# Pratt & Whitney J52

The Pratt & Whitney J52 (company designation JT8A) is an axial-flow dual-spool turbojet engine originally designed for the United States Navy, in the 40 kN (9,000 lbf) class. It powered the A-6 Intruder and the AGM-28 Hound Dog cruise missile. As of 2021 the engine was still in use in models of the A-4 Skyhawk.
The engine is the basis for the Pratt & Whitney JT8D, a popular civilian low-bypass turbofan engine.

## Design and development

The J52 was developed in the mid-1950s for the US Navy as a scaled-down derivative of the J57/JT3A. It was initially intended to power the A4D-3 Skyhawk, an advanced avionics model that was canceled in 1957. After being canceled, the U.S. Air Force selected the J52 to power the AGM-28 Hound Dog cruise missile. The engine was designed with several unique features for this application, including a "conical centerbody mounted in the intake" and a "variable central plug ... in the nozzle". Then, in 1958, the US Navy selected the engine to power what became the A-6 Intruder.
The J52-P-6 model, designed for the YA2F-1 (YA-6A) Intruder, had a unique nozzle that could be angled downward at 23 degrees for STOL takeoffs; this was not used on production A-6s. Returning full circle, the J52 was selected to power the A4D-5, another model of the A-4 Skyhawk, remaining in all subsequent new-built models.
The twin-spool J52 employs a split 12-stage axial compressor consisting of a five-stage low pressure unit and a seven-stage high pressure unit. Behind the compressor is a nine-unit can-annular combustion chamber and a two-stage split turbine.

## Operational history

In 1960, U.S. Air Force's Strategic Air Command (SAC) developed procedures so that the Boeing B-52 Stratofortress could use the Hound Dog's J52 engine for additional thrust while the missile was located on the bomber's two pylons. This helped heavily laden B-52s fly away from their airbases faster, which would have been useful in case of nuclear attacks on the bases. The Hound Dog could then be refueled from the B-52's wing fuel tanks.

## Variants
### J52-P-3

    Flown in: AGM-28 Hound Dog. This variant produced 7,500 lbf (33,000 N) of thrust. The design of the P-3 model included a variable inlet duct to improve engine efficiency at the various altitudes the cruise missile was designed to fly at.

### J52-P-6

    Flown in: A-6A. This variant produced 8,500 lbf (38,000 N) of thrust and included the 23-degree downward swiveling nozzle.

### J52-P6A

    Flown in: A-4E, TA-4J, EA-6B (the first few). This variant produced 8,500 lbf (38,000 N) of thrust.

### J52-P-8A/B

    Flown in: A-4F/G/H/K, TA-4E/F/G/H, A-6E, EA-6B. This variant produced 9,300 lbf (41,000 N) of thrust.

### J52-P-408

    Flown in: A-4M/N, TA-4KU, EA-6B. This variant included variable inlet guide vanes (VIGV) in the LPC, air-cooled turbine blades, and produced 11,200 lbf (50,000 N) of thrust. Still in operation with Argentina, Brazil, and Indonesia

### J52-P-409

    (PW1212) 12,000 lbf (53 kN) thrust version of the J52-P-408 with an improved low pressure turbine (LPT) and faster acceleration. Designed for the EA-6B and was additionally marketed as an upgrade for the A-4. The J52-P-409 was also proposed as a cost-effective upgrade to the A-6E as an alternative to the A-6F Intruder II, but was not purchased. The P-409 engine was also proposed for use in the EA-6B ADVCAP, but that program was canceled after three prototypes were built and flown. The P-409 would have been available as a new engine or as an upgrade kit for P-408 engines, but was never ordered in significant quantities.

### PW1212

    J52-P-409 re-designated

### PW1216

    An afterburning derivative of the J52-P409 engine proposed for the Grumman Sabre II concept (the project later evolved into the JF-17 Thunder). The afterburner, designed in China, would have increased thrust to 16,000 lbf (71 kN).

### JT8A

    Company designation for initial versions of the J52

### JT8B-1

    (J52-P-6 / P-6A)

### JT8B-3

    (J52-P-8A)

## Applications

* AGM-28 Hound Dog
* Dassault Super Mystère
* Douglas A-4 Skyhawk
* Grumman A-6 Intruder
* Lockheed Martin A-4AR Fightinghawk
* Northrop Grumman EA-6B Prowler
* LIMRV - On 14 August 1974, the LIMRV achieved a world record speed of 255.7 mph (411.5 km/h)

## Specifications (J52-P-408)

Data from Flight

#### General characteristics

* Type: turbojet
* Length: 118 in (300 cm)
* Diameter: 38 in (96.5 cm)
* Dry weight: 2,318 lb (1,052 kg)

#### Components

* Compressor: axial flow, 5-stage LP, 7-stage HP
* Turbine: single stage HP, single stage LP
* Fuel type: JP-4

#### Performance

* Maximum thrust: 11,200 lbf (50 kN)
* Overall pressure ratio: 14.6 : 1
* Air mass flow: 143 lb/s
* Specific fuel consumption: 0.79 lb/(lbf⋅h) (22 g/(kN⋅s))
* Thrust-to-weight ratio: 4.83