Chapter 36

1. Introduction

Commercial aircraft carry a Flight Data Recorder (FDR), which records various aircraft parameters throughout the entire duration of every flight. The FDR has two main functions:

• Primary function: Preserve aircraft data to determine the cause of any aircraft accident (accident investigation).
• Secondary function: Gather information for trend analysis and trouble-shooting of aircraft systems.

On smaller aircraft, the FDR may be combined with the Cockpit Voice Recorder (CVR) into a single unit.

2. FDR Designs

The FDR records the last 10 or 25 hours of aircraft data (depending on MTOM — see regulations) on a digital storage device. Key physical characteristics:

3. FDR Components

The FDR system consists of four main components:

• A recording system
• A control unit on the overhead panel
• A control unit on the pedestal
• A Data Interface and Acquisition Unit (DIAU)

The DIAU collects inputs from aircraft systems including: air conditioning, auto-flight, flight controls, fuel, landing gear, navigation systems, pneumatic systems, APU, and engines. This information is sent to the Aeroplane Condition Monitoring System (ACMS) and is used for system monitoring, trend analysis, and can be downloaded via the aircraft printer, ACARS, or the ATSU.

Overhead Panel Control Unit — GND CTL Switch

This control unit also controls the CVR. It has a spring-loaded switch labelled GND CTL with two positions:

Pedestal Control Unit — EVENT Button

A push-button labelled 'EVENT' sets an event mark on the DFDR recording. This acts as a bookmark to enable rapid location of a specific event during subsequent analysis.

4. Aircraft Integrated Data Systems (AIDS)

AIDS processes data from various aircraft systems to ease maintenance tasks. Key components:

flowchart TD
    A[Aircraft Systems
Air Cond / Autoflight / Engines / Fuel etc.] --> B[Data Management Unit
DMU]
    B --> C[Flight Data Interface Unit
FDIU]
    B --> D[Separate Flight
Maintenance Recorder]
    C --> E[FDR
Mandatory Parameters]
    B --> F[Aircraft Printer
In-flight & Ground]
    B --> G[ACARS / VHF Data Link
Ground Transmission]
    D --> H[Printout for
Maintenance]

The Data Management Unit (DMU) collects and processes system data to compile reports for storage and printing. Some mandatory flight parameters are sent via the Flight Data Interface Unit (FDIU) to the FDR. The remainder is recorded on a separate flight maintenance recorder.

Data can be transmitted to ground stations via ACARS (Airborne Communications and Reporting System) on a VHF data link, allowing aircraft performance monitoring from the ground at certain intervals.

5. Parameters Recorded

The mandatory parameters recorded on the FDR depend on the age and size of the aircraft and are specified in OPs Regulations. They fall into two categories:

Mandatory (Main) Parameters

• Time or relative time count
• Attitude (pitch and roll)
• Airspeed
• Pressure altitude
• Heading
• Normal acceleration
• Propulsive thrust/power on each engine
• Cockpit thrust/power lever position
• Flaps/slats configuration or cockpit selection
• Ground spoilers and/or speed brake selection

Additional Parameters

(Required for aircraft > 27,000 kg MTOM)

• Positions of primary flight controls and trim
• Radio altitude and navigation information displayed to flight crew
• Cockpit warnings
• Landing gear position

6. European Regulations — Carriage Requirements

Minimum Recording Times

7. Other Regulatory Requirements

Dispatch with Inoperative FDR

flowchart TD
    A[FDR Unserviceable] --> B{Practicable to repair
before flight?}
    B -- Yes --> C[Repair/Replace FDR
before departure]
    B -- No --> D{Check all 3 conditions}
    D --> E[≤ 8 consecutive flights
since u/s?]
    D --> F[≤ 72 hours since
u/s discovered?]
    D --> G[CVR serviceable?
unless combined]
    E -- All YES --> H[MAY dispatch
with u/s FDR]
    F -- All YES --> H
    G -- All YES --> H
    E -- Any NO --> I[CANNOT dispatch
Must repair first]

Master Reference Tables

Numerical Values — Quick Reference

Answer Key