NTSB Factual Report

HISTORY OF FLIGHT

On August 20, 2005, about 0854 central daylight time, a Boeing 757-33N, N557TZ, operated by American Trans Air as flight 4625, sustained substantial damage on impact with a fence while taxing to runway 22L for takeoff at the Chicago Midway International Airport (MDW), Chicago, Illinois. The 14 CFR Part 121 scheduled, domestic, passenger flight was operating on an instrument flight rules (IFR) flight plan. Visual meteorological conditions prevailed at the time of the accident. The 3 flight crewmembers, 5 cabin crewmembers, and 163 passengers were uninjured. The flight was destined for the San Francisco International Airport, near San Francisco, California.

The captain stated:

Taxiing for [takeoff] 22L. Switched tower. Advised of 9 [minute]

delay for release. Maneuvered A/C [aircraft] out of the way of other

departing A/C. Went to place A/C in corner west of terminal "C";

east of hold short line as previously done. Both [captain and first

officer] closely monitored the final left turn with respect to aircraft

proximity to perimeter fence. Toward end of turn, nose wheel

skipped as if crossing wet/slick pavement. Made P/A explaining the

shudder that the passengers had felt. [Flight attendant] called to state

that [a passenger] had said wing had struck the fence. Asked her to

confirm. We had.

The first officer (FO) stated:

Tower notified us that we were going to wait 9 minutes on release, so

the Captain started to pull off to the side. The Captain headed straight

toward the fence and did his turn to parallel it. We had the room. Just

after we were straightening out, the plane skipped and we both thought

that it was the nose wheel skipping on wet pavement because he still

had the tiller turned to the left. The Flight attendants called up and

informed us that we had struck the fence with the wing tip.

DAMAGE TO AIRCRAFT

The airplane's right wing tip was damaged and the right wing's number ten leading edge slat sustained damage. A leading edge wing rib was dented, cracked about 1.25 inches, and was bowed.

OTHER DAMAGE

The airport perimeter fence was damaged. The top section of an approximately 14 foot tall fencing panel, the top cap that goes over it, and conduit on that cap for red obstruction lighting were found impacted by the right wing.

PERSONNEL INFORMATION

Captain:

The captain held an airline transport pilot (ATP) certificate with an airplane multiengine land rating. He was type-rated for a Boeing 757 airplane. His last medical examination was completed on July 13, 2005, and he was issued a first-class medical certificate with no limitations. The operator reported the captain as having accumulated a total flight time of approximately 9,929 hours and approximately 2,298 hours in a Boeing 757 airplane. He flew 76.16 hours during the last 3 months, .29 hours during the previous 30 days, and did not fly any hours during the prior 24 hours.

First Officer:

The FO held an ATP certificate with an airplane multiengine land rating. He was type-rated for a Boeing 757 airplane. His last medical examination was completed on May 9, 2005, and he was issued a first-class medical certificate with no limitations. The operator reported the FO as having a total flight time of approximately 8,731 hours, and approximately 2,185 hours in the Boeing 737. He flew 110.12 hours during the last 3 months, 27.58 hours during the previous 30 days, and did not fly any hours during the prior 24 hours.

An additional FO was assigned to the flightcrew.

AIRCRAFT INFORMATION

N557TZ, a Boeing 757-33N, serial number 32591, was a pressurized, low-wing, narrow-body transport category airplane. The airplane had metal, full-cantilevered wing and tail surfaces, a semi-monocoque fuselage, and fully retractable landing gear. The airplane was powered by two wing mounted Rolls Royce RB211-535E4-C-37/43 turbofan engines which each produced 43,100 lbs of thrust. The operator reported the airplane was configured to accommodate 232 passengers. The airplane had a maximum gross takeoff weight of 271,000 lbs.

According to the operator, the airplane had accumulated 10,821 hours total time in service. The airplane was being maintained under the provisions of a FAA approved continuous airworthiness program. The last inspection was completed on May 9, 2005, and the airplane had accumulated 1,204 hours since the inspection.

According to a manufacturer's drawing, the general dimensions for the airplane are a 124 foot, 11 inch wing span and a 177 foot, 7 inch overall length. The nose landing gear is 19 feet, 4 inches aft of the airplane's nose. The main landing gear are 73 feet, 4 inches aft of the nose landing gear. The drawing is appended to the docket material associated with the case.

METEOROLOGICAL INFORMATION

At 0853, the recorded weather at MDW was: Wind 210 degrees at 10 knots; visibility 10 statute miles; sky condition few clouds 1,100 feet, scattered 10,000, broken 20,000; temperature 24 degrees C; dew point 22 degrees C; altimeter 29.89 inches of mercury.

AIRPORT INFORMATION

MDW was located approximately 9 miles southwest of Chicago, Illinois, and was owned and operated by the city of Chicago, Illinois. MDW was a certificated airport under 14 CFR Part 139.

The East Central US Airport/Facility Directory (A/FD) indicated MDW's field elevation was 620 feet above mean sea level (MSL). The A/FD listed five runways: Runway 13C/31C - 6,522 feet by 150 feet, concrete/grooved; runway 4R/22L - 6,446 feet by 150 feet, asphalt/concrete/grooved; runway 4L/22R - 5,507 feet by 150 feet, asphalt/grooved; runway 13L/31R - 5,141 feet by 150 feet, asphalt/grooved; and runway 13R/31L - 3,859 feet by 60 feet, concrete.

WRECKAGE AND IMPACT INFORMATION

The airplane was found parked by hold short line for runway 22L with its right wing impacted in the perimeter fence. The airplane was not on a taxiway centerline. The area was marked as a movement area. Approximately the outboard four foot section of the right wing's leading edge slat was crush rearward and the slat was imbedded in an I-beam channel that held up the perimeter fence panels there. The I-beams were yellow and the panels were gray in color. Green and clear glass like media were found on the ground by the damaged fence panel. The wingtip, position lights, and strobe lights were damaged.

ADDITIONAL DATA/INFORMATION

The parties to the investigation included the FAA, American Trans Air Airlines, Inc., and the Airline Pilots Association.

The operator's safety recommendation, in part, stated:

In addition to providing all of our flight crews with instructions not

to enter this area, we conducted a survey of the area and recommend

the following:

Contact Jeppesen and recommend that the charts for the MDW

Airport be revised to show this area as a "Push Back Zone" and

note that aircraft should not taxi into any part of the push back

zone.

I spoke to several crewmembers about this recommendation and the

consensus among those interviewed was that a notice on the chart

would not be necessary; however, it might alert them to the fact that

this is a tight area and should not be used as an alternate holding area.

They believe that crews in general do not move off of marked taxi

lines under any circumstance and good aviation practices, if observed,

would keep this type of event from occurring.

NTSB Probable Cause

The flightcrew's failure to maintain clearance from a fence while taxiing.