McDonnell Douglas DC-10-40-Air Cond and Press-1

C H A P T E R 2

AIR CONDITIONING AND PRESSURIZATION

Page

TABLE OF CONTENTS 02-00-01/02

DESCRIPTION

General 02-10-01

Description • 02-10-01

Controls and Indicators 02-10-04

COMPONENTS (NOT USED)

CONTROLS AND INDICATORS

Air Conditioning Pack Controls and Indicators 02-30-01

Compartment Temperature Controls and Indicators . . ., 02-30-02

Cabin Altitude and Rate Indicators 02-30-04

Cabin Pressurization Controller 02-30-05

Standby Cabin Pressurization Controller 02-30-06

Manual Cabin Altitude Control 02-30-07/08

CHARTS AND SCHEDULES

Automatic Pressurization Schedule 02-35-01

Cabin Versus Aircraft Altitude Chart 02-35-02

FUNCTIONAL SCHEMATICS

Air Conditioning System 02-40-01/02

02-00-01/02

AIR CONDITIONING AND PRESSURIZATION

GENERAL

The air conditioning system serves fourindependently controlled zones; the cock-pit and three passenger zones. The sys-tem provides air that is conditioned byheating, cooling, and dehumidification.Temperature control for automatic ormanual conditioning of the four zones isprovided on individual temperatureselectors. The cockpit, passengercabin, avionics, center accessory andcargo compartments are pressurized.Engine bleed air is the source for pres-surization and is controlled by regulatingthe outflow of conditioned air from thepressurized section.

DESCRIPTION

AIR CONDITIONING SYSTEM

The air conditioning packs (three aircycle machines) are powered by pressur-ized air from the pneumatic manifold.This hot, pressurized air is supplied tothe packs where it is cooled and routedto a common manifold. This air is thenmixed with hot air which has bypassedthe packs and distributed to the cockpit,and the three cabin zones. Also, groundconnectors are installed to provide pre-conditioned air from a ground source tothe conditioned air manifold.

Pressurized air is supplied by the auxil-iary power unit (APU), the engines, or aground pneumatic source. The APU canprovide sufficient airflow to operate allthree air conditioning systems with theengine pneumatic supply selectors turnedoff to achieve high-performance takeoffsand initial climb.

The cooling or heating output of an airconditioning pack is accomplished byautomatically or manually modulatingthe turbine bypass valves and the coolingram air inlet and outlet doors.

The inlet temperature signals from eachof the four zone controllers also influ-ence the three air conditioning packcontrollers. The signals are comparedin a controller to determine the lowesttemperature demand.

When the pack function selectors are inthe automatic position, the control ofnumber one pack is determined by thetemperature demand of the cockpit. Con-trol of the number two and three packsis determined by the lowest temperaturedemanded by forward, center and aftcabin.

Individual zone temperature requirementsare adjusted by mixing hot, trim air fromthe pneumatic duct with air from the con-ditioned air manifold.

A ram air distribution system provides abackup supply of outside ambient air tothe conditioned air distribution system ifthe three air conditioning packs are shutdown in flight. The system is located inthe left air conditioning compartment andconsists of ducting, a valve manuallycontrolled by a cable, and a tee handle.The valve control tee handle (lockwired)is located in the avionic compartmentimmediately below the access door in theleft rear of the cockpit floor. To openthe valve, a strong pull is required onthe tee handle to snap the lockwire, andthen continued until bottomed. The valveis located in pack one and must be closedby ground maintenance personnel, beforepneumatic operation of pack one is to beresumed.

