What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
(-23) On August 10, 1999, a BE-35 operated by paul wells crashed into the water of spotted bear river approximately 5 miles east of spotted bear ranger station during a pleasure flight. The flight originated at tom sand's airfield with an intended destination of benchmark (3UY) airfield. No flight plan was filed and VFR conditions prevailed. The aircraft was substantially damaged and an ambulance helicopter transported pilot and single passenger to hospital in serious condition. Air ambulance medic reported that pilot indicated an engine overtemperature condition/prop vibration at 7000 feet AGL and attempted to land a spotted bear airport. (.4) the pilot observed a RPM overspeed with oil temperature rise. Throttling back relieved the overspeed situation; however, he observed a rapid loss of remaining power after turning back toward a potential emergency landing airstrip. He stated that the propeller had continued windmilling until impact. Pistons 1, 2, 4, 5, and 6 had few combustion deposits on their combustion faces. Piston 3 exhibited evidence of detonation, including a hole of about 1 inch diameter, and a combustion surface with the appearance of er osion. As originally manufactured, minimum octane requirement for this engine fuel was 91/96 octane. Teledyne Continental motors amended the recommended fuel to 100 octane after 91/96 octane fuel became obsolete. Placards on the airplane fuel tanks stated that minimum fuel required was 100 octane. No evidence was found of a supplemental type certificate for use of automotive gasoline in the subject airplane or engine. A sample of the automotive fuel removed from the airplane after the accident was tested: research octane number was 94, motor octane number was 83.8, and anti-knock index was 88.9. The pilot stated that he had been using automotive gasoline in the airplane for approximately 700 hours.
As the FAA filed it
(-23) ON AUGUST 10, 1999, A BE-35 OPERATED BY PAUL WELLS CRASHED INTO THE WATER OF SPOTTED BEAR RIVER APPROXIMATELY 5 MILES EAST OF SPOTTED BEAR RANGER STATION DURING A PLEASURE FLIGHT. THE FLIGHT ORIGINATED AT TOM SAND'S AIRFIELD WITH AN INTENDED DESTINATION OF BENCHMARK (3UY) AIRFIELD. NO FLIGHT PLAN WAS FILED AND VFR CONDITIONS PREVAILED. THE AIRCRAFT WAS SUBSTANTIALLY DAMAGED AND AN AMBULANCE HELICOPTER TRANSPORTED PILOT AND SINGLE PASSENGER TO HOSPITAL IN SERIOUS CONDITION. AIR AMBULANCE MEDIC REPORTED THAT PILOT INDICATED AN ENGINE OVERTEMPERATURE CONDITION/PROP VIBRATION AT 7000 FEET AGL AND ATTEMPTED TO LAND A SPOTTED BEAR AIRPORT. (.4) THE PILOT OBSERVED A RPM OVERSPEED WITH OIL TEMPERATURE RISE. THROTTLING BACK RELIEVED THE OVERSPEED SITUATION; HOWEVER, HE OBSERVED A RAPID LOSS OF REMAINING POWER AFTER TURNING BACK TOWARD A POTENTIAL EMERGENCY LANDING AIRSTRIP. HE STATED THAT THE PROPELLER HAD CONTINUED WINDMILLING UNTIL IMPACT. PISTONS 1, 2, 4, 5, AND 6 HAD FEW COMBUSTION DEPOSITS ON THEIR COMBUSTION FACES. PISTON 3 EXHIBITED EVIDENCE OF DETONATION, INCLUDING A HOLE OF ABOUT 1 INCH DIAMETER, AND A COMBUSTION SURFACE WITH THE APPEARANCE OF ER OSION. AS ORIGINALLY MANUFACTURED, MINIMUM OCTANE REQUIREMENT FOR THIS ENGINE FUEL WAS 91/96 OCTANE. TELEDYNE CONTINENTAL MOTORS AMENDED THE RECOMMENDED FUEL TO 100 OCTANE AFTER 91/96 OCTANE FUEL BECAME OBSOLETE. PLACARDS ON THE AIRPLANE FUEL TANKS STATED THAT MINIMUM FUEL REQUIRED WAS 100 OCTANE. NO EVIDENCE WAS FOUND OF A SUPPLEMENTAL TYPE CERTIFICATE FOR USE OF AUTOMOTIVE GASOLINE IN THE SUBJECT AIRPLANE OR ENGINE. A SAMPLE OF THE AUTOMOTIVE FUEL REMOVED FROM THE AIRPLANE AFTER THE ACCIDENT WAS TESTED: RESEARCH OCTANE NUMBER WAS 94, MOTOR OCTANE NUMBER WAS 83.8, AND ANTI-KNOCK INDEX WAS 88.9. THE PILOT STATED THAT HE HAD BEEN USING AUTOMOTIVE GASOLINE IN THE AIRPLANE FOR APPROXIMATELY 700 HOURS.
NTSB investigation
The NTSB’s investigation of this event, with its probable cause and findings. Matched to this report by N-number and date.