シカゴ ミッドウェー空港オーバーラン事故続報

　やはり NTSB: National Transportation Safety Board （米国運輸安全委員会）も 6500ft という今となっては短い滑走路長と、滑走路の先に 1000ft のバッファ領域が無かった、という点に着目しているようです。

ミッドウェー空港は、プロペラ機時代の１９２３年に開港した飛行場で、もともと滑走路長が短かった上に、ダウンタウンの真ん中という立地条件から、ジェット時代になって滑走路伸張したものの、もはやスペースが無いのが実情です。

この上、滑走路の先に 1000ft （約３００ｍ）の安全領域を設けることは実質的に不可能であり、それに代わるものとして、EMAS: Engineered Materials Arresting System の導入が考えられています。
滑走路をオーバーランした領域にクラッシャブル・コンクリートを敷きつめることで、オーバーランした機体の速度を落とし捕捉しようとするものらしいです。
EMAS は１９９９年５月にニューヨークのケネディ国際空港に設置されて以来、今では全米では１４空港１８滑走路に備えられており、この EMAS により事故にいたる可能性があったオーバーランを停止させた事例が３件あるそうです。

ミッドウェー空港でも類似のシステム導入を検討していたらしいのですが、とにかくそれを設置する余地すらない状況なのだそうです。

事故に遭遇したサウスウエスト航空については、ブロク“Cassiopeia Sweet Days”の著者が詳しく、この事故についても「 サウスウエスト航空創立以来の悪夢？ 」なるタイトルで言及しております。
新興航空会社なのですが、安全性をはじめとして極めてしっかりしたエアラインで、不謹慎な言い方ですが、サウスウエスト航空だからこの程度で済んだのかもしれません。

それにしても流石は航空先進国、マスコミも着眼点が適切で、初期段階で最も疑わしい原因・要因（今回は滑走路長とオーバーランに対するマージンの無さ）を冷静に分析、伝えてます。

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Accident description

Status:	Preliminary
Date:	08 DEC 2005
Time:	19:15
Type:	Boeing 737-7H4
Operator:	Southwest Airlines
Registration:	N471WN
Msn / C/n:	32471/1535
Year built:	2004
Crew:	0 fatalities / 5 on board
Passengers:	0 fatalities / 98 on board
Total:	0 fatalities / 103 on board
Ground casualties:	1 fatality
Airplane damage:	Substantial
Location:	Chicago-Midway Airport, IL (MDW) (United States of America)
Phase:	Landing (LDG)
Nature:	Domestic Scheduled Passenger
Departure airport:	Baltimore/Washington International Airport, MD (BWI)
Destination airport:	Chicago-Midway Airport, IL (MDW)
Flightnumber:	1248

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Midway Accident Spotlights Short Runways (AP Associated Press) - Yahoo! NEWS

CHICAGO - A deadly accident in which a Boeing 737 slid off the end of a snowy runway brought renewed demands Friday for buffer zones or other safety measures at hundreds of airports around the nation to give pilots a wider margin for error.

In Thursday night's tragedy at Midway Airport, a Southwest Airlines jet making a landing plowed through a fence and into a street, killing a 6-year-old boy in a car. Ten other people, most of them on the ground, were injured.

National Transportation Safety Board said the cause of the accident was still under investigation, and the plane's voice and data recorders were sent to Washington for analysis. But much of the attention focused on the 6,500-foot runway.

Like nearly 300 other U.S. commercial airports, Midway lacks 1,000-foot buffer zones at the ends of its runways. Midway, a compact one mile square, was built in 1923 during the propeller era and has shorter runways than most major airports, with no room to extend them because it is hemmed in by houses and businesses.

Safety experts say such airports can guard against accidents by instead using beds of crushable concrete that can slow an aircraft if it slides off the end of a runway.

The concrete beds — called Engineered Material Arresting Systems, or EMAS — are in place at the end of 18 runways at 14 airports. They have stopped three dangerous overruns three times since May 1999 at Kennedy Airport in New York.

