Case for night-time landing

DESCENT: The lit runway of Queenstown Airport at dusk, shot from the Remarkables hillside in 2012.
DESCENT: The lit runway of Queenstown Airport at dusk, shot from the Remarkables hillside in 2012.

How safe are night flights into Queenstown Airport? Grant Bryant investigates.

While some whisper fears about the safety of night flights into Queenstown's infamously difficult airport, the New Zealand Airline Pilots' Association has come out in support of the proposal.

Queenstown Airport Corporation announced last week the New Zealand Civil Aviation Authority and its Australian counterpart, the Civil Aviation Safety Authority, had accepted a safety case that allowed provisional approval for night flights - pending infrastructure additions - by mid-2016.

The pilots' association came out with a statement a day after acknowledging ZQN was one of the country's "most challenging airports for pilots" because of its "geographic location and changeable weather" but said the safety improvement package automatically required with night flights would drastically reduce those challenges.

The association's technical director, Rob Torenvlied, said the group had long campaigned for improved safety at the airport, which the night flight package would deliver.

"The widening of the runway, installing of an approach runway lighting system, improved runway lighting and installing of additional obstacle lighting are all most welcome improvements for pilots operating into and out of the airport," he said.

"Although these improvements are being made to facilitate night-time operations, they will, in addition, provide significant safety benefits for daylight operations as well."

More safety would be added by airlines having to get Civil Aviation Authority approval to operate within the new regime.

The lowdown Required Navigation Performance (RNP)

● Hailed as the key to safety at the airport is a system based on an on-board computer receiving signals from multiple satellites to keep a plane on a pre-determined flight path. RNP creates a "virtual highway in the sky", mapped in 3D, which planes can "drive" through.

● While not completely auto-pilot, the pilot engages the system at an "initial approach fix" point of 10,000ft when the plane will be doing about 240knots. In an auto-pilot mode the pilot monitors the plane's progress as it slows and descends, with lateral and vertical position controlled by RNP.

● As the plane descends to 400ft and slows to 140knots, it reaches "decision altitude", where the pilot "goes visual", deciding whether to land or "go round" for another approach, and disengages auto-pilot. If landing, the pilot will use new runway lights as a landing guide. The pilot, aided by RNP, will "ensure precise touchdown and deceleration."

● RNP can be used night and day, and is commonly used when RNP-equipped planes fly into Queenstown Airport during winter.

● RPN was pioneered in Alaska in 1996, and has spread worldwide to airports that have mountainous approaches.

The Southland Times