ATR 42/72-600 Systems Guide — Chapter A: Aircraft General

2026-06-23

Chapter A. AIRCRAFT GENERAL (CONTINUED)¶

1. AIRCRAFT DIMENSIONS AND CATEGORIES (ATA 20)¶

For Freighter aircraft, refer to annex 3 [72-600F].

1.1. AERODROME REFERENCE CODE¶

As per ICAO Annex 14, reference to ICAO Airport design manual (Doc 9157): The aerodrome reference code is composed of two elements which are related to the aircraft performance characteristics and dimensions.

Code Element 1: Performance Characteristics¶

Code Number	Aeroplane Reference Field Length
1	Less than 800 m
2	800 m up to but not including 1200 m
3	1200 m up to but not including 1800 m
4	1800 m and over

Code Element 2: Dimensions¶

Code Letter	Wingspan	Outer Main Gear Wheel Track
A	Up to but not including 15 m	Up to but not including 4.5 m
B	15 m up to but not including 24 m	4.5 m up to but not including 6 m
C	24 m up to but not including 36 m	6 m up to but not including 9 m
D	36 m up to but not including 52 m	9 m up to but not including 14 m
E	52 m up to but not including 65 m	9 m up to but not including 14 m
F	65 m up to but not including 80 m	14 m up to but not including 16 m

For the ATR 42-600:¶

The reference field length is 1140m: Code number 2
The wingspan is 24.57m: Code letter C
An airport 2C or more, is suitable for the 42-600

For the ATR 72-600:¶

The reference field length is 1360m: Code number 3
The wingspan is 27.05m: Code letter C
An airport 3C or more, is suitable for the 72-600

1.2. AEROPLANE CATEGORY¶

The aeroplane category is based on the indicated airspeed at threshold ($V_{AT}$) equivalent to $V_{REF}$ or 1.3 times $V_{S0}$ at maximum certified landing weight.

Aeroplane Category	$V_{AT}$ Speed Range
A	Less than 91 kt
B	From 91 to 120 kt
C	From 121 to 140 kt
D	From 141 to 165 kt
E	From 166 to 210 kt

The ATR 42-600 and ATR 72-600 are Aeroplane Category B.

1.3. CARGO COMPARTMENT CLASSIFICATION¶

For Freighter aircraft, refer to annex 3 [72-600F].

For the standard ATR passenger version with aft passenger door, the FWD and AFT cargo compartments classification is: Class B

A Class B cargo or baggage compartment is defined as one in which:

There is sufficient access in flight to enable a crewmember, standing at any one access point and without stepping into the compartment, to extinguish a fire occurring in any part of the compartment using a hand fire extinguisher.
When the access provisions are being used, no hazardous quantity of smoke, flames, or extinguishing agent will enter any compartment occupied by the crew or passengers.
There is a separate approved smoke detector or fire detector system to give warning at the pilot station.

2. DOORS LOCATION (ATA 52)¶

For Freighter aircraft, refer to annex 3 [72-600F].

The exact physical distribution of entry points, service doors, and escape routes across the airframe structure is mapped as follows:

Pilot Communication Hatch: Located forward left on the flight deck ceiling framework.
Cargo Door: Main loading structural door located on the forward left fuselage.
Emergency Exit Type III: Two overhead window-line escape exits located mid-cabin above the wing structure (one Left Hand, one Right Hand).
Passenger Entry Door / Emergency Exit Type I: Located on the aft left side of the fuselage, featuring an integrated passenger airstair assembly.
Service Door / Emergency Exit Type I: Located on the forward right side of the fuselage.
Pilot Emergency Hatch: Located directly overhead in the cockpit center roof structure.
Aft Avionics Compartment Door: Underbelly access hatch located externally beneath the rear fuselage section.
Forward Avionics Access Hatch: Underbelly access hatch located externally beneath the forward nose fuselage section.

3. CARGO DOOR CONTROL PANEL (ATA 52)¶

For Freighter aircraft, refer to annex 3 [72-600F].

The physical switch configuration and indicators on the external door operating panel located next to the forward left cargo door structure are arranged as follows:

CARGO DOOR OPERATING PANEL ┌────────────────────────────────────────────────────────┐ │ CARGO DOOR │ │ ARMED LCHD GND HDL │ │ ( ) ( ) ( ) │ │ │ │ CARGO ON │ │ [OPEN] [CLOSE] LIGHT BAT 5001VU │ │ [ ] [ ] │ └────────────────────────────────────────────────────────┘

Signal Logic and Switch Mechanics:¶

ARMED light (Green): Illuminates when actuator selection switch working conditions are met:
Outer protection cover panel is opened.
Door is unlocked by operating handle (all physical hooks are disengaged and the FWD latch lock is unfastened).
LCHD light (Blue): Illuminates when all door hooks and latch locks are fully engaged and locked.
GND HDL light (Red): Ground Handling Bus ON BAT red light is active when the ground handling bus is directly supplied by the HOT MAIN BAT BUS. This alerts the crew that the battery is discharging even if the main BAT toggle switch inside the cockpit is set to OFF. This red light illuminates automatically when:
The refueling control panel is open.
The cargo door control panel cover is open.
The passenger door is open.
Actuator Selection Switch: Toggle used to drive the hydraulic door actuators to OPEN or CLOSE when the green ARMED light is illuminated.
Panel Cover Switch: Automatically connects the ground handling bus on line when the panel cover is opened. During opening, a self-test of MFC 1A and 2A is triggered to initiate the control and monitoring pathways.
CARGO LIGHT Switch: Selects internal cargo bay lighting from outside the airframe.

