United Express Flight 7512

After departure, the first officer was unable to raise the landing gear handle to retract the landing gear. The flight crew discussed the situation and did not believe they had a landing gear malfunction, as they did not receive an Engine Indicating and Crew Alerting System (EICAS) message. They decided to press the "Downlock Release" button to raise the gear, the landing gear subsequently retracted, and the flight continued to the destination airport area uneventfully. As the flight crew attempted to extend the landing gear for landing, the nose landing gear (NLG) did not extend. They prepared for an emergency landing, and touched down "normally" on the main landing gear. The airplane came to rest on the runway, and during the evacuation, one passenger was seriously injured. Three days prior to the accident, the airplane had its NLG strut serviced as part of its approved maintenance program. The following day, a pilot reported that the NLG was "low" and "sounded like it was bottoming out." The NLG strut was checked by maintenance personnel, and found to be within limits. Additionally, during the day prior to the accident, a pilot reported that the landing gear did not retract after takeoff. Maintenance personnel believed the problem to be the landing gear control lever, and replaced it. Examination of the NLG, after the accident, revealed the NLG fluid volume was approximately two-fifths of what a normally serviced NLG should contain. Disassembly of the NLG revealed evidence of "bottoming," or under-service operation. A review of the operator's maintenance job card titled "Servicing NLG Shock Strut," revealed discrepancies when compared to the manufacturers Aircraft Maintenance Manual (AMM). The operator's maintenance job card did not contain a procedure to fill the shock strut with the final volume of hydraulic fluid. The accident airplane was equipped with Proximity Sensor Electronics Modules (PSEMs), which relayed the position of the landing gear to the EICAS. The model of PSEM, which was installed on the airplane, was not the most current model, and by design, would not generate an EICAS message ("LG WOW SYS FAIL") if the nose gear did not retract or extend. Examination of the operator's "Gear Lever Cannot Be Moved Up" checklist revealed discrepancies when compared to the airplane manufacturer's checklist. The operator's checklist began with the condition: "LG WOW SYS FAIL message displayed," and the manufacturer's checklist did not. Since the crew did not receive a "LG WOW SYS FAIL" message, they did not have clear written guidance on what action to take when the landing gear handle could not be moved to the retracted position.

Verbatim NTSB analysis and probable cause from the NTSB dataset