ATR 42/72-600 Systems Guide — Chapter C: Flight Warning System

2026-06-23

Chapter C. FLIGHT WARNING SYSTEM (FCOM DSC 31)¶

1. COCKPIT COLORS PHILOSOPHY¶

The ATR glass cockpit utilization of color parameters complies with standard ergonomics criteria to establish an immediate, intuitive understanding of structural abnormalities and priority ratings.

1.1. Color Coding Meanings and System Responses¶

Color Identifier	System Meaning	Required Crew Actions / Responses
RED	Emergency / Configuration Failure	Requires immediate operational crew intervention. Accompanied by continuous repetitive aural chime and flashing Master Warning light.
AMBER	Abnormal / Cautionary Parameter	Identifies an abnormal system state. Requires crew awareness and subsequent checklist or troubleshooting execution. Accompanied by single chime and Master Caution light.
GREEN	Normal Operation / Armed State	Indicates normal system verification, regular functional validation, or active target engagement profiles.
CYAN	Advisory / Advisory Memo	Used to identify selected optional status modes or standard system configurations (e.g., SEAT BELT sign illumination).
WHITE	Scale / Informational Data	Used for regular digital value readouts, baseline scales, non-alert markers, and layout boundaries.
MAGENTA	Target / Computed Selection	Displays automated target values or computed reference bounds injected by the Flight Management System (FMS).

2. FWS DESCRIPTION¶

The Flight Warning System (FWS) provides integrated tracking of all system warning thresholds, power plant anomalies, and flight envelope protections.

2.1. System Core Components¶

Central Advisory Computers (CAC): Two independent computers tasked with gathering global system parameters, sorting status inputs, and feeding advisory lines to the multi-function displays.
Flight Warning Computers (FWC): Process critical sensor strings to determine real-time hazard urgency levels. They generate corresponding auditory chimes and drive the Master Warning and Caution light modules.

2.2. Alert Level Hierarchy Matrix¶

The FWS prioritizes conflicting warning scenarios based on four alert levels:

  ALERT PROCESSING FLOW
  ┌───────────────┐
  │  Level 3: RED │ ──► Immediate Emergency Checklists (e.g., ENG FIRE)
  └───────┬───────┘
          ▼
  ┌───────────────┐
  │Level 2: AMBER│ ──► Abnormal Operational Recovery (e.g., HYD LOW PR)
  └───────┬───────┘
          ▼
  ┌───────────────┐
  │Level 1: AMBER│ ──► Localized System Loss / Single Computer Dropout
  └───────┬───────┘
          ▼
  ┌───────────────┐
  │ Level 0: CYAN │ ──► Normal Advisories and Status Updates
  └───────────────┘

3. ALERT WINDOW ARCHITECTURE¶

The Engine and Warning Display (EWD) dedicates its left lateral display section to the dynamic presentation of active warning alerts and operational guidance sequences.

3.1. EWD Warning Field Partition Layout¶

  EWD ALERT REGION DISPLAY MATRIX
  ┌───────────────────────────────────────────────────────┐
  │ [MASTER ALERT TITLE]        (Highest Priority Red)   │
  │  ↳ System Operational Step 1                         │
  │  ↳ System Operational Step 2                         │
  │                                                       │
  │ [SECONDARY ALERT TITLE]     (Lower Priority Amber)   │
  │  ↳ Cautionary Step 1                                 │
  │  ───────────────────────────────────────────────────  │
  │ STATUS MESSAGE FIELD        (Cyan / General Memo)     │
  └───────────────────────────────────────────────────────┘

3.2. Alert Display Behaviors and Clearing Priority Logic¶

Hierarchical Sorting: Red Level 3 alerts append automatically at the top of the display stack, pushing down any active Amber Level 2 alerts.
Procedural Feedback Loops: As flight crews execute specified actions outlined on the EWD display lines, corresponding sensor state changes trigger the FWS to erase the completed line entry automatically.
Inhibition Scheduling: To maintain cockpit focus during high-workload phases, specific non-critical Level 1 and Level 2 alerts are inhibited during the takeoff run and final approach segments. Critical configuration warnings (such as T.O CONFIG anomalies) bypass all inhibition filters.

