NATOPS FLIGHT MANUAL NAVY MODEL AV--8B/TAV--8B 161573 AND UP AIRCRAFT (2008)

A1-AV8BC-410-100

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Alphabetical Index (Continued)

Subject

Page No.

Secondary Heat Exchanger

Skin Temperature Sensor

Temperature Regulating Valve

Venturi/Choke

Water Separator

Windshield Defog Nozzles/Fixed Canopy Ventilation Nozzles

Windshield Overtemperature Switch

System Controls and Indicators

CABIN Switch

Cabin Temperature Control

Max Defog Relay

PRESS Switch

Rear WSHLD Caution Light

Windshield Overtemperature Relay

WSHLD Caution Light

System Description

Related Systems

DC Power System

Landing Gear and Related Systems

Power Plant and Related Systems

Warning/Caution/Advisory Lighting System

Operation

Component Operation

Cabin ECS Air Filter Assembly

Cabin ECS Check Valve

Cabin ECS Pressure Regulating and Shutoff Valve

Cabin Temperature Sensor

Cold Air Unit

Defog Shutoff Valve

Duct Temperature Sensor

ECS Control Panel Assembly

ECS Louvers

ECS Pressure Switch

Fixed Canopy Ventilation Nozzles

Forward Vent/Defog Valve

Primary Heat Exchanger

Rear Vent/Defog Valve

Secondary Heat Exchanger

Skin Temperature Sensor

Temperature Regulating Valve

Water Separator

Windshield Defog Nozzles

Windshield Overtemperature Switch

System Operation

Emergency Operation

Normal Operation

A1-AV8BC-410-100

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Record of Applicable Technical Directives

Type/

Date

Title and ECP or RAMEC No.

Remarks

Number

Incorp.

AV8AFC-416

— TAV-8B Polyimide Wire Replacement/

15 May 04

—

Power Wire Separation (ECP MDA-AV8B-

0277)

1. DESCRIPTION.

9. Water Separator. The water separator is a swirl

frame, a woven cloth coalescer, and a bypass valve

2. SYSTEM DESCRIPTION. The cabin cooling and

in a common housing.

defog system conditions hot sixth stage engine bleed

air to satisfy cockpit environmental requirements.

10. Forward Vent/Defog Valve. The vent/defog

valve is a solenoid controlled, pneumatically

3. COMPONENT DESCRIPTION. System

actuated, two position valve. The valve is made up

components are described and listed in the

of a housing, movable piston and a control solenoid.

paragraphs below. For component locator, refer to

WP005 00.

11. ECS Louvers. The ECS louvers are adjustable

metal air outlets.

4. Cabin ECS Air Filter Assembly. The cabin ECS

air filter assembly is a reusable, steel mesh filter

12. Windshield Defog Nozzles/Fixed Canopy

element encased in a housing with a spring loaded

Ventilation Nozzles. The windshield defog nozzles

bypass valve.

and fixed canopy ventilation nozzles are tapered,

slotted, metal tubes.

5. Cabin ECS Pressure Regulating and Shutoff

13. ECS Control Panel Assembly. The ECS control

Valve. The cabin ECS pressure regulating and

panel is a console mounted, illuminated control

shutoff valve is an electrically controlled,

panel which provides mounting for environmental

pneumatically operated valve. The valve is made up

control system controls.

of a solenoid controlled shutoff section and a

pneumatically controlled pressure regulating

14. Windshield Overtemperature Switch. The

section. The shutoff section is made up of a

windshield overtemperature switch is an in-line

solenoid operated control valve and a spring loaded

temperature sensitive, bimetallic, electrical switch.

shutoff piston mounted on a shaft. The pressure

regulating section is made up of two sensing

15. Skin Temperature Sensor. The skin

chambers, a relief valve, and a spring loaded piston

temperature sensor is a thermometer element

mounted on a shaft.

imbedded in a contact strip.

6. Venturi/Choke. The venturi/choke is a metal

16. Duct Temperature Sensor. The duct

duct assembly with a constricted throat.

temperature sensor is a thermistor enclosed in a

threaded housing.

7. Temperature Regulating Valve. The

temperature regulating valve is an electrically

17. Cabin Temperature Sensor. The cabin

driven butterfly type valve. The valve is made up of

temperature sensor is a thermistor enclosed in a

a butterfly valve, actuator, an integral follow-up

housing attached to a mount bracket.

resistor and a brake.

18. Cabin ECS Check Valve. The cabin ECS check

8. Cold Air Unit. The cold air unit is a compressor

valve is a flapper type, spring loaded closed check

turbine and expansion turbine, mounted at opposite

valve.

ends of a common shaft, in a common housing. The

cold air unit has a serviceable bearing lubrication

19. Defog Shutoff Valve. The defog shutoff valve is

system and a bearing cooling system.

an electrically controlled, pneumatically actuated

shutoff valve.

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20. ECS Pressure Switch. The ECS pressure switch

MLG weight on wheels (WOW) switch and the

is a pneumatically actuated electrical switch.

weight on wheels relay no. 1.

30. SYSTEM CONTROLS AND INDICATORS.

21. Rear Vent/Defog Valve. The rear vent/defog

valve is a solenoid controlled, pneumatically

31. CABIN Switch. The CABIN switch, located on

actuated, two position valve. The valve is made up

the ECS control panel assembly, is a single pole

of a housing, movable piston, and a control

toggle switch. The switch controls airflow for cabin

solenoid.

and windshield defogging. The switch has three

positions: NORM, DFOG, and MAX DFOG.

22. Primary Heat Exchanger. The primary heat

exchanger is a crossflow, air to air heat exchanger.

32. Setting the CABIN switch to NORM does the

The heat exchanger is made up of a finned core

below:

enclosed in a housing.

a. Applies essential 28vdc to energize the

23. Secondary Heat Exchanger. The secondary

forward vent/defog valve and rear vent/defog valve,

heat exchanger is a crossflow, air to air heat

causing them to go to the unrestricted position.

exchanger. The heat exchanger is made up of a

finned core enclosed in a housing.

b. Applies essential 28vdc through the weight

on wheels relay no. 1 to the defog shutoff valve. The

24. RELATED SYSTEMS.

defog valve will close if the aircraft is weight on

wheels and system pressure is less than 20 psi.

25. Power Plant and Related Systems. Hot, high

33. Setting the CABIN switch to DFOG does the

pressure bleed air is provided by the engine sixth

below:

stage compressor (A1-AV8BD-290-100, WP003 00).

a. Removes essential 28vdc to deenergize the

26. Warning/Caution/Advisory Lighting System.

forward vent/defog valve and rear vent/defog valve,

The warning/caution/advisory lighting system

causing them to go to the restricted position.

(A1-AV8BB-440-100, WP007 00) provides visual

indication of normal aircraft functions and system

b. Removes essential 28vdc to open the defog

malfunctions affecting safety of flight operations.

shutoff valve.

The warning/caution/advisory lighting system

34. Setting the CABIN switch to MAX DFOG

includes the annunciator light controller and the

applies essential 28vdc power to energize the max

caution/advisory indicator light assembly. The

defog relay causing an increase in system air

annunciator light controller receives data from

temperature.

various aircraft systems and provides logic to turn

on and off warning/caution/advisory lights.

35. PRESS Switch. The PRESS switch, located on

the ECS control panel assembly, is a four pole, lever

27. The annunciator light controller will turn on

lock toggle switch. The switch provides on/off

the WSHLD caution lights and the MASTER

control for the cabin cooling and defog system and

CAUTION lights when defog air temperature

mode selection for the cabin pressurization system.

exceeds 250°F.

Refer to WP006 00 for operation of the cabin

pressurization system. The switch has three

28. DC Power System. The DC power system on

positions; NORM, DUMP, and RAM.

162747; ALSO 162963 THRU 163861 BEFORE

AV8AFC-416 (A1-AV8BB-420-100, WP004 00) or

36. Setting the PRESS switch to NORM prevents

164113 AND UP; ALSO 162963 THRU 163861

28vdc essential or 28vdc emergency power from

AFTER AV8AFC-416 (A1-AV8BD-420-100, WP004

energizing the cabin ECS pressure regulating and

00) provides 28vdc essential and 28vdc emergency

shutoff valve, allowing normal system operation.

power for the cabin cooling and defog system.

37. Setting the PRESS switch to RAM applies

29. Landing Gear And Related Systems. The

28vdc essential and 28vdc emergency power to

landing gear system (A1-AV8BB-130-100,

energize the cabin ECS pressure regulating and

WP003 00) provides a weight on wheels signal for

shutoff valve. The valve closes when energized,

the cabin cooling and defog system through the

stopping system operation.

A1-AV8BC-410-100

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38. Setting the PRESS switch to DUMP has no

44. WSHLD Caution Light. The WSHLD caution

affect on system operation.

light, located on the caution/advisory indicator light

assembly, is a dual lamp, indicator light.

39. Cabin Temperature Control. The cabin

temperature control, located on the ECS control

45. The WSHLD caution light is controlled by the

panel assembly, controls manual (MAN) and

windshield overtemperature switch through the

automatic (AUTO) cabin temperature selection.

windshield overtemp relay and the

warning/caution/advisory lighting system.

40. In the MAN mode, setting and holding the

46. Rear WSHLD Caution Light. The rear WSHLD

cabin temperature control knob to the COOL or

caution light, located on the rear caution/advisory

WARM settings applies emergency 28vdc power

indicator light assembly, is a dual lamp indicator

through the deenergized windshield overtemp relay

light.

to the open (warm) or closed (cool) contacts of the

temperature regulating valve. Voltage is applied to

47. The rear WSHLD caution light is functionally

the valve as long as the knob is held in COOL or

identical to the WSHLD caution light.

WARM setting.

48. Windshield Overtemperature Relay. The

41. In the AUTO mode, the cabin temperature

windshield overtemperature relay, located on the

control functions as an electronic processor and as

forward relay no. 1 panel assembly, is a dual pole,

one leg of a temperature control bridge circuit. The

double throw, 5 amperes, permanent magnet drive,

other legs of the bridge circuit include the cabin

armature relay.

temperature sensor, duct temperature sensor, and

skin temperature sensor and follow-up resistor.

49. The relay is energized when the windshield

overtemperature switch senses defog air

42. Selecting the desired setting in the AUTO mode

temperature is more than 250° ±8°F. With the relay

applies emergency 28vdc power to the processing

energized:

electronics and to the normally open contacts of the

a. Emergency 28vdc is removed from the cabin

heat and cool relays, and provides a resistance value

temperature control and is applied directly to the

for one leg of the bridge. The cabin temperature

close (cool) contacts of the temperature regulating

control continuously receives signals from all legs of

valve, causing a decrease in system temperature.

the bridge circuit. The bridge circuit compares the

selected resistance of the AUTO setting with the

b. A ground is removed to enable the WSHLD

sensed resistance of the other bridge circuit legs.

caution light and the rear WSHLD caution light.

