After 1943 the letters AN were included to indicate the engine met both Army/Air Force and Navy requirements.
For example, the Curtiss V-1150-1 is a Vee-type engine with a displacement of 1150 cubic inches and is an Army model.
A jet 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: The prefixes X for experimental and Y for service test are used.
For example, the TF39-GE-1C is a Turbofan built by General Electric and was an Air Force model, which has powered the Lockheed C-5 Galaxy and the Pratt & Whitney TF30-P-414A is a turbofan built by Pratt & Whitney and was a Navy model, which has powered the Grumman F-14A Tomcat.
Have a similar system to jet engines but use three basic types: The prefixes X for experimental and Y for service test are used.