DLR trials system to keep idle-thrust descents during ATC speed changes

Researchers at the German aerospace research centre DLR have been testing a system that recalculates an aircraft's vertical flight profile when air traffic control issues tactical speed instructions. The aim is to allow idle-thrust approaches at busy airports.

Approach sequencing in dense airspace around hubs often brings short-notice calls to speed up or slow down. Those instructions can work against a continuous descent flown at idle thrust, which keeps fuel burn low.

The concept is called DYN-MARS. It recalculates the profile as those instructions arrive, which according to the project lets an aircraft stay at idle thrust for as long as possible while conditions change. SESAR, the technological pillar of the Single European Sky, funded the work along with other air navigation interests, to look at more energy-efficient approaches into busy airports.

More than 70 pilots flew close to 1,000 simulated approaches to seven airports to test the concept under realistic conditions. Project co-ordinator Fethi Abdelmoula said the trials show the principle can also be implemented in complex, busy airport approach areas.

The team also tested how route changes, including expected short-cuts, could be delivered through controller-pilot datalink messages uploaded directly to the flight-management system. Abdelmoula said digital transmission of the route improves predictability of the approach for both the cockpit and air traffic control, cuts manual inputs and provides an important prerequisite for more automated and efficient approach procedures.

The route is held as a secondary flight plan and is activated by the crew after clearance is given, so the flight-management system has the revised path available in advance.