3.3. Alert Clearing and Status Storage Logic (Page 31)¶

Active Alert Stack: The FWS manages real-time inputs dynamically. When an alert condition is physically corrected (e.g., fluid level restores or pressure rises above a threshold), the alert line vanishes from the EWD stack immediately, and the remaining alerts shift upward to close the gap.
CLR (Clear) Pushbutton Mechanics: Located on the EFCP / MCP panel space. Pressing CLR acknowledges and removes active Level 2 (Amber) alert messages from the primary viewing column, hiding them from the active display list.
Recall Logic: Cleared alerts are not deleted from memory. Pressing the RCL (Recall) pushbutton forces the FWS to re-interrogate system loops and re-display all hidden, currently active alerts back onto the EWD interface.

3.4. Flight Phase Inhibition Controls (Page 32)¶

To minimize pilot distraction during critical regimes, the FWS actively blocks specific low-priority warnings during high-workload operational segments.

Inhibition Phases:
Takeoff Phase: Activated from $V_1 - 15\text{ kt}$ up to $400\text{ ft}$ RA or 20 seconds after liftoff. Non-critical cautions (Level 1 and Level 2) are suppressed.
Approach/Landing Phase: Activated from $400\text{ ft}$ RA down to touchdown.
Non-Inhibited Alerts: High-criticality warnings bypass all inhibition filters completely. These include:
Engine Fire / Smoke warnings.
Stall warnings.
Windshear warnings.
Takeoff Configuration alerts (T.O CONFIG).

4. AUDIO WARNINGS AND ALARM TYPES (Page 33)¶

The Flight Warning System utilizes specific acoustic profiles to immediately communicate alert levels without requiring visual verification:

Acoustic Sound Type	Associated System Alert / State	Priority Level
Continuous Repetitive Chime (CRC)	Red Master Warning Conditions (e.g., Engine Fire, Excess Cabin Altitude)	Level 3
Single Chime (SC)	Amber Master Caution Conditions (e.g., Hydraulic Low Pressure, Fuel Low Level)	Level 2
C-Chord	Altitude Alerting (Approach to or deviation from assigned altitude)	Level 0 / Advisory
Cavalry Charge	Autopilot Manual or Automatic Disengagement	High Priority
Cricket	Aerodynamic Stall Warning	Maximum Priority
Clacker	Over-speed Warning ($V_{MO} / M_{MO}$ or Flaps Extension Speed Limits exceeded)	Maximum Priority
Woop-Woop	TAWS / GPWS Terrain Separation Warnings	Maximum Priority

5. EMER AUDIO CANCEL & TO CONFIG PANEL LAYOUT (Page 34)¶

Located on the center pedestal assembly directly behind the power management controls.

  PEDESTAL WARNING INTERFACE PANEL
  ┌────────────────────────────────────────────────────────┐
  │                                                        │
  │                     EMER AUDIO                         │
  │                       CANCEL                           │
  │                      ┌───────┐                         │
  │                      │GUARDED│                         │
  │                      └───────┘                         │
  │                                                        │
  │                      T.O CONFIG                        │
  │                        [TEST]                          │
  │                                                        │
  └────────────────────────────────────────────────────────┐

5.1. EMER AUDIO CANCEL Switch Mechanics¶

Guarded Design: Protected under a physical flip-open guard to prevent accidental actuation.
Functional Logic: Pressing this button suppresses an active Continuous Repetitive Chime (CRC) associated with specific Level 3 structural warnings if the mechanical or electrical sensor remains stuck. It isolates the acoustic driver line while preserving the visual alert on the EWD.

5.2. T.O CONFIG Pushbutton and Check Sequence (Page 35)¶

Prior to advancing power levers for takeoff, depressing the T.O CONFIG pushbutton commands the Multi-Function Computers (MFC) and FWS to evaluate the current status of critical systems against the takeoff configuration database.

Monitored System Parameters:¶

Flaps Lever Position: Must be selected to the designated takeoff setting ($15^\circ$).
Pitch Trim Position: Mechanical actuator setting must fall inside the marked green takeoff band.
Lateral Trim Settings: Rudder and Aileron trim indications must be centered within neutral tolerances.
Parking Brake Status: Must be fully released (OFF).
Gust Lock Control: Mechanical flight control lock must be fully disengaged and stowed.
Power Management Selector: Must be explicitly set to the TO mode selection.

System Output: If any parameter is out of tolerance, the Red T.O CONFIG MEMO FAULT warning flashes on the EWD accompanied by the Continuous Repetitive Chime (CRC). If all parameters are correct, the system displays a green T.O CONFIG OK status line.