Bay St. Louis, MS, USA
N6742S
Beech A36
The pilot/owner of the airplane heard a low thumping noise during takeoff on several occasions, which he associated with the landing gear. He flew the airplane to an airport to have a mechanic familiar with his airplane troubleshoot the noise. After a visual inspection failed to reveal the problem, a test flight was initiated. The mechanic seated in the rear of the airplane heard the noise, and after flying around for a few minutes, requested a return to the airport. During extension of the landing gear, the 3 green (gear down/locked) lights failed to illuminate. The pilot cycled the gear, but the lights again failed to illuminate. He stated he thought he had heard all the appropriate sounds associated with proper landing gear extension, and elected to continue the landing, without attempting the manual extension of the gear as prescribed in the "Emergency Procedures" section of the pilot's operating handbook. During the landing roll the landing gear collapsed. Postaccident testing of the landing gear was conducted with the airplane on jacks. Tests revealed that the charge on the battery was insufficient to extend the electrically operated landing gear completely. The battery was found to be capable of taking a charge, but further tests revealed no output from the alternator. The alternator's rotor was found to be defective and the electrical brushes excessively worn.
On February 10, 2005, about 1730 central standard time, a Beech A36 airplane, N6742S, sustained substantial damage when the landing gear collapsed during landing at the Stennis International Airport, Bay St. Louis, Mississippi. The airplane was being operated by the pilot as a visual flight rules (VFR) local personal flight under Title 14, CFR Part 91 when the accident occurred. The private pilot and two passengers were not injured. Visual meteorological conditions prevailed, and no flight plan was filed. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on February 11, the pilot said he had flown the accident airplane to Stennis International Airport to pickup an aircraft mechanic, and have him listen to a "low thumping" noise the airplane was making during takeoff. He said after returning from the flight, the landing gear down and locked indicator's three green lights failed to illuminate when he extended the landing gear. The pilot said none of the remedial actions he took resulted in a green, down and locked indication, but he felt the gear was down and locked. He said during the landing roll the nose gear collapsed, followed by the collapse of the right main gear. He said the right wing sustained structural damage when the landing gear collapsed. In a subsequent written statement dated February 15, 2005, the pilot reported that he had contacted Beechcraft in reference to a low thumping noise he routinely heard during initial takeoff. Beechcraft suggested an inspection of the landing gear and associated mechanisms for security. After inspecting the airplane himself, and finding nothing unusual, the pilot flew the airplane to an airport where a mechanic familiar with his specific airplane could troubleshoot the problem. The mechanic visually inspected the airplane, and found no mechanical anomalies. They decided to fly the airplane with the mechanic in the rear seat, to facilitate listening to the gear during retraction. During takeoff-initial climb, the low thumping noise was heard prior to gear retraction. During gear retraction the pilot reported hearing all the normal sounds associated with the retraction process. They flew the airplane for a short time, and returned to the airport for landing. The pilot reported that prior to landing, he heard all the appropriate sounds associated with the extension of the landing gear, but the 3 green lights associated with the gear down and locked condition did not illuminate. The pilot cycled the landing gear, and heard what he believed were all the appropriate sounds associated with the retraction and re-extension of the landing gear. He reported the 3 green lights again did not illuminate. He elected to continue the landing without executing the emergency gear extension procedures. He reported that during the landing sequence he retarded the throttle specifically to see if the gear warning horn would activate. The warning horn did not activate, adding to his belief the landing gear was down and locked. The landing gear collapsed during the landing roll. After recovery the airplane was placed on jacks for gear retraction tests. During the initial test the 3 green gear down and locked lights did not illuminate, and it was found the nose gear light was burned out. After replacing the nose gear light the tests continued. The gear cycled normally on the first test, but the battery went dead. The airplane's gear retraction system is an electrically driven mechanical system. The tests were continued using auxiliary power, and proceeded without incident. The battery was tested, and found to be in good condition, but uncharged. The alternator was removed, and sent to a certified shop for inspection. The alternator was tested, and found to have zero output. During teardown and inspection, the alternator's rotor was found to be defective, and the electrical brushes worn excessively. The airplane is equipped with a manual hand crank to extend the landing gear in the event of a landing gear system failure. The procedures for manual extension are contained in the pilot's operating handbook under "Emergency Procedures."
The pilot's failure to use the manual emergency landing gear extension mechanism during the approach to land, which resulted in the electrically actuated main landing gear collapsing during the landing roll. A factor associated with the accident is an inoperative alternator.
Source: NTSB Aviation Accident Database
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