VT-AIM

1.1 History of Flight

On December 19, 2005, at 2030 Pacific standard time, the four right body landing gear (RBLG) tires on a Boeing 747-400, Indian registry VT-AIM, operating as Air India 136, burst during takeoff from Los Angeles International Airport, Los Angeles, California. Air India was operating the airplane under the provisions of 14 CFR Part 129. The captain, first officer, a relief captain, 14 flight attendants, and 256 passengers were not injured; the airplane sustained substantial damage. The scheduled international passenger flight was originating at the time and was destined for Frankfurt International Airport, Frankfurt, Germany. Visual meteorological conditions prevailed and an instrument flight plan was in effect.

Following the airplane's liftoff from runway 25R, a member of the Los Angeles airport operations was notified that there appeared to be foreign object debris (FOD) on the runway. The airport operations specialist was positioned near the end of runway 25R, on the taxiway, and had heard two loud, succinct booms as the airplane rotated from the runway. The specialist proceeded down runway 25R and noted a substantial amount of debris on the runway and adjoining taxiways.

The majority of the debris was located about 2,500 feet to 10,000 feet from the east end of the 12,091-foot runway. The first identified debris field contained two sections of rubber and was located about 2,500 feet from the east end of the runway. About 4,000 feet from the east end of the runway were metal pieces identified as landing gear wheel fragments. The majority of the debris continued down the runway to about the 10,000-foot point, and contained large sections of the wheels and rubber portions of the tires.

After the event, the airplane circled off shore to jettison fuel in order to land. The specialist that reported and identified the initial debris on runway 25R reported that after the airplane landed there was some debris on runway 25L. As the airplane approached the east end of runway 25L to land, the specialist noted that none of the main body landing gear tires on the right side were evident. The airplane touched down at 2155.

Examination of the runway 25R surface revealed no marks along the right side of the runway centerline prior to the 2,500-foot point. Rubber tire marks were noted in a feather-like, brush pattern approximately 3,000 feet from the east end of the runway, and again approximately 10,000 feet from the east end of the runway. Groove marks along the runway centerline and to the right of the centerline were present intermittently on the surface about mid-runway length.

Following the landing, emergency crews responded and sprayed water on the airplane's brake system to keep them cool. The passengers were deplaned using the stairs while the airplane was on the runway. Airport operations personnel closed both runway 25L and 25R overnight to facilitate the clean up of the runways.

The captain, the flying pilot for this leg of the flight, reported that the time leading up to the takeoff was uneventful. They taxied the airplane for 15 to 20 minutes. As he rotated the airplane for takeoff, he felt a slight vibration. He continued the takeoff, which he identified as normal, but felt a shudder. At 400 feet above ground level (agl), the engine indication and crew alerting system (EICAS) displayed warning messages to the flight crew. Shortly thereafter, a tower controller informed the crew that there was debris on the runway. After receiving a series of messages from EICAS, the captain climbed the airplane to 15,000 feet and attempted to retract the flaps. The flaps remained extended 10 to 20 degrees. As the airplane was climbing, an air traffic controller advised the captain that there were metal hinges and brake parts on the runway. The captain jettisoned the fuel and returned to land. While on an extended final for runway 25L, he extended the flaps to 25 degrees, however, the landing gear warning horn went off and the flaps automatically retracted to 20 degrees. During the touchdown, the thrust reversers came to the interlock position; however, engines 2 and 3 did not go past interlock. The airplane was brought to a stop using manual braking. The rescue crews confirmed that there was no fire and the passengers were deplaned.

Prior to the flight, the first officer (FO) performed a walk-around of the airplane. No mechanical problems or abnormalities were identified by the FO or reported to the captain. A maintenance engineer also examined the airplane prior to its departure with no problems noted.

Information regarding the takeoff portion of the flight was obtained from the flight data recorder (FDR). Approximately 39 seconds after the airplane began its takeoff roll, the lateral acceleration increased from approximately 0 g to 0.153 g down to -0.161 g and the airplane traveled approximately 3,000 feet. About 18 seconds later, the vertical acceleration peaked at 1.96 g, the lateral acceleration peaked at -1.083 g, and the airplane traveled approximately 7,290 feet. Less than 1 second later, the air-to-ground discrete transitioned from "Ground" to "Air". Twelve seconds later, the gear disagree discrete transitioned from "Normal" to "Disagree."

