The principle is simple enough: planes coming in to land will be spaced out by time rather than by distance. It has taken a team at NATS (formerly National Air Traffic Control Services) four years of scientific study to make sure the system is safe, and Heathrow is about to become the first airport on the planet to trial it.
It all comes down to wind. Wind is the biggest single cause of landing delays at London’s Heathrow airport, messing up flights on around 65 days each year.
If airliners are fighting against a headwind, even if they maintain the same speed through the air, they take longer to reach the runway. And that creates delays.
Think of it like this. If you’re walking the wrong way down an escalator, and the escalator speeds up while you keep walking at the same speed, it takes you longer to reach the bottom. A strong wind has exactly the same effect on flight.
The new Time-Based Separation (TBS) system simply moves the aircraft closer together, thus cutting those delays.