Aviation Accident Summaries

Aviation Accident Summary CHI99IA204

CHICAGO, IL, USA

Aircraft #1

N384AA

Boeing 767-323

Analysis

An American Airlines, Boeing 767-323, Flight 80, collided with an American Airlines B-767-223, N328AA, which was stopped on the International Ramp at the Chicago O'Hare International Airport. Both airplanes received minor wing damage. N328AA was being repositioned by two mechanics from gate M-3 at the International Terminal to the domestic side of the airport. They received a push back clearance from the Inbound Ground Controller. The airplane was pushed back onto the ramp facing north and was waiting for traffic to clear before taxiing. Flight 80 was cleared by the Ground Metering Controller from gate K-19 to Runway 32R via the Bravo Taxiway. As flight 80 taxied north on Bravo, its right wing contacted the left wing of N328AA. The flight crew reported that they saw N328AA, but did not think the airplane was a factor. The left wing of N328AA and the right wing of Flight 80 were both over hanging a green painted 'grass' area on the ramp when the collision occurred. The fuselage of N328AA was on the movement side of the 'nonmovement area' and its left main gear was on the taxiway centerline. Flight 80 was facing north on the Bravo Taxiway with its nose gear approximately 3-feet left of the taxiway centerline. A 1993 letter regarding ramp control guidelines states, 'Due to the close proximity of the International gate positions M1-M3 to the Outer Taxiway [Bravo], only O'Hare ATCT [Air Traffic Control Tower] will issue clearance to and from these gate positions.' O'Hare ATCT personnel reported that even though they provide pushback clearances from gate M-3, they do not prevent other traffic from using taxiway Bravo when a pushback is in progress as they do with pushbacks from M-1 and M-2. Inspection of the international ramp area and interviews with ramp personnel revealed there is not sufficient ramp space to push back from gate M-3 and remain clear of the movement area, cross taxiways, and vehicle traffic lanes.

Factual Information

On June 29, 1999, at 1717 central daylight time, a Boeing 767- 323, N384AA, operated by American Airlines as Flight 80 collided with an American Airlines B-767-223, N328AA, which was stopped on the International Ramp at the O'Hare International Airport, Chicago, Illinois. There were no injuries to the 3 cockpit crew, 10 cabin crew, and 173 passengers on board Flight 80. In addition, there were no injuries to the two mechanics on board N328AA. N384AA received minor damage to its right wingtip and N328AA received minor damage to its left wing. The 14 CFR Part 121 flight was operating in visual meteorological conditions. Flight 80 was preparing to depart the O'Hare International Airport, for Stockholm, Sweden, when the incident occurred. N328AA was being repositioned by two mechanics from gate M-3 at the International Terminal to the gate K-15 on the domestic side of the airport. They received their push back clearance from the O'Hare Inbound Ground Controller and were instructed to "...push it back facing north." American Airlines ramp personnel pushed N328AA back from the gate and positioned the airplane on the ramp facing north. The mechanics reported they were going to taxi north on taxiway Bravo, cross over on Alpha 20, and taxi south on taxiway Alpha to the gate area. They reported that once positioned on the ramp they set the parking brake and were waiting for traffic to clear the "alley" and taxiway Alpha when their left wing was struck by Flight 80. Flight 80 had been parked at gate K-19 and was given clearance by the Ground Metering Controller to taxi to Runway 32R via the Bravo Taxiway. Flight 80 turned left out of the terminal area onto the Bravo Taxiway. As flight 80 was taxing north on Bravo, its right wing contacted the left wing of N328AA. The flight crew reported that they saw the 767 (N328AA) parked on the International Ramp; however, they did not think it was a factor. The left main gear on N328AA was jacked up and the right main gear tires on Flight 80 were deflated in order to dislodge the airplanes from each other. A review of photographs taken by American Airlines revealed the left wing of N328AA and the right wing of Flight 80 were both over hanging a green painted "grass" area on the ramp when the collision occurred. N328AA was positioned facing north on the International Ramp just southwest of the M-3 gate. The fuselage of the airplane was on the movement side of the "nonmovement area" and its left main gear was on the taxiway centerline. Flight 80 was facing north on the Bravo Taxiway with its nose gear approximately 3-feet left of the taxiway centerline. Damage on N384AA consisted of the right wing tip. Damage on N328AA consisted of the left wing tip and minor damage to the left aileron. A letter from CICA, the contracting ramp control company, dated October 13, 1993, entitled T-5 [International Terminal] Ramp Control Guidelines addresses procedures for pushing back from the International Terminal. This document states, "Due to the close proximity of the International gate positions M1-M3 to the Outer Taxiway [Bravo], only O'Hare ATCT [Air Traffic Control Tower] will issue clearance to and from these gate positions. Aircraft in gate position M4 will be directed by International Gate Coordinator and must be pushed back to the south in a nose north configuration." O'Hare ATCT personnel were interviewed and were questioned regarding the above procedure. They reported that when an airplane is pushed back from gates M-1 and M-2, the airplane cannot remain clear of taxiway Bravo due to the amount of ramp space. In this case they stop additional traffic from using Bravo until the airplane is moved. They reported that even though they are giving pushback clearances from gate M-3, they do not prevent other traffic from using taxiway Bravo when a pushback is in progress. They reported that it is the responsibility of the ramp personnel and cockpit crew to maintain clearance from taxiway Bravo when pushed back from gate M-3. The International Terminal gate/ramp area was inspected by the NTSB, the Federal Aviation Administration Airport and Air Traffic Control Personnel, O'Hare International Operations Personnel, and American Airlines Personnel. The ramp area used when an airplane is pushed back from gate M-3 consists of a space bordered by two vehicle traffic lanes, a cross taxiway (Alpha 20), and the nonmovement area line. Several ramp personnel, including those who pushed back N328AA, were interviewed during the course of this investigation. All of them said that it would be very difficult if not impossible to push back an airplane from gate M-3, keep it on the nonmovement side of the ramp, and not block a vehicle traffic lane or cross taxiway. Therefore, they try and position the airplane in an area to keep the traffic lanes and cross taxiways clear; however, this puts the airplane on the movement side of the ramp. In addition, they reported that the turn radius is too sharp for them to position an airplane on the nonmovement side of the ramp. They reported that it was routine for a portion of the airplane to extend over the nonmovement line. A pushback was observed by the NTSB and what the ramp personnel said was found to be true. A Letter of Agreement between the O'Hare ATCT and the City of Chicago effective April 6, 1993 addresses Designated Airport Movement Areas. The diagram attached to the agreement depicts the taxiways and runways as movement areas on the airport. The agreement also states, "The Southwest Cargo ramp, Signature/General Aviation ramp, International ramp taxi lane, and the terminal gate areas are all nonmovement areas once the aircraft clears the adjacent taxiway and has entered the ramp area." Taxiway Bravo is 75 feet wide. The nonmovement line is 160 feet from the center of taxiway Bravo placing it 122.5 feet into the International ramp area near gate M-3. The placement of the nonmovement line is contradictory to the letter of agreement regarding Designated Airport Movement Areas which shows all ramp areas as nonmovement areas. According to Boeing Aircraft the wingspan of a 767-200 is 156 feet 1 inch. Given the width of the taxiway, a Boeing 767-200 taxing on the centerline of Bravo would have 41 feet of its wing extending over each side of the taxiway.

Probable Cause and Findings

the pilot's failure to maintain clearance from the parked aircraft while taxiing. A factor in the accident was the failure of ATC to issue a traffic advisory.

 

Source: NTSB Aviation Accident Database

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