Any difference in the signals is an unbalance. The

unbalance is electronically processed and used to

50. With the relay deenergized:

energize either the heat or cool relay. Energizing the

relays applies emergency 28vdc power to the open

a. Emergency 28vdc is applied to the cabin

(warm) or closed (cool) contacts of the temperature

temperature control allowing removal system

regulating valve. The valve moves as required,

operation.

adding or removing hot air. Out of balance signals

are proportional to sensed temperature changes.

b. A ground is provided to disable the WSHLD

The resistance of the sensors and follow-up resistor

caution light and rear WSHLD caution light.

changes as the valve opens and closes until a

balance in the bridge circuit is arrived at.

51. Max Defog Relay. The max defog relay, located

on the forward relay no. 1 panel assembly, is a dual

43. An unbalance will occur by changing the

pole, double throw, 5 amperes, permanent magnet

selected temperature or by any change in

drive, armature relay.

temperature as sensed by any leg of the bridge.

Such changes may be a drastic change in ambient

52. The relay is energized when the CABIN switch

temperature because of increased or decreased

is set to MAX DFOG. The relay allows windshield

altitude. The cabin temperature control will

defogging air temperature to increase in the MAX

automatically compensate for these changes to

DFOG setting. With the relay energized, signals

maintain the selected temperature.

from the cabin temperature sensor and duct

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temperature sensor are routed through three fixed

chamber is held constant by the relief valve.

valve resistors. The three resistors increase the total

Differences of pressure between the two chambers

signal resistance, causing an imbalance in the

determines piston position, controlling air pressure

temperature control bridge circuit. The cabin

passing into the system. Pressure is regulated to

temperature control will increase air temperature

approximately 62 psi.

until the bridge circuit is brought back into balance.

60. Temperature Regulating Valve. The

53. With the relay deenergized, cabin temperature

temperature regulating valve is located in door 128

sensor and duct temperature sensor signals are

between the cabin pressure regulator and shutoff

routed directly through the cabin temperature

valve and the water separator. The valve is

control bridge circuit.

electrically controlled and electrically actuated.

54. OPERATION.

61. Acting in response to electrical signals from the

cabin temperature control, the valve moves open or

55. COMPONENT OPERATION.

closed. Opening the valve allows more hot air to mix

with cold discharge air from the cold air unit.

56. Cabin ECS Air Filter Assembly. The cabin

Closing the valve allows less hot air mixing. Cycle

ECS air filter assembly is located in door 11L. Sixth

time of the valve from fully open to fully closed is

stage engine bleed air is sent by way of ducting to

approximately 15 seconds.

the filter assembly. The filter assembly removes

particulate contamination before it can cause

The valve motor has limit switches and a brake to

damage further downstream in the environmental

prevent overtravel of the valve. The closed limit

control systems. If the filter element becomes

switch is open when the valve is closed. The limit

blocked, pressure build up opens a bypass valve

switch opens the circuit for the valve and

allowing air to bypass the filter element. The bypass

deenergizes the brake coil. Power to the motor is

valve opens at 4 psid. The filter element is

interrupted and the brake engages. As the valve

replaceable independent of the housing or may be

opens, the closed limit switch closes. When the

cleaned and reused. With the filter element

valve is fully open, the process repeats for the open

removed, a ground air source can be adapted and

limit switch.

used for ground testing.

62. The follow-up resistor is a variable resistor

57. Cabin ECS Pressure Regulating and Shutoff

mechanically controlled by position of the valve

Valve. The cabin pressure regulating and shutoff

actuator. Resistance values increase as the valve

valve is located in the bleed air duct between the

moves to open, decrease as the valve moves to

cabin ECS air filter assembly and primary heat

closed. The resistance value range is approximately

exchanger in door 128. Operation of the pressure

0 to 33 ohms. The resistance value is supplied to

regulating section and shutoff section is separate.

the automatic mode of the cabin temperature

Both sections require engine bleed air for operation.

control as part of one leg of the bridge circuit.

58. The shutoff section is controlled by the PRESS

63. Primary Heat Exchanger. The primary heat

switch on the ECS control panel assembly. With the

exchanger is located in door 128 between the cabin

solenoid deenergized, bleed air is applied to the

ECS pressure regulating and shutoff valve and the

upstream side of the shutoff piston, moving it to the

cold air unit. Hot bleed air passes through the heat

open position. With the solenoid energized the

exchanger core where ram air, forced across the

control valve opens equalizing bleed air pressure on

core, absorbs heat from the bleed air. The bleed air

both sides of the shutoff piston which closes by

passes through the heat exchanger then to the cold

spring tension. In the event of an aircraft or valve

air unit compressor turbine. The pre-cooled,

electrical failure, the valve will fail to the open

compressed bleed air is then sent to the secondary

position. The shutoff section will be inoperative, but

heat exchanger.

the pressure regulation section will continue to

operate.

64. After passing across the primary heat

exchanger, the ram air exits through either the ECS

59. The pressure regulating section operates only

bay or the engine intake, depending on flight

with the shutoff section open. Bleed air pressure

conditions. In low speed flight or ground operation,

enters both sensing chambers. Pressure in one

flapper valves at the bottom of the heat exchanger

A1-AV8BC-410-100

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are pulled open by suction in the engine air intake,

by centrifugal force. The droplets are collected by

allowing engine intake suction to pull ram air across

the sump assembly and allowed to drain overboard.

the heat exchanger core. In normal flight, ram air

flow causes a positive pressure in the ram air ducts,

71. If the coalescer becomes blocked, normally

pulling the flapper valves closed. The ram air then

because of freezing, a bypass valve will open at a 10

exits to the ECS bay and then overboard.

psi differential pressure.

65. Secondary Heat Exchanger. The secondary

72. Cabin ECS Check Valve. The cabin ECS check

heat exchanger is located in door 128 between the

valve is located between the water separator and

cold air unit compressor turbine outlet and

the duct temperature sensor in internal door NWA.

expansion turbine inlet. Pre-cooled, compressed

The valve prevents cabin depressurization by

bleed air from the cold air unit compressor turbine

stopping the reverse flow of cabin air, through ECS

passes through the heat exchanger core where ram

louvers, windshield defog nozzles, and fixed canopy

air, forced across the core, absorbs heat gained

ventilation nozzles when cabin cooling and defog

through compression. The cooled air then passes to

system is not operating. The valve flappers are held

the expansion turbine inlet of the cold air unit.

closed by spring tension and are normally closed

with no air pressure applied. Approximately 4 psi is

66. The exit path of the ram air is the same as the

required to open the check valve.

primary heat exchanger.

73. Forward Vent/Defog Valve. The forward

67. Cold Air Unit. The cold air unit is located in

vent/defog valve, located between the water

door 128 between the heat exchangers and the

separator and the cockpit ECS louvers in door 10,

water separator. The compressor turbine receives

provides restricted or unrestricted flow. The valve

pre-cooled air from the primary heat exchanger

solenoid is energized when the CABIN switch is set

where it is compressed to approximately two times

to NORM and deenergized when the CABIN switch

its inlet value. The compressed air then passes to

is set to DFOG or MAX DFOG. With the solenoid

the secondary heat exchanger where the heat from

energized, pneumatic pressure is turned off,

compression is lost, then to the expansion turbine

allowing system pressure to force the movable

end of the cold air unit where heat energy is

piston to the unrestricted position. With the valve

converted to mechanical energy by spinning the

in the unrestricted position, most of the airflow will

expansion turbine. The expansion turbine drives the

be directed to the cockpit ECS louvers.

compressor turbine through the common shaft.

With the heat lost, cold air is left and sent by way

74. Deenergizing the solenoid applies pneumatic

of ducting to mix with hot air from the temperature

pressure to the movable piston, causing it to move

regulating valve.

to the restricted position; most of the airflow will

then be directed to the windshield defog nozzles

68. Lubrication for the common shaft is provided

and the fixed canopy ventilation nozzles.

by oil stored in a cotton wool pack sump and

transported to the shaft by a system of oil wicks.

75. Rear Vent/Defog Valve. The rear vent/defog

The sump has fill and drain plugs located to allow

valve, located between the duct temperature sensor

periodic servicing of oil while the cold air unit is

and the rear cockpit ECS louvers in door 121,

still in the aircraft.

provides restricted or unrestricted flow. The valve

69. Shaft bearing cooling is provided by a flexible

solenoid is energized when the CABIN switch is set

tube. Expansion turbine discharge air is used to

to NORM and deenergized with the CABIN switch

cool the bearings as the common shaft spins.

set to DFOG or MAX DFOG. With the solenoid

energized, pneumatic pressure is turned off allowing

70. Water Separator. The water separator is

system pressure to force the movable piston to the

located between the cold air unit and the cabin ECS

unrestricted position. With the valve in the

check valve in internal door NWA. Cool moist air

unrestricted position, most of the airflow will be

enters the water separator coalescer. The coalescer

directed to the rear cockpit ECS louvers.

converts moisture in the air into water droplets

through the wettable, high surface area of the

76. Deenergizing the solenoid applies pneumatic

woven cloth coalescer. The swirl frame sends these

pressure to the movable piston, causing it to move

droplets to the outer wall of the collector sump area

to the restricted position; most of the airflow will

A1-AV8BC-410-100

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then be directed to the fixed canopy ventilation

shut off. Spring tension overcomes pneumatic

nozzles and windshield defog nozzles.

pressure to open the valve.

77. ECS Louvers. The ECS louvers, located in the

82. ECS Pressure Switch. The ECS pressure switch

cockpit and rear cockpit, provide desired

is located in door 128 in the primary heat exchanger

distribution of air entering the cockpits. Each of the

outlet. The switch is pneumatically operated and

louvers has adjustable vanes at the openings. The

controls electrical signals to the defog shutoff valve.

vanes can be adjusted by the pilot for his own

heating and cooling comfort. Airflow to the ECS

83. With system pressure less than 20 psi, a ground

louvers is controlled by the forward vent/defog

is supplied to energize the defog shutoff valve. With

valve and the rear vent/defog valve. The louvers

system pressure greater than 20 psi, the pneumatic

also act as an air inlet for cabin pressurization

switch opens to remove the ground signal, to

(WP006 00).

deenergize the defog shutoff valve.