"Certainly Midway airport officials should have already been trying to come up with something similar to this," said Jim Hall, NTSB chairman from 1993 to 2001. "There's really no margin for error at the end of that runway."

Hall said the lack of a 1,000-foot overrun area and the absence of an EMAS system would probably be a key focus of the investigation.

"The bottom line is you have an increasing frequency of flights on a runway with an inadequate margin for error," he said. "It's a tragedy that did not have to occur."

Chicago Department of Aviation spokeswoman Wendy Abrams could not immediately say whether an arresting system had been considered at Midway.

Though the airport had about 7 inches of snow, aviation officials said conditions at the time were acceptable. And the plane did not appear to have any maintenance problems and had undergone a service check Wednesday in Phoenix, Southwest chief executive Gary Kelly said.

Southwest said the 59-year-old captain has been with the airline for more than 10 years, and the 35-year-old first officer who has flown with Southwest for 2 1/2 years. It was the first fatal crash in Southwest's 35-year history.

NTSB member Ellen Engleman Conners said air traffic controllers had rated the braking condition of the runway at the time of accident as "fair" for most of the pavement and "poor" at the end.

Investigators have not yet determined the exact spot where the plane touched down because it continued to snow after the accident.

"We can't say X marks the spot physically, but we will be able to determine that through a simulation," she said.

The plane hit the fence 32 seconds after it touched down. The jet's ground speed was 152 mph as it landed. It hit the fence at about 46 mph, Conners said.

Earlier, Conners stressed that a variety of factors need to be looked at before any cause is determined, including questions about the crew's performance, how the aircraft handled and air traffic control.

"Often, the first guess is not correct," Conners said. "So, we're not going to guess. We're going to focus on facts and science and data."

The plane may be moved out of the street and into a hangar Saturday, and the streets and runway may reopen by Sunday, Conners said. Interviews with the pilot, flight attendants and a witness were also planned for Saturday, she said.

A recently passed federal law seeks to encourage more airports to build EMAS systems or extend their runway barriers by requiring them to do one or the other by 2015. There are 284 such airports with neither feature, according to the FAA.

Sen. Frank Lautenberg (news, bio, voting record), D-N.J., sponsored the measure after several runway overruns at his home state's Teterboro Airport, near New York. Last February, a corporate plane carrying 11 people ran off the end of the Teterboro runway during an aborted takeoff, sped across a busy road and hit a warehouse. Twenty people were injured.

"My bill, which was signed into law last week by the president, will finally force these airports and the FAA to make these runways safer," he said Friday.

In June 1999, an American Airlines jetliner slid past the end of the runway in Little Rock, Ark., killing 11 passengers and injuring 86. And it was only the remarkable speed of the passengers' evacuation — less than two minutes — that prevented serious injury or death when an Air France Airbus skidded off the runway in Toronto and burst into flames in August.

Hall was NTSB chairman when a Southwest Airlines 737 overran a runway at Burbank Airport in Los Angeles, stopping within feet of a gas station. Burbank's runway is even shorter than Midway's at 5,800 feet.

But other safety experts said the length of the runway should not be used as a scapegoat in overrun accidents.

"It is not the runway length that's the issue," said Bernard Loeb, who was director of aviation safety at the NTSB during the mid-1990s. "Runways are either adequate or they're not."

Some pilots acknowledged that relatively short runways like Midway's pose a challenge in icy or snowy weather, forcing them to touch down as close as possible to the beginning of the runway to allow more braking time.

"The shorter the runway, the quicker you want to get it on the ground, especially landing on ice and snow," said Bert Yetman, a retired Southwest captain. "If you're not down in the first 1,000 feet or so, take it around and try it again."

Paul Czysz, professor emeritus of aerospace engineering at Saint Louis University, likened landing at Midway in bad weather to landing on an aircraft carrier.

"You've got to stick it and brake like heck," Czysz said. "But poor visibility and any wind shear can make that tough to do."

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Associated Press Writer Leslie Miller contributed to this report from Washington.

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By MIKE COLIAS, Associated Press Writer