Paul Lamar wrote:

Technically speaking frontal area is rarely around the front of the
airplane. It is defined as the maximum cross-sectional area of the
aircraft. In the case of many pushers it occurs about 2/3-rds of the way
towards the back.

If you park the airplane at night in front of a brick wall
and you shine a spot light on if from a distance located on the
longitudinally axis a shadow will appear on the brick wall. If you
count the bricks that are in the shadow and add up their total
area then that is the frontal area of the aircraft.

Actually, for that to work the light rays must be parallel, i.e. the "spotlight" would need to be very,
very far away.  Like as far away as the Sun.  :-)

But you can still make it work by multiplying the counted brick area by the correction factor:

    1 / (( Dsub2 / Dsub1 ) ^ 2)

where Dsub1 is the distance from the spotlight to the "location" of the maximum cross-sectional area,
and Dsub2 is the distance from the spotlight to the brick wall.  The "location" of the maximum
cross-sectional area would be the average of all the spots where the plane's surface transitions from
lighted to dark.  Generally it's about the same spot as the Cg.

Russell Kent
(I knew those four semesters of physics in school would come in handy... :-)

Run some of these numbers Russell for the airplane parked right
in front of the brick wall and the spot 100 feet away and get back
to us :)

Paul Lamar

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