JLFeb 1/75 02-10-01

AVIONICS COOLING SYSTEM

The avionics cooling system consists of cooling

fans, venturi, and the ducting necessary tocool the instrument panels and the electronic

and electrical units in the avionics compart-

ment. Cooling fans are installed in the systemto provide the necessary airflow when on the

ground or at low cabin/ambient differential

pressure. An indicator on the center instru-ment panel provides visual indication thatairflow exists at the instrument panels when

the airplane is on the ground with normal

electrical power applied and the air condition-ing packs off. In flight, when cabin/ambient

pressure is sufficient, the fans shut off and

ventilation is provided by overboard Venturis.One cooling fan and a shutoff valve are in-

stalled in the avionic compartment overboard

venturi duct. The valve is normally open inflight to permit avionic venturi operation and

closed on the ground to prevent inflow. In-dividual overboard Venturis are installed forpositive inflight cooling of the inertial naviga-

tion units (INU) and individual fans are

installed for cooling at low differential pressureand ground cooling. INU fan exhaust air is

discharged into the avionic compartment. An

avionic flow override switch is installed to turnon the avionic cooling fans and close theavionic overboard venturi shutoff valve in

case of system failure during pressurized flightor to maintain cabin pressure during singlepack operation.

The AVIONIC FLOW OFF light comes on whenthe cooling airflow through the avionics com-partment or main radio rack is below normal. An

INS FLOW OFF light comes on when coolingairflow through an INU is below normal.

The DUCT-AVIONIC COMP OVERHEATlight is armed when the trim air switch ispositioned to TRIM AIR. If an overheat con-dition occurs in the trim air system, thermalswitches will shut off the source of hot trim airand the DUCT-AVIONIC COMP OVERHEATlight will come on. The overheat light will alsocome on if an over-temperature conditionoccurs in the avionics compartment due toexcessive trim air duct leakage.

Center Accessory CompartmentVentilation

The electrical equipment in the center acces-sory compartment is cooled on the ground andin flight by a continuous duty fan drawingtunnel airflow through the compartment.Adequate airflow through the compartment isprovided in flight even when the fan hasfailed. An amber center accessory compart-ment flow off light comes on when coolingairflow through the center accessory compart-ment is below normal.

GALLEY/LAVATORY VENTILATIONAND CARGO COMPARTMENTHEATING SYSTEM

Air from pneumatic system 2 assist in ventila-tion of the aft lavatories and galleys by jet-pump action and provides airflow around thecenter and aft cargo compartments for heat-ing. The aft lavatories and galleys are sup-plied conditioned air from the cabin area forventilation. Pneumatic system 1, by jet-pumpaction, assists in ventilation of center and for-ward lavatories and center and forward gal-leys, and provides airflow around the forwardcargo compartment for heating.

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Jul 15/95

The forward and aft cargo compartments haveindividual temperature control systems. Eachsystem consists of bleed air pressureregulators, temperature sensors, a controller,a motor actuated modulating valve, and acirculation system with flow detection.

PRESSURIZATION

Cabin pressure is controlled and maintainedin either an automatic, semi-automatic,standby, or manual mode. Electric power isrequired for all but the manual mode.

The cabin pressure controller maintains thedesired cabin pressure in relation to thealtitude set on the landing altitude tape whenthe automatic or semi-automatic mode isselected. In the automatic mode, cabin pres-surization is automatically controlled duringtakeoff, climb, cruise and descent conditions,to the lowest cabin altitude compatible withaircraft and flight requirements.

Destination altitude is set with the Altitude Setknob and will automatically schedule depres-surization during descent to 300 feet belowthe selected destination altitude when in theautomatic or semi-automatic mode.

The descent mode is initiated in the auto-matic mode when the aircraft descendsapproximately 1000 feet in one minute. Thedescent mode is initiated in the semi-automatic mode when the landing field al-titude is set in the ALT SET scale.

If destination field elevation is above cabinaltitude at start of aircraft descent, cabinaltitude will climb at a rate not exceeding theselected rate limit, nominally set to 500 ft permin, until cabin altitude is equal to 300 feetbelow the destination field elevation.

At nosegear touchdown the aircraft willdepressurize at 350 feet per minute.

In the semi-automatic mode, cabin altitude isselected on the altitude-set tape by positioningthe altitude set knob to the desired altitude.Desired cabin altitude rate of change can beselected manually by adjusting the rate limitselector.