1.2 Damage to Aircraft

The airplane was examined on the United Airlines maintenance ramp at Los Angeles International Airport on December 21, 2005. National Transportation Safety Board investigators, personnel from the Federal Aviation Administration (FAA), and Air India were present.

The forward end of the RBLG wheel well is the station (STA) 1350 bulkhead, and the aft end of the wheel well is the STA 1480 bulkhead. The third vertical stiffener from the inboard end of the wheel well on the STA 1350 bulkhead exhibited impact damage and a cracked upper cap. A hydraulic return line located between the brake control valve and the anti skid valve was pierced by the cracked vertical stiffener. There was deformation to a flight control hydraulic pressure line that ran along the STA 1350 bulkhead and a clamp had torn away where it attached to a stiffener. The electrical control unit on top of the flap control valve exhibited impact damage. There was a small puncture (1 inch by 1/2 inch) in the upper pressure deck, and a light assembly attached to the pressure deck had a piece of rubber embedded in it. There were several areas of black rubber transfer on the wheel well structure, and numerous small pieces of rubber debris were found in the wheel well. No evidence of any metal rim debris was found in the wheel well. Towards the aft end of the wheel well was a damaged hydraulic pressure line situated between the brake control valve and RBLG, and a damaged pressure line that runs from the brake accumulator through the STA 1480 bulkhead. There was no damage evident to any of the flight control cables or flap torque tubes that run through the wheel well.

There was puncture damage and many areas of black rubber transfer to the exterior of the forward body landing gear door that normally stays closed unless the landing gear is in transit. There was puncture damage through both the interior and exterior surfaces of the main body landing gear door that is slaved to the RBLG, and the link that attaches the door to the gear was broken at each end where the tie rods attach. The downlock bungee failed at its attach point to the downlock link. The exterior of the main wing landing gear door exhibited black rubber transfer and puncture damage.

The wing-to-body fairing exhibited several areas of puncture damage between STA 1480 and the end of the fairing at STA 1680. There were pieces of the wheel assemblies and brake fragments found within the fairing. The wing-to-body fairing frames at STA 1540, 1580, and 1620 exhibited impact damage. The 1540 frame had a small puncture in the web and cracked upper cap. The 1580 frame was missing a large piece of the web and lower cap while the upper cap was present but deformed. The 1620 frame had a hole in the web and a cracked upper cap. The fuselage skin underneath the wing-to-body fairing had several punctures adjacent to the fairing damage and several large pieces of the fragmented wheels were found embedded in the skin. The damage to the fuselage under the wing-to-body fairing was located in the area between two lap joints on the lower right side of the fuselage. Between STA 1520 and 1560, there were three relatively large holes, which measured 10 inches by 8 inches, 10 inches by 10 inches, and 8 inches by 4 inches, respectively, along with several smaller holes and scraping damage. There were three additional holes between STA 1600 and 1640 that measured 3 inches by 3 inches, 8 inches by 2 inches, and 10 inches by 16 inches, along with several more areas with dents and scraping damage. The lower fuselage skin aft of the wing-to-body fairing between STA 1680 and 1720 sustained two small punctures, which measured 1 inch by 1/2 inch and 2 inches by 2 inches, respectively.

The lap joint on the aft cargo door sustained impact damage that peeled a small section of skin upwards. There was some scraping, and paint and rubber transfer associated with this damage. The leading edge of the right horizontal stabilizer had some rubber transfer and impact damage, and the right inboard elevator sustained puncture damage.

Examination of the wheel fragments revealed that the bead flanges fractured at the transition area to the hub. The failed outer flange pieces from both wheels were smaller than the inner flange pieces. A majority of the fragments from all four flanges were recovered and reconstructed on the tarmac. There was significant abrasion damage on the outer most circumferences of all the bead flanges. The outer hub circumferences also exhibited the same abrasion damage. The intact wheel assemblies that remained on the forward axle also exhibited the same abrasion dama...