78. Windshield Defog Nozzles. The windshield

84. ECS Control Panel Assembly. The ECS control

defog nozzles, at the base of the windshield, provide

panel assembly is located in the cockpit on the right

even flow of air across the windshield and canopy.

console. The panel provides mounting for the

Cabin air is used for windshield and canopy

PRESS switch, CABIN switch, cabin temperature

defogging. Air flow to the nozzles is controlled by

control, and EQUIP switch (WP008 00).

the forward vent/defog valve, rear vent/defog valve,

and defog shutoff valve. The nozzles also act as an

85. Windshield Overtemperature Switch. The

air inlet for cabin pressurization (WP006 00).

windshield overtemperature switch is located in

door 120 in the defog shutoff valve outlet duct. A

79. Fixed Canopy Ventilation Nozzles. The fixed

bimetallic temperature sensitive device senses an

canopy ventilation nozzles at the base of the fixed

overtemperature condition. The bimetallic

canopy provide an even flow of air across the fixed

properties allow the device to expand and contract

canopy. Cabin air is used for fixed canopy

to actuate the switch.

defogging. The nozzles also provide thorough

86. The switch is calibrated to close its contacts at

ventilation in and around the rear cockpit. Airflow

250 ±8°F increasing temperature and open at 220

to the nozzles is controlled by the forward

±10°F decreasing temperature.

vent/defog valve, rear vent/defog valve and defog

shutoff valve. The nozzles also act as an air inlet for

87. Closing the switch contacts provides a ground to

cabin pressurization (WP006 00).

complete a circuit which applies emergency 28vdc

power to energize the windshield overtemperature

80. Defog Shutoff Valve. The defog shutoff valve is

relay.

located in the common windshield defog and fixed

canopy ventilation duct in door 121. The valve

88. Skin Temperature Sensor. The skin

controls the flow of air to the windshield defog

temperature sensor is located on the left side nose

nozzles and fixed canopy ventilation nozzles when

landing gear wheelwell. The sensor senses changes

the aircraft is on the ground and system pressure is

in aircraft skin temperature. The sensing device

low. The valve is electrically controlled and

contact strip is attached directly to the aircraft

pneumatically actuated. The valve is controlled by

skin. A dielectric compound is used between the

the weight on wheels relay no. 1 and the ECS

sensor and the aircraft skin to make sure the sensor

pressure switch.

is electrically isolated from the skin, but still able to

measure temperature.

81. With aircraft weight on wheels and system

pressure less than 20 psi, the defog shutoff valve is

89. As sensed temperature increases, sensor

closed. The valve is energized and pneumatic

resistance increases. As sensed temperature

pressure is allowed to pass. The pressure, acting on

decreases, sensor resistance decreases. At a

a diaphragm, overcomes spring tension to close the

temperature range of 0 to 100°F (−17 to 40°C),

valve butterfly by way of a mechanical linkage.

sensor resistance is approximately 38 to 57 ohms.

With aircraft weight off wheels or system pressure

The resistance values are supplied to the automatic

greater than 20 psi, the defog shutoff valve is open.

mode of the cabin temperature control as part of

The valve is deenergized and pneumatic pressure is

one leg of the bridge circuit.

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90. Duct Temperature Sensor. The duct

97. Distribution of air in the cockpits is determined

temperature sensor is located in a duct between the

by the forward vent/defog valve and the rear

water separator and the vent/defog valves in door

vent/defog valve through the ECS louvers. With

121. The sensor senses changes of air temperature

CABIN switch set to NORM, most of the airflow

in the cabin ECS duct.

will pass unrestricted to the ECS louvers. With the

CABIN switch set to DFOG or MAX DFOG, most

91. As sensed temperature increases, sensor

of the airflow will be directed to the windshield

resistance decreases. As sensed temperature

defog nozzles and fixed canopy ventilation nozzles.

decreases, sensor resistance increases. At a

temperature range of 32 to 100°F (0 to 40°C),

98. With weight on wheels and system pressure less

sensor resistance is approximately 1075 to 4850

than 20 psi, the defog shutoff valve is closed to

ohms. The resistance values are supplied to the

direct all airflow to the crewmembers through the

automatic mode of the cabin temperature control as

ECS louvers. With weight off wheels and system

one leg of the bridge circuit.

pressure greater than 20 psi, the defog shutoff valve

opens to allow a more balanced airflow between

92. Cabin Temperature Sensor. The cabin

nozzles and louvers.

temperature sensor is located on the forward

pressure bulkhead, in door 7L. The sensor senses

99. Cabin temperature can be controlled

changes in cabin air temperature.

automatically or manually. In automatic operation,

the cabin temperature control working with the

93. As sensed temperature increases, sensor

cabin temperature sensor, duct temperature sensor,

resistance decreases. As sensed temperature

and skin temperature sensor and follow-up resistor

decreases, sensor resistance increases. At a

automatically adjust temperature regulating valve

temperature range of 32 to 100°F (0 to 40°C),

position to control the temperature of air entering

sensor resistance is approximately 1075 to 5000

the cabin.

ohms. The resistance values are supplied to the

automatic mode of the cabin temperature control as

100. With the cabin temperature control set to

one leg of the bridge circuit.

MAN WARM or MAN COOL, 28vdc is applied to

the temperature regulating valve to control the

94. SYSTEM OPERATION.

temperature of the air entering the cabin.

95. Normal Operation. In normal operation, hot

101. Air for canopy and windshield defogging and

engine bleed air passes through the cabin ECS air

fixed canopy ventilation is provided through the

filter (figure 1) to the cabin ECS pressure regulating

windshield defog nozzles and fixed canopy

and shutoff valve which regulates pressure to

ventilation nozzles. Setting the CABIN switch to

approximately 62 psi. The regulated air passes

DFOG will direct most of the airflow to the

through the venturi/choke where airflow is limited

windshield defog nozzles. With CABIN switch set to

to approximately 36 pounds per minute. Regulated

MAX DFOG, the max defog relay is energized,

air then passes into two circuits, one remains hot,

causing the temperature of the airflow to increase.

the other passes to the primary heat exchanger to

The windshield overtemperature switch limits

be cooled. Hot air entering the primary heat

windshield defog air temperature to approximately

exchanger is cooled by cross flowing ram air. Partly

250°F. If an overtemperature condition exists, the

cooled air is then transported by way of ducting to

switch provides a ground to energize the windshield

the compressor turbine of the cold air unit where it

overtemperature relay. With the relay energized, the

is compressed to approximately two times its inlet

temperature regulating valve will close and the

value. Heat gained from the cold air unit

WSHLD caution lights are enabled.

compressor turbine is lost in the secondary heat

exchanger. Air from the secondary heat exchanger is

cooled further by rapid expansion in the cold air

unit expansion turbine section.

96. The temperature regulating valve controls the

amount of hot bleed air to be mixed with cold air

unit discharge air. Hot and cold air are mixed to the

required temperature.

A1-AV8BC-410-100

005 00

Change

Page

Nomenclature

Index No.

Ref Des

ANNUNCIATOR LIGHT CONTROLLER

27A-D007

BULKHEAD MOUNTED EQUIPMENT COOLING

—

NOZZLE

CABIN ECS AIR FILTER ASSEMBLY

22FAJ506

CABIN ECS CHECK VALVE

22MAD509

CABIN ECS PRESSURE REGULATING AND

22L-K021

SHUTOFF VALVE

CABIN TEMPERATURE SENSOR

22R-E045

CAUTION/ADVISORY INDICATOR LIGHT

27A-F011

ASSEMBLY

WSHLD CAUTION LIGHT

—

COLD AIR UNIT

22MAK507

DC CIRCUIT BREAKER PANEL ASSEMBLY

52A-C104

CABIN ECS NO. 2 (ZONE B3)

22CBC015

CAB ECS NO. 1 (ZONE D7)

22CBC016

CKPT TEMP RLY (ZONE B12)

22CBC041

VENT/DEFOG (ZONE D8)

22CBC068

DC EMERGENCY PANEL ASSEMBLY

52A-P132

CABIN ECS CB NO. 2 (ZONE F8)

22CBP015

CKPT TEMP RELAY (ZONE F10)

22CBP068

DC ESSENTIAL/MAIN PANEL ASSEMBLY

52A-P133

CABIN ECS CB NO. 1 (ZONE D3)

22CBPO16

VENT/DEFOG (ZONE E5)

22CBP068

DEFOG SHUTOFF VALVE

22L-D100

DUCT TEMPERATURE SENSOR

22R-D046

ECS CONTROL PANEL ASSEMBLY

22A-F048

CABIN SWITCH

22S-F017

CABIN TEMPERATURE CONTROL

22A-F042

PRESS SWITCH

22S-F033

ECS PRESSURE SWITCH

22S-K101

FIXED CANOPY VENTILATION NOZZLES

—

FORWARD RELAY NO. 1 PANEL ASSEMBLY

52A-C015

WINDSHIELD OVERTEMPERATURE RELAY

22K-C052

MAX DEFOG RELAY

22K-C053

Figure 1. Cabin Cooling and Defog System Component Locator (Sheet

A1-AV8BC-410-100

005 00

Change

Page

Nomenclature

Index No.

Ref Des

FORWARD RELAY NO. 2 PANEL ASSEMBLY

52A-C113

WEIGHT ON WHEELS RELAY NO. 1

12K-C053

FORWARD VENT/DEFOG VALVE

22L-D019

LEFT CENTER ECS LOUVER

—

LEFT ECS LOUVER

—

PRIMARY HEAT EXCHANGER

—

REAR BULKHEAD MOUNTED EQUIPMENT

—

COOLING NOZZLE

REAR CAUTION/ADVISORY INDICATOR LIGHT

27A-H045

ASSEMBLY

WSHLD CAUTION LIGHT

—

REAR LEFT CENTER ECS LOUVER

—

REAR LEFT ECS LOUVER

—

REAR RIGHT CENTER ECS LOUVER

—

REAR RIGHT ECS LOUVER

—

REAR VENT/DEFOG VALVE

22L-C096

RIGHT CENTER ECS LOUVER

—

RIGHT ECS LOUVER

—

SECONDARY HEAT EXCHANGER

—

SKIN TEMPERATURE SENSOR

22R-B044

TEMPERATURE REGULATING VALVE

22L-K043

VENTURI/CHOKE

—

WATER SEPARATOR

22MAD508

WINDSHIELD DEFOG NOZZLES

—

WINDSHIELD OVERTEMPERATURE SWITCH

22S-D018

LEGEND

162747; ALSO 162963 THRU 163861 BEFORE AV8AFC-416.

