wolit@rabbit.UUCP (Jan Wolitzky) (09/05/84)
The North American B-70 "Valkyrie" was the second of the U.S.'s four unsuccessful attempts at a supersonic bomber (the Convair B-58 "Hustler"; the General Dynamics FB-111, also known as the "TFX"; and the original Rockwell B-1 "Budget Buster" being the other three). It had fold-down wingtips for pretty much the same reason that the TFX and the B-1 have swing wings, the B-36 had pusher props, and the new Grumman X-29A is built backwards -- you gotta have a gimmick to win a defense contract. The program was scrapped after just two prototypes were built, when one crashed, which was lucky for the crew of the second and for those of us footing the bill. Interestingly, it appears that the crashes of the B-70 and B-1 prototypes occurred for the same reason -- the planes went out of control trying to avoid chase planes taking publicity photos. (What this says about their combat performance, I'll leave up to you!) It might be noted, too, that the same manufacturer was involved in both cases: Rockwell and North American merged some time ago. A fairly detailed, though incredibly biased (in favor) account of the plane came out 15 or 20 years ago -- I believe it was titled "B-70: Monarch of the Skies" or some such hype. Jan Wolitzky, AT&T Bell Labs, Murray Hill, NJ
dpw@bonnie.UUCP (David P. Williams) (09/06/84)
With regard to numerous aircraft mentioned in a previous article: The XB-70 served a couple of purposes even if it never went into production: it inspired the Soviets to produce the Foxbat and load it up with an immense radar set and jp-guzzling engines, and it served as a hypersonic testbed for engines and airframe. The crash occurred when a chase plane maneuvered into a wing vortex and was spun into the upper wing surface and exploded - it would be pretty hard to fly out of that situation. The XB-70 crew had one casualty. The B-58 (produced by Convair, now General Dynamics), when in service, could outrun every aircraft in the U.S. inventory except the F-106. My understanding is that the airframe was years ahead of the engines, which were a maintenance nightmare and had a tendency to shed fan blades on takeoff. The X-29 looks like a conservative engineering approach on the part of Grumman to check out principles that are well-understood, previously flown, and attractive in light of new materials technology. The forward-swept wing offers superior maneuverability, but it requires the stiffness of graphite-epoxy. Also, that wing placement allows a smaller fuselage and wing and a smaller, lighter, more maneuverable aircraft. Grumman has got to be the most solid of the aircraft manufacturers and they are developing the X-29 in concert with DARPA, which has sponsored successful programs like HIMAT. Grumman is using an F-5 fuselage forward half and mating it to new hardware to cut down on expenses. The FB-111 (General Dynamics) is still in the inventory and will be there until 1995 or later. Its problem is the same basic engine set that the Navy is scrapping for the F-14. The Navy is replacing the Pratt & Whitneys with GE F110s, the same powerplants that are in the B-1. I don't think there is any problem with Rockwell. As North American, they produced the P-51 and F-86, two respected fighters, and as Rockwell they are doing a respectable job with the Space Shuttle. There aren't very many details of the B1 crash, but if the pilot was trying to avoid a chase plane, low altitudes and high speeds put him at a disadvantage. David Williams AT&T Bell Labs Whippany, NJ
knutson@ut-ngp.UUCP (Jim Knutson) (09/10/84)
The crash of the XB-70 occured during low speed testing. A chase plane had moved in behind to get photos. Unfortunately, the rather large wings on the XB-70 created a large suction. The chase pilot had moved in just above and behind and ended up being sucked right into the plane. I have seen the footage of the accident but I can't remember where. It may possibly have been at the NASA museum at Langley AFB, VA (a very interesting place by the way).
dsmith@hplabsc.UUCP (David Smith) (09/10/84)
It had fold-down wingtips for pretty much the same reason that the TFX
and the B-1 have swing wings, the B-36 had pusher props, and the new
Grumman X-29A is built backwards -- you gotta have a gimmick to win a
defense contract.
This is pure bile. There were good reasons behind all of those design features.
The program was scrapped after just two prototypes
were built, when one crashed, which was lucky for the crew of the
second and for those of us footing the bill.
The B-70 bomber program was cancelled before the first prototype rolled
out. The downing of Gary Powers' U-2 made it clear that high altitude
was not a sanctuary, and forced bombers to go low. The B-70 and B-58
could not be effective at low altitude. Thus, the B-70 program was stopped,
and B-58 production was halted. But the B-70 program was far enough along
that two prototypes were completed for testing, with results to inform the
SST project.
Interestingly, it
appears that the crashes of the B-70 and B-1 prototypes occurred for
the same reason -- the planes went out of control trying to avoid
chase planes taking publicity photos. (What this says about their
combat performance, I'll leave up to you!)
The second XB-70 prototype was lost during a photo session. General Electric
wanted pictures of a formation of planes powered by GE engines: XB-70,
F-4, F-104, and T-38. The photo plane was a Lear Jet at a comfortable
distance. Joe Walker moved his F-104 out of position, apparently to
examine something at the tail of the XB-70. The XB-70's vortex caught the
F-104, which cartwheeled across the top of the XB-70 and knocked off its
vertical tails. The F-104 exploded. The XB-70 continued in straight
flight for ten or fifteen seconds, then went into a spin.
If you want to flame, please be reasonably sure you know what you are
talking about.tggsu@resonex.UUCP (Tom Gulvin Root) (09/12/84)
Some people caught on that the XB-70 had drooping wing tips so as to catch the compression shock wave for added lift. While this is partially true, the main reason is that the center of lift moves back along a wing at supersonic speeds due to the compression wave along the wing leading edges. There are several methods of countering this tendancy - the B-58 and Concorde (and to some extent the B-1) move fuel around to modify the center of gravity so that it agrees with the center of lift. Times were simpler back then (?!?) and they mearly changed the effective wing area of the rear of the aircraft by rotating the wing tips away from the lift producing horizontal. BTW, it was made out of a stainless-steel/fiberglass honeycomb, not titanium. Tom Gulvin - Resonex, Inc. - Sunnyvale CA.