Investigation Summary
The aircraft was participating in a Cold War airborne alert mission when a failure in the hot air vents caused cockpit temperatures to rise between 125 and 160 degrees Fahrenheit. The extreme heat eventually shattered a cockpit window and damaged flight instruments. To survive the conditions, the crew depressurized the aircraft and descended from 33,500 feet to 12,000 feet. This lower altitude flight, combined with a stuck fuel gauge for the #1 main tank, resulted in the aircraft reaching a critical fuel state earlier than anticipated. Although a tanker was eventually launched and a rendezvous initiated, the B-52 ran out of fuel while positioned just two miles behind the tanker. The pilot, Major DeWitt Clay, steered the aircraft toward an unpopulated barley field before ejecting at 4,000 feet. The two 3.8-megaton nuclear bombs were thrown from the aircraft on impact; one remained largely intact while the other broke apart, scattering its primary and secondary stages. Safety modifications (Alt 197) to the Arm/Safe switches prevented a nuclear detonation, although one weapon's thermal batteries activated due to impact-related short circuits.
Final Conclusions
The Air Force accident report attributed the crash to fuel exhaustion resulting from a failure of the cabin pressurization system and subsequent low-altitude flight. The investigation confirmed that all design safety features of the nuclear weapons performed adequately, preventing a nuclear catastrophe. A secondary fatality occurred on the ground when Air Force Master Sergeant Francis W. Barnish (sometimes referred to in reports as a fireman) was killed in a vehicle accident while responding to the crash site.
Video Analysis
No video analysis linked for this case file yet.
Systems & Failure Modes
Cabin Pressurization System
Failed due to a window crack and excessive heat, forcing a low-altitude flight that increased fuel burn.
Fuel Gauging System
The #1 main tank gauge stuck at 10,030 pounds, causing the crew to miscalculate their remaining flight time.
MC-1288 Arm/Safe Switch
A safety modification (Alt 197) designed to prevent battery charging when set to 'Safe', which successfully prevented detonation.
Interesting Facts
- 01The aircraft was carrying two Mark 39 Mod 2 thermonuclear bombs, each with a 3.8-megaton yield.
- 02All eight crew members survived the ejection, though four sustained injuries.
- 03The crash is classified as a 'Broken Arrow' incident due to the involvement of nuclear weapons.
- 04One weapon's high explosives were found 'crumbled' and the other's were shattered and scattered.
- 05The Arm/Safe switches remained in the 'Safe' position, preventing nuclear detonation.
Safety Actions & Advisories
Alt 197 Safety Modification
The accident validated the Alt 197 modification, which replaced the MC-722 switch with the MC-1288 to prevent inadvertent battery activation during crashes.