At the time the standby mode is selected, thestandby control system will hold the cabinaltitude constant. Rotation of the cabinaltitude rate selector will provide the desiredclimb and descent rates.

If the automatic and standby systems malfunc-tion, manual control of pressurization is pos-sible by direct mechanical control of theoutflow valves. An outflow valve positionindicator displays the outflow valve position inall operating modes.

When manual control is selected, the controlwheel engages a locking mechanism to securethe outflow valve in its existing position. Afterselection, manual control is achieved by press-ing the control wheel inward (to disengage thecontrol wheel locking device) and rotating thewheel to position the outflow valve to attainthe desired cabin altitude. When the controlwheel is released, the outflow valve is againlocked in its existing position. Selecting thevalve at more than two thirds open can causea negative pressure and create a noise in thecabin. At touchdown, the Flight Engineermust manually depressurize the aircraft.

One air conditioning pack will supply ade-quate pressurization, even at maximumaltitude.

JLJul 15/95 02-10-03

CABIN PRESSURE RELIEF VALVES

The cabin pressure relief valves limit cabindifferential pressure. Flapper doors at each ofthe three relief valve over-board exhausts fairwith the aircraft skin and are located immedi-ately aft of the forward lower cargo door. Theflapper doors open if the associated reliefvalve opens. The relief valves open any timecabin pressure exceeds the white arc on thecabin differential gage. The valves will limitthe cabin pressure to 9.1 psi.

Once a relief valve has opened, the flapperdoors will be held open about 1/8 inch by asmall rubber tab. This will not affect valve

leakage or performance; it is only an indica-tion that the relief valve has previously beenopen. The edge of the flapper is painted redto enhance visibility from the ground.

CONTROLS AND INDICATORS

The controls, indicators, and annunciatorlights are on the Flight Engineer's Upper PanelNo. 2 and the overhead panel. Illustrations ofthese major panels are in Chapter 1. Theindividual controls and indicators areillustrated and described in another section ofthis chapter.

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Jul 15/95

AIR CONDITIONING - Controls and Indicators

Air Conditioning Pack Controls and Indicators

PACK OFF Light (1,2,3)Indicates the respective air conditioning pack is shutoff by either an overheat condition or the loss ofpneumatic supply pressure. Also indicates that theflow control valve is closed when the pack functionselector is in any position but PACK OFF.

PACK Function Selector (1.2.3)PACK OFF - Closes flow control valve which shuts

down associated system.AUTO — Provides automatic control of selected

temperature for the air conditioningdistribution manifold.

MAN - When the selector is forced througheither the left or right detent position itbecomes spring-loaded to the STOPposition. Holding the selector in theCOLD or HOT position will drive itsassociated turbine bypass valve andram air doors in the selected direction.

Pack TURB INLETTEMP GageIndicates pack turbineinlet temperature.

PACK TEMP VALVEPOS Indicatorindicates position of tur-bine bypass valve andram air doors. At "C,"doors are open. At "H,"doors are closed.

PACK DISCH TEMPGageIndicates pack dis-charge temperature.

PACK IND SelectorSelects which respectiveair conditioning packturbine inlet tempera-ture, pack temperaturevalve position, and packdischarge temperatureindication will be dis-played.

Pneumatic FLOWGage (3)Indicates flow througheach air conditioningsystem. Normal is insidethe upper half-arc. Thepointer at the indexmark below LO indicatesno flow.

Ram Air Valve Control (Tee) Handle (Under floor)To open valve use strong pull to snap lockwire and pulluntil bottomed. Provides a backup supply of outside airto the conditioned air distribution system if all packsare shut down inflight and the cabin is depressurized.The valve must be closed before operating pack 1 andis normally closed by maintenance. The valve cannotbe closed by re-setting the handle.

