MOONEY INTERNATIONAL CORPORATION
M20V SERVICE AND MAINTENANCE MANUAL
Page
Date
6
MAR 2017
Rev Date
21-50-00 - COOLING (OPTIONAL EQUIPMENT)
GENERAL
The type of cooling system installed in an aircraft oper-
ates on a closed vapor cycle concept using refrigerant
(R- 134a) as the heat absorption media. The (R- 134a)
Air conditioning System cools the aircraft in the same
manner as a cooling system in an automobile or home.
However, one major difference in the two systems is
that the (R- 134a) system contains components which
are designed to be light weight, compact, provide high
performance and operate at extreme altitudes and am-
bient temperatures.
REFRIGERANT (R- 134a) SYSTEM OPERATION
The concept of air conditioning a room, cabin or cockpit
is actually very simple. Figures 21- 2 and 21- 3 show
the electrical and refrigerant schematics for a typical
system (refer to schematics in back of this Service
Manual for specific electrical schematics). The refriger-
ant is the media which absorbs the room or cabin heat.
By continuous recirculation of the warm cabin air, heat
is absorbed in the evaporator module(s). When the
system is turned ON the compressor is connected to
the drive belt through an electrically actuated clutch.
The compressor compresses the R- 134a refrigerant
gas to a high pressure. The hot, high pressure gas then
passes through the condenser coil where it is cooled
and condensed into a warm liquid at constant pressure.
The warm liquid is then routed into a receiver- dryer
container where the liquid and any remaining gas are
separated and any moisture is absorbed. This liquid is
then directed to the evaporator module expansion
valve where the high pressure liquid is expanded to a
low pressure. The expansion process creates a super
cool gas which passes through the evaporator coil and
absorbs heat from the warm cabin air passing over the
coils. The warm low pressure refrigerant then enters
the R- 134a compressor where the process starts all
over again.
In addition to cooling cabin air, a refrigerant type sys-
tem also removes a large percentage of moisture from
the air.
The air conditioning system consists of various compo-
nents installed in several areas of the aircraft (Figure
21- 4). The Compressor Installation Engine Driven - lo-
cated on the rear (RH side) of the engine case, Switch
Installation/on cabin lower console; Evaporator Instal-
lation/hat rack; Outlet Duct Installation/over head of the
hat rack; Receiver- Dryer in Tailcone AFT of Hatrack;
Air Inlet Installation/tailcone (R/H tailcone panel); Dif-
fuser Assembly/tailcone (R/H access panel); Con-
denser Installation/tailcone (R/H access panel), and
Exhaust Duct/tailcone (lower tailcone).
21-51-00 - SYSTEM LEAK CHECK PROCEDURE
(R-134a)
Leak check of a refrigerant plumbing system is very im-
portant to assure that the system maintains its charge
to provide the designed performance and reduce dam-
age to system components. Plumbing systems on air-
craft are subject to excessive vibration and expansions
or contractions due to extreme ambient temperatures
and altitudes. Therefore, a periodic check of the sys-
tem charge is required to determine if any loss of refrig-
erant has occurred.
1. The system leak check is required whenever the
following conditions occur:
A. New system plumbing installation.
B. Component replacement in the plumbing sys-
tem.
C. Line or hose rupture.
D. Loss of refrigerant charge.
21-50-00
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