The Blackbird
During the 1960s, the USAF developed the SR-71 Blackbird, an aircraft capable of flying at speeds over three times faster than the sound from its own engines. December 22, 1964, marked the initial flight of an SR-71, and in January 1966, the first service-ready SR-71 was delivered to the 4200th (later 9th) Strategic Reconnaissance Wing at Beale Air Force Base in California. The Blackbird stood in a class of its own compared to all previous aircraft. “Everything had to be invented. Everything,” was how Skunk Works’ legendary aircraft designer Kelly Johnson described it in a fascinating article published on the Lockheed Martin website.
The SR-71 was the first aircraft to use its own fuel for hydraulic fluid
A claim confirmed by the fact that the SR-71 was the first aircraft to use its own fuel for hydraulic fluid. It was called the fuel hydraulic system.
An engine-driven pump provided 1800 psi of recirculating fuel to actuate various engine components and then returned it back to the aircraft fuel system to be burned. Fuel was used in the actuators to control the afterburner nozzles, which maintain the proper exhaust gas temperature and control the thrust output. The fuel was also used in the engine actuators to shift the two-position inlet guide vanes from their axial position to the cambered position and back again. This was just another of the many first-ever inventions of the SR-71.
As already explained, the fuel that powered the Blackbird was JP-7, which had a high flash point and high thermal stability. These unique features were required because the SR-71 became so hot while cruising at a speed of Mach 3.2, and conventional jet fuel could not be used in it.
However, emergency fuels could be used in the SR-71 if the crew was low on fuel and had to use any tanker they could find to avoid the loss of the aircraft. The emergency fuels were the JP-4 and JP-5, and they were limited to Mach 1.5 to prevent autogenous ignition of the aircraft.
The lifeblood of the fastest manned airplane in the world
The Blackbird had six main fuselage tanks. All of the 80,285 pounds of JP-7 fuel were carried in six main fuselage tanks. The tanks numbered one through six moved forward to aft (back). Tank 6B could hold 7,020 pounds of gravity-fed fuel and two tank sumps. This was also called the “doghouse” and was located in the extreme back portion of the fuselage.
These are just a few interesting facts that I found by reading Rich Graham’s “SR-71 Revealed: The Inside Story.” This book was published in 1996, before some of the facts about the Blackbird became unclassified.
Last year, when I was visiting SR-71 #972 on display at the Steven F. Udvar-Hazy Center in Chantilly, VA., one of my Grandson’s friends asked me, “Why is this airplane so big? My immediate answer was… they needed the room to hold as much fuel as possible.
Fuel was the lifeblood of the fastest manned airplane in the world.
Check out Habubrats SR-71 X page and Born into the Wilde Blue Yonder Habubrats Facebook page for further Blackbird photos and stories.
Photo by Mike Freer – Touchdown-aviation via Wikipedia
