"Paul J. Adam" wrote:

In message , John S. Shinal
writes
"Paul J. Adam" wrote:
Sure, but then the Tornado was designed to fight from Day One when
control of the air was disputed, and it can do so. (The F-15E has a
great many many strengths, but with that large wing it's not really a
low-level penetrator except in emergencies: not if you want the crews to
keep their eyeballs in their heads)

When carrying a typical warload for deep interdiction, doesn't
the increased wing loading cure the rough ride ?

Still a rougher ride than a F-111 or Tornado or other airframe designed
for the job. (The F-15 is a superb airframe for both air superiority and
mid-level strike, but designed as a low-level penetrator it is not)

The F-15E's ride is rougher for two primary reasons, wing loading and aspect
ratio. Even at MTOW of 81,000 lb., the wing loading is only 133 lb./ sq. ft
(wing area is 608 sq. ft.). Aspect ratio of the F-15 is 3.01 (span is 42'
9.75": Aspect ratio is span^2 /area). By comparison, an F-111C at 110,000 lb.
has a wing loading of at least 200 lb./sq.ft. and an aspect ratio of 2.10. I
say "at least" because I only have handy the area for the wing when at minimum
sweep, 550 sq. ft. At max sweep (span 33' 11.5") some of the wing area will
be covered by the fairing. Tornado's wing loading is a bit higher (on
unverified MTOW and area I get 215 lb./sq.ft.) than the F-111, while its
aspect ratio at max. sweep is also a bit higher, about 2.78.

As the aspect ratio increases, small changes in wing angle of attack will
cause relatively larger changes in lift than is the case with a lower aspect
ratio wing. In bumpy air down low (caused by the wind flowing
around/over/through terrain, as well as differential heating of the ground),
every bump may cause a change in wing angle of attack and lift (and thus
instantaneous g loading, positive or negative), as the a/c is constantly going
up and down. These changes in lift will be greater on a higher aspect ratio
wing, causing the ride to be much bumpier than on a lower aspect ratio wing.
In addition, the a/c with the higher wingloading will need more of a bump to
affect it than is the case with a more lightly loaded wing - bumps that would
be throwing a Cessna all over the sky would probably be unnoticeable in a 747
(at the same speed).

Guy