Flight Data Recorder — Page 501, Lesson 594

Let's get into the Flight Data Recorder. I want to start with the big picture, then we'll break down the system, the data it captures, and the European rules that govern it. First, the fundamental idea. The Flight Data Recorder, or FDR, is the unit that captures a set of mandatory flight parameters so that, after an incident or accident, investigators can reconstruct exactly what the aircraft did. There's a specific operational detail I want you to note right away: when the aircraft is on the ground, the FDR is automatically stopped 5 minutes after the final engine shutdown. That's a deliberate design feature—it preserves the recording of the last moments of flight and the taxi-in, without wasting recording capacity while parked. Now, the FDR doesn't work alone. Let's look at the system architecture, using the Boeing 767 as our example. The heart of this is the Aircraft Integrated Data Systems, or AIDS. AIDS processes data from various aircraft systems, and its primary purpose is to ease maintenance tasks. It does this through a data management unit, the DMU, which collects and processes data to compile reports. Those reports are stored and can be printed. Here's the key split. Some of the information processed by the DMU is sent to the FDR, but it doesn't go directly. It goes through a flight data interface unit, the FDIU, which is the gateway that selects and forwards the mandatory flight parameters to the recorder. The rest of the information—the non-mandatory stuff—is recorded on a separate unit called the flight maintenance recorder. That one is purely for maintenance; data from it can be printed out on the ground for troubleshooting. So you have two parallel paths: the FDR for mandatory flight data, and the flight maintenance recorder for maintenance data. And the DMU itself can print out its stored data both in flight and on the ground, again for maintenance purposes. There's one more capability I want to highlight. AIDS can transmit relevant data to the ground at certain intervals, so the aircraft's performance can be monitored from the ground in real time. This transmission is done via ACARS—that's the Airborne Communications and Reporting System—using a VHF data link. So ACARS is the communication path, VHF data link is the medium. Now, what exactly gets recorded? The mandatory parameters depend on the age and size of the aircraft, and they're specified in the OPs Regulations—that's the Operations Regulations. Let me list the main parameters, because you need to know these cold: - Time, or a relative time count - Attitude, meaning both pitch and roll - Airspeed - Pressure altitude - Heading - Normal acceleration - Propulsive thrust or power on each engine - Cockpit thrust or power lever position - Flaps and slats configuration, or the cockpit selection of those - Ground spoilers and/or speed brake selection Then there are additional parameters, which are recorded on larger aircraft: - Positions of the primary flight controls and trim - Radio altitude and navigation information displayed to the flight crew - Cockpit warnings - Landing gear position Now the European Regulations on carriage. FDR equipment is required on EU registered commercial air transport aircraft. The rules depend on several factors: the number of passenger seats, the type of propulsion, the Maximum Take-off Mass—that's MTOM—and the date of first registration. Let me walk you through the three cases. Case 1: all aeroplanes over 5700 kg MTOM, or turbine powered less than 5700 kg but with more than 9 passenger seats, registered since 1 April 1998. Case 2: all aeroplanes over 5700 kg MTOM registered since 1 June 1990. Case 3: all turbine powered aeroplanes over 5700 kg MTOM registered before 1 June 1990. Now the recording time requirements. For aircraft over 5700 kg MTOM, the minimum recording time is 25 hours, and all the main parameters I listed must be recorded. For aircraft less than 5700 kg MTOM—that's the turbine powered ones with more than 9 passenger seats registered after 1 April 1998—the recording time may be no less than 10 hours. And finally, the additional parameters I mentioned—primary flight control positions, radio altitude, cockpit warnings, landing gear position—those are required on aircraft over 27,000 kg MTOM. Let me show you the system layout so you can see how the DMU, FDIU, and FDR connect. And here's the Boeing 767 block diagram showing the full data flow. So to tie it together: the DMU collects and processes data for maintenance, the FDIU forwards the mandatory parameters to the FDR, the flight maintenance recorder handles the rest, and ACARS over VHF data link lets ground crews monitor performance. The FDR stops recording 5 minutes after final engine shutdown on the ground, and the recording duration and parameter set are dictated by the aircraft's mass, propulsion, passenger capacity, and registration date under the OPs Regulations.