So you tell ATC where you're going, at what altitude, and for how long — Page 212, Lesson 316

I want to walk you through the fuel jettisoning procedure — a critical emergency operation that the commander alone is responsible for initiating. Let's start with the authority: the decision to jettison fuel rests with the commander alone, but that decision must be compatible with safety and the ability of the aeroplane to continue flying. So the commander has the final say, but they can't just dump fuel anywhere or anyhow — the aircraft must remain safe and airworthy throughout. Now, if the aircraft is operating within controlled airspace and needs to dump fuel, the flight crew must coordinate with Air Traffic Control, or ATC, on several specific items. First, the route to be flown — this should, if possible, be clear of cities and towns, preferably over water, and away from areas where thunderstorms have been reported or are expected. Second, the level to be used — this must be not less than 1800 metres, which is 6000 feet. And third, the duration of the fuel dumping. So you tell ATC where you're going, at what altitude, and for how long. There's also a mechanical restriction: if the use of flaps or slats adversely affects the jettisoning of fuel — meaning if deploying them interferes with the fuel leaving the aircraft — then their use during jettisoning must be prohibited. And a placard stating this prohibition must be positioned adjacent to the jettison control, so the crew sees it right where they operate the system. Let's move to the safety section. Unless there is an overriding requirement to jettison fuel — meaning an immediate emergency that forces you to dump right away — the aeroplane should first be flown to an allocated area at an allocated height before commencing jettison. So you go to the designated zone and altitude first, then start dumping. Consideration must be given to weather conditions. Areas of electrical storm activity should be avoided, as should areas of excessive turbulence. The no smoking light is to be illuminated, and passengers must be briefed on what's happening. ATC is to be informed that jettison is about to commence. Once jettison has begun, electrical switching should be restricted to essential use only. HF radio transmission must be suspended — that's High Frequency radio — and VHF transmissions, Very High Frequency, should be restricted to further emergency or flight safety communications only. So you minimise electrical activity and radio chatter to reduce any risk of ignition or distraction. The flow of fuel from the jettison vents is to be visually monitored, where possible, confirming that flow started and flow stopped as required. So someone — usually a crew member — looks out to see the fuel actually leaving and then stopping when you want it to. During jettison, manoeuvres should be smooth, and the operation of flaps, slots, or slats restricted to essential use only. Once the jettison is complete, ATC should be informed. So to summarise: the commander decides, but coordinates with ATC on route, altitude — minimum 1800 metres or 6000 feet — and duration. You avoid populated areas, storms, and turbulence. You brief passengers, turn on the no smoking light, restrict electrical and radio use, visually monitor the fuel flow, keep manoeuvres smooth, and tell ATC when you're done. And if flaps or slats interfere with jettisoning, they're prohibited and placarded accordingly.