Incident Overview
On September 28, 2010, at approximately 1940 mountain daylight time, a Beechcraft F90 King Air, registration N124BK, experienced a contact between its ventral tail strakes and the runway during a go-around from the landing roll at Idaho Falls Regional Airport, Idaho Falls, Idaho. The commercial pilot, the sole occupant, was not injured. The airplane, owned and operated by MTB Investments LLC, sustained minor damage. The flight, which departed West Yellowstone Airport, Yellowstone, Montana about 25 minutes prior, was conducted under 14 Code of Federal Regulations Part 91 for personal purposes in visual meteorological conditions. No flight plan was filed.
Pilot's Account
According to the pilot, during his straight-in approach for a planned full-stop landing, he lowered the landing gear and observed that all three green "gear-down" indicator lights illuminated and the red "gear unsafe" light extinguished. After a normal touchdown on the main landing gear, as the nose gear was being lowered, the gear warning horn sounded, the red "gear unsafe" light illuminated, and the airplane began settling toward the runway. The pilot immediately initiated a go-around. As the airplane lifted off, both ventral tail strakes and the ventral/tie-down fin contacted the runway surface. After departing the traffic pattern, the pilot performed a manual gear extension and flew by the tower to confirm the landing gear appeared fully extended. The tower confirmed the gear position, and the pilot made an uneventful landing.
Post-Inspection Findings
Initial post-incident inspection revealed that the actuator rod extending from the left main gear electro-mechanical actuator assembly had fractured. After recovery to a hangar, further inspection showed 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. The circuit breaker protecting the gear actuator electrical circuit had also popped.
Investigation Details
According to the Federal Aviation Administration (FAA) Airworthiness Inspector from the Salt Lake City Flight Standards District Office (FSDO) who responded, the operator shipped both the left and right electro-mechanical actuator assemblies to Aerospace Turbine Rotables, Inc., for inspection and overhaul. 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 found no evidence of an anomaly or malfunction that would have contributed to an uncommanded gear retraction.
Analysis by Manufacturer Representative
During a discussion with a representative of Hawker Beechcraft, it was determined that both the popped circuit breaker and the damage or fracturing of the brackets mounting 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 had been transferred to the gear actuator assembly.
Conclusion
In conversations with the NTSB Investigator-In-Charge, the FAA Airworthiness Inspector, and later an FAA Operations Inspector from the same FSDO, the pilot was adamant that the landing gear was down, the three green "gear safe" lights were illuminated, and the red "gear unsafe" light had extinguished. 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.