Bill Freeman wrote:

Paul,

A source discussing equivalent flat plate area
comparison of various bodies.  It's toward the bottom
of the page.

  http://142.26.194.131/aerodynamics1/Drag/Page4.html

Bill

Quote:
Comparison of Drag Characteristics for Different Aircraft

CDp Comparison

The best method of comparing the relative efficiency of two aircraft is by comparing the CDp for those aircraft. Since CDp is independent of the size of the
aircraft it tells us how aerodynamically "clean" the design is.

Equivalent Flat Plate Area Comparison

Although the CDp is the best value for comparing the drag efficiency of one airplane to another the term Equivalent Flat Plate area (f.) is useful for comparing
the absolute parasite drag of two aircraft.  is defined as:

f = CDp x S

Note: Despite the name, f does not tell us "how many square feet of plywood" would produce the same amount of drag. 

The advantage of using f is that it allows comparison of the total drag from one airplane to another. For example a C-172 has a CDp of about 0.035 and S=174
ft2. A B-747 has a Dp, but the equivalent flat plate area of the C-172 is only 6 ft2 while for the Boeing it is 154 ft2. 

End of quote

I never ever said Equivalent flat plate area was perfect. In fact I pointed 
out that it DOES NOT take into consideration induced drag which changes 
with speed. I did say that induced drag was a secondary effect.

Paul Lamar
 
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