164113 AND UP; ALSO 162963 THRU 163861 AFTER AV8AFC-416.

Figure 1. Cabin Cooling and Defog System Component Locator (Sheet

A1-AV8BC-410-100

006 00

Change 7 - 15 May 2004

Page 1

ORGANIZATIONAL MAINTENANCE

PRINCIPLES OF OPERATION

CABIN PRESSURIZATION SYSTEM

Reference Material

Electrical Systems

A1-AV8BB-420-100

DC Power System

WP004 00

Electrical Systems

A1-AV8BD-420-100

DC Power System

WP004 00

Environmental Control System

A1-AV8BC-410-100

Canopy Seal System

WP007 00

Description and Operation - Cabin Cooling and Defog System

WP004 00

Lighting Systems

A1-AV8BB-440-100

Interior Lighting System

WP005 00

Ejection Seat and Canopy System

A1-AV8BB-120-100

Canopy System Description and Operation

WP007 00

Alphabetical Index

Subject

Page No.

Cabin Pressurization System Component Locator, Figure 1

Cabin Pressurization System Simplified Schematic, Figure 2

Description

Component Description

Cabin Dump Control Valve

Cabin Inlet Pressure Test Port

Cabin Pressure Regulator

Cabin Pressure Regulator and Safety Relief Check Valves

Cabin Static Pressure Test Port

Pressurized Compartment Altimeter AAU-38/A

Safety Relief Valve

Related Systems

Aircraft Structure

Cabin Cooling and Defog System

Canopies

Canopy Seal System

DC Power System

Interior Lighting System

System Controls and Indicators

Ground Test Valve

PRESS Switch

Pressurized Compartment Altimeter AAU-38/A

System Description

A1-AV8BC-410-100

006 00

Change 7

Page 2

Alphabetical Index (Continued)

Subject

Page No.

Operation

Component Operation

Cabin Dump Control Valve

Cabin Inlet Pressure Test Port

Cabin Pressure Regulator

Cabin Pressure Regulator Check Valve

Cabin Static Pressure Test Port

Safety Relief Check Valve

Safety Relief Valve

System Operation

Dump

Ground Test

Normal Flight

Record of Applicable Technical Directives

Type/

Date

Title and ECP or RAMEC No.

Remarks

Number

Incorp.

AV8AFC-416

— TAV-8B Polyimide Wire Replacement/

15 May 04

—

Power Wire Separation (ECP MDA-AV8B-

0277)

1. DESCRIPTION.

check valves. The valve body is threaded at each

end.

2. SYSTEM DESCRIPTION. The cabin is

pressurized by conditioned air from the cabin

6. Cabin Pressure Regulator. The cabin pressure

cooling and defog system (WP004 00) to provide a

regulator is an outflow valve and a self contained

comfortable, less fatiguing environment for the

controller in a single unit. The outflow valve is

pilot. Pressurization is done by controlling the rate

made up of a base, outflow valve, actuator

of airflow from the sealed cabin. The airflow is

diaphragm, valve return spring, and a control

routed to equipment bays, where it augments

chamber. The base includes the valve seat and

avionics cooling.

forms the passage for discharge air from the

pressurized area. The controller is made up of an

3. COMPONENT DESCRIPTION. System

orifice, filter, ground test valve, and two control

components shown in figure 1 are described and

systems: the isobaric control system and the

listed in paragraphs below.

differential control system.

4. Cabin Dump Control Valve. The cabin dump

7. Pressurized Compartment Altimeter AAU-38/A.

control valve is a solenoid operated, two position air

The Pressurized Compartment Altimeter AAU-38/A

control valve. The valve is made up of a body with

is a self contained aneroid, single pointer, integrally

inlet and outlet connections and a solenoid with an

lighted instrument. The altimeter measures and

electrical connection. The solenoid is mounted to

indicates cabin pressure from 0 to 50,000 feet. The

the valve body.

altimeter face is graduated every 1000 feet, major

increments each 5000 feet, and markings at the

5. Cabin Pressure Regulator and Safety Relief

even major increments.

Check Valves. The cabin pressure regulator and

safety relief check valves are poppet type, in line

A1-AV8BC-410-100

006 00

Change 7

Page 3

8. Safety Relief Valve. The safety relief valve is an

AFTER AV8AFC-416 (A1-AV8BD-420-100, WP004

outflow valve made up of a head section and a base

00) supplies emergency 28vdc power for the cabin

section. The head section consists of a pressure

pressurization system.

relief metering valve, pressure relief calibration

18. SYSTEM CONTROLS AND INDICATORS.

spring and two pressure relief control diaphragms.

System controls and indicators are described in

The base section consists of an outflow valve,

paragraphs below.

mounting base and operating mechanism. The

outflow valve provides the passage for discharge air

19. PRESS Switch. The PRESS switch, located on

from the pressurized area.

the ECS control panel assembly, is a four pole lever

lock toggle switch. The switch provides mode

9. Cabin Inlet Pressure Test Port. The cabin inlet

selection for cabin pressurization and on/off control

pressure test port is a capped port installed through

of the cabin cooling and defog system. Refer to

the rear cockpit floor.

WP004 00 for cabin cooling and defog system. The

switch has three positions; NORM, DUMP, and

10. Cabin Static Pressure Test Port. The cabin

RAM. The switch is locked in all positions.

static pressure test port is a capped port installed

through the rear cockpit floor.

20. Setting the switch to DUMP or RAM from

NORM, applies emergency 28vdc power to energize

11. RELATED SYSTEMS. Related systems are

the cabin dump control valve.

described in paragraphs below.

21. Setting the switch to NORM from RAM or

12. Cabin Cooling and Defog System. The cabin

DUMP, removes emergency 28vdc power to

cooling and defog system (WP004 00) provides

deenergize the cabin dump control valve.

conditioned air to pressurize the cabin. Air enters

the sealed cabin through the cockpit ECS louvers,

22. Pressurized Compartment Altimeter

windshield defog nozzles and fixed canopy

AAU-38/A. The Pressurized Compartment

ventilation nozzles.

Altimeter AAU-38/A is located in the cockpit on the

right vertical console. The altimeter senses and

13. Canopy Seal System. The canopy seal system

indicates cabin altitude. Cabin altitude is artificially

(WP007 00) provides an inflatable seal interface

created by the cabin pressurization system by

between the forward canopy, aft canopy, windshield

regulating pressurized air exiting the sealed cabin.

arch, fixed canopy, and aircraft structure.

The altimeter has an aneroid (evacuated bellows)

which expands and contracts in response to sensed

14. Interior Lighting System. The interior lighting

changes in pressure. As the aneroid moves, a

system (A1-AV8BB-440-100, WP005 00) provides

mechanical linkage moves the pointer to indicate

illumination for the Pressurized Compartment

cabin altitude.

Altimeter AAU-38/A. Rotating the CONSL control,

on the INTR LT control panel, varies altimeter

23. The pilot can use the cabin altitude to compare

lighting from off to bright. A lights test function is

with aircraft altitude. With this comparison, the

also provided.

pilot can determine whether the cabin is over,

under, or correctly pressurized.

15. Aircraft Structure. Cockpit floors, aft seat

24. Illumination of the altimeter is provided by the

bulkhead, aircraft side skins, forward pressure

interior lighting system.

bulkhead, windshield, and fixed canopy provide the

pressurized area.

25. Ground Test Valve. The ground test valve,

located on the face of the cabin pressure regulator,

16. Canopies. The forward and aft canopies

is a manually operated three position selector valve.

(A1-AV8BB-120-100, WP007 00), when locked

The valve handle is rotated to select normal flight

closed, complete the pressurized area.

or test positions. The three settings are FLIGHT,

TEST ONLY DIFF ON, and TEST ONLY ALL

17. DC Power System. The DC power system on

OFF.

162747; ALSO 162963 THRU 163861 BEFORE

AV8AFC-416 (A1-AV8BB-420-100, WP004 00) or

26. The FLIGHT position is used to provide

164113 AND UP; ALSO 162963 THRU 163861

automatic in-flight cabin pressurization control.

A1-AV8BC-410-100

006 00

Change 6

Page 4

Cabin pressure will maintain the prescribed

33. With the valve energized, cabin pressure

schedule as the aircraft altitude increases or

regulator and safety relief valve control chamber

decreases. The valve handle is lockwired to the

pressure is lost. Spring tension will open both

FLIGHT position.

regulator and relief valve allowing cabin pressure to

dump.

27. The TEST ONLY DIFF ON position is used to

test the differential control portion of the cabin

34. Cabin Pressure Regulator Check Valve. The

pressure regulator. Setting the handle to this

cabin pressure regulator check valve is located in

position, renders the isobaric control portion of the

door 1 in the cabin pressure regulator atmospheric

regulator inoperative by closing the isobaric

vent line. The check valve will prevent a dual

metering valve outlet. Only the differential control

failure if the safety relief valve fails or leaks

portion will operate.

internally.

28. The TEST ONLY ALL OFF position is used to

35. The cabin pressure regulator and safety relief

test safety relief valve operation. Setting the handle

valve control chambers are connected

to this position renders both the isobaric and

pneumatically. Without the check valve installed in

differential control positions of the regulator

the atmospheric vent line, if the safety relief valve

inoperative by closing both the isobaric and

failed or developed an internal leak, regulator

differential metering valve outlets. The regulator

control chamber pressure would also be lost. The

will not operate and cabin pressure will be

check valve prevents control chamber pressure loss.

controlled by the safety relief valve.

36. Safety Relief Check Valve. The safety relief

29. OPERATION.

check valve is located in the rear cockpit under the

right vertical console in the atmospheric port of the

30. COMPONENT OPERATION.

safety relief valve. The check valve will prevent a

dual failure if the cabin pressure regulator fails or

NOTE

leaks internally.

During normal operation of the cabin

37. The safety relief valve and cabin pressure

pressurization system, cabin pressure is

regulator control chambers are connected

controlled by air pressure measured in

pneumatically. Without the check valve installed in

pounds per square inch (psi). Cabin

the atmospheric vent line, relief valve control

pressure is the difference between cabin

chamber pressure would be lost if the regulator

atmospheric pressure and ambient

developed an internal leak or failed. The check

atmospheric pressure, expressed in

valve prevents control chamber pressure loss.

pounds per square inch differential

(psid). The psid value is used only during

38. Cabin Pressure Regulator. The cabin pressure

ground testing of the system. During

regulator, located outside the pressurized

normal flight, the cabin pressure is

compartment in door 1, automatically controls cabin

expressed as pressure altitude.

pressure throughout the aircraft flight envelope.

