ft from the ground, looking up.  In order to get
a loop that looked round from a typical judge/pilot position, I had to
squish it from the top a fair bit - indicating to me that as we fly our
planes over the top, it's not enough to keep the radius consistent, we
actually have to pull harder on the top side, to keep everything looking
right - in other words, we don't actually fly a true constant radius loop,
because of perspective effects.  Makes it all so much harder than just
keeping airspeed and angle of attack constant - because we have to vary the
shape to make it look right.  While I didn't go back to look at other
maneuvers in more detail, it has always stuck with me that this effect also
rears it's head everywhere else too.  Kind of the visual version of the
upwind/downwind debates - so much depends on the frame of reference.  Would
be interesting to hear others take on this subject..

 

Ted Sander 

 

-----Original Message-----
From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org] On
Behalf Of Bob Pastorello
Sent: Tuesday, August 17, 2004 6:14 PM
To: NSRCA
Subject: Some Diagrams

 

After getting some feedback about geometry, I thought I'd draw out a few of
my more problematic ones.  They may help you, too....

http://www.rcaerobats.net/ManueverDiagrams.htm


Bob Pastorello
rcaerobob at cox.net
www.rcaerobats.net

 

 

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