Idaho Falls, ID, USA
N124BK
BEECH F90
According to the pilot, he lowered the landing gear handle during a straight-in approach to a planned full-stop landing. Subsequently all three green "gear safe" lights illuminated, and the red "gear unsafe" light terminated its illumination. The pilot executed a normal landing touchdown on the main landing gear; however, during the landing roll the gear warning horn sounded, the red "gear unsafe" light illuminated, and the airplane began to settle toward the runway. The pilot then executed a go-around, during which the tail contacted the runway. The pilot continued the go-around, lowered the gear manually, and made an uneventful landing. A postaccident inspection revealed that for reasons that were unable to be determined, the weight of the airplane, which should have been carried by the over-center gear down locks, had been carried by the gear actuator system instead. This led to the tripping of the circuit breaker protecting the actuator electrical system, and ultimately to structural failures within the mechanical portion of the actuator system, which allowed the landing gear to partially retract.
On September 28, 2010, about 1940 mountain daylight time, the ventral tail strakes of a Beechcraft F90 King Air, N124BK, contacted the runway during a go-around from the landing roll at Idaho Falls Regional Airport, Idaho Falls, Idaho. The commercial pilot, who was the sole occupant of the airplane, was not injured, but the airplane, which is owned and operated by MTB Investments LLC, sustained minor damage. The 14 Code of Federal Regulations Part 91 personal flight, which departed West Yellowstone Airport, Yellowstone, Montana, about 25 minutes prior to the incident, was being operated in visual meteorological conditions. No flight plan had been filed. According to the pilot, during his straight-in approach to a planned full-stop landing, he lowered the gear, and subsequently all three green "gear-down" indicator lights illuminated and the red "gear unsafe" light terminated its illumination. He then made a normal touchdown on the main landing gear, but about the time that the nose gear was being lowered, the gear horn sounded, the red "gear unsafe" light illuminated, and the airplane began to settle toward the runway. The pilot therefore immediately initialed a go-around, and as the airplane was lifting off the runway surface, both ventral tail strakes and the ventral/tie down fin contacted the runway surface. After departing the pattern, the pilot performed a manual gear extension, and then flew by the tower to make sure that the landing gear appeared to be in the full down position. After the tower confirmed the position of the gear, the pilot made an uneventful landing. The initial post-incident inspection of the landing gear system revealed that the actuator rod that extends from the left main gear electro-mechanical actuator assembly had fractured. After being recovered to a hangar, further inspection revealed that the left main gear electro-mechanical actuator assembly had broken loose from both of its airframe mounting brackets, and the right main gear electro-mechanical actuator assembly had broken loose from one of its airframe mounting brackets. It was also determined that the circuit breaker that protects the gear actuator electrical circuit had popped. According to the Federal Aviation Administration (FAA) Airworthiness Inspector from the Salt Lake City Flight Standards District Office (FSDO) who responded to the incident, after the airplane was recovered, the operator shipped both the left and right electro-mechanical actuator assemblies to Aerospace Turbine Rotables, Inc., for inspection and overhaul. Reportedly, during that process no anomalies were noted that would have contributed to a malfunction of the landing gear system or led to an uncommanded retraction of either main landing gear. The FAA Inspector also stated that upon inspection of the airplane's landing gear system, maintenance personnel did not find any evidence of an anomaly or malfunction that would have contributed to an uncommanded gear retraction. During a discussion with a representative of Hawker Beechcraft, it was determined that both the popped circuit breaker and the damage and/or fracturing of the brackets that mount the electro-mechanical actuators to the airframe are indicative of a situation where the load that should be carried by the landing gear mechanical over-center down locks has been transferred to the gear actuator assembly. In conversations with the NTSB Investigator-In-Charge, and with both the FAA Airworthiness Inspector who responded to the incident, and a later discussion with an FAA Operations Inspector from the same FAA FSDO, the pilot was adamant about the landing gear being down, the three green "gear safe" lights being illuminated, and the red "gear unsafe" light terminating its illumination. At the conclusion of the investigation it could not be determined why the load that should have been carried by the over-center down locks had been transferred to the landing gear actuator assemblies.
The partial retraction/collapse of the main landing gear during the landing roll for undetermined reasons.
Source: NTSB Aviation Accident Database
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