4. DOORS PANEL (ATA 52)¶

For Freighter aircraft, refer to annex 3 [72-600F].

Located on the Left Lateral overhead layout, this panel provides continuous physical structural monitoring of all door microswitches.

DOORS OVERHEAD INDICATOR (LEFT LATERAL PANEL) ┌────────────────────────────────────────────────────────┐ │ DOORS FWD COMPT │ │ CAB [UNLK][UNLK] │ │ [ ] │ │ SVCE │ │ [ ] CABIN CARGO EMER SVCE │ │ [UNLK][UNLK] [UNLK][UNLK] │ │ SW TEST │ │ [ O ] │ └────────────────────────────────────────────────────────┘

System Logic Controls:¶

CAB OK and SVCE OK Annunciators: Illuminate when the SW TEST pushbutton is depressed to verify microswitch system integrity.
SW TEST Pushbutton: Tests electrical continuity of the door microswitch networks (operational on ground with doors open).
UNLK Annunciators (Amber): Illuminate if at least 1 associated microswitch circuit is broken/open, indicating an unlatched door. The annunciator blocks display split dual-text fields for safety redundancy:
FWD COMPT [UNLK][UNLK]
CABIN CARGO [UNLK][UNLK]
EMER SVCE [UNLK][UNLK]

MFD Cabin Synoptic Page¶

The exact door status parameters are fed to the CAC (Centralized Cabin Application) and displayed graphically on the MFD CABIN page. Unlocked entries generate amber text identifiers next to the respective structural door symbol.

5. EXTERNAL LIGHTS (ATA 33)¶

The physical distribution layout of all external illumination systems arrays across the aircraft structural edges:

A - Navigation Lights: Dual-element assemblies located on the wing tips (Red Left, Green Right) and a white navigation light on the tail trailing edge tail cone.
B - Taxi and Take-Off Lights: Mounted directly to the nose landing gear shock strut assembly to track centerline profiles.
C - Landing Lights: High-intensity retractable illumination fixtures located on the lower inboard wing fairing structures (Left Hand and Right Hand).
D - Wing Lights: Fuselage skin mounts focused on wing leading edge scan lines to check for ice accumulation or nacelle issues.
E - Beacon Lights: Red anti-collision flashing beacon units located on the upper fuselage centerline and lower belly center points.
F - Strobe Lights: High-intensity white flashing strobe units located on the absolute outer wing tip edges trailing sections adjacent to navigation light clusters.
G - Logo Lights: Horizontal stabilizer upper skin surface looking up at vertical tail fin surface for tail logo illumination.
H - Emergency Light: Exterior emergency egress lighting path assemblies focused on main exit slides and ground line clearance areas.

6. EXT LT PANEL (ATA 33)¶

Located on the central overhead control panel structure.

EXT LT OVERHEAD SWITCH PANEL ┌────────────────────────────────────────────────────────┐ │ EXT LT │ │ BEACON NAV STROBE LOGO │ │ (UP) (UP) (UP) (UP) │ │ [OFF] [OFF] [OFF] [OFF] │ │ │ │ TAXI & T.O L LAND R WING │ │ (UP) (UP) (UP) (UP) │ │ [OFF] [OFF] [OFF] [OFF] │ └────────────────────────────────────────────────────────┘

Electrical Source Assignment Logic:¶

BEACON Switch: Controls upper and lower strobe units. Supplied by SVCE BUS / DC BUS 1.
NAV Switch: Controls position lights. Supplied by SVCE BUS / DC BUS 1.
STROBE Switch: Controls wingtip strobe units. Supplied by ACW BUS 1 (Left Hand) and ACW BUS 2 (Right Hand).
LOGO Switch: Controls vertical tail fin face scan units. Supplied by SVCE BUS.
TAXI & T.O Switch: Controls taxi lighting array on the nose gear. Supplied by ACW BUS 2.
LAND L Switch: Controls left main landing light deployment and power. Supplied by ACW BUS 1.
LAND R Switch: Controls right main landing light deployment and power. Supplied by ACW BUS 2.
WING Switch: Controls leading edge illumination arrays. Supplied by DC BUS 2.

7. MEMO PANEL DISPLAY (ATA 33)¶

Status messages render onto the central MFD status column according to switch input logic:

SEAT BELT (Cyan): Displayed when the cabin Seat Belt switch is selected ON.
SEAT BELT (Amber / Crossed-Out): Indicates the control signal validation has failed or a sensor configuration fault is present.
NO DEVICE (Cyan): Displayed when the cabin electronic device restriction switch is active.
NO DEVICE (Amber / Crossed-Out): Indicates the underlying control line or relay is invalid.

