History of Flight
On February 7, 2010, at approximately 0840 mountain standard time, a Nanchang China CJ-6A, registration N6263D, experienced a loss of engine power. The pilot performed a forced landing in a park adjacent to Falcon Field Airport in Mesa, Arizona. The flight, which departed Falcon Field at about 0810, was operated under 14 CFR Part 91 by a certificated commercial pilot. Visual meteorological conditions prevailed, and no flight plan was filed.
According to the pilot, about 30 minutes into a planned 45-minute flight, engine vibrations were felt. The pilot turned back toward Falcon Field. While on the downwind leg, a loud bang was heard, followed by a loss of engine power that prevented the aircraft from maintaining altitude. The pilot executed a 180-degree turn intending to land in a nearby park. During final approach, a person was observed in the intended landing area. The pilot banked left and landed; during the ground roll, the airplane collided with a restroom facility on park property.
The right wing, firewall, and forward fuselage structure sustained substantial damage during the accident sequence.
Aircraft Information
The airplane, serial number 4732023, was manufactured in 1984 and imported from China to the United States. It was equipped with a Housai H6 air-cooled, nine-cylinder radial engine (serial number 201-H6A822361) and a metal two-bladed constant-speed propeller. On June 1, 1998, the FAA issued registration N6263D and an experimental-exhibition airworthiness certificate.
No maintenance records prior to 1998 were located. Airframe logbook records indicated the last recorded maintenance was a conditional inspection at 2,338.8 total flight hours on April 9, 2009. The engine logbook reported an 'unknown' total engine time at that inspection. The first logbook entry, dated November 22, 1999, noted a total airframe time of 2,022 hours. No entries indicated major maintenance or overhaul of the engine.
Engine Examination
The NTSB investigator-in-charge and an Airframe and Powerplant mechanic specializing in Housai radial engines examined the engine. The engine remained attached to the radial portion of its mount, which had separated from the airframe. External examination revealed that cylinder number four had detached from the crankcase at its flange; eight cylinder head studs separated at the crankcase, with shanks remaining affixed at varying lengths. The cylinder head remained partially attached by spark plug leads and fuel lines. The piston, upper section of its connecting rod, both pushrods, and all cylinder head nuts were ejected and not located.
Hand rotation of the propeller resulted in free, smooth, and unrestricted movement. Green-colored translucent oil was observed in the crankcase and rocker covers. The oil shutoff valve on the firewall was in the open position.
Internal examination showed catastrophic damage. All remaining piston rods were still attached to their pistons but had separated from the master rod bearing. Rod ends for pistons 1, 2, 3, 5, and 6 remained attached to the master rod flange, separated about 2 inches from their knuckle pins, and moved smoothly by hand. Rod ends for pistons 7, 8, and 9 had detached from their knuckle pins; associated master rod pin mating surfaces were clean and shiny. Except for cylinder and piston number 5, all separated rod surfaces exhibited peening damage with obliterated surface features consistent with continued movement after failure.
Cylinder sleeves and areas adjacent to carry-through bolts sustained gouging consistent with connecting rod contact. Crankshaft balance weights had radial scoring along outer edges. Pistons had scoring on lower skirts consistent with contact with rotating crankshaft weights and piston rods. External examination of cylinder flanges showed no obvious signs of oil leaks.
Examination of remaining ancillary engine components revealed no defects that would have affected engine operation.
Cylinder number four, a section of its associated engine case flange, and piston number five with its connecting rod were sent to the NTSB materials laboratory. Laboratory examination of one cylinder head stud within the case flange revealed a smooth arced fracture surface in the root of the stud thread, oriented perpendicular to the axis. Closer view showed ratchet marks initiating in the root of the thread, with an adjacent torn section of thread bent away from the arced surface. Three more studs displayed similar fracture features.
The number five piston connector rod fracture face showed a deformed section with bent flanges displaying slant planes and mechanical damage, consistent with continued engine rotation after failure.