The type numerals and type letter symbol are
assigned consecutively by each of the services. The
numerals begin as follows:
! 100—Air Force
! 400—Navy
! 700—Army
Model Indicator
The third part is the model indicator. It is a dash and
a model number, or a dash and a model number with a
suffix letter.
Each configuration of the engine has an assigned
model number. Each of the services assigns a block of
numbers that are used consecutively.
! 100—Air Force
! 400—Navy
! 700—Army
NOTE:
If one service uses another services'
designated engines, the designation remains the same
unless a model change is required. Only in this case will
the model indicator change to indicate the engine has
been modified.
F401-PW-400 is an example of a MIL-STD-1812
engine designation.
! F
Turbofan
! 401
Second Navy turbofan in designation
system
! PW
Pratt and Whitney Aircraft Division,
United Aircraft Corporation
! 400
First Navy model of this particular
engine
Q6-18.
What are the two engine designation systems
used to identify aircraft power plants?
Q6-19.
What does the letter X or Y preceding the
basic designation signify?
Q6-20.
What
are
the
three
parts
of
the
MIL-STD-1812 designation system?
Q6-21.
F401-PW-400 is an example of what engine
designation system?
POWER PLANT SAFETY
PRECAUTIONS
LEARNING
OBJECTIVE:
Recognize
power plant safety precautions that apply to the
intake ducts, exhaust area, and engine noise.
Operational readiness of a maximum number of
aircraft power plants is necessary if naval aviation is to
successfully perform its mission. Keeping aircraft and
power plants in top operating condition is the principal
function of naval aviation maintenance personnel. This
maintenance work must be performed without injury to
personnel.
Every
person
connected
with
power
plant
maintenance
is
responsible
for
discovering
and
eliminating unsafe work practices. In the following
section, we will discuss a few standard safety
precautions. You must follow these precautions to
prevent injury to yourself or others working on or near
aircraft jet engines.
INTAKE DUCTS
The air intake ducts of operating jet engines are an
extreme hazard to personnel working near the aircraft.
Ducts are also a hazard to the engine itself if the area
around the front of the aircraft is not kept clear of
debris. The air intake duct develops enough suction to
pull an individual, or hats, eye glasses, etc., into the
intake. The hazard is obviously greatest during
maximum power settings. Protective screens for the
ducts are part of the aircraft's ground-handling
equipment. These screens must be installed prior to all
maintenance turnups.
EXHAUST AREA
Jet engine exhausts create many hazards to
personnel. The two most serious hazards are the high
temperature and the high velocity of the exhaust gases
from the tailpipe. High temperatures are present several
hundred feet from the tailpipe. The closer you get to the
aircraft, the higher the exhaust temperatures and the
greater the danger.
When a jet engine is starting, sometimes excess
fuel will accumulate in the tailpipe. When this fuel
ignites, long flames shoot out of the tailpipe at very
high velocity. You will want to stay clear of this danger
at all times.
6-19
