J.Kahn wrote:

The normal subsonic LD would be very low, about 6 or 7 to 1 at best. The
supersonic shockwave riding phenomenon they are talking about is
something else though and could I guess be true, although it's
surprising no other supersonic a/c has tried to exploit it.

The note in Wikipedia regarding the L/D for the XB-70 says:

"There is a popular belief and some sources claim that this helps the
XB-70 have the highest lift-to-drag ratio on a powered, manned
aircraft.[2]", so they clearly state that someone else believes it,
but they make no claim to the truth of it.

Now, note [2] points to:

http://easyweb.easynet.co.uk/~portwi...ft/xb_70a.html

which says:

"Overall, the XB-70 has the best lift-to-drag ratio of any manned
airplane ever built, being bettered only on the unmanned S-21 drone..."

As Mr. Kahn points out, the L/D of this aircraft subsonically will be
well below 10, which is nothing to speak of. Supersonically, we can
reference:

http://www.aerospaceweb.org/design/w...shtml#complift

which indicates that at Mach 3, we can expect L/D ratios of 5-6, max.
for aircraft using compression lift. Now, that's pretty good for
supersonic flight, and if the claims above had said "the best L/D
ratio of any manned SUPERSONIC aircraft", it would probably be true.

But it's clearly not the highest L/D of any manned aircraft - my COZY
MKIV has a glide ratio of about 14:1, which I proved just last
December by losing my propeller and gliding down 17 NM to L64 from
9500 ft. Gliders, of course, are much higher - up to 50:1, or even
better.

--
Marc J. Zeitlin
http://www.cozybuilders.org/
Copyright (c) 2007