United States military aero engine designations

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The United States military aero engine designation system was introduced in 1926, originally for piston engines it was expanded in the 1947 to include a separate system for turbine and rocket engines.

Piston engines[edit]

A piston engine designation has three separate elements, a type prefix, a number representing engine displacement and a model number.

Type Prefix
The type prefix is based on the engine disposition:
H Two-row inline
L Inline
O Opposed
R Radial
V Vee
W W engine
X X engine

Some early engines had the type letter prefixed by a modification letter

  • G - geared
  • I - inverted
  • S - supercharged
A number related to the engine displacement within 5 cubic inches.
Model Suffix

Letters were used between 1926 and 1933 then suffixes were numerals with odd number for Army and later Air Force engines and even numbers for Navy engines. After 1943 the letters AN were included to indicate the engine met both Army/Air Force and Navy requirements. Some engines fitted with water-injected engines had the W added to the suffix.

For example the Curtiss V-1150-1 is a Vee-type engine with a displacement of 1150 cubic inches and is an Army model.

Turbine engines[edit]

A turbine engine designation consists of four separate elements in the format TSS-MM-NN where T is the type letter, SS is the sequence number, MM is the manufacturer designation (one or two characters), and NN is the model number:

Type letter
J Jet engine
T Turboprop
TF or F Turbofan

The prefixes X for experimental and Y for service test are used.

Sequence number
Each type has its own sequence which started at 30.
Manufacturer designation
A Allison Engine Company
AC Allis-Chalmers
AJ Aerojet
B Buick
BO Boeing
CW Curtiss-Wright
F Ford
FF Frederic Flader
G Garrett AiResearch
GE General Electric
GN Giannini
K Kellog
L Lycoming
LA Lockheed
LD Avco Lycoming
MA Marquardt
MN Mensasco
NH Northrop-Hendy
OEL Orenda
P Pratt & Whitney / United Aircraft of Canada
R Fairchild
RM Reaction Motors
T Continental
V Packard
W Wright
WE Westinghouse
Model number
Odd numbers for the United States Air Force and even numbers for the United States Navy

For example the J79-GE-10 is a Turbojet built by General Electric and is a Navy model.

Rocket engines[edit]

Have a similar system to turbine engines but use three basic types:

LR Liquid-fuel
PS Pulsejet
RJ Ramjet


