The UK’s National Air Traffic Services (NATS) has introduced a permanent 250-knot speed restriction for standard instrument departures (SIDs) from London’s Heathrow, Gatwick, Stansted, Luton, Northolt and London City airports. Aircraft are required to maintain and not exceed 250 knots below FL100.

Air traffic controllers will not remove the 250-knot restriction unless there are “overriding safety reasons” for doing so, or if the pilot requests it due to the aircraft configuration and controllers can meet this request. NATS has asked pilots not to request removal of the speed limit in any other circumstances.

The new restriction has been tested in the London area for the past nine months. NATS wants to maintain a more regular flow of departing traffic from the main London airports and reduce the need for communications between controllers and pilots.

According to the ATC provider, further changes might include the introduction of new speed limit points on standard arrival routes (STARs) and speed restrictions on aircraft moving to and from en route sectors. “Increasing traffic levels are forcing a move away from the tactical controlling of aircraft toward a more strategically managed environment,” said a NATS statement on the change.

The company has said that the introduction of PRnav SIDs and STARs in the London terminal area within two or three years will require “a more systemized airspace structure with a different type of tactical interaction required by controllers.”

According to a report on the speed-limit trial, the study has found that departure separations are maintained for longer, traffic flows are more predictable, radio communications are reduced, track keeping and SID adherence are improved and, for most aircraft types, climb performance is more efficient.