Boeing 757-236 N977FD

This accident occurred when the flight crew of Federal Express flight 1376, a Boeing 757-236, was unable to extend the landing gear during their approach to Chattanooga Metropolitan Airport-Lovell Field (CHA), Chattanooga, Tennessee. The main landing gear (MLG) and nose landing gear (NLG) are hydraulically retracted and extended under normal conditions by the left hydraulic system. To retract or extend the landing gear, a flight crewmember must move the landing gear control lever out of its detent and position it to its up or down position. Lever movement is transmitted through control cables to the landing gear selector valve. Operation of the valve supplies left hydraulic pressure through hydraulic lines to either retract or extend the landing gear and operate the landing gear doors. Shortly after takeoff from CHA, the captain of flight 1376 called for gear up and the first officer (FO) raised the landing gear control lever to retract the landing gear. The flight crew indicated that both the MLG and the NLG retracted to their up and locked position. Digital flight data recorder (DFDR) data showed that 22 seconds after gear retraction the hydraulic fluid quantity and pressure in the left hydraulic system began to decrease. A left hydraulic system low quantity indication and master caution were recorded shortly thereafter. After troubleshooting the hydraulic issue per the procedures in the Quick Reference Handbook (QRH), the flight crew made the decision to return to CHA. While preparing to land, the MLG and NLG did not extend as expected after the landing gear control lever was positioned to its down position. Cockpit voice recorder (CVR) data indicated that a triple chime was audible, and the captain said, “Gear disagree.” The first officer confirmed, “Gear disagree. The gear is not coming down.” The captain contacted air traffic control (ATC) to break off their approach and reported that they had an unsafe gear indication. Following the failed attempt to lower the landing gear, the crew went methodically through the Hydraulic System Pressure checklist of their QRH. Following the procedures, the crew attempted to lower the landing gear using the alternate landing gear extension system. This system uses a dedicated hydraulic circuit within the left hydraulic system to release the uplocks on the landing gear doors and gear when activated. To extend the gear with this system, a flight crewmember would move the ALTN GEAR EXTEND switch (a guarded switch) to the down position. Because the checklist indicated that nose wheel steering would be inoperative following the alternate gear extension and the aircraft would not be able to clear the runway on its own, the crew declared an emergency with ATC. The crew performed the alternate gear extension procedure, and the landing gear did not come down. The crew completed the procedure several more times over the next 7 minutes, including re-completing the Hydraulic System Pressure (L only) checklist in full.  As the crew set the aircraft up for the final approach, they began following the Gear Disagree checklist. ATC cleared the flight to land. The captain briefed the FO that he was planning to aim close to the runway threshold and the FO verbally updated the captain on wind conditions and airspeeds. They agreed that a jumpseat occupant on board the airplane would open the left forward main entry door after they landed. Upon landing on runway 20, the flight crew was unable to stop the airplane, and it slid off the departure end of the runway and impacted localizer antennas before coming to rest about 830 ft beyond the end of the runway.   After the airplane came to a complete stop, the flight crew performed the evacuation checklist in the QRH, and the jumpseat occupant attempted to open the left (L1) door. The door rotated halfway open but would not open fully, and the slide did not deploy. The jumpseat occupant then attempted to open the right (R1) door, but it lodged on the slide pack. The jumpseat occupant used force to open the R1 door, and the slide deployed normally. The flight crew and the jumpseat occupant exited the airplane via the R1 door and slide. Both flight crewmembers and the jumpseat occupant were uninjured. The event was classified as an accident because the airplane sustained substantial damage.  Postaccident inspections of the landing gear system found that hydraulic fluid was leaking from the left landing gear door actuator retract hydraulic hose. Inspections also found that the engine indication and crew alerting system (EICAS) indicated that the left hydraulic system had only 32% fluid quantity remaining after the MLG door retraction shortly after takeoff, which is considered fully depleted. After the hose was replaced as part of this investigation and hydraulic fluid was added to the system, the landing gear extended using the normal extension system. A review of the left hydraulic system found that a leak from this hose could result in the left hydraulic system losing the hydraulic pressure required to overcome the internal locks within the door actuator. When there is a loss of left hydraulic system pressure, the landing gear doors cannot be opened, and the landing gear cannot be lowered using the normal gear extension system. Analysis of the failed hydraulic hose revealed that it had multiple broken wire strands along its length and a rupture in its polytetrafluoroethylene (PTFE) inner