Airways (BA) has commenced trials of a new approach procedure at London
Heathrow Airport designed to explore the benefits of increased navigation
accuracy and more-efficient descent manoeuvres.
the six-month trial, BA long-haul Boeing 747 and 777 aircraft arriving before
06:00 will be given the opportunity to fly precision area navigation (P-RNAV)
flight-paths and conduct a continuous-descent approach.
Virgin Atlantic is also preparing to take part in the tests.
is a more precise variation of the ‘basic’ area navigation (B-RNAV) capability
required of all aircraft operating within European airspace. B-RNAV enables an
aircraft to follow a particular flight path to within a lateral accuracy of 5nm
(9.2km) for 95% of the time. P-RNAV increases the lateral accuracy to just 1nm
flight-path tracking accuracy would allow airlines to operate more efficient
approach and departure routes. This, in turn, would reduce noise footprints and
emission levels in the vicinity of the airport.
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 a resulting safety benefit.
of P-RNAV at Heathrow will be combined with the introduction of
continuous-descent approaches, a technique which allows aircraft to descend
into the airport approach stream in a single, continuous manoeuvre.
normal operating procedures, a Heathrow-bound aircraft would be released from
the holding pattern at a height of around 7,000ft; the subsequent descent would
typically bring it over central London at about 3,000-4,000ft.
aircraft using a continuous-descent approach would effectively be able to maintain
a higher altitude during the earlier segments of their descent – cutting down
noise – while the overall flight path would be more direct.
spokesman for UK airspace authority National Air Traffic Services (NATS), which
is helping to manage the trial, says: “It will reduce the fuel and noise
penalty – but also the radio communication workload.
you’re following a complex approach there is a lot of dialogue between the air
traffic controllers and the aircraft. In traffic capacity terms you can be constrained
as much by the amount of instruction time on the radio as by the airspace
trial will encompass off-peak BA flights arriving at Heathrow via the Lambourne
holding point to the northeast of the airport; this is the normal routing for long-haul
services arriving from the Middle East and Asia-Pacific regions.
spokeswoman for BA says that the 747 and 777 aircraft involved in the tests are
already equipped to carry out the procedure, so the only investment being made
is in preparatory simulation and procedural training.
Navigation will be undertaken using the aircraft flight management system
air traffic management project manager for area navigation (RNAV) Kevin
O’Sullivan says that procedures for the P-RNAV approach have been drawn up by
the CAA’s Directorate of Airspace Policy, and adds: “These are coded into the
normal navigation database as a procedure – like the standard arrivals and
standard departures – using the FMS.”
says that the aircraft achieves its navigation accuracy for P-RNAV using
DME/DME input. Other navigation data – for example, from VOR/DME navaids or
Global Positioning System satellites – can be used for P-RNAV and even an
inertial reference system (IRS) can maintain the accuracy for a short time, although
O’Sullivan says: “We could use the IRS but it drifts a fair bit; it’s not used
as a primary source.”
the P-RNAV trial will take care of the intermediate approach stage, he says
that BA is “looking to get together” with NATS to examine even tighter
navigation accuracy for final approach – taking the navigation tolerance down
to just 0.3nm. If the plan takes shape an operational trial, probably on
approaches into London Gatwick, could take place in six months to a year.