N328SK

HISTORY OF FLIGHTOn August 11, 2018, about 1056 Pacific daylight time, an experimental, amateur-built Zenith CH-750 airplane, N328SK, was substantially damaged during a forced landing near Napa County Airport (APC), Napa, California. The commercial pilot/owner and his pilot-rated passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. Visual meteorological conditions existed at APC about the time of the accident. The local flight had originated from APC about 25 minutes earlier.

According to the pilot, who was also the builder of the airplane, the airplane was for sale, and the accident flight was a demonstration/familiarization flight for a potential buyer. The pilot reported that they flew in the local area for about 20 minutes, and then he handed airplane control to the potential buyer, who was in the right seat. The buyer wanted to see how slowly the airplane could fly, and decelerated to about 30 knots, which resulted in a significant airplane-nose-up pitch attitude. The airplane began "sinking," so the pilot/owner took back control and pushed the nose over to regain airspeed. Almost immediately smoke entered the cockpit. The pilot declared an emergency and headed towards APC. Within a minute or two, the engine lost all oil pressure, and then ceased developing power.

The pilot initially attempted to glide to the airport, but then realized that the airport was too distant. He then decided to land on a road atop a nearby levee. The airplane touched down on the road, and the initial rollout was satisfactory. However, due to wind, the left wingtip struck the ground, and spun the airplane around. Due to the narrow width of the road and levee, the airplane then veered off the levee, and damaged the wing and fuselage. The airplane came to rest below the top of the levee, about 0.6 miles west of the APC runway 6 threshold.

According to Federal Aviation Administration (FAA) information, about 1050 the pilot reported to the APC air traffic control tower (ATCT) local controller (LC) that he had an "oil pressure issue." The LC asked the pilot if he required any assistance, and the pilot replied in the negative. At 1055 the pilot re-contacted the LC, advising that he was having "more issues," but did not elaborate. The ATCT controller in charge (CiC) declared an emergency for the pilot. The pilot then radioed that he had lost all engine power and was attempting to reach runway 6. At 1056 the pilot advised the LC that he could not make the runway and was landing on a levee about 1/2 mile short of the runway. After the airplane came to rest, the pilot notified the LC of their situation. PERSONNEL INFORMATIONFAA records indicated that the pilot held a commercial pilot certificate with airplane single-engine land, rotorcraft-helicopter, and instrument airplane ratings. He also held a repairman experimental aircraft builder certificate valid for the accident airplane. According to information provided by the pilot, he had approximately 7,700 total hours of flight experience, including about 200 hours in the accident airplane make and model. His most recent flight review was completed in September 2017, and his most recent medical certificate was issued under the Basic Med program in April 2017. AIRCRAFT INFORMATIONGeneral

FAA records indicated that the airplane was built by the pilot, and received its initial airworthiness approval in 2014. The airplane was equipped with a Belgian ULPower brand 350iS series piston engine that was rated at 130 horsepower.

Engine Fuel

The ULPower Operating Manual (OM) for the engine stated that "regular unleaded automotive fuel…should be used to operate" the engine. The OM specified minimum octane rating values of 98 RON, 90 MON, or 94 AKI. "RON" and "MON" are two different methods and indices for determining the octane value. "AKI" stands for anti