Pratt & Whitney J58 Turbojet

Designed to sustain Mach 3 speeds at over 80,000 ft, the Pratt & Whitney J58 turbojet engine powered the Lockheed A-12 and SR-71. An engineering marvel, the J58 had a single-shaft rotor design with a novel compressor bleed bypass when in extreme high-speed operation. What made this engine so unique is the six bypass tubes, which directed airflow from the compressor stage directly into the afterburner. This allowed the SR-71 to operate at a much higher fuel efficiency than other afterburning jet engines when in full afterburner. These bypass tubes are easily visible in the middle section of the J58 on display. The extended high temperature environment necessitated the flash-resistant JP-7 fuel, which required a chemical to ignite. The engine generated a maximum thrust of 32,500 pounds — more than 160,000 shaft horsepower.

Did you know?

Originally developed as a US Navy project in the late 1950s, the US Air Force and CIA took over the engine project for the super-secret A-12 spy plane and subsequently the Lockheed SR-71 “Blackbird”.

Powered by two J58 engines, the SR-71 set a world altitude record of 85,069 ft and a world speed record of 2,193 mph in 1976.

About this engine 

This Pratt & Whitney J58 (civilian designation JT11D-20) was last flown in 1989, and was removed from the left hand position of SR-71 Serial number 61-7960. This engine accumulated only 1408 hours total since its USAF acceptance in 1966. It is on loan from the National Museum of the US Air Force in Ohio.
Pratt & Whitney J58 Engine
Type: Afterburning turbojet with compressor bleed bypass
Compressor: 8-stage, axial flow
Turbine: 2-stage axial flow
Length: 180 in (an additional 6 in at max. temp.)
Diameter: 50 in
Dry weight: 6,000 lb
Col. Richard Graham, USAF Ret, SR-71 pilot and friend of the Museum, explains how the J58 engine works as he walks around the J58 located in the Museum's SR-71 Gallery.
Video Credit: "SR-71 J58 Engine Tour," by Erik Johnston, 2013