The airplane was damaged during landing with the nose landing gear in the up position. According to statements from the flight crew and communications transcripts, the flight crew attempted to lower the landing gear and did not receive a gear down indication for the nose landing gear. The flight crew requested and performed a low-approach at which time the air traffic control tower personnel confirmed that the nose landing gear was not extended. The flight crew executed a climb to 6,000 feet and contacted American Airlines maintenance in an attempt to troubleshoot the problem. After performing the steps in the appropriate emergency checklists, including an attempted manual extension of the nose landing gear, proved unsuccessful, the flight crew executed a landing on runway 14R with the main landing gear extended and the nose landing gear in the up position. Examination of the airplane revealed that the nose landing gear spray deflector center link had fractured and the right hand urethane deflector was displaced. The deflector was rotated aft and was not in the track within the wheel well that contains the deflector when in the retracted position. When attempting to lower the nose landing gear, the deflector was observed to impinge on the nose landing gear wheel well structure preventing the nose landing gear from extending. The nose landing gear spray deflector components were sent to the NTSB Materials Laboratory for examination. The center deflector assembly was fractured along three separate lines where the right side deflector is attached. The aft right side of the center deflector was fractured through the bolt holes and the vertical and horizontal plate members. Magnified optical examinations of the three fracture faces revealed rough, crystalline matte gray surfaces consistent with overstress separations in cast aluminum alloys at each location. No evidence of porosity, corrosion or preexisting cracking was noted on any of the fracture faces. The engineering drawing specified the center deflector, p/n 5952241, as cast aluminum alloy C355 per federal specification QQ-A-596, solution heat treated and aged to T61 temper. A Brinell hardness impression on a piece of the center deflector measured 101 HB, which was consistent with the specified alloy and heat treatment.
The jammed nose landing gear due to a failure of the nose landing gear spray deflector for undetermined reasons.
| Time | Event | Page |
|---|---|---|
| SRN 89,555 | Autopilot went from engaged to off descending through 3,470 ft pressure altitude (first approach) | 3 |
| SRN 89,602 | Right gear down parameter in the down state | 3 |
| SRN 89,741 | Airplane descended to 728 ft pressure altitude, then climbed (go-around, nose gear unsafe) | 3 |
| SRN 89,794-90,239 | Autopilot engaged at SRN 89,794 during the climb to 6,000 ft (reached SRN 90,239); right gear down briefly 'not down' from SRN 90,062 to 90,082 (gear recycled) | 3 |
| SRN 91,330-91,506 | Final descent began at SRN 91,330; autopilot off SRN 91,444-91,506; pitch down to 0.4 deg AND at SRN 91,480, a 3.8 deg forward control column input four seconds later, vertical acceleration 1.679 g at SRN 91,485 and pitch up to 13.8 deg ANU the following second (attempt to shake the nose gear down) | 3 |
| SRN 91,920 | Autopilot off at 1,660 ft pressure altitude (final approach) | 3 |
| SRN 92,013-92,014 | At 128 kts the left main gear WOW indicated ground, spoilers began to deploy; right main WOW ground the following second; nose gear WOW stayed 'air' throughout; pitch 2.5 deg ANU at SRN 92,014 | 3 |
| SRN 92,027-92,029 | Pitch went and remained nose down (nose lowered onto the runway); longitudinal acceleration -0.191 g, vertical acceleration 1.349 g the next second, longitudinal acceleration -0.815 g at SRN 92,029 | 4 |
| SRN 92,035-92,043 | Airspeed decreased to 33 kts at SRN 92,035; deceleration ended about SRN 92,043 (stopped) | 4 |
Docket: data.ntsb.gov/Docket/?NTSBNumber=CHI06FA158. This brief is an analytical aid assembled from public records; it is not an investigative finding.