Kalispell, MT, USA
N38906
PIPER PA-28R-201T
After takeoff, between 300 and 500 feet above ground level over a residential area, the airplane's engine started to sputter and lose power. The pilot selected the longest street on which to make a forced landing, lowered the flaps, and slowed the airplane to a minimum controllable airspeed. The airplane collided with a number of vehicles and trees, and, in the process, the left wing separated from the fuselage. The airplane rotated inverted and embedded itself into the front of a residential house. Postaccident examination and testing of the left magneto revealed that the magneto’s distributor block bushing was worn to an extent that it provided significant radial play between the bushing and distributor block. The bushing, which holds the distributor gear axle in place, would permit the distributor gear to intermittently disengage from the drive gear. Once the distributor gear had disengaged from the drive gear, the internal timing of the magneto would be off, which could disrupt the normal ignition sequence and operation of the engine. If the pilot had switched to the right magneto, engine power would have likely been restored. The most recent magneto overhaul was performed in 1989. The engine manufacturer recommends that magnetos be overhauled or replaced 5 years after the date of manufacture or last overhaul, or 4 years after the date placed in service, whichever occurs first, without regard to accumulated operating hours since new or last overhaul.
HISTORY OF FLIGHT On February 4, 2012, at 1315 mountain standard time, a Piper PA-28R-201T, N38906, experienced a partial loss of engine power shortly after takeoff, at Kalispell City Airport, Kalispell, Montana. The pilot initiated a forced landing on a residential street where during the landing, the airplane collided with parked vehicles, and a residence. The airplane was registered to the pilot and was operated under the provisions of Title 14 Code of Federal Regulations Part 91. The commercial pilot and his two passengers received minor injuries, and the airplane was substantially damaged. Visual meteorological conditions prevailed, and no flight plan had been filed. The pilot stated to the National Transportation Safety Board investigator-in-charge (IIC) that he fueled the airplane with 45 gallons of AVGAS, taxied to pick up his passengers, and performed a complete engine run-up and preflight checks. During takeoff, the airplane behaved normally and accelerated smoothly. After takeoff, between 300 and 500 feet above ground level (agl) over a residential area, the airplane's engine started to sputter and lose power. The pilot selected the longest street on which he could make a forced landing. He lowered the flaps, and slowed the airplane to a minimum controllable airspeed. The airplane collided with a number of vehicles and trees, and in the process, the left wing separated from the fuselage. The airplane rotated inverted, and embedded itself into the front of a house. The pilot egressed through the pilot's side window, and he assisted with the egress of his passengers. AIRCRAFT INFORMATION The low-wing, four-seat, retractable landing gear airplane, serial number 28R-7703283, was manufactured in 1977. It was powered by a Continental Motors Incorporated (CMI) TSIO-360-F, serial number 305278, 200-hp engine, equipped with a Hartzell model BHC-C2YF-1BF constant speed propeller. A review of the airplane's maintenance records showed that an engine overhaul was completed on July 18, 1989. An annual inspection was completed on July 29, 2011, at a recorded tachometer (tach) time of 1,770.3 hours, and time since major overhaul (SMOH) of 322.3 hours. The tach time observed at the accident site was 1,772.65. Engine Roughness Procedure The Piper PA-28R-201T Cherokee Turbo Arrow III, Pilot Operating Handbook (POH) provides the following information concerning engine roughness. Mixture – adjust for max. smoothness Alternate Air – OPEN Fuel Selector- switch tanks Engine Gauges- check Magneto Switch- L then R then both “The magneto switch should then be moved to ‘L’ then ‘R’ then back to ‘BOTH.’ If operation is satisfactory on either magneto, proceed on that magneto at reduced power with full ‘RICH’ mixture to a landing at the first available airport. WRECKAGE AND IMPACT The main wreckage consisted of the fuselage, engine, tail, and right wing, which impacted a residence at ground level. The left wing had been sheared off at the wing root by a parked pickup truck located approximately 50 yards further up the airplane's line of travel. Light blue colored fluid was observed leaking out of the severed wing. There was no post-accident fire. The engine and cockpit area of the airplane was embedded into the building structure. The following day, Sunday February 5th, the airplane was recovered and moved to a storage location in Belgrade, Montana. During the recovery, approximately 45 gallons of AVGAS was recovered from both wing tanks combined. On February 22, 2012, technical representatives from the airframe and engine manufacturer examined the airplane under the oversight of a Federal Aviation Administration (FAA) inspector. Both ailerons were attached to their respective wing, and control cables were attached to both the aileron bell cranks. The horizontal and vertical tail surfaces remained attached to the rear empennage section; the rudder and the stabilator remained attached. The fuel selector handle was in the left tank position; the throttle and mixture control levers were full forward. The AUX fuel pump switch was in the center OFF position. The auxiliary electric fuel pump was functionally tested by applying battery power to the airplane’s electrical system. The pump was found to function normally on both the low and high switch power settings, drawing in and discharging fuel. The fuel gascolator bowl was removed and bluish fluid consistent with AVGAS was observed. Engine power-train continuity was established by rotating the engine’s crankshaft. The engine driven fuel pump was removed, tested, and found to function normally. The magnetos remained attached to the engine and both produced spark at all of their ignition leads when the engine’s crankshaft was rotated by hand. The airframe manufacturer technical representative reported that the airframe revealed no pre-impact failure to any flight control surface or flight control system component. The engine manufacturer technical representative reported that the inspection of this engine did not reveal any anomalies that would have prevented its ability to produce rated horsepower. TESTS & RESEARCH Video A surveillance video camera mounted on an airport hangar captured the airplane’s takeoff departure path. The video shows an airplane immediately after takeoff moving at a constant altitude approximately 75 feet above ground level (agl) from right to left across the screen at a constant speed. Magneto Under the direction of the NTSB IIC, an Airframe & Powerplant (A&P) mechanic removed both magnetos from the engine on April 5, 2013. Both magnetos were Bendix model S6LN-25. On April 15, 2013, under the supervision of an FAA inspector, both magnetos were placed in a test fixture, and tested at normal operating speeds. The right magneto, serial number A186072, produced spark on all posts. The left magneto, serial number A186084, produced spark on one post. The A&P mechanic and FAA inspector disassembled the magneto (SN: A186084) and found a worn bushing. This magneto was then packaged, sent to the Analytical Department of Continental Motors, Inc. (CMI), and examined under the supervision of an NTSB investigator. CMI technical experts determined that the magneto’s distributor block bushing was worn to an extent that it provided significant radial play between the bushing and distributor block. The bushing, which holds the distributor gear axle in place, was worn to such an extent that it would permit the distributor gear to intermittently disengage from the drive gear. Once the distributor gear disengaged from the drive gear, the internal timing of the magneto would be off, which could disrupt the normal ignition sequence and operation of the engine. Review of the engine maintenance records showed that the magneto was last overhauled on July 18, 1989, and had accumulated 324.65 hours since overhaul. Review of the S-20 Series Magneto Service Support Manual showed CMI recommends magnetos be inspected after the first 500 hours in service and every 500 hours thereafter. In addition, magnetos should be overhauled or replaced 5 years after the date of manufacture or last overhaul, or 4 years after the date placed in service, whichever occurs first, without regard to accumulated operating hours since new or last overhaul.
The partial loss of engine power due to magneto malfunction. Contributing to the accident was the lack of adherence to the manufacturer’s recommended magneto overhaul schedule.
Source: NTSB Aviation Accident Database
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