Flight Data Recorder — Page 501, Lesson 594

Let’s start with the Flight Data Recorder itself — the FDR. This is the crash-protected, tamper-proof box that continuously records the mandatory flight parameters so that, after an incident, investigators can reconstruct exactly what the aircraft did. First, a key operational detail: when on the ground, the FDR is automatically stopped 5 minutes after the final engine shutdown. So it doesn’t run forever on the ramp — it captures the flight, then shuts itself down five minutes after the last engine is off. That’s a precise limit you should remember. Now, the FDR doesn’t work alone. It’s part of a larger data-handling system. Let me introduce the Aircraft Integrated Data Systems, or AIDS. AIDS processes data for various aircraft systems to ease maintenance tasks. It does this through a data management unit — the DMU — which collects and processes data to compile reports for storage and for printing. Here’s the split: some of that information is sent to the FDR via the flight data interface unit — the FDIU — for recording the mandatory parameters of the flight. The rest of the information is recorded on a separate flight maintenance recorder, from which data can be printed out for maintenance purposes. So you have two recording paths: the FDR for the mandatory flight parameters, and a separate maintenance recorder for the rest. Data stored on the DMU can be printed out both in flight and on the ground, again for maintenance. And there’s a third capability: it’s possible to transmit relevant data from AIDS to the ground at certain intervals so that aircraft performance can be monitored from the ground. That transmission is done via ACARS — the Airborne Communications and Reporting System — on a VHF data link. So ACARS is the datalink that pushes AIDS data down to the ground. Now, what does the FDR actually record? The mandatory parameters depend on the age and size of the aircraft, and they’re specified in OPs Regulations — the Operations Regulations. Let me list the main parameters: - time or relative time count — so you can correlate events chronologically - attitude — that’s pitch and roll - airspeed - pressure altitude - heading - normal acceleration — the vertical g-loading - propulsive thrust/power on each engine - cockpit thrust/power lever position - flaps/slats configuration or cockpit selection - ground spoilers and/or speed brake selection Then there are additional parameters, required on larger aircraft: - positions of 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: number of passenger seats, type of propulsion, Maximum Take-off Mass — the MTOM — and date of first registration. There are 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. And the recording requirements scale with mass. For aircraft over 5700 kg MTOM, the minimum recording time is 25 hours, and all the main parameters 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 aircraft over 27,000 kg MTOM must also record the additional parameters. So the pattern is: heavier and newer aircraft carry more recording burden — longer duration and more parameters. That’s the regulatory spine of the FDR chapter.