power unit (APU) is running. The AMP interacts with
regulator, which regulates the outflow of air from the
the APU to such an extent that it is referred to as the
In addition to the major components, various
valves, controls, and other related units are neces-
air-conditioning system. The design, construction, and
The P-3 aircraft has two EDCs (fig. 6-1), to supply
use of these components may vary somewhat with
air to each of the two air cycle cooling systems. During
different manufacturers; however, the systems on all jet
EDC operation, there is no interconnect between the
aircraft operate on the same principles.
flight station and cabin systems until well downstream
in the air distribution and exhaust system. The no. 2
Q6-4. List the five requirements necessary for
engine EDC supplies air to the right (flight station) air
cycle cooling system and the no. 3 EDC supplies air to
the left (cabin) air cycle cooling system. The duct
Q6-5. List three systems that are included in the
crossover is in the APU compartment and allows the
environmental control system.
ducts some flexibility for expansion. The EDC is
mounted to a drive pad on the left side of the engine
AIR CYCLE AIR-CONDITIONING
reduction gearbox assembly. The EDCs are adjusted for
to deliver 60 pounds of air per minute at sea level.
LEARNING OBJECTIVE: Recognize the
components and operating principles of air
cycle air-conditioning systems (ACS).
The APU/AMP combination supplies air to the air
Most naval aircraft are designed with an air cycle
cycle cooling systems during ground operation only. It
ACS because it is efficient for the weight and space
required and is relatively trouble-free. The name air
cycle or air-to-air comes from the principle of cooling
the air without the use of refrigerants by compression
and expansion of bleed air. The P-3 air cycle ACS is an
example of this type of system.
The P-3 air-conditioning system is comprised of
two independent air cycle cooling systems of identical
capacity, each with its own temperature control system,
and fresh air sources. Fresh air sources are comprised
multiplier package (AMP).
Fresh Air Sources
In order for the air-conditioning system to function,
air at the proper temperature and flow volume must be
available. The fresh air sources are the EDCs and the
fully automatic controls. They supply air to the air cycle
cooling systems during flight and are operable only
when no. 2 and no. 3 engines are running. The EDCs
also serve as a secondary air source for the air cycle
cooling systems during ground operations. The AMP is
the primary air source for the air cycle cooling systems
only during static ground operations when the auxiliary
Figure 6-1.--EDC view from left.