What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
(.19) On December 12, 1999, at 1750 central standard time, a king Lancair 235/320 amateur-built experimental airplane, N717SK, owned and operated by the pilot, was substantially damaged during a forced landing following the separation of the propeller near Sterling city, Texas. The instrument rated private pilot, sole occupant of the airplane, was not injured. Visual meteorological conditions prevailed, and an IFR flight plan was filed for the 14 code of federal regulations part 91 personal flight. The cross-country flight originated from kerrville, Texas, at 1624, with big spring, Texas, as its destination. The pilot reported that while being radar vectored at 12,000 feet MSL, he felt a vibration and smelled an odor which resembled wire burning. He contacted fort worth center and obtained a clearance to descend to 6,500 feet. The pilot reduced throttle and the vibration decreased. While leveling off at 6,500 feet, the propeller separated from the engine and a forced landing was initiated to a road. During the approach the aircraft impacted a power line and touched down on the shoulder of the road and "bounced." The right wing struck a sign, and the airplane crossed the ro AD and traveled through a ravine before coming to a stop. The pilot further reported that the right wing was separated from the fuselage, and the left main landing gear was shoved up into the wing. (.4)during descent, the propeller separated from the experimental airplane. The pilot initiated a forced landing to a county road, and during the approach, the left main landing gear 'struck the bottom wire of a two wire service line,' which crossed over the road. The airplane 'stalled,' yawed 20 degrees to the left, and 'hit the middle of the road on all three [landing] gear.' It then headed off the left shoulder of the road where the right wing hit a road sign, shearing off the outboard 4 feet of the wing. The propeller system was not recovered. Examination of four of the six propeller attaching bolts revealed that they failed as a result of fatigue. The shank of one of the bolts, in the area located immediately adjacent to the fracture face had been subjected to 'extensive rubbing damage.' Two of the submitted bolt pieces contained washers. Examination showed that both washers were permanently deformed into dish shapes and were galled by rubbing. Rubbing and galling damage was also found on contact surfaces of the self locking nuts on all four bolts. The 3-bladed wooden experimental propeller had 47.4 hours since installation. The combination of low time since insta installation and rubbing damage on the bolts indicates the application of inadequate pre-stress (low torque) during propeller installation.
As the FAA filed it
(.19) ON DECEMBER 12, 1999, AT 1750 CENTRAL STANDARD TIME, A KING LANCAIR 235/320 AMATEUR-BUILT EXPERIMENTAL AIRPLANE, N717SK, OWNED AND OPERATED BY THE PILOT, WAS SUBSTANTIALLY DAMAGED DURING A FORCED LANDING FOLLOWING THE SEPARATION OF THE PROPELLER NEAR STERLING CITY, TEXAS. THE INSTRUMENT RATED PRIVATE PILOT, SOLE OCCUPANT OF THE AIRPLANE, WAS NOT INJURED. VISUAL METEOROLOGICAL CONDITIONS PREVAILED, AND AN IFR FLIGHT PLAN WAS FILED FOR THE 14 CODE OF FEDERAL REGULATIONS PART 91 PERSONAL FLIGHT. THE CROSS-COUNTRY FLIGHT ORIGINATED FROM KERRVILLE, TEXAS, AT 1624, WITH BIG SPRING, TEXAS, AS ITS DESTINATION. THE PILOT REPORTED THAT WHILE BEING RADAR VECTORED AT 12,000 FEET MSL, HE FELT A VIBRATION AND SMELLED AN ODOR WHICH RESEMBLED WIRE BURNING. HE CONTACTED FORT WORTH CENTER AND OBTAINED A CLEARANCE TO DESCEND TO 6,500 FEET. THE PILOT REDUCED THROTTLE AND THE VIBRATION DECREASED. WHILE LEVELING OFF AT 6,500 FEET, THE PROPELLER SEPARATED FROM THE ENGINE AND A FORCED LANDING WAS INITIATED TO A ROAD. DURING THE APPROACH THE AIRCRAFT IMPACTED A POWER LINE AND TOUCHED DOWN ON THE SHOULDER OF THE ROAD AND "BOUNCED." THE RIGHT WING STRUCK A SIGN, AND THE AIRPLANE CROSSED THE RO AD AND TRAVELED THROUGH A RAVINE BEFORE COMING TO A STOP. THE PILOT FURTHER REPORTED THAT THE RIGHT WING WAS SEPARATED FROM THE FUSELAGE, AND THE LEFT MAIN LANDING GEAR WAS SHOVED UP INTO THE WING. (.4)DURING DESCENT, THE PROPELLER SEPARATED FROM THE EXPERIMENTAL AIRPLANE. THE PILOT INITIATED A FORCED LANDING TO A COUNTY ROAD, AND DURING THE APPROACH, THE LEFT MAIN LANDING GEAR 'STRUCK THE BOTTOM WIRE OF A TWO WIRE SERVICE LINE,' WHICH CROSSED OVER THE ROAD. THE AIRPLANE 'STALLED,' YAWED 20 DEGREES TO THE LEFT, AND 'HIT THE MIDDLE OF THE ROAD ON ALL THREE [LANDING] GEAR.' IT THEN HEADED OFF THE LEFT SHOULDER OF THE ROAD WHERE THE RIGHT WING HIT A ROAD SIGN, SHEARING OFF THE OUTBOARD 4 FEET OF THE WING. THE PROPELLER SYSTEM WAS NOT RECOVERED. EXAMINATION OF FOUR OF THE SIX PROPELLER ATTACHING BOLTS REVEALED THAT THEY FAILED AS A RESULT OF FATIGUE. THE SHANK OF ONE OF THE BOLTS, IN THE AREA LOCATED IMMEDIATELY ADJACENT TO THE FRACTURE FACE HAD BEEN SUBJECTED TO 'EXTENSIVE RUBBING DAMAGE.' TWO OF THE SUBMITTED BOLT PIECES CONTAINED WASHERS. EXAMINATION SHOWED THAT BOTH WASHERS WERE PERMANENTLY DEFORMED INTO DISH SHAPES AND WERE GALLED BY RUBBING. RUBBING AND GALLING DAMAGE WAS ALSO FOUND ON CONTACT SURFACES OF THE SELF LOCKING NUTS ON ALL FOUR BOLTS. THE 3-BLADED WOODEN EXPERIMENTAL PROPELLER HAD 47.4 HOURS SINCE INSTALLATION. THE COMBINATION OF LOW TIME SINCE INSTA INSTALLATION AND RUBBING DAMAGE ON THE BOLTS INDICATES THE APPLICATION OF INADEQUATE PRE-STRESS (LOW TORQUE) DURING PROPELLER INSTALLATION.
NTSB investigation
The NTSB’s investigation of this event, with its probable cause and findings. Matched to this report by N-number and date.