The regulator has a three mode normal operating

31. Cabin Dump Control Valve. The cabin dump

capability and a two mode ground test capability.

control valve is located in the rear cockpit under

the right vertical console. The valve is connected

39. During normal flight, the regulator ground test

pneumatically to the cabin pressure regulator and

valve handle is set to FLIGHT. This allows the

safety relief valve. The valve allows the pilot to

regulator to operate in its three normal modes;

rapidly remove (dump) cabin pressure, if required.

unpressurized, isobaric, and differential.

32. Valve operation is controlled by the PRESS

40. In the unpressurized mode, pressure in the

switch. With the valve deenergized, spring pressure

cabin is maintained slightly higher than

in the valve closes the valve poppet. The poppet

atmospheric pressure. The unpressurized mode is

prevents control chamber pressure in the cabin

from sea level to approximately 8000 feet. Control

pressure regulator and safety relief valve from

chamber pressure is enough to compress the

venting to atmosphere. This allows normal

isobaric bellows, keeping the isobaric metering valve

operation of the regulator and relief valve.

open to the atmosphere. Control chamber pressure

A1-AV8BC-410-100

006 00

Page 5

41. In the isobaric mode, cabin pressure is

diaphragm overrides the pressure relief calibration

maintained at a pressure equal to approximately

spring. The metering valve assembly moves and the

8000 feet while aircraft altitude is approximately

metering valve is off seated by the pressure relief

8000 to 23,100 feet.

calibration screw. The open metering valve vents

the control chamber and allows the outflow valve

42. Control chamber pressure constantly decreases

return spring to open the outflow valve and vent

with an increase in aircraft altitude. The decreased

excess cabin pressure. The safety relief valve works

control chamber pressure cannot compress the

with smooth modulation rather than erratic relief.

isobaric bellows as much and the isobaric metering

bellows begin to close. As metering valve closes, less

48. Negative pressure is ambient pressure greater

control chamber pressure is vented. Pressure

than cabin pressure. This occurs during rapid

coming into the control chamber through the orifice

aircraft descent. Normal operation of the system

and pressure venting to atmosphere through the

cannot always react to change cabin pressure as fast

now closing metering valve is balanced as aircraft

as the aircraft can descend. When this occurs, the

altitude increases from 8000 to approximately

safety relief valve will open and allow ambient

23,100 feet. The balanced pressures allow the cabin

pressure to enter the cabin to equalize pressure.

pressure regulator to maintain a constant cabin

pressure in the isobaric mode.

49. The higher ambient pressure overrides the

lower cabin and control chamber pressure and

43. As aircraft altitude increases above

outflow valve return spring. The higher ambient

approximately 23,100 feet, the isobaric metering

pressure moves the outflow valve open to allow

valve is fully closed. Closing the metering valve

ambient pressure to enter the cabin. As the

builds sufficient control chamber pressure to begin

pressures equalize, the outflow valve will close

the differential mode of operation.

under pressure from the outflow valve return

spring.

44. In the differential mode, cabin pressure is

maintained at a constant differential pressure

50. Cabin Inlet Pressure Test Port. The cabin inlet

versus ambient pressure. The constant differential

pressure test port is located in the nose landing gear

pressure is 5.00 ±0.23 psid.

wheelwell. The test port allows a ground air source

and a cabin pressure tester to be used for ground

45. As aircraft altitude exceeds approximately

testing of the cabin pressurization system. The test

23,100 feet, the increasing control chamber pressure

port allows the external air to enter the cabin.

overcomes spring tension and moves the differential

diaphragm mechanism. Moving the mechanism

51. Cabin Static Pressure Test Port. The cabin

opens the differential metering valve which vents

static pressure test port is located in the nose

control chamber pressure. The venting causes a

landing gear wheelwell. The test port allows a

lower control chamber pressure which allows spring

ground air source and a cabin pressure tester to be

tension to open the outflow valve. The open valve

used for ground testing of the cabin pressurization

vents enough cabin pressure to maintain a constant

system. The test port allows the cabin pressure to

differential pressure of 5.00 ±0.23 psid between

be measured externally.

cabin and ambient.

52. SYSTEM OPERATION.

46. Safety Relief Valve. The safety relief valve is

located in the rear cockpit under the right vertical

53. Conditioned air from the cabin cooling and

console. The valve will limit cabin pressure to 5.35

defog system (WP004 00) is controlled to maintain

±0.23 psid and provide negative pressure relief.

cabin pressure. The system operates in three modes,

normal flight, ground test, and dump.

47. Cabin pressure enters the control chamber

through the air filter screen. Control chamber

54. Normal Flight. During normal flight, air

pressure overrides outflow valve return spring

pressure entering the cabin also enters the control

tension and holds the outflow valve closed through

chambers of the cabin pressure regulator and the

the cabin pressure schedule. As control chamber

safety relief valve. The relief valve will remain

pressure increases with cabin pressure to 5.35 ±0.23

closed until cabin pressure exceeds 5.35 ±0.23 psid.

psid, control chamber pressure acts on the metering

The control chamber pressure in the regulator is

valve assembly diaphragm. Pressure on the

not enough to close the outflow valve from sea level

A1-AV8BC-410-100

006 00

Page 6

to 8000 feet. Thus, cabin pressure will remain at

valve return spring opens the valve to equalize

slightly above ambient pressure until the aircraft

pressure.

arrives at 8000 feet.

59. Ground Test. The cabin pressure regulator has

55. As the aircraft reaches 8000 feet, cabin pressure

a ground test valve which allows the system to be

entering the regulator control chamber is enough to

tested on the ground. The ground test has two

act on the isobaric bellows which begins to move

modes, TEST ONLY DIFF ON and TEST ONLY

and close the isobaric metering valve. The closing

ALL OFF. The TEST ONLY DIFF ON mode

metering valve allows control chamber pressure to

allows the cabin pressure regulator to bypass the

build and close the outflow valve as required to

unpressurized and isobaric modes and maintain

maintain a cabin altitude of 8000 feet while aircraft

cabin pressure at the 5.00 ±0.23 psid differential

altitude increases from 8000 to 23,100 feet.

mode. The TEST ONLY ALL OFF mode allows the

safety relief valve to regulate cabin pressure at 5.35

56. As the aircraft reaches 23,100 feet, cabin

±0.23 psid and bypass the regulator setting entirely.

pressure entering the regulator control chamber has

fully closed the isobaric metering valve and begins

60. During ground testing, an external air source

to open the differential metering valve. The opening

and special test equipment is required. Three test

differential metering valve vents control chamber

fittings are located in the nose landing gear

pressure to allow the regulator to maintain 5.00

wheelwell for test equipment hookup. One port

±0.23°ba psid between cabin and ambient pressure.

provides an air inlet to the cabin, one provides

This schedule is maintained from 23,100 feet and

cabin pressure sensing, and one provides pressure to

higher.

the canopy pressure seal. Refer to WP007 00 for

canopy seal system.

57. If cabin pressure exceeds the regulator setting,

the safety relief valve will open and relieve pressure.

61. Dump. The dump mode allows all cabin

As cabin pressure increases to 5.35 ±0.23 psid,

pressure to be removed (dump) from the cabin. If

control pressure in the relief valve which has held it

fumes or smoke enter the cabin, the pilot can select

closed is vented and the outflow valve return spring

DUMP with the PRESS switch. This will open the

opens the valve.

cabin dump control valve, venting control chamber

pressure and opening the cabin pressure regulator

58. In the event of negative cabin pressure, (cabin

and relief valve. Cabin pressure drops and vents the

pressure less than ambient pressure) the lower

cabin. Selecting RAM with the PRESS switch will

control chamber pressure in the safety relief valve is

also dump cabin pressure and disable the cabin

not enough to hold the valve closed. The outflow

cooling and defog system (WP004 00).

A1-AV8BC-410-100

007 00

Change 7 - 15 May 2004

Page 1

ORGANIZATIONAL MAINTENANCE

PRINCIPLES OF OPERATION

CANOPY SEAL SYSTEM

Reference Material

Ejection Seat and Canopy System

A1-AV8BB-120-100

Canopy System Description and Operation

WP007 00

Environmental Control System

A1-AV8BC-410-100

Description and Operation - Cabin Cooling and Defog System

WP004 00

Description and Operation - Cabin Pressurization System

WP006 00

Description and Operation - Anti-G System

WP009 00

Electrical Systems

A1-AV8BB-420-100

DC Power System

WP004 00

Electrical Systems

A1-AV8BD-420-100

DC Power System

WP004 00

Landing Gear and Related Systems

A1-AV8BB-130-100

Landing Gear System

WP003 00

Alphabetical Index

Subject

Page No.

Canopy Seal System Component Locator, Figure 1

Canopy Seal System Simplified Schematic, Figure 2

Description

Component Description

Aft Canopy Pressure Seal

Anti-G/Canopy Seal Check Valve

Anti-G/Canopy Seal Test Port

Canopy Seal Control Valve

Canopy Seal Pressure Regulator and Check Valve

Forward Canopy Pressure Seal

Related Systems

Aircraft Structure

Cabin Cooling and Defog System

Canopy System

DC Power System

Landing Gear and Related Systems

System Control and Indicators

Press Switch

System Description

Operation

Component Operation

Aft Canopy Pressure Seal

Anti-G/Canopy Seal Check Valve

A1-AV8BC-410-100

007 00

Change 7

Page 2

Alphabetical Index (Continued)

Subject

Page No.

Anti-G/Canopy Seal Test Port

Canopy Seal Control Valve

Canopy Seal Pressure Regulator and Check Valve

Forward Canopy Pressure Seal

System Operation

Ground Operation

Normal Operation

Record of Applicable Technical Directives

Type/

Date

Title and ECP or RAMEC No.

Remarks

Number

Incorp.

AV8AFC-416

— TAV-8B Polyimide Wire Replacement/

15 May 04

—

Power Wire Separation (ECP MDA-AV8B-

0277)

1. DESCRIPTION.

seal. The seal is made of silicone rubber reinforced

with polyester.

2. SYSTEM DESCRIPTION. The canopy seal

system provides a pressure regulated seal between

8. Canopy Seal Control Valve. The canopy seal

the windshield arch, canopy sills, forward canopy,

control valve is a solenoid operated, double acting

aft canopy, and fixed canopy. Pneumatic pressure

air control valve. The valve is made up of a solenoid

for the canopy seal system is supplied from the

and a valve body with inlet, outlet, and vent

cabin cooling and defog system (WP004 00) or from

connections.

an external air source through the anti-g/canopy

seal test port.

