MIL-PRF-21480B
This specification is approved for use by all Departments and Agencies of the Department of
Defense.
1. SCOPE
1.1 Scope. This specification establishes the general requirements for three phase, four
wire, wye-connected, 400 Hertz, alternating current (AC), constant input speed, electric power
generator systems for use on aircraft.
Classification.
1.2
1.2.1
Generator class. Generator systems are classified as follows (see 6.1):
Class N Generator systems designed to operate within a narrow speed range (393 to 407
Hertz). Typical drive mechanisms with narrow speed range include hydro-
mechanical constant speed drives and Auxiliary Power Units (APUs) with
precision speed control.
Class W Generator systems designed to operate within a wide speed range (380 to 420
Hertz). Typical drive mechanisms with wide speed range include propeller
gearboxes, helicopter rotor transmissions, hydraulic motors, ram air turbines, and
APUs with electromechanical speed control.
1.2.2 Part or identifying number (PIN). Each component PIN will consist of the letter
"M"; the general specification number; a slash followed by the specification sheet number; and
an assigned dash number (example: M21480/3-01).
2. APPLICABLE DOCUMENTS
General. The documents listed in this section are specified in sections 3 or 4 of
2.1
this specification. This section does not include documents cited in other sections of this
specification or recommended for additional information or as examples. While every effort
has been made to ensure the completeness of this list, document users are cautioned that they
must meet all specified requirements of documents cited in sections 3 or 4 of this specification,
whether or not they are listed.
2.2
Government documents.
2.2.1 Specifications and standards. The following specifications and standards form a part
of this document to the extent specified herein. Unless otherwise specified, the issues of these
documents are those cited in the solicitation or contract (see 6.2).
FEDERAL STANDARD
FED-STD-595/17875
Miscellaneous, Gloss
1
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