8. SIGNS PANEL (ATA 33)¶

Located on the overhead framework.

SIGNS CONTROL PANEL ┌────────────────────────────────────────────────────────┐ │ NO SEAT SIGNS │ │ DEVICE BELTS ON EMER EXIT LT │ │ (UP) (UP) ARMED [DISARM] │ │ [OFF] [OFF] DISARM │ └────────────────────────────────────────────────────────┘

System Configuration Logic:¶

NO DEVICE and SEAT BELTS Switches:
ON (Toggle Up): Continuous sign activation in cabin. Generates the respective Cyan status string on the MFD Memo panel. Supplied by DC BUS 2.
OFF (Toggle Down): Signs extinguished.
EMER EXIT LT Switch:
ON: Forces all internal emergency path illumination tracks and signs to illuminate. Supplied by DC STBY BUS or local 6V battery backup packs.
ARMED: Automatically activates all internal path lights and exit signs if the aircraft loses normal DC electrical power (defined as voltage dropping $<18\text{V}$ on the STBY bus or if both DC Generators go offline). Emergency lights automatically extinguish when voltage recovers $>20\text{V}$ on the STBY bus and at least 1 Generator is operating.
DISARM: System completely deactivated. Displays a yellow label background text [DISARM] within panel toggle track window.

9. INTERNAL LIGHTING (ATA 33)¶

The flight deck control configuration uses designated knobs and specialized switches to vary cockpit ambient illumination:

MIP/PED Knob: Located on the LT panel, selects activation and intensity of integral lighting of the main instrument panels (MIP) and pedestal (PED).
OVHD Knob: Located on the LT panel, selects activation and intensity of overhead panels integral lighting.
CAPT READING LT Knob: Located on the lateral console structure, varies cockpit reading spot beams.
CAPT CONSOLE LT Knob: Located on the lateral console structure, regulates console base background lighting levels.
FLT COMPT LT Panel Switches: Centrally located on the rear overhead zone panel.
STORM Switch: Overrides the flood knob to put in the maximum intensity setting.
LT FLOOD Knob: Controls direct cockpit background instrumentation lighting levels.

10. LT PANEL (ATA 33)¶

Located on the overhead panel. Contains the following rotary rheostats:

MIP / PED Rheostat: Varies the intensity of all integral panel lighting across the Main Instrument Panel and Center Pedestal.
OVHD Rheostat: Varies the intensity of all integral panel lighting across the Overhead Console.
FLOOD Selector: Regulates cockpit ambient flood light bars (OFF to BRT range).

11. ANN LT PANEL (ATA 33)¶

Located on the overhead panel. Controls the global test loop and day/night lighting modes.

ANNUNCIATOR LIGHT TEST PANEL ┌────────────────────────────────────────────────────────┐ │ ▲ │ │ [TEST] │ │ [BRT ] │ │ [DIM ] │ │ ▼ │ └────────────────────────────────────────────────────────┘

System Logic States:¶

TEST Position: Overrides normal logic to illuminate all cockpit annunciator bulbs, digital push-button labels, and overhead system flow bars at full intensity.
BRT Position: Selects high-intensity illumination for normal daytime flight operations.
DIM Position: Reductions light intensity for night flight deck configurations.

12. SIDE PANEL (ATA 33)¶

Located on the Captain and First Officer lateral console structures:

READING LT Knob: Rotary rheostat controlling the map reading spotlight.
CONSOLE LT Knob: Rotary rheostat controlling integral accent panel lighting along the side console framework.

13. FLT COMPT LT PANEL (ATA 33)¶

Located on the aft overhead panel space.

FLIGHT COMPARTMENT LIGHT PANEL ┌────────────────────────────────────────────────────────┐ │ FLT COMPT LT │ │ STORM │ │ (UP) │ │ [OFF] │ │ │ │ DOME │ │ [BRT] │ │ [DIM] │ │ [OFF] │ │ STBY │ │ COMPASS │ │ (UP) │ │ [OFF] │ └────────────────────────────────────────────────────────┘

Functional Switching States:¶

STORM Switch: - ON (Toggle Up): Overrides all individual dimmer rheostats and forces all floodlights and integral cockpit indicators to maximum brightness to maintain panel legibility during lightning events.
OFF (Toggle Down): Retains normal rheostat-driven dimming configurations.
DOME Switch:
BRT: Energizes both flight deck dome lights to maximum intensity.
DIM: Drops dome light tubes to half intensity.
OFF: Both dome lights are off.
Emergency Backup Logic: The F/O side dome light bypasses standard switching and illuminates automatically to full brightness (BRT) if a total dual DC Generator loss occurs, or during ground actions when running on BATTERY ONLY conditions.
STBY COMPASS Switch: Direct toggle switch to control the internal illumination bulb of the mechanical standby compass (ON or OFF tracking).