Sunday, December 11, 2005

The trouble at Midway



The Southwest Airlines cockpit crew has been interviewed by the NTSB. The Captain, a ten year veteran of the airline, has stated the reverse thruster system on the Boeing 737-300 didn't work right. That's huge, but is it the only issue here?

The last time a commercial jet overshot a runway during bad weather happened in Toronto, Canada this past summer with wet runways with an ongoing thunderstorm. Fortunately no one died in that incident, but the same cannot be said for a previous crash of an American Airlines MD-80 at Little Rock, Arkansas in 1999, also during a thunderstorm. In that crash, the NTSB probable cause was the crew's failure to engage the reverse thrusters on the wet runway, but also contributing was a strong crosswind, earlier clocked at nearly 80 mph.

The 6500 foot runways at Midway are plenty enough concrete for a 737. Such aircraft land there 24/7/365 in all types of weather and we've seen no previous crashes. This pundit is therefore concerned with early reports the airplane landed on the snowy runway with a tailwind.

Landings and takeoffs work much better 'into the wind' for reasons of simple aerodynamics--a head wind increases air over the wing surface, which enhances lift. When runway and visibility conditions are less than optimal, it is imperative to land in the most ideal configuration, especially at places like Midway.

If indeed the aircraft landed with a tailwind of more than 7-8 mph that could be a contributing factor in light of the reverse thruster issue.

MEANWHILE, HALF WAY ROUND THE WORLD..

The crash of the DC9 in Nigeria also has a bad weather component written all over it,
Senior officials visiting the site of Saturday's disaster said the crowded Sosoliso Airlines DC-9 passenger jet appeared to have slewed off the runway shortly after landing in heavy rain.

yet the press plays up this angle...
The crash, which came just seven weeks after a similar disaster killed 117 people, sparked the fury of President Olusegun Obasanjo, of the press and of the relatives of the victims. Many blamed the poor safety record of Nigeria's motley crew of private airline operators.

Again, check the weather. Heavy rain often means wind shear/downdrafts or sudden cross winds. It's not always shoddy maintenance or the pilot.

UPDATE 12/15

From a Fox News story quoting the NTSB:
The jet's actual stopping distance was about 5,000 feet, the NTSB said. A tail wind also contributed to the accident because it caused the plane to land faster than normal.

Investigators said last week that the plane's reverse thrusters, which should have slowed the jetliner, didn't immediately kick in when the pilots tried to deploy them.

It appears to have been a tri-fecta of causes-- the tail wind, poor response of the reverse thrusters, and a runway with fair to poor braking action. God rest the soul of little Joshua Wood. He was singing a Christmas song at this death, now he's with Christ.

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