FLIGHT ENGINEER'SUPPER PANEL NO. 2

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Compartment Temperature Controls and Indicators (Sheet 1)

INS FLOW OFF Lights (1, 2 & 3)Comes on when cooling airflow over theinertial navigation units (1NU) is belownormal.

(OVERHEAD PANEL)

AIRFLOW INDICATORIndicates presence of airflow to in-struments when on the ground with nor-mal electrical power applied and air con-ditioning pack off.

(CENTER INSTRUMENT PANEL)

COMPT/DUCT Temperature Gage (4)Dual temperature gages indicate theinlet duct and compartment tempera-ture for the respective compartment(zone). DUCT-AVIONIC COMPT

OVERHEAT LightIndicates overheat in one of the fourzone inlet ducts or the avionic compart-ment. When overheat is sensed, trimair is automatically shut off.

Temp Selector (4)AUTO - Provides automatic control of

selected temperature for theapplicable zone. The centerdot position will result in an o m i n a l 24°C (75°F)temperature. Total automaticrange is approximately 18°C(65°F) to 29°C (85°F).

MAN -When the selector switch isforced through either left or rightdetent position it becomes springloaded to the STOP position.Holding the selector in the COLDor HOT position will drive itsassociated trim air valve in theselected direction. When all com-partment temperature selectorsare in MAN, the operating packsare automatically programmed todischarge air at a moderatelycold temperature.

TRIM AIR SwitchTRIMAIR - In theTRIM AIR normal position,

hot air (modulated) is permittedto temper the air conditioningsystem on demand. Here, theheated air is taken from sys-tems 1 and 3 and mixed withcooler conditioned air in the in-dividual compartment ducts.

OFF — Prohibits hot air from entering themanifold. If the DUCT AVIONICCOMPT OVERHEAT light comeson and remains on after the trimair switch has been placed to OFF,the DUCT AVIONIC COMPTOVERHEAT light remaining on in-dicates Avionic Compt overheatstill exists and the TRIM AIRSwitch cannot be reset in flight.

AIR COND TRIM AIR PRESS HI LightIndicates pressure in the number oneor number three trim air manifolds isexcessive.

CTR ACCESS COMPT FLOW OFF LightComes on when cooling airflow throughthe center accessory compartment isbelow normal.

AVIONIC FLOW OFF LightComes on when cooling airflow throughavionic compartment or main radiorack is below normal.

AVIONIC FLOW SwitchNORM- Provides automatic cooling

airflow through avionics com-partment.

OVRD — Provides electrical manualoverride to close venturi valveand turn on avionics coolingfans.

FLIGHT ENGINEER UPPER PANEL NO. 2

NOTE: INS FLOW OFF lights effective on international versions.

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Jul 15/95

AIR CONDITIONING - Controls and IndicatorsCompartment Temperature Controls and Indicators (Sheet 2]

VALVE POS Indicator (4)Indicates the position of the trim airvalve for the respective compartment(zone). LAV/GALLEY VENT & CARGO

HEAT SwitchProvides control of galley and cargo ven-tilation, cargo compartment heat, andlavatory ventilation through jet pumpaction.OFF - The OFF position turns off the

heating and ventilation system.

CARGO COMPT TEMP Gage(FWD. CTR. AFT)Indicates temperature in the associatedcargo compartment.

FWD CARGO TEMP SelectorA controlled temperature of either ap-proximately 4°C (40°F) or 18°C (65°F) isselectable by LO-HI position.MAN — When the selector is forcedthrough either left or right detent positionit becomes spring loaded to the STOPposition. Holding the selector in the COLDor HOT position will drive its associatedvalve in the selected direction.

AFT CARGO TEMP SelectorA control led cargo compartmenttemperature of from approximately 4°C(40°F) to 27°C (80°F) is selectable on theupper portion of rotation.MAN — When the selector is forcedthrough either left or right detent positionit becomes spring loaded to the STOPposition. Holding the selector in the COLDor HOT position will drive its associatedvalve in the selected direction.

