ANA Bulletin Number 306
that it will not perform satisfactorily under all
operating conditions. The designation applies to
As stated before, this bulletin is an Air Force-
an engine or device that has a specific function
Navy bulletin. It is the older system, and it has
rather than a general one, or that the engine has
no provisions for Army designations.
only completed a 50-hour qualification test. Upon
satisfactory completion of the 150-hour qualifica-
Type Symbols
tion testing, the engine is approved as a J type.
The first part of the designation consists of
MANUFACTURER SYMBOLS
a letter (or letters) with a number showing each
basic engine type.
The second part of the designation is a dash
The following are letter-type symbols:
and the manufacturer's letter(s) symbol.
The following are some prominent engine
manufacturers:
R . . . . . . . . . . Internal-combustion, air-cooled,
radial engine (reciprocating)
GE . . . . . . . . . . . . . . . . . . . . .. General Electric
J . . . . . . . . . . . Aviation gas-turbine (turbojet)
A . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Allison
T . . . . . . . . . . Aviation gas-turbine (turboprop
WE . . . . . . . . . . . . . Westinghouse Electric Co.
and turboshaft engines for heli-
copters)
P
. . . . . . . . . . . . . . . . . . . . Pratt and Whitney
TF . . . . . . . . . Turbofan engine
W . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wright
PJ . . . . . . . . . Pulsejet engine
AC . . . . . . . . . . . . . . . . . . . . . .. Allis Chalmers
RJ . . . . . . . . . Ramjet engine
BA . . . . . . . . . . . . . . . . . . . .. Bell Aircraft Co.
R M . . . . . . . . . . . . Rocket motors
LA . . . . . . . . . . . . . . .. Lockheed Aircraft Co.
Following the letter symbol(s) is a number.
The Navy or-Air Force assigns numbers with the
MD . . . . . . . . . . . . . . . McDonald Aircraft Co.
letter. These numbers are arbitrary; they do not
represent any characteristics of the units involved.
V . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Packard
The Navy uses even numbers beginning with 30.
MODEL NUMBERS
The Air Force uses odd numbers beginning with
31.
Although an engine may carry an odd or an
The third part of the designation consists of
even number, it does not restrict the engine to the
a dash and a numeral showing the model number.
service sponsoring or approving them. Engines
Model numbers, like type symbols, use odd
numbers for Air Force models and even numbers
selection and use, by the various services, depends
for Navy models. Air Force model numbers for
on their satisfactory application for a particular
airframe.
each type of jet engine begin with 1 and continue
with consecutive odd numbers. Navy numbers
SPECIAL DESIGNATIONS
begin with 2 and continue with consecutive even
numbers. Model numbers show the service that
The letter X or Y before the basic designation
approves the model. The Naval Air Systems
Command approves all even model numbers. The
shows an experimental or restricted engine.
Air Materiel Command approves all odd model
The letter X used as a prefix show experimen-
numbers.
tal and service test of a particular engine. After
A given engine design has only one type and
exhaustive tests confirming the ability of an engine
model designation for both services. For example,
to perform under all operating conditions, you
if the Navy uses an Air Force-approved engine
remove the X prefix.
without any changes, the Navy uses the numbers
The letter Y shows restricted service designa-
assigned. If the Air Force uses a Navy-approved
tion. Its application is self-explanatory in the sense
1-9
