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FOD = Foreign Objects and Debris
EFB = Electronic Flight Bag. A flight bag, traditionally, contains charts and checklists. EFB means you have a device that contains those documents 20 years ago, I was an avionics technician on F-16 fighter jets in the USAF. We had 'FOD Walks' daily, which involved slowly walking down the flightline while staring at the ground, and picking up any loose objects Even a tiny object, when ingested into a jet engine, can cause catastrophic damage. And F-16s have intakes very low to the ground, making them a much higher FOD risk. The worst FOD events were when something broke. We used bit drivers to remove aircraft panels, and the bits were fairly standard screwdriver bits. Sometimes, one of those bits would shatter when applying force to remove a stubborn fastener. If that happens, you have to retrieve every single piece of metal. If you return your toolbox at the end of the day and it is missing anything that can't be accounted for, the entire flightline could be shut down while a search is carried out. Dropping things in the cockpit could sometimes be much worse. If it drops down into a void left by removing a control panel, then it could potentially fall to the 'bottom' of the aircraft. If that happens, you'll be taking off all the panels in that vicinity, you'll have multiple people looking with flashlights, borescopes, etc. If something is dropped but can't be found, that's probably a multi-day event that will involve some fairly high ranking people. FOD was considered a serious threat, and a tiny piece of metal broken off of a tool could hinder operations for days at a time |
While taking off from Charles de Gaulle Airport, the aircraft ran over debris on the runway, causing a tyre to explode and disintegrate. Tyre fragments, launched upwards at great speed by the rapidly spinning wheel, violently struck the underside of the wing, damaging parts of the landing gear – thus preventing its retraction – and causing the integral fuel tank to rupture. Large amounts of fuel leaking from the rupture ignited, causing a loss of thrust in the left-hand-side engines 1 and 2. The aircraft lifted off, but the loss of thrust, high drag from the extended landing gear, and fire damage to the flight controls made it impossible to maintain control. The jet crashed into a hotel in nearby Gonesse two minutes after takeoff. All nine crew and 100 passengers on board were killed, as well as four people in the hotel. Six other people in the hotel were critically injured.
<https://en.wikipedia.org/wiki/Air_France_Flight_4590>
The debris was a metal strip "435 millimetres (17.1 in) long, 29 to 34 millimetres (1.1 to 1.3 in) wide, and 1.4 millimetres (0.055 in) thick", which had detached from a DC-10 which had taken off five minutes prior to the Concorde.