Did you know the SR-71 was the first aircraft to use its own fuel for hydraulic fluid? The Blackbird’s fuel hydraulic system.

Did you know the SR-71 was the first aircraft to use its own fuel for hydraulic fluid? The Blackbird’s fuel hydraulic system.

By Linda Sheffield Miller
Jun 30 2024
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The Blackbird

In the 1960’s, the US Air Force (USAF) developed the SR-71 Blackbird, a plane that could travel more than 3 times as fast as the sound produced by its own engines.

B-58 navigator recalls dropping Mark-53 nuclear bomb (without plutonium pit) while flying at 500 feet and at 628 knots, low level recce missions, dinner with Doolittle Raiders and Jimmy Stewart
CLICK HERE to see The Aviation Geek Club contributor Linda Sheffield’s T-shirt designs! Linda has a personal relationship with the SR-71 because her father Butch Sheffield flew the Blackbird from test flight in 1965 until 1973. Butch’s Granddaughter’s Lisa Burroughs and Susan Miller are graphic designers. They designed most of the merchandise that is for sale on Threadless. A percentage of the profits go to Flight Test Museum at Edwards Air Force Base. This nonprofit charity is personal to the Sheffield family because they are raising money to house SR-71, #955. This was the first Blackbird that Butch Sheffield flew on Oct. 4, 1965.

The first flight of an SR-71 took place on Dec. 22, 1964, and the first SR-71 to enter service was delivered to the 4200th (later 9th) Strategic Reconnaissance Wing at Beale Air Force Base, Calif., in January 1966.

The Blackbird was in a different category from anything that had come before. “Everything had to be invented. Everything,” Skunk Works legendary aircraft designer Kelly Johnson recalled in an interesting article appeared on 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-71was 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 accurate 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 veins 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 the 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.

Did you know the SR-71 was the first aircraft to use its own fuel for hydraulic fluid? The Blackbird’s fuel hydraulic system.
This print is available in multiple sizes from AircraftProfilePrints.com – CLICK HERE TO GET YOURS.  Dawn at 80.000ft – SR-71 Blackbird

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 ingnition 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 tanks 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.

Be sure to check out Linda Sheffield Miller (Col Richard (Butch) Sheffield’s daughter, Col. Sheffield was an SR-71 Reconnaissance Systems Officer) Twitter X Page Habubrats SR-71 and Facebook Page Born into the Wilde Blue Yonder Habubrats for awesome Blackbird’s photos and stories.

Photo credit: Mike Freer – Touchdown-aviation via Wikipedia

Cool Video Explains how SR-71 Blackbird’s J58 Turbo-Ramjet Engine Works
This model is available in multiple sizes from AirModels – CLICK HERE TO GET YOURS.

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Linda Sheffield Miller

Linda Sheffield Miller

Grew up at Beale Air Force Base, California. I am a Habubrat. Graduated from North Dakota State University. Former Public School Substitute Teacher, (all subjects all grades). Member of the DAR (Daughters of the Revolutionary War). I am interested in History, especially the history of SR-71. Married, Mother of three wonderful daughters and four extremely handsome grandsons. I live near Washington, DC.
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