Fort Worth, TX, USA
N20
BEECH C90
As the landing gear was extended, the flightcrew heard a loud "bang" and observed a “Gear Unsafe” indication. After making a low pass, tower personnel reported that the main gear appeared to be down but that the nose gear was only partially extended. The certificated flight instructor raised the landing gear and made another low pass. Tower personnel said the main gear was up, but the nose gear was still only partially extended. The flightcrew elected to return to their home base and land. As speed dissipated, the nose gear folded and the airplane slid to a stop. A postaccident examination revealed that the nose gear actuator had failed due to insufficient lubrication of the nut assembly threads. The manufacturer recommends that the actuator be overhauled or replaced every 8000 cycles, or 6 years, whichever occurs first. At this time, the screw and nut assembly is to be greased. The failed actuator had accrued 1,576 cycles and 951.2 hours time-in-service. The maintenance manual does not require in-service lubrication of landing gear actuator.
On June 3, 2010, approximately 1430 central daylight time, a Beech C90, N20, registered to and operated by the Federal Aviation Administration, was substantially damaged when the nose landing gear collapsed on landing at Alliance Fort Worth Airport (AFW), Fort Worth, Texas. Visual meteorological conditions (VMC) prevailed at the time of the accident. The training flight was being conducted under the provisions of Title 14 Code of Federal Regulations (CFR) Part 91 without a flight plan. The two pilots on board the airplane were not injured. The local flight originated at 1305 from AFW. The purpose of the flight was to maintain inspector currency. After completion of air work, the airplane proceeded to Waco (ACT), Texas, where takeoffs and landings were to be made. As the landing gear was extended during the first approach, the crew heard a loud "bang" and observed a GEAR UNSAFE indication. After making a low pass ACT tower reported the main gear appeared to be down, but the nose gear was only partially extended. The instructor raised the landing gear and made another low pass. Tower personnel said the main gear was up, but the nose gear was still only partially extended. The crew returned to AFW and, after consulting with FSDO, Oklahoma City maintenance, and Hawker Beechcraft, the decision was made to land the airplane on runway 34L. As speed dissipated, the nose gear folded and the airplane slid to a stop. The nose wheel bulkhead was damaged. Post-accident examination revealed the nose gear actuator (p/n 50-820208-5, s/n 93963) had failed. The actuator was sent to Aerospace Turbine Rotables, Inc., Wichita, Kansas, where it was disassembled and examined. According to their Teardown and Inspection Report, “The most probable root cause of the actuator failure was relevant to insufficient lubrication of the nut assembly threads.” According to FAA, Hawker Beechcraft maintenance manual does not require in-service lubrication of landing gear actuator. The mechanical actuator is suppose to be overhauled or replaced every 8000 cycles, or 6 years, whichever occurs first. During this time, the screw and nut assembly is to be greased. FAA said that the actuator on N20 accrued 1,576 and 951.2 hours time-in-service before it failed. Hawker Beechcraft confirmed that there was no requirement for lubricating the landing gear actuator. Consequently, the company reported it had implemented a change to the King Air maintenance manual that will include a lubrication requirement for the screw and nut assembly.
The failure of the nose gear actuator due to insufficient lubrication of the nut assembly threads.
Source: NTSB Aviation Accident Database
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