9. Canopy Seal Pressure Regulator and Check

Valve. The canopy seal pressure regulator and

3. COMPONENT DESCRIPTION. System

check valve is a pressure reducing valve, a check

components shown in figure 1 are described and

valve, and a pressure relief valve in a single unit.

listed in paragraphs below.

10. RELATED SYSTEMS. Related systems are

4. Anti-G/Canopy Seal Check Valve. The

described in paragraphs below.

anti-g/canopy seal check valve is a poppet type in

line check valve.

11. Cabin Cooling and Defog System. The cabin

cooling and defog system (WP004 00) provides

5. Anti-G/Canopy Seal Test Port. The

conditioned air to pressurize the forward and aft

anti-g/canopy seal test port is an in line capped tee.

canopy pressure seals. Conditioned air is tapped off

the outlet of the secondary heat exchanger. The air

6. Forward Canopy Pressure Seal. The forward

is transported by way of tubing to the canopy seal

canopy pressure seal is a single piece, tubular

system.

inflatable seal. The seal is made of silicone rubber

reinforced with polyester.

12. Canopy System. The forward and aft canopy

pressure seals are mounted in a track on the

7. Aft Canopy Pressure Seal. The aft canopy

periphery of each canopy (A1-AV8BB-120-100,

pressure seal is a single piece, tubular, inflatable

WP007 00).

A1-AV8BC-410-100

007 00

Page 3

15. Aircraft Structure. The forward and aft canopy

valve. The system operates identically with either

pressure seals, when inflated, mate with and provide

the normal air source or ground air source in use.

a pressure seal between the canopy sills, windshield

arch, and fixed canopy.

25. Forward Canopy Pressure Seal. The forward

canopy pressure seal is installed in a track on the

16. SYSTEM CONTROLS AND INDICATORS.

periphery of the forward canopy. A flexible inlet

tube on the aft end of the seal connects the seal

17. PRESS Switch. The PRESS switch, located

pneumatically with the canopy seal system.

on the ECS control panel assembly, provides on/off

control for the cabin cooling and defog system

26. The seal is inflated to provide a pressure tight

(WP004 00) and mode selection for the cabin

air seal between the forward canopy sill, windshield

pressurization system (WP006 00). The switch has

arch, fixed canopy, and forward canopy frame. The

three positions; NORM, DUMP and RAM.

seal is inflated to approximately 20 ±1 psi with

regulated air from the canopy seal control valve.

18. Setting the PRESS switch to RAM applies

When inflated, the seal expands approximately 3/8

emergency 28vdc to energize the solenoid of the

inch. When deflated, the seal collapses into itself so

canopy seal control valve. With the canopy seal

not to interfere with canopy opening and closing.

control valve energized both canopy pressure seals

will deflate.

27. Aft Canopy Pressure Seal. The aft canopy

pressure seal is installed in a track on the periphery

19. OPERATION.

of the aft canopy. It is functionally identical to the

20. COMPONENT OPERATION.

forward canopy pressure seal.

21. Anti-G/Canopy Seal Check Valve. The

28. Canopy Seal Control Valve. The canopy seal

anti-g/canopy seal check valve is located between

control valve is located in door 10. The valve passes

the primary heat exchanger and the expansion

conditioned air to inflate the forward and aft

turbine inlet of the cold air unit (WP004 00). The

canopy pressure seals when deenergized and deflate

check valve allows air flow in one direction only.

the seals when energized.

With air pressure applied, spring tension is

overcome by air pressure and the check valve opens

29. The canopy seal control valve is energized

to allow air flow. With no air pressure applied, the

through the PRESS switch when set to RAM and

valve is held closed by spring tension, allowing no

the weight on wheels relay no. 1 when aircraft

reverse air flow. If cabin cooling and defog system

weight is on wheels. The energized solenoid opens a

pressure is lost, the check valve will hold canopy

vent and closes the supply to deflate the forward

seal system and anti-g system (WP009 00) pressure.

and aft canopy pressure seals.

22. The check valve also isolates the canopy seal

system for ground operation. With the normal air

30. The valve is deenergized with the PRESS

source off, a ground air source can be connected to

switch set to NORM or DUMP and through the

the anti-g/canopy seal test port. The check valve

weight on wheels relay no. 1 when aircraft is weight

will prevent loss of ground air source air through

off wheels. The deenergized solenoid closes a vent

the nonoperating normal system.

and opens the supply to inflate the forward and aft

canopy pressure seals.

23. Anti-G/Canopy Seal Test Port. The

anti-g/canopy seal test port is a capped tee located

31. The canopy seal control valve functions

in the nose wheelwell. The test port allows a ground

identically whether the air source is from the cabin

air source to be used for ground testing of the

cooling and defog system or from a ground air

canopy seal system.

source.

24. The test port is tapped into the anti-g/canopy

seal line between the anti-g/canopy seal check valve

32. If an electrical failure of the aircraft or valve

and the canopy seal pressure regulator and check

occurs, the valve solenoid will fail to the

valve. The ground air source connected to the test

deenergized position, allowing the canopy pressure

port is isolated by the anti-g/canopy seal check

seals to inflate.

A1-AV8BC-410-100

007 00

Page 4

33. Canopy Seal Pressure Regulator and Check

for normal operation. Conditioned air is tapped off

Valve. The canopy seal pressure regulator and

the air duct between the secondary heat exchanger

check valve is located in door 10. The valve

and the cold air unit. The air passes through the

regulates conditioned air from the cabin cooling and

anti-g/canopy seal check valve. The check valve

defog system (WP004 00) or air from a ground air

prevents loss of canopy seal system pressure if cabin

source to approximately 20 ±1 psi.

cooling and defog system pressure is lost. The air is

transported by way of tubing to the canopy seal

34. Air pressure enters the canopy seal pressure

pressure regulator and check valve where pressure is

regulator and check valve through the check valve.

regulated to 20 ±1 psi. The regulated air then passes

The air pressure acts on the diaphragm moving it

to the canopy seal control valve.

down against spring tension. Moving the diaphragm

down begins to move the inlet valve towards its

39. The canopy seal control valve is controlled

seat. The inlet valve will pass 20 ±1 psi. When the

electrically through the PRESS switch and the

air pressure acting on the diaphragm is above 20 ±1

weight on wheels relay no. 1.

psi, the inlet valve will be closed. Further increasing

pressure will move the diaphragm down away from

the relief valve plate. An opening in the diaphragm

40. With the PRESS switch set to NORM or

and spring cup will pass air pressure in excess of 20

DUMP and aircraft weight off wheels, the canopy

±1 psi to the pressure relief valve.

seal control valve is deenergized. Deenergizing the

control valve closes a vent and opens the supply

35. The check valve prevents loss of canopy

port allowing regulated air to pass through the

pressure seal pressure if the cabin cooling and defog

control valve and inflate both canopy pressure seals.

system or ground air source pressure is lost.

41. Setting the PRESS switch to RAM or with

36. SYSTEM OPERATION.

aircraft weight on wheels the control valve is

energized. Energizing the control valve closes the

37. The canopy seal system (figure 2), provides an

supply port and opens the vent. Air exits through

inflated seal between the canopies and surrounding

the vent and both canopy seals deflate.

structure. The forward canopy pressure seal and aft

canopy pressure seal can be inflated by one of two

42. Ground Operation. Ground operation of the

air sources; the cabin cooling and defog system or a

canopy seal system is the same as normal operation

ground air source.

except for the air source. For ground operation, the

anti-g/canopy seal test port is used to connect a

38. Normal Operation. The cabin cooling and

ground air source to the system.

defog system provides air to the canopy seal system

A1-AV8BC-410-100

007 00

Change

Page

Nomenclature

Index No.

Ref Des

AFT CANOPY PRESSURE SEAL

—

ANTI-G/CANOPY SEAL CHECK VALVE

22VAK516

CANOPY SEAL CONTROL VALVE

22L-D031

CANOPY SEAL PRESSURE REGULATOR AND

22MAJ514

CHECK VALVE

CANOPY SEAL WATER DRAIN VALVE

—

DC CIRCUIT BREAKER PANEL ASSEMBLY

52A-C104

CAB ECS NO. 1 (ZONE D7)

22CBC016

CABIN ECS NO. 2 (ZONE B3)

22CBC015

DC EMERGENCY PANEL ASSEMBLY

52A-P132

CABIN ECS CB NO. 2 (ZONE F8)

22CBP015

DC ESSENTIAL/MAIN PANEL ASSEMBLY

52A-P133

CABIN ECS CB NO. 1 (ZONE D3)

22CBP016

ECS CONTROL PANEL ASSEMBLY

22A-F048

PRESS SWITCH

22S-F033

FORWARD CANOPY PRESSURE SEAL

—

FORWARD NO. 2 RELAY PANEL ASSEMBLY

52A-C113

WEIGHT ON WHEELS RELAY NO. 1

12K-C053

LEGEND

162747; ALSO 162963 THRU 163861 BEFORE AV8AFC-416.

164113 AND UP; ALSO 162963 THRU 163861 AFTER AV8AFC-416.

Figure 1. Canopy Seal System Component Locator (Sheet 5)

A1-AV8BC-410-100

008 00

Change 7 - 15 May 2004

Page 1

ORGANIZATIONAL MAINTENANCE

PRINCIPLES OF OPERATION

FORWARD AVIONICS COOLING SYSTEM

Reference Material

Air Data Computer System

A1-AV8BB-560-100

Operation

WP005 00

Electrical Systems

A1-AV8BB-420-100

AC Power System

WP003 00

DC Power System

WP004 00

External Electrical Power System

WP006 00

Electrical Systems

A1-AV8BD-420-100

AC Power System

WP003 00

DC Power System

WP004 00

External Electrical Power System

WP006 00

Environmental Control System

A1-AV8BC-410-100

Description and Operation - Cabin Cooling and Defog System

WP004 00

Cabin Pressurization System

WP006 00

Landing Gear and Related Systems

A1-AV8BB-130-100

Landing Gear System

WP003 00

Lighting System

A1-AV8BB-440-100

Warning/Caution/Advisory Lighting System

WP007 00

Alphabetical Index

Subject

Page No.

Description

Component Description

Anti-G/Canopy Seal Test Port

Avionics Cooling Air Fittings

Cockpit Avionics Cooling Fan

Cockpit Differential Pressure Switch

Ground Cooling Control Valve

Ground Cooling Fan

Ground Cooling Valve

INS Check Valve

INS Plenum Check Valve

Ram Air Inlet

Ram Air Vent Check Valve

Rear Cockpit Avionics Cooling Fan

Speed Sensor

A1-AV8BC-410-100

008 00

Change 7

Page 2

Alphabetical Index (Continued)

Subject

Page No.

