posted on Sep, 19 2009 @ 11:54 PM
Originally posted by mxboy15u
I want these speeds clarified are we talking A/S True A/S or Groundspeed.
We are talking TAS or groundspeed, definitely not indicated airspeed. None of the aircraft mentioned, with the possible exception of Rare Bear (the
Reno racer converted Bearcat) could go anywhere near their top speed at sea level. The top speeds you see qouted for almost all aircraft, except
un-turbocharged/supercharged piston engine aircraft, are always achieved at higher altitudes, so the indicated airspeeds are much lower than true, and
much lower than the top speeds quoted in the books.
WHen I was flying F-5s back in the 80s I would routinely cruise at 0.95 mack on cross country flights, but the indicated airspeed would generally be
below 300 knots at the altitudes I was flying (usually high 40s). In B-52s I would see 240knots when flying at out typocal cruise speed of .77 mach
in the high 40s. A WW2 P-51 (not a Reno air race prepped one) could only go about 250 knots indicated in level flight. It's quoted top speed of
about 440 mph was achieved in the mid 20,000 foot range I believe (maybe even higher) and the pilot probably only saw around 250 on the airspeed
COme to think of it the structural limiting airspeed of the entire F-5/T-38 series of jet fighters/trainer, was 710 knots indicated. But the F-5E
could go mach 1.6 (over 1,000mph). The fastest mach number I ever remember seeing in an F-5 was about 1.3, but the indicated airspeed was only about
350 knots if I remember correctly (in the mid 30,000ft range). The structural limiting airspeed of many civil jets is only in the high 200 to low 300
knot range, yet these aircraft normally cruise in the .75 - .8 mach range, though at 30- 40 thousand feet. Even an F-15 has a limiting airspeed of
800 knots, but the top speed is 1650knots if I remember correctly. Virtually all of the very fast fighters of the past 40-50 years has top speeds of
about mach 1.2 at low altitude, well below their absolute top speeds that we see quoted. The point of all this is that most aircraft cannot go their
top speed, even in a dive, at low altitudes.