WPR09LA171

The pilot was executing a full-stop landing, prior to which he had confirmed the illumination of the three green "gear-down" lights. Although the touchdown was uneventful, during the landing roll the right main landing gear actuator shaft retracted into its housing, resulting in the retraction of the right main landing gear into its wheel well. The airplane then departed the runway and impacted the adjacent runway lights. A series of postaccident inspections and tests were unable to determine what anomaly or malfunction initiated the retraction of the actuator shaft.

On March 29, 2009, about 1535 mountain daylight time, a Cessna Citation 550, N44FR, impacted runway lights as it slid off the runway at Salt Lake City International Airport, Salt Lake City, Utah. The pilot, co-pilot, and their passenger were not injured, but the airplane, which is owned and operated by Fritzi Jet LLC, sustained substantial damage. The 14 Code of Federal Regulations Part 91 business flight, which departed Great Bend Municipal Airport, Great Bend, Kansas, about three hours prior to the accident, was being operated in visual meteorological conditions. An instrument flight rules (IFR) flight plan had been filed and activated. According to the pilot, all three green "gear down" lights were illuminated prior to touchdown, but during the landing roll, the right main landing gear retracted into the wheel well, and the right wing then contacted the runway. Although the pilot tried to keep the airplane on the runway after the gear retracted, the airplane veered to the right and departed the runway surface. After it departed the runway, the airplane's right wing impacted runway lights, resulting in substantial damage to its leading edge and the initiation of a fuel spill. After the airplane was lifted from the ground, it was determined that the right main landing gear hydraulic actuator shaft had retracted into its housing, thus allowing the gear to retract. During the post-accident investigation the right main landing gear extend/retract actuator (Decoto Part Number 2-7442-2, Serial Number DA885) was shipped to the facilities of Cessna Aircraft Company in Wichita, Kansas, where it underwent a series of tests and inspections monitored by the Federal Aviation Administration's Wichita Aircraft Certification Office (ACO). While at that facility, the actuator underwent radiographic inspection, load testing, external examination, and a teardown/disassembly inspection. After those actions were completed, the actuator components were sent to GE Aviation Systems of Yakama, Washington (the current owner of the Decoto product line) for further visual and dimensional inspections and non-destructive testing (NDT). Thes actions were monitored by the Federal Aviation Administration's Flight Standards District Office (FSDO) at Spokane, Washington. Although the inspection and testing at the facilities of Cessna Aircraft Company found three significant anomalies associated with the actuator, none was considered to be a clear independent initiator of the retraction event. The three observed anomalies were the mis-rigging of the actuator downlock switch, worn or over-trimmed back up rings at the Lock Piston seals, and the lack of the required sealant at the downlock switch and the visual indicator. In addition, it was noted that the safety wire on the downlock switch was missing the lead tamper-proof indicator seal. The dimensional, visual, and NDT inspections that took place at GE Aviation Services did not produce any findings that the technicians feltwould impact or impair the locking function of the actuator. The NTSB's review of the airplane's records revealed that the actuator was originally installed at the time of the airplane's manufacture, and that it was removed and reinstalled for an undocumented reason on April 28, 1988. At that time, the airplane had completed 1,915 hours of flight time, and 1,440 landings. It was further noted that on May 5, 2004, the life limit of the actuator, as well as the life limit of numerous other landing gear components, was recalculated in accordance with the instructions provided in New Flight Corporation's "Increase Maximum Takeoff Weight" Supplemental Type Certificate (STC) number SA4954NM. The incorporation of this STC into the airframe of N44FR called only for recalculation of the actuator's life limit, and not for any maintenance activity on the actuator itself. At the time of the STC's incorporation, the airplane had completed 4,695 landings. At the time of the accident, the airplane had completed 5,739 landings, and accumulated 7,709 hours of flying time. As of the date of this report, the airplane is back in operation, and no anomalies or malfunctions associated with the main landing gear's extension and locking functions have been reported.