Posts Tagged ‘Compression Lift’

I think the North American XB-70 Valkyrie is one of the coolest airplanes to never enter military service.  First flown in 1964, the aircraft had its roots in design and feasibility studies from the mid 1950’s.  At that time, the Strategic Air Command had Boeing’s B-52 Stratofortress as its primary heavy bomber.  It carried an enormous payload for long distances, but it was a slow subsonic aircraft.  SAC also had Convair’s B-58 Hustler coming online (it entered service in 1960), and it was a relatively small, supersonic “dash-and-blast” bomber.  It set all kinds of speed records in its day, but didn’t have good range or payload capacity.

The XB-70 was designed to be the best of both, combining Mach 3 speed with huge range and payload capacity.  North American Aviation, already famous for the P-51 Mustang (and the F-86 Sabre and F-100 Super Sabre), was selected for the project.  Every possible bit of technology was utilized to make the monstrous B-70 a reality, but the neatest was the use of compression lift.  Designers built the outer wingtips to tilt down at supersonic speeds, which trapped the shock waves between the wingtips and engine nacelle, providing even more lift.

The first prototype was beset with problems, mostly due to the advanced designs being implemented and exotic materials being used, but many of them were fixed in the 2nd prototype, which first flew in 1965.  And fly it did!!  In 1966, it flew at Mach 3 (three times the speed of sound) on several occasions, maintaining that speed on May 19th for more than 30 minutes.  The XB-70 achieved its top speed of Mach 3.05 on June 6th.

But just two days later, on June 8, 1966, disaster struck.  The XB-70 was flying in close formation with several other planes in a photoshoot for General Electric (the Valkyrie used six massive GE engines in a “six-pack” configuration), when an F-104 Starfighter flying behind it rolled over the top of bomber, clipping its wing and destroying the rudders.  The 104 exploded (killing its pilot) and the XB-70 spun out of control and crashed, and while the pilot was able to eject, the co-pilot could not and was killed as well.  The photo to the left was taken just after the mid-air collision.

But it was the mid-60s now, and missile technology had advanced to the point that even a bomber flying at 70,000 feet could be shot down, and the B-70’s prodigous cost couldn’t be justified.  The program was cancelled with just the one aircraft (prototype 1) remaining.  It flew tests for NASA for several years and was then retired.

I think the XB-70 Valkyrie was, without question, one of the most beautiful and unique aircraft ever to lift off.  If you ever get a chance, see the remaining XB-70 at the National Museum of the USAF in Dayton, Ohio.  I’m pretty sure you won’t be disappointed.

Recommended Reading: North American XB-70 Valkyrie – A Photo Chronicle – I can’t tell you how many times I’ve leafed through my copy.  This plane continues to fascinate me.

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