How Vietnam Nearly Shot Down America's SR-71 Spy Plane (Fastest on Earth)

Dario Leone

Security,

Almost...

On May 15, 1972, Majs Tom Pugh and Ronnie Rice were airborne in SR-71 61-7978 (known as the “Rapid Rabbit” because of the Playboy logo she sported on both rudders throughout most of her career) on Tom’s 236th Blackbird sortie. They were flying a routine Giant Scale mission (as operational sorties flown out of Det 1 were called), scheduled to be a double looper up through the Gulf of Tonkin for a front door entry. Just short of Haiphong, Tom’s concern over a strange cyclical hum in the interphone system was relieved when the generator bus tie circuit split, allowing independent operation of each of the 60 KVA AC generators, one of which had been responsible for the varying frequency, hence the hum.

Freed of the AC bus load sharing, the system seemingly returned to normal. The Go-No-Go checklist allowed the mission to proceed. While Tom was maintaining Mach 3.18 at 79,500ft, a generator failed. That failure was a mandatory abort item, so the crew began making provisions to divert into Thailand.

As told by Paul F Crickmore in his book Lockheed Blackbird: Beyond the Secret Missions (Revised Edition), just over a minute later the other generator failed, and they were in real trouble. Emergency AC and DC power did not come online and the fuel boost pumps stopped pumping JP-7 to the engines. Without electrical power, the Stability Augmentation System (SAS) cut out, and lacking boost pump pressure the fuel flow to both engines stopped, causing them to flameout. To add to the crew’s grief, the-inlet spikes went full forward and, as ‘978 began pitching and rolling rapidly, Tom knew the aircraft was approaching the limits of its supersonic flight envelope.