brett@tle.enet.dec.com (Bevin Brett) (02/11/91)
From: brett@tle.enet.dec.com (Bevin Brett) A recent posting badly overstated the acceleration capabilities of an F-4. The info available in such texts as Klaus Huenecke's "Modern Combat Aircraft Design" show that an F-4C/D, at 35000 ft, will take 10 min's to go from M=1.0 to M=1.8, at about 45000 initial lbs weight. If you start off with the plane as light as possible, then you may be able to get it down to 4 mins. Furthermore if you are really interested in avoiding SAM's, then you'll keep your airspeed down (a) below M=0.95, and (b) below 450 Kts CAS - otherwise you won't be able to turn fast enough and its lead-pursuit guidance system will guarantee that it hits you. An F-4's max-G's "pullable" drop hit "pilot- limited" (9-12 G) at around 360-450 kts CAS, but drop to 3 G's as you go through M=1.0. Now, these are level flight, if you went ballastic downwards then you may be able to do it in under a minute - but I think you'll find that you'll get too low to get much above M=1.5. A little bit of physics will show that doing this "in seconds" is something missiles, not aeroplanes, do. Consider that M=1.0 corresponds to about 340 metres-per-second at sea-level, 300 mps at 30_000 ft. So to go from M=1.0 to M=2.0 you have to accelerate about 300 mps, which even at 1G=10mps2 will take you 30s. But no plane has that kind of excess thrust after coping with drag. Now, a Sidewinder goes from M=1.0 to about M=2.5 in about 3-6 seconds .. not bad. And a bullet does it before it leaves the barrel! Some missiles hit as much as 100G's during the launch... /Bevin