Related Systems

AC Power System

Air Data Computer System

Cabin Cooling and Defog System

DC Power System

External Electrical Power System

Landing Gear System

Warning/Caution/Advisory Lighting System

System Controls and Indicators

Cockpit Cool Cancel Relay

Cockpit Cooling Fan Relay

Cockpit Fan Fail Relay

CS COOL Caution Lights

Fwd Fus Cooling Fan Control Relay

Fwd Fus Fan Fail Relay

Gnd Pwr Fan Control Relay

PRESS Switch

Rear Cockpit Cool Cancel Relay

Rear Cockpit Cooling Fan Relay

Rear Cockpit Fan Fail Relay

System Description

Forward Avionics Cooling System Component Locator, Figure 1

Forward Avionics Cooling System Simplified Schematic-162747; ALSO 162963 THRU 163861

BEFORE AV8AFC-416, Figure 2

Forward Avionics Cooling System Simplified Schematic-164113 AND UP; ALSO 162963

THRU 163861 AFTER AV8AFC-416, Figure 3

Operation

Component Operation

Anti-G/Canopy Seal Test Port

Avionics Cooling Air Fittings

Cockpit Avionics Cooling Fan

Cockpit Differential Pressure Switch

Ground Cooling Fan

Ground Cooling Control Valve

Ground Cooling Valve

INS Check Valve

INS Plenum Check Valve

Ram Air Inlet

Ram Air Vent Check Valve

Rear Cockpit Avionics Cooling Fan

Speed Sensor

System Operation

Emergency Operation

Ground Operation

Normal Operation

A1-AV8BC-410-100

008 00

Change 7

Page 3

Record of Applicable Technical Directives

Type/

Date

Title and ECP or RAMEC No.

Remarks

Number

Incorp.

AV8AFC-416

— TAV-8B Polyimide Wire Replacement/

15 May 04

—

Power Wire Separation (ECP MDA-AV8B-

0277)

1. DESCRIPTION.

8. Ground Cooling Control Valve. The ground

cooling control valve is a solenoid operated, double

2. SYSTEM DESCRIPTION. The forward avionics

acting air control valve.

cooling system provides a temperature controlled

environment for forward fuselage mounted avionics

9. Ground Cooling Fan. The ground cooling fan is

equipment. Avionics equipment mounted in the

an electrically driven axial flow fan. The fan is

forward and rear cockpits is cooled by air pulled

made up of a flow impeller mounted directly to the

across the equipment by the cooling fans. Forward

shaft of a 3 phase, 400 Hz electrical motor.

fuselage mounted equipment is cooled several ways.

During normal operation, conditioned air from the

10. Ground Cooling Valve. The ground cooling

cabin cooling and defog system (WP004 00) is

valve is a pneumatically controlled and actuated

transported, by way of ducting, to individual

shutoff valve. The valve is made up of a housing

components. Airflow from the cabin pressurization

which contains a piston attached to a springloaded

system (WP006 00) is routed to equipment bays,

diaphragm that controls a hinged valve. The valve

where it augments avionics cooling. During ground

has an air inlet port.

or emergency operation, ambient air is pulled in by

the ground cooling fan and transported, by way of

11. Ram Air Inlet. The ram air inlet is an opening

ducting, to individual components.

in aircraft skin at the base of the windshield.

3. COMPONENT DESCRIPTION. System

12. Ram Air Vent Check Valve. The ram air vent

components shown in figure 1 are described and

check valve is a flapper type, spring loaded, check

listed in paragraphs below.

valve.

4. Anti-G/Canopy Seal Test Port. The

13. Speed Sensor. The speed sensor is an

anti-g/canopy seal test port is an inline capped tee

electronic processing unit in a sealed case.

fitting.

14. INS Check Valve. The INS check valve is a

5. Avionics Cooling Air Fittings. Several different

flapper type spring loaded check valve.

types of fittings are used. Cooling requirements and

mounting provisions vary for different avionics

15. INS Plenum Check Valve. The INS plenum

units. Some fittings are collapsible, self sealing

check valve is a spring loaded check valve.

assemblies. Other fittings are duct flanges. Fittings

may or may not include filters and/or orifices.

16. Cockpit Differential Pressure Switch. The

cockpit differential pressure switch is a normally

6. Cockpit Avionics Cooling Fan. The cockpit

closed, pneumatically controlled, pressure switch.

avionics cooling fan is an electrically driven, axial

The switch is threaded to be installed in a duct.

flow fan. The fan includes a flow sensor, 3 phase

400 Hz electrical motor and shaft, rotor assembly,

17. RELATED SYSTEMS. Related systems are

and housing.

described in paragraphs below.

7. Rear Cockpit Avionics Cooling Fan. The rear

18. Cabin Cooling and Defog System. The cabin

cockpit avionics cooling fan is identical to the

cooling and defog system (WP004 00) provides

cockpit avionics cooling fan.

conditioned air for normal forward avionics cooling

system operation.

A1-AV8BC-410-100

008 00

Change 7

Page 4

19. AC Power System. The AC power system on

26. SYSTEM CONTROLS AND INDICATORS.

162747; ALSO 162963 THRU 163861 BEFORE

System controls and indicators are described in the

AV8AFC-416 (A1-AV8BB-420-100, WP003 00) or

paragraphs below.

164113 AND UP; ALSO 162963 THRU 163861

AFTER AV8AFC-416 (A1-AV8BD-420-100, WP003

27. PRESS Switch. The PRESS switch, located on

00) provides essential 115 vac power for the forward

the ECS control panel assembly (WP004 00), is a

avionics cooling system.

four pole, lever lock, toggle switch. The switch

provides mode selection for the forward avionics

20. DC Power System. The DC power system on

cooling system. The switch has three positions;

162747; ALSO 162963 THRU 163861 BEFORE

NORM, DUMP, and RAM. The switch is locked in

AV8AFC-416 (A1-AV8BB-420-100, WP004 00) or

all positions.

164113 AND UP; ALSO 162963 THRU 163861

AFTER AV8AFC-416 (A1-AV8BD- 420-100, WP004

28. Setting the PRESS switch to NORM or RAM,

00) provides essential 28vdc power for the forward

allows cabin cooling and defog system (WP004 00)

avionics cooling system.

air to be tapped and transported by way of ducting

to the avionics equipment.

21. Warning/Caution/Advisory Lighting System.

The warning/caution/advisory lighting system

29. Setting the PRESS switch to RAM, applies

(A1-AV8BB-440-100, WP007 00) provides visual

28vdc to energize the ground cooling control valve

indication of normal aircraft functions and system

and the fwd fus cooling fan control relay. The

malfunctions affecting safety of flight operations.

ground cooling valve will open and the ground

The warning/caution/advisory lighting system

cooling fan will start to run.

includes the annunciator light controller and the

caution/advisory indicator light assembly. The

30. Cockpit Cool Cancel Relay. The cockpit cool

annunciator light controller receives data from

cancel relay, located on the forward relay no. 2

various aircraft systems and provides logic to turn

panel assembly, is a 5 amperes, 2 pole, double

on and off warning/caution/advisory lights.

throw, permanent magnet drive, armature relay.

The relay is energized when the MASTER

CAUTION light is reset.

22. The annunciator light controller will turn on

the CS COOL caution lights and the MASTER

CAUTION lights if either cockpit avionics cooling

31. When energized, the relay provides a ground to

fan fails.

turn off the rear CS COOL caution light. A holding

circuit keeps the relay energized until the cockpit

23. Landing Gear System. The landing gear system

avionics cooling fan resumes operation.

(A1-AV8BB-130-100, WP003 00) provides ground

control for the ground cooling fan and the ground

32. Cockpit Cooling Fan Relay. The cockpit

cooling control valve through the weight on wheels

cooling fan relay, located on the forward relay no. 1

relay no. 1.

panel assembly, is a 5 amperes, 4 pole, double

throw, permanent magnet drive, armature relay.

24. External Electrical Power System. The

The relay is energized when the cockpit avionics

external electrical power system on 162747; ALSO

cooling fan thermal protector is closed.

162963 THRU 163861 BEFORE AV8AFC-416

(A1-AV8BB-420-100, WP006 00) or 164113 AND

33. When energized, the relay provides 115vac

UP; ALSO 162963 THRU 163861 AFTER

power to the cockpit avionics cooling fan. When

AV8AFC-416 (A1-AV8BD-420-100, WP006 00)

deenergized, the relay removes 115vac power from

provides electrical power for the forward avionics

the fan.

cooling system.

34. Cockpit Fan Fail Relay. The cockpit fan fail

25. Air Data Computer System. The air data

relay, located on the forward relay no. 2 panel

computer system (A1-AV8BB-560-100, WP005 00)

assembly, is a 5 amperes, 2 pole, double throw,

provides an altitude signal to the forward avionics

permanent magnet drive, armature relay. The relay

cooling system, through the 20K ft alt relay.

is energized when the cockpit avionics cooling fan

speed is approximately 60 percent rpm or greater.

A1-AV8BC-410-100

008 00

Change 6

Page 5

35. When energized, the relay disables the CS

relay no. 2 panel assembly, is a 5 amperes, 2 pole,

COOL caution lights by providing a ground to the

double throw, permanent magnet drive, armature

warning/caution/advisory lighting system.

relay. The relay is energized when the MASTER

CAUTION light is reset.

36. When deenergized, the relay;

44. When energized, the relay provides a ground to

a. Removes a ground to the

turn off the CS COOL caution light. A holding

warning/caution/advisory lighting system to enable

circuit keeps the relay energized until the rear

the CS COOL caution lights.

cockpit avionics cooling fan resumes operation.

b. Provides a ground to the rear cockpit cooling

45. Rear Cockpit Cooling Fan Relay. The rear

cancel relay holding circuit.

cockpit cooling fan relay, located on the forward

relay no. 1 panel assembly, is a 5 amperes, 4 pole,

37. Fwd Fus Cooling Fan Control Relay. The fwd

double throw, permanent magnet drive, armature

fus cooling fan control relay, located on the forward

relay. The relay is energized with the rear cockpit

relay no. 1 panel assembly, is a four pole, double

avionics cooling fan thermal protector closed.

throw, 5 amperes, permanent magnet drive,

46. With the relay energized, 115vac is applied to

armature relay.

the rear cockpit avionics cooling fan. With the relay

38. The relay is energized with aircraft weight on

deenergized, 115vac power is removed from the rear

wheels, or aircraft altitude less than 20,000 feet, or

cockpit avionics cooling fan.

cabin pressure less than 2.00±0.5 psi, or PRESS

switch set to RAM. With the relay energized,

47. Rear Cockpit Fan Fail Relay. The rear cockpit

essential 115 vac power is applied to three phases of

fan fail relay, located on the forward relay no. 2

the ground cooling fan motor. With the relay

panel assembly, is a 5 amperes, 2 pole, double

deenergized, essential 115 vac power to the fan

throw, permanent magnet drive, armature relay.

motor is lost.

