TwoDogs' Territory

Months after miraculously escaping from the twisted wreckage of a USAir DC-9 in which 37 passengers and crew perished. Captain Michael Greenlee relived the final moments of Flight 1016.

He and first officer James Hayes had routinely prepared for touching down at the international airport in Charlotte, North Carolina, after being told by air traffic controllers that pilots from two previous landings reported "smooth rides".

About 90 seconds before the crash — the same time a wind shear alert was issued by the control tower-, heavy rain beat down on the cockpit windows. Captain Greenlee, drawing on more than 8,000 hours in the cockpit decided to abort the landing and go around.

Then disaster struck: A micro burst, a rare weather phenomenon accompanied by severe and sudden winds violently engulfed the aircraft.

As Captain Greenlee tried desperately to regain speed and altitude, the DC-9 was on the brink of stalling and falling out of the sky. A major wind change had sharply reduced its speed and caused it to lose precious altitude. A voice warning system in the cockpit blared: "TERRAIN! TERRAIN!" as the pilots went for maximum power.

By then it was too late. Flight 1016 tore a swathe through tree-tops before slamming into a house near the airport, killing most of the 57 people on board. The body of a six-year-old boy 4as the last to be removed from the wreckage.

"We just dropped," Captain Greenlee told safety board investigators probing the July 1994 disaster. "I have never had a sensation like that. It was like having a rug pulled out from under you after having such a smooth ride."

Of all the situations pilots dread, microbursts and wind shear are the most terrifying. Winds of 100 kilometres per hour inside a short-lived microburst can shift from headwind to tail wind in seconds, with massive downdraft forces which confuse even vastly experienced aviators. As micro bursts often occur close to the ground at a critical stage of an aircraft’s approach, the risk of crashing short of the runway is higher.

"You may be the best pilot at the controls of the best aircraft in the world and you could still crash," says Ian Fogarty, a Cathay Pacific flight simulator instructor who helps prepare the airline’s pilots for wind shear and micro burst scenarios at the new airport.

Cathay’s flight training manual warns pilots that the best defence against wind shear "is to avoid it altogether. This is especially important because shears can exist which are beyond the capability of any pilot or aircraft".

Before the opening of Chek Lap Kok, pilots with military and civilian experience throughout the world wondered and worried about the siting of a vast airport in the lee of Lantau’s mountains, although Hong Kong had precious few alternative sites to offer.

From a safety perspective, say many, Chek Lap Kok is compromised because of its susceptibility to south-easterly winds, which descend on the airport after being violently interrupted by Lantau’s peaks. Like large river boulders, which disturb and break up flowing water, the rough terrain around Chek Lap Kok has a similar effect on the prevailing winds. The dangers are obvious for aircraft entering this disturbed air.

Airport planners, pilots, air traffic controllers and meteorologists realised years ago there would be turbulence and wind shear risk at Chek Lap Kok as a result of the terrain and the higher incidence of more intense thunderstorms compared with Kai Tak. But they hoped safety would be enhanced by the development of the world’s most sophisticated wind shear and turbulence warning systems, which Kai Tak did not have.

In the next few months, Chek Lap Kok and the systems — described by one expert as "outstanding" — designed after years of wide consultation and testing will face their sternest test. There are more thunderstorms in May and June in Hong Kong than at any other time of the year, meaning the likelihood of wind shear and severe micro burst activity is also higher.

Aircraft crash reports are littered with references to low-level wind shear and micro bursts, which can occur so suddenly that pilots have little time to react. Turbulence is generally not as dangerous but several pilots interviewed by the Post expressed concern and surprise that aircraft landing and taking off at the new airport are "knocked around" more violently than anticipated.

"The difference is that the mechanical turbulence at Kai Tak was predictable and progressive, but the effect of running into the lee of those mountains at Chek Lap Kok is not. It’s like running into a brick wall," warned a Cathay captain.

"What is on everyone’s mind is how bad is it going to be when we are near the ground in worse conditions than we’ve experienced so far..