liner adjacent to the cluster of broken wire strands. The cause of the broken wire strands most likely originated from an overload event as evidenced by the necking down of the wire strands and a reduction in their area. There were no signs of fatigue on the broken wires. Postaccident electrical system inspections of the alternate extension system found no electrical continuity between the alternate gear extend switch and the alternate extension power pack (AEPP). A visual examination of the alternate extension system wiring revealed a break (open) in a wire between the circuit breaker and the alternate gear extend switch. The failed wire was sent to the Boeing Equipment Quality Analysis (EQA) lab for further examination. Analysis of the wire’s fracture surfaces showed a reduction in area and circumferential cracking of the coating, consistent with tensile loading. No obvious defects or anomalies were observed on the fracture surfaces. The wire was inside a wire bundle, so the probability that maintenance personnel could have detected this fault is low. There is no inspection interval for the inside of the wire bundle, which would likely have identified the break in the wire. Since the accident, FedEx has implemented a 275 Flight Hour check on the alternate extension system, including performing a general visual inspection while the NLG and MLG doors are open while on the ground. Findings from the NTSB’s investigation indicate different reasons for the jumpseat occupant’s difficulty opening the L1 and R1 doors to deploy the respective evacuation slides. Postaccident examination of the R1 door found that the R1 bannis latch (which releases the slide pack when an armed door is opened) did not conform to the then-current configuration of the release cable assembly. Specifically, the assembly is supposed to have three links added with two spacers and hardware, as required by Federal Aviation Administration (FAA) Airworthiness Directive [AD] 86-09-09 by reference to Boeing Service Bulletin (SB) 757-25A0058, dated April 18, 1986. Instead, the R1 bannis latch on the accident airplane had only one link and lacked other required hardware, which caused the slide pack to jam before the jumpseat occupant was eventually able to force the door to open. Postaccident examination of the L1 door found that a misrouted deployment strap caused the L1 door not to fully open, prohibiting the occupants from using that door for evacuation. After the CHA accident, FedEx inspected the L1 and R1 doors on the 97 other airplanes in its Boeing 757 fleet and found no other instances of a misrouted deployment strap as found on the L1 door. However, the inspection found 46 doors (about 24%) that were not compliant with either AD 86-09-09 or AD 2001-15-01 (applicable to Boeing 727, 737, and 757-200, -200CB, and -300 series airplanes because these models used the same bannis latch design). The accident airplane was manufactured in 1988 and should have been delivered with bannis latches that complied with AD 86-09-09. It is currently unknown why noncompliant components were present at the time of the accident. The accident airplane was operated by multiple carriers before FedEx acquired it, and the NTSB does not have maintenance records for these other carriers. FedEx records indicate that the bannis latch was inspected on January 12, 2023. The work card indicated to check the cables for fraying. At that time, there should have been a chain in the latch assembly and not a cable. As a result of this investigation, the NTSB issued four new safety recommendations to the FAA and three new recommendations to Boeing on March 27, 2025. The recommendations are open - acceptable at this time. Crew Resource Management (CRM) Hallmarks of good CRM include effective communication, strong leadership, assertiveness, adaptability to changing situations, open feedback loops, appropriate task allocation, situational awareness, stress management, and a culture of actively listening to all crewmembers' opinions and concerns, allowing for diverse perspectives to be considered. The crew of FedEx flight 1376 demonstrated good CRM by remaining calm and professional throughout the accident sequence of events. They displayed effective workload management by distributing the tasks of handling the emergency amongst themselves to avoid overload and maintain optimal performance which, resulted in the captain flying and the FO working to resolve the issue with ATC. The crew maintained clear and concise communication between all crewmembers to include a jumpseat occupant, and with ATC, actively soliciting feedback and input, and crosschecking with one another to ensure everyone was working with the same mental model. Once the crew realized the landing gear was inoperable, they methodically worked through the QRH, confirming each step out loud, and demonstrated flexibility by adjusting their plans and strategies based on changing circumstances. The crew used all available resources and included some non-standard attempts at troubleshooting, such as pulling circuit breakers, while under the direction of FedEx maintenance staff. NTSB staff concedes there is some concern that troubleshooting attempts not previously established on any checklist could yield results that would be unknown to the flight crew, and those attempts should be limited as they can introduce additional risk to an already hazardous situation.

Quoted verbatim from the NTSB record.