The relay is energized when the rear cockpit

avionics cooling fan is operating at 60 percent rpm

39. Fwd Fus Fan Fail Relay. The fwd fus fan fail

or greater.

relay, located on the forward relay no. 2 panel

48. When energized, the relay disables the rear CS

assembly, is a 2 pole, double throw, 5 amperes,

COOL caution light by providing a ground to the

permanent magnet drive, armature relay. The relay

warning/caution/advisory lighting system.

is energized when the speed sensor senses ground

cooling fan speed of approximately 60 percent rpm

49. When deenergized, the relay;

or less.

a. Removes a ground to the

40. With the relay energized, 28vdc is removed to

warning/caution/advisory lighting system to enable

deenergize the fwd fus cooling fan control relay.

the CS COOL caution lights.

With the relay deenergized, 28vdc is applied to

energize the fwd fus cooling fan control relay.

b. Provides a ground to the cockpit cooling

cancel relay holding circuit.

41. Gnd Pwr Fan Control Relay. The gnd pwr fan

control relay, located on the forward relay no. 1

50. CS COOL Caution Lights. The CS COOL

panel assembly, is a 5 amperes, double pole, double

caution lights are located on the caution/advisory

throw permanent magnet drive, armature relay. The

indicator light assembly and the rear

relay is energized when the rear cockpit avionics

caution/advisory indicator light assembly.

cooling fan speed is approximately 60 percent rpm

51. The CS COOL caution lights are controlled by

or greater.

the cockpit avionics cooling fan, rear cockpit

42. With the relay energized, a ground signal is

avionics cooling fan, cockpit fan fail relay, rear

provided to the COCKPIT switch of the external

cockpit fan fail relay, cockpit cool cancel relay, and

electrical power system.

rear cockpit cool cancel relay through the

warning/caution/advisory lighting system.

43. Rear Cockpit Cool Cancel Relay. The rear

52. Both CS COOL lights will come on and flash if

cockpit cool cancel relay, located on the forward

the cockpit avionics cooling fan or the rear cockpit

A1-AV8BC-410-100

008 00

Change 6

Page 6

avionics cooling fan fail. Resetting the master

Electrical circuits in the flow sensor compare

caution will cause the CS COOL light in the

voltage outputs of the two temperature sensing

affected cockpit to come on steady, the light in the

devices. If the voltage difference exceeds a

unaffected cockpit will go off.

predetermined limit, which corresponds to

approximately less than 60 percent of normal fan

53. OPERATION.

speed, the CS COOL caution lights are enabled and

avionics ground power application is inhibited.

54. COMPONENT OPERATION.

60. The fan has a built in thermal protector. The

55. Anti-G/Canopy Seal Test Port. The

thermal protector is normally closed and will open

anti-g/canopy seal test port is located in the

when the fan motor overheats. Opening the thermal

forward end of the nose landing gear wheelwell. The

protector will deenergize the cockpit cooling fan

test port allows a ground air source to be used to

relay and remove essential 115vac power from the

test the operation of the ground cooling control

fan motor. The thermal protector will close when

valve and ground cooling valve. With either ground

the fan motor cools.

air source or normal air source used, the valves

operate the same.

61. Rear Cockpit Avionics Cooling Fan. The rear

cockpit avionics cooling fan, located in the rear

56. Avionics Cooling Air Fittings. Avionics cooling

cockpit under the main instrument panel, pulls

air fittings, located on equipment mounting racks in

cabin air through rear cockpit mounted avionics

the cockpit, rear cockpit, and door 125L, provide

equipment. The fan operation is identical to the

the cooling system interface between rack mounted

cockpit avionics cooling fan.

equipment and equipment rack. When a unit is

installed on the equipment rack, it makes contact

62. Ground Cooling Control Valve. The ground

with a cooling air fitting. The fitting makes a seal

cooling control valve is located in door 121. When

between the unit and the rack, allowing cooling air

deenergized by weight off wheels or the PRESS

to flow through the unit. Some fittings contact the

switch in other than RAM, the valve allows air from

unit on the back and some contact on the bottom,

the cabin cooling and defog system (WP004 00) to

depending on unit mounting. The different types of

flow through and hold the ground cooling valve

fittings used are required for the different cooling

closed. With the valve energized by weight on

requirements of each unit.

wheels or the PRESS switch in RAM, air is vented

to atmosphere and the ground cooling valve opens

57. Cockpit Avionics Cooling Fan. The cockpit

by spring tension.

avionics cooling fan, located in the cockpit under

the main instrument panel, pulls cabin air through

63. Ground Cooling Fan. The ground cooling fan is

cockpit mounted avionics equipment. The fan

located in door 121. The motor and impeller are

operates when the cockpit cooling fan relay is

enclosed in a housing which has guide vanes built in

energized.

on the outlet side of the impeller. The guide vanes

straighten the airflow before discharge from the fan.

58. The rotor assembly is mounted on the end of

The motor includes an electrical sensing unit and

the shaft, which is driven by the motor. The

overheat protection devices. The electrical sensing

spinning rotor assembly pulls cockpit air across the

unit provides an electrical signal to the speed sensor

cockpit mounted avionics equipment. The fan

based on fan speed. The overheat protection devices

exhaust air is directed to the rudder pedal area.

will automatically stop the fan if an overheat

occurs. When the overheat condition no longer

59. The flow sensor is made up of electrical circuits,

exists, the fan will resume normal operation. The

an open ended tube and two temperature sensing

fan motor is cooled by its own airflow.

devices. The tube faces the airstream and directs a

small amount of air over the temperature sensing

devices. The temperature sensing devices produce

64. With the fan operating, cooling air is pulled in

an output voltage proportional to their temperature.

through the ground cooling valve. The cooling air is

One temperature sensing device is heated at a

given a high velocity by the fan impeller and is

constant rate. Its voltage output and temperature

transported by way of ducting to forward fuselage

are proportional to the amount of cooling air

mounted avionics equipment. The fan will operate

passing over it, which changes with fan airflow.

when electrical power is applied and weight is on

A1-AV8BC-410-100

008 00

Change 6

Page 7

wheels, or aircraft altitude less than 20,000 feet, or

flappers are spring loaded closed and allow airflow

cabin pressure less than 2.00±0.5 psi, or PRESS

in one direction only.

switch set to RAM.

70. INS Plenum Check Valve. The INS plenum

65. Ground Cooling Valve. The ground cooling

check valve is located in the distribution duct

valve is located in the ram air inlet. When air

between the air communication duct and the

pressure tapped from the cabin cooling and defog

Inertial Navigation Unit CN-1516/ASN-130A or

system (WP004 00) is applied to the valve inlet

CN-1649/ASN-139 cooling plenum assembly. The

port through the ground cooling control valve, the

check valve prevents loss of equipment cooling air

spring loaded diaphragm is compressed, the piston

through the cockpit and rear cockpit during ground

moves and closes the valve. When air pressure is

operation. The valve flappers are spring loaded

not applied or is lost, the spring loaded diaphragm

closed and allow airflow in one direction only.

moves the piston and opens the valve. The valve,

with the ground cooling fan, allows ambient air to

71. Cockpit Differential Pressure Switch. The

flow and cool forward fuselage mounted avionics

cockpit differential pressure switch is located in the

equipment for ground operation or inflight if a

air communication duct in door 10. The switch

cooling system failure occurs.

senses cabin pressure. When cabin pressure is less

than 2.0±0.5 psid, the switch is closed and applies

66. Ram Air Inlet. The ram air inlet, located on the

28vdc power to energize the fwd fus cooling fan

windshield forward fairing, allows ram or ambient

control relay. When cabin pressure is greater than

air to enter the forward avionics cooling system

2.0±0.5 psid, the switch opens and removes 28vdc

during ground or emergency operation. The inlet

power to deenergize the fwd fus cooling fan control

faces forward so aircraft forward motion will force

relay.

air into the inlet. During ground operation, the

ground cooling valve will open and allow ambient

72. SYSTEM OPERATION.

air to be pulled in the inlet. During inflight

emergency operation, ram air flows to equipment

73. Normal Operation. The forward avionics

cooling system and to each cockpit.

cooling system (figure 2) provides conditioned air

for cooling avionics equipment. Conditioned air is

67. Ram Air Vent Check Valve. The ram air vent

tapped off the cabin cooling and defog system

check valve is located in door 10. The check valve

(WP004 00). The conditioned air is transported by

prevents loss of ambient air through the nose cone

way of ducting to forward fuselage mounted

during ground cooling fan operation. The valve

avionics equipment. Check valves in the distribution

flappers are spring loaded closed and allow airflow

ducting prevent loss of airflow through the ram air

in one direction only.

inlet and ground cooling fan. Cockpit and rear

cockpit mounted avionics equipment is cooled by

68. Speed Sensor. The speed sensor is located in

cockpit avionics cooling fans. Cabin air is pulled

door 121. The speed sensor receives an electrical

across the equipment by the fans. Caution lights

signal from the ground cooling fan electronic

warn the crewmembers of a fan malfunction.

sensing unit. The signal is proportional to fan

rotational speed. If the signal received by the speed

74. The ground cooling fan operates with aircraft

sensor is within a predetermined limit, the speed

weight on wheels, or altitude less than 20,000 feet,

sensor will complete an electrical circuit and allow

or cabin pressure less than 2.0±0.5 psig.

avionics ground power to be applied. If the signal is

out of limits, the speed sensor will inhibit

75. Ground Operation. During ground operation,

application of avionics ground power.

the ground cooling fan pulls ambient air in through

the open ground cooling valve. The cooling air is

69. INS Check Valve. The INS check valve is

transported by way of ducting to the avionics

located in the equipment cooling distribution duct

equipment. A check valve prevents loss of airflow

between the Inertial Navigation Unit

through the cabin cooling and defog system

CN-1561/ASN-130A or CN-1649/ASN-139 cooling

(WP004 00).

plenum assembly and the ground cooling fan. The

check valve prevents the loss of cockpit air through

76. Emergency Operation. In flight during a

the non-operating ground cooling fan. The valve

forward avionics cooling system failure, the pilot

NATOPS FLIGHT MANUAL NAVY MODEL AV--8B/TAV--8B 161573 AND UP AIRCRAFT (2008) - page 12