CARGO FLOW OFF (FWD & AFT)Light (2)Comes on when CARGO VENT switch ison and no airflow is detected throughthe cargo compartment ventilationducts.

CARGO VENT (FWD & AFT) Switch (2)VENT — Provides ventilation airflow con-

trol to forward and aft cargoc o m p a r t m e n t s w h e n t h eL A V / G A L L E Y VENT andCARGO HEAT switch is on.

OFF — Shuts off cargo ventilationsystem.

FLIGHT ENGINEER'S UPPER PANEL NO. 2

JLFeb 1/79 02-30-03


Cabin Altitude and Rate Indicators

BARO PRESS ScaleWhen set to local altimeter setting, thisscale will cause the CAB ALT pointer todisplay cabin height in relation to sealevel. If set to 29.92" Hg the pointer willindicate cabin pressure altitude.

CABIN ALT/DIFF PRESS GageThe cabin altitude pointer indicates thepressure altitude of the cabin interior de-pendent upon the setting of the BAROPRESS scale in relation to local altimetersetting.The cabin differential pressure pointerindicates the difference between internalcabin pressure and ambient atmosphericpressure.

White band (arc) 8.4 to 8.8 psiRelief valves start to open any time cabinpressure exceeds white band.

BARO Pressure Set KnobControls altimeter setting displayed bythe BARO PRESS scale.

CABIN ALT RATE IndicatorIndicates rate of altitude change withinthe cabin in feet per minute.


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Feb 1/75

PRESSURIZATION - Controls and IndicatorsCabin Pressurization Controller

RATE LIMIT SelectorProvides selection of increased or decreasedcabin altitude rate limits when cabin pressuremode selector switch is in SEMI-AUTO mode.Normally left at the rate limit index mark foroptimum system operation when in the AUTOmode.Rate limit selector is ineffective when movedtoward INCR when in AUTO mode and onschedule, however, it will work in the DECRdirection.It will work in either INCR or DECR if cabin al-titude is off schedule or SEMI-AUTO mode isselected.

LDG BARO ScaleIndicates barometric pressure setting selected bythe landing barometric pressure knob.

ALT SET ScaleIndicates selected landing airport altitudewhen operating in AUTO mode. Indicatesselected cabin altitude when operating in theSEMI-AUTO mode.

SEMI-AUTO ON LightLight will come on when the SEMI-AUTO modeis selected.

Cabin Press MODE SwitchSwitch is normally in the AUTO position.AUTO — Automatical ly controls cabin

pressurization schedule duringclimb, cruise, and descent.

SEMI-AUTO-Permits desired cabin altitude tobe selected by the altitude setknob and the climb or descentschedule to be programmed bythe rate limit knob.

ALT SET KnobSelects destination pressure altitude at stan-dard atmosphere. Controller will automaticallyschedule depressurization to this altitude dur-ing descent when in AUTO mode.Selects cabin altitude when in SEMI-AUTOmode, and desired landing altitude at start ofdescent.

LDG BARO KnobCorrects selected destination pressure altitudeto field elevation when destination altimetersetting is applied.

FULL COUNTERCLOCKWISE(11 O'CLOCK) POSITION1OO'/MIN UP OR60V Ml N DOWN

FULL CLOCKWISE(7 O'CLOCK) POSITION2000VMlN UP OR1200VMlN DOWN

500'/MIN UP OR300'/ MlN DOWN


JLFeb 1/79 02-30-05


Standby Cabin Pressurization Controller

Cabin Pressure STANDBY ON Switch/light.Comes on when the cabin altitude rate control knob ispulled out.When the switch/light is pushed, the landing gear isbypassed and permits pressure control checkout ifrequired.

STANDBY CABIN ALT RATE SelectorUsed to control cabin altitude rate of climb or descentwhen operating with standby pressurization system.The knob is pulled out to activate the system. Knob mustbe at "0" position before pulling out. This action holds orlocks in the cabin altitude existing at the time of engage-ment. Rotating the knob toward UP or DOWN will es-tablish the desired rate of climb or descent. Cabin willcontinue to climb or descend at selected rate.Returning the knob to "0" position will hold existingcabin altitude. Knob must be at "0" position to push inand de-activate the standby control system.

