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The heart of the SR-71 "Blackbird" : the mighty J-58 engine

by Philippe Ricco
translation : Graham Warrener
Marc Binazzi


1.6 : Note about designations

The military designation for this engine is J-58, but that given by its constructor is JT-11. The test-bench testing conducted in 1958 was with the YJ-58 prototypes. The turbofan version envisaged in the 1960s for the American SST ("Super Sonic Transport") projects carried the designation of JT-11-F4. A JT-11-B4 variant with increased thrust was envisaged during the same era for studying Mach 3 flight. It seems that the designation J-58-P4 corresponds to the JT-11-D20B series as the J-58-P2 is the version developed for the US Navy, without bypass, with only a 4 stage compressor (eight stages in all) against five in the J-58-P4. The letter "B" at the end of a Pratt & Whitney engine designation signifies that it is modified for high-altitude flight (for example with burners adapted for JP-7 fuel).

The American system of engine designation is almost identical to that used for aircraft; a letter indicates the type of engine (for example R -"radial" ) followed by a distinguishing number. With jet motors, their designation commences with "J" (for jet engine), e.g. J-58 or J-75. double-flux engines, which appeared much later, are designated by a letter "F" (for fan), e.g. The Pratt & Whitney F-100, which equipped the F-15 and F-16 fighters. These letter-number combinations continue with one or two letters indicating the factory of manufacture, ("GE" for General Electric, "P" for Pratt & Whitney) and a "batch number" indicating a particular production batch. For example the J-79-GE15 which equipped the McDonnell F-4D Phantom II, or the J-57-P55 which equipped the McDonnell F-101 Voodoo whereas the Lockheed U-2 is fitted with the J-57-P31. The entire designation can also be preceded by a special letter, for example "X" for an experimental unit, or "Y" for a pre-series unit, or even "R" (for a ramjet).

Aérostories 2002

1 : Genesis

> 1.1 Development
> 1.2 Evolutions
> 1.3 Ground and flight tests
> 1.4 Improvements
> 1.5 Projects and variants
> 1.6 Note about designations

2: Technical description (soon in N°13)

> 2.1 Compressor
> 2.2 Combustion chambers
> 2.3 Turbine
> 2.4 Afterburning
> 2.5 Bypass system
> 2.6 Accessories and equipments
> 2.7 Regulation system
> 2.8 Lubrication
> 2.9 Special propellants
> 2.10 Performances

3: The J-58 in use (soon in N°14)

> 3.1 Introduction
> 3.2 The Pratt & Whitney turbo-ramjet
> 3.3 Inlet
> 3.4 Exhaust
> 3.5 In flight
> 3.6 Unstarts
> 3.7 Automatic controls
> 3.8 Technology updates
> 3.9 Ground starting

> More infos about  SR-71

The maneuvering dolly specially adapted for the J-58-P4 equipping the SR-71 "Blackbird".
© Pratt & Whitney