Aim is for quieter, more accurate approaches that simplify air traffic management

British Airways has begun trials of high-accuracy, continuous-descent approach techniques at London Heathrow airport. Working with the Civil Aviation Authority's Directorate of Airspace Policy and National Air Traffic Services (NATS), its aim is to make approaches quieter, more accurate, simpler in air traffic management terms, and more fuel-efficient.

During the six-month trial, BA Boeing 747s and 777s arriving between 05:00 and 06:00 will fly precision area navigation (P-RNAV) flightpaths using a continuous-descent approach. Virgin Atlantic is also preparing to take part.

P-RNAV requires a lateral accuracy of 1nm (1.85km) compared with the existing basic RNAV (B-RNAV) allowance of 5nm. Eurocontrol is also keen to drive the introduction of P-RNAV procedures in terminal airspace because it will generate consistency in procedure design and execution, and has the potential to improve safety.

Use of P-RNAV at Heathrow will be combined with the increasing use of continuous-descent approaches, allowing aircraft to descend into the airport in a single, continuous manoeuvre rather than an altitude step-down flightpath. Aircraft would be able to maintain a higher altitude during the earlier segments of their approach, and use lower power during descent, cutting down noise.

NATS, which is helping to manage the trial, says: "It will reduce the fuel and noise penalty - but also the radio communication workload. In traffic capacity terms, you can be constrained as much by the amount of instruction time on the radio as by the airspace itself."

The trial will involve BA flights arriving via the Lambourne holding point to the north-east of Heathrow. This is the normal routing for long-haul services arriving from the Middle East and Asia-Pacific regions. BA says its 747s and 777s are already equipped with flight management systems (FMS) that can carry out the procedure, so the only investment being made is in preparatory simulation and procedural training.

BA's air traffic management project manager for area navigation, Kevin O'Sullivan, says procedures for the P-RNAV approach have been drawn up by the CAA. "These are coded into the normal navigation database as a procedure - like the standard arrivals and standard departures - using the FMS." P-RNAV normally relies on DME/DME fixes for navigation, but this can be aided by VOR/DME, satellite navigation or inertial navigation, says O'Sullivan. He adds that BA and NATS want to examine reducing the navigation tolerance to 0.3nm.

Source: Flight International