ALT SCHED PlacardIndicates the schedule of cabin altitude versus air-plane altitude for manual and standby operation atmaximum differential pressure on the right handscale, and with automatic pressurization on the lefthand scale.

EFFECTIVEON SOME-

AIRPLANES

CABIN PRESS RELIEF OPEN LightComes on to indicate that cabin pressure has ex-ceeded limits and that one or more of the cabinpressure relief valves has opened.

CABIN ALT Light (2)Comes on to indicate that cabin altitudehas exceeded maximum limit.NOTE: One light is located on the Pilots'

overhead panel.

CABIN ALT WARN HORN ButtonAural warning will sound when cabin altitudeexceeds 10,000 feet. Pushing the buttonwill silence the horn.


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Feb 1/79

AIR CONDITIONING — Controls and Indicators

Manual Cabin Altitude Control

OUTFLOW VALVE Position IndicatorIndicates the relative position of the outflow valve. Theindicator will operate in the automatic, semi-automatic,standby and manual control modes. When the indicator isfull up, the outflow valve is full open.

Manual CAB ALT Control WheelUsed to position the outflow valve manually to adjust cabinpressure. When the cabin pressure manual/auto selectoris in the MAN position, pushing the control wheel inwardand rotating the wheel upward will mechanically cause theoutflow valve to move toward open and the cabin altitudeto go up. Rotating the wheel downward results in an oppo-site reaction. When the control wheel is released the outflowvalve will be locked until the wheel is again pushed inwardand rotated.When cabin pressure manual/auto selector is in AUTOposition the control wheel follows cabin outflow valvemotion, therefore providing an indication of direction andrate of movement.

CAB PRESS MAN/AUTO HandleSelects either manual or automatic control of the pressuri-zation system. Selector is normally in AUTO position.

AUTO — Permits electrical outflow valve operation by cabinpressure controllers in automatic, semi-automaticand standby modes.

MAN - Positioning the selector to MAN locks the out-flow valve in its existing position, and permitsmanual positioning of the outflow valves.

FLIGHT ENGINEER'S LOWER PANEL

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02-30-07/08

AUTOMATIC PRESSURIZATION SCHEDULE

TAKEOFFFIELD ELEV

BELOW 2700 FT

2700-4500 FT

ABOVE 4500 FT

DESTINATIONFIELD ELEV

BELOW 2700 FT2700-4500 FTABOVE 4500 FT

BELOW 2700 FT

2700-4500 FTABOVE 4500 FT

BELOW 2700 FT2700-4500 FT

ABOVE 4500 FT

CABIN ALTITUDEREACTION

GOES TO DEST FLD ELEVCLIMBS TO DEST FLD ELEVCLIMBS TO 4500 FT

DESCENDS TO 2700 FT

GOES TO DEST FLD ELEVCLIMBS TO 4500 FT

DESCENDS TO 2700 FTGOES TO DEST FLD ELEVDESCENDS TO 4500 FT

PROGRAMMED ALTITUDE FUNCTION (AUTO SCHEDULE)

SAMPLE PROFILE 1

SAMPLE PROFILE 2 SAMPLE PROFILE 3

PRESSURIZATIONSAMPLE FLIGHT PROFILES

JLFeb 1/76 02-35-01

CABIN VERSUS AIRCRAFT ALTITUDE CHART

MODEL DC-10

MAX CABAMB d P

8 6 PSIG

MAX A/CALT

42,000 FT

CABIN ALT ATMAX A/C ALT

7610 FT

PROGRAMMED AUTO SCHEDULE

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Feb 1/79

AIR CONDITIONING SYSTEM

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Documents

McDonnell Douglas DC-10-40-Air Cond and Press-1