Ed Rasimus wrote:

On Sat, 14 Aug 2004 23:45:17 GMT, Guy Alcala
wrote:

John Carrier wrote:

Generally, the sustained turn rate was around 14-15 degrees/second for
the F-4 hard-wing and about 12.5-13.5 for the F-105.

H'mm, those numbers seem kind of high for both, as far as sustained
capability
goes.

400 KTAS, turn rate in Deg./sec. (rounded off) = 19 (7g); 22 (8g).

500KTAS, turn rate in Deg./sec. (rounded off) = 15 (7g); 17 (8g); 20 (9g).

600KTAS, turn rate in Deg./sec. (rounded off) = 13(7g); 14 (8g); 16 (9g).

I'm missing something here. You say the numbers are high and then offer
higher numbers. Or are these just basic computations of turn rates w/o
regard to airframe factors?

snip

Yes. I wanted to show what the maximum turn rate was for the various KTAS/g
combinations; sustained would be less.

Guy

I woke in the middle of the night thinking about this discussion--I
know, it indicates some level of neuroses....

I've said that KIAS not True Air Speed is the relevant number, you
indicate a desire to relate G available and hence turning performance
to KTAS.

Consider this. At low altitude, true air speed can be quite close to
indicated. It will always be higher than indicated, but not
exceptionally higher. So, if you are running around at corner velocity
(always expressed in KIAS) of say 420 KIAS, you might be at 475 KTAS
and you could pull max allowable G.

Now, move the airplane up to FL450 and establish the same 475 KTAS
condition. Ooopps! You're cruising around at something less than 300
KIAS (don't dissect the number, it's an approximation but reasonable).
You only have aerodynamic capability to pull about 3.5 G.

But, you've got the same KTAS. The point is that True Air Speed
doesn't consistently offer aerodynamic performance. It's those little
molecules doing their Bernoulli thing over the wing surface that makes
it happen--KIAS!

Ed, I know. But the question was about max. degrees per second (instantaneous or
sustained) capability, and that is a function of TAS and g, irrespective of
altitude. If you look at KIAS/KCAS and g, you can say that the a/c reaches corner
at say 420KCAS, but does that tell you how many degrees per second you're turning?
No, because you have to take account of the altitude and then translate IAS/CAS
into TAS, and then use g to have any idea of what the radius/rate is. It's
certainly possible to calculate radius/rate using IAS/CAS and g, but far more
tedious than just using TAS, which applies at any altitude without conversion.
Other than that, I think we all know that best turn rate/radius happens in the
densest air, with the rate decreasing and the radius increasing with altitude,
given constant IAS/CAS.

In short, we're in complete agreement about the effects, just using the numbers for
different purposes. You are approaching the problem from the pilot's perspective
using KIAS/KCAS, a relative value; you don't really care what the actual number is
or what the measurement system is (radians per hour, anyone?), just that it will
give you the quickest, tightest turn or a Zero Ps turn (and in combat, knowing that
you will be advantaged/disadvantaged against a particular opponent). I'm
approaching it from the perspective of an absolute value, which is necessary to
answer the OP's question about deg./sec.

Guy