Originally posted by emile
I can not see why F-23 using F-120 won't fly beyond M2.6 and do supercruise at M2.0?
Using this picture
And basic planform aerodynamic rule M = 1/sin(beta)
Where beta is the "sweep" angle from aircraft nose to wingtip.
Beta is 32 degrees approx, giving a planform speed of Mach 1.88 or so.
Here is the YF-22:
Using the same ruling gives an aerodynamic design mach number of 2.2 approx.
In the absence of verified hard evidence, I'm not going against the basic rules of aerodynamic design. Therefore, I'll happy presume the YF-23 did
not go faster than the YF-22. Also, the nozzles on the YF-23 are fixed, and therefore will not use afterburners as efficiently as the F-22
[whose nozzles do vary in size].
edit: Went searching for some info, it kinda backs up my position:
Two YF-23 prototypes were designed and built by the contractor team of Northrop and McDonnell Douglas as part of the demonstration and
evaluation phase of the US Air Force's Advanced Tactical Fighter selection program, which concluded in 1990. During the ATF program, one YF-23 was
powered by twin Pratt and Whitney YF119 turbofan engines, while two General Electric YF120 turbofan engines were installed in the other prototype.
Featuring a diamond-shaped planform, two large, sharply-canted ruddervators, and a serrated aft profile, the high performance aircraft was larger than
the F-15 it was designed to replace. The YF-23 prototypes are 67.4 feet in length and have wingspans of 43.6 ft. The YF-23 employed stealth
characteristics and was capable of supersonic cruise flight without afterburner. The aircraft achieved a speed of Mach 1.8 during the
program.
Note that doesn't say supercruised at, as is made clear below:
There was no official USAF "nickname" for the YF-23A. The Northrop YF-23A team personnel chose the name "Black Widow II" -- commemorating the
Northrop P-61 Black Widow, the first American aircraft specifically designed as a night-fighter.
The YF-22 and YF-23 were different in many ways. The YF-23 was designed for speed and maneuverability. The YF-22, however, was designed more for
maneuverability. Both aircraft, were designed for a type of flight called supercruise. Supercruise is when an aircraft is designed to be flown at Mach
1 or above in cruise, that is without afterburners. For this reason, both aircraft had to be more aerodynamic. The YF-23 was slightly more
aerodynamic as it's cruising speed was Mach 1.25, Mach 0.08 faster than the YF-22 (roughly).
Source:
www.globalsecurity.org...
The YF-23 prototypes are 67.4 feet in length and have wingspans of 43.6 ft. During the Advanced Tactical Fighter program, one YF-23 was powered
by twin Pratt and Whitney YF119 turbofan engines, while the other had two General Electric YF120 turbofan engines installed. The aircraft achieved
a speed of around Mach 1.8 throughout the program.
www.globalaircraft.org...
same at:
www1.dfrc.nasa.gov...
I think people have assumed the aircraft never attained it's maximum speed during the test program... then invented cruise speeds of Mach 2+ and dash
speeds of near Mach 3. Reality may be somewhat different, as the evidence hints towards Mach 1.8 being its approximate top end speed.
[edit on 2-12-2006 by kilcoo316]
[edit on 2-12-2006 by kilcoo316]
