OTD in 1969, The Iconic XB-70 Valkyrie Mach 3 Super Bomber Made Its Last Flight

Three drag chutes were needed to slow down the landing roll of the XB-70. (Image credit: Reddit edit The Aviationist)

The massive XB-70 Valkyrie is the largest and heaviest airplane ever to fly at Mach 3.

The North American XB-70 Valkyrie was the most ambitious super-bomber project of the Cold War. The massive six-engine bomber was slated to be the ultimate American high-altitude, high-speed, deep-penetration manned nuclear bomber designed to fly high and fast, so as to be safe from Soviet interceptors.

Two Valkyrie prototypes were been built at North American Aviation before the Kennedy Administration cancelled the program as a consequence of the doubts that surrounded the future of manned bombers believed to be obsolete platforms. The threat posed by Soviet SAMs (Surface-to-Air Missiles) put the near-invulnerability of the strategic bomber at high altitudes in doubt. In low-level penetration role, the B-70 offered little performance improvement over the B-52 it was designed to replace (!) and it was much more expensive with shorter range.

Some fascinating variants of the aircraft were proposed. Some envisaged the B-70 carrying an Alert Pod, or flying as a Supersonic Refueler or as a Recoverable Booster Space System (RBSS). You can find all the details about these crazy concepts in this story we have posted last year.

The B-70 program was canceled in 1961 and development continued as part of a research program to study the effects of long-duration high-speed flight with the two XB-70A.

XB-70A number 1 (62-001) made its first flight from Palmdale to Edwards Air Force Base, CA, on Sept. 21, 1964. The second XB-70A (62-207) made its first flight on Jul. 17, 1965. The latter differed from the first prototype for being built with an added 5 degrees of dihedral on the wings as suggested by the NASA Ames Research Center, Moffett Field, CA, wind-tunnel studies.

While the 62-001 made only one flight above Mach 3, because of poor directional stability experienced past Mach 2.5, the second XB-70, achieved Mach 3 for the first time on Jan. 3, 1966 and successfully completed a total of nine Mach 3 flights by June on the same year.

Photo of the XB-70 #1 cockpit, which shows the complexity of this mid-1960s research aircraft. On the left and right sides of the picture are the pilot’s and co-pilot’s control yokes. Forward of these, on the cockpit floor, are the rudder pedals with the NAA North American Aviation trademark. Between them is the center console. Visible are the six throttles for the XB-70’s jet engines. Above this is the center instrument panel. The bottom panel has the wing tip fold, landing gear, and flap controls, as well as the hydraulic pressure gages. In the center are three rows of engine gages. The top row are tachometers, the second are exhaust temperature gages, and the bottom row are exhaust nozzle position indicators. Above these are the engine fire and engine brake switches. The instrument panels for the pilot left and co-pilot right differ somewhat. Both crewmen have an airspeed/Mach indicator, and altitude/vertical velocity indicator, an artificial horizon, and a heading indicator/compass directly in front of them. The pilot’s flight instruments, from top to bottom, are total heat gage and crew warning lights; stand-by flight instruments side-slip, artificial horizon, and altitude; the engine vibration indicators; cabin altitude, ammonia, and water quantity gages, the electronic compartment air temperature gage, and the liquid oxygen quantity gage. At the bottom are the switches for the flight displays and environmental controls. On the co-pilot’s panel, the top three rows are for the engine inlet controls. Below this is the fuel tank sequence indicator, which shows the amount of fuel in each tank. The bottom row consists of the fuel pump switches, which were used to shift fuel to maintain the proper center of gravity. Just to the right are the indicators for the total fuel top and the individual tanks bottom. Visible on the right edge of the photo are the refueling valves, while above these are switches for the flight data recording instruments. (Image credit: NASA)

A joint agreement signed between NASA and the Air Force planned to use the second XB-70A prototype for high-speed research flights in support of the American supersonic transport (SST) program.

However, on June 8, 1966, the XB-70 62-207 was involved in one of the most famous and tragic accidents in military aviation when it collided with a civilian registered F-104N while flying in formation as part of a General Electric company publicity photo shoot over Barstow, California, outside the Edwards Air Force Base test range in the Mojave Desert. The aircraft were flying in formation with a T-38 Talon, an F-4B Phantom II, and a YF-5A Freedom Fighter.

North American XB-70A Valkyrie just after collision. Note the F-104 is at the forward edge of the fireball and most of both XB-70A vertical stabilizers are gone. (U.S. Air Force photo)

As explained in a previous post here at The Aviationist:

Towards the end of the photo shooting NASA registered F-104N Starfighter, piloted by famous test pilot Joe Walker, got too close to the right wing of the XB-70, collided, sheared off the twin vertical stabilizers of the big XB-70 and exploded as it cartwheeled behind the Valkyrie. North American test pilot Al White ejected from the XB-70 in his escape capsule, but received serious injuries in the process. Co-pilot Maj. Carl Cross, who was making his first flight in the XB-70, was unable to eject and died in the crash.

The root cause of the incident was found to be wake turbulence: wake vortices spinning off the XB-70’s wingtip caused Walker’s F-104N to roll, colliding with the right wingtip of the huge XB-70 and breaking apart. As explained in details in this post, wingtip vortices form because of the difference in pressure between the upper and lower surfaces of a wing. When the air leaves the trailing edge of the wing, the air stream from the upper surface is inclined to that from the lower surface, and helical paths, or vortices, result. The vortex is strongest at the tips and decreasing rapidly to zero nearing midspan: at a short distance from the trailing edge downstream, the vortices roll up and combine into two distinct cylindrical vortices that constitute the “tip vortices.

Although research activities continued with the first prototype with a first NASA flight on April 25, 1967, the last one was on Feb. 4, 1969.

The only remaining XB-70 Valkyrie super bomber in on display at the National Museum of the U.S. Air Force at Wright-Patterson AFB in Dayton, Ohio. In October last year, it had to briefly moved outside for display maintenance. Here you can watch a video of the monumental move.

A view of the six massive afterburners on the XB-70 Valkyrie as the aircraft is towed out of its display hangar temporarily for museum maintenance. (Photo: National Museum of the U.S. Air Force via YouTube)
About David Cenciotti 4320 Articles
David Cenciotti is a freelance journalist based in Rome, Italy. He is the Founder and Editor of “The Aviationist”, one of the world’s most famous and read military aviation blogs. Since 1996, he has written for major worldwide magazines, including Air Forces Monthly, Combat Aircraft, and many others, covering aviation, defense, war, industry, intelligence, crime and cyberwar. He has reported from the U.S., Europe, Australia and Syria, and flown several combat planes with different air forces. He is a former 2nd Lt. of the Italian Air Force, a private pilot and a graduate in Computer Engineering. He has written four books.