14 CFR § 145.61

The FAA may issue a limited rating to a certificated repair station that maintains or alters only a particular type of airframe, powerplant, propeller, radio, instrument, or accessory, or part thereof, or performs only specialized maintenance requiring equipment and skills not ordinarily performed under other repair station ratings. Such a rating may be limited to a specific model aircraft, engine, or constituent part, or to any number of parts made by a particular manufacturer.

The FAA issues limited ratings for—

Airframes of a particular make and model;

Engines of a particular make and model;

Propellers of a particular make and model;

Instruments of a particular make and model;

Radio equipment of a particular make and model;

Accessories of a particular make and model;

Landing gear components;

Floats, by make;

Nondestructive inspection, testing, and processing;

Emergency equipment;

Rotor blades, by make and model;

Aircraft fabric work;

Any other purpose for which the FAA finds the applicant's request is appropriate.

For a limited rating for specialized services, the operations specifications of the repair station must contain the specification used to perform the specialized service. The specification may be—

A civil or military specification currently used by industry and approved by the FAA, or

A specification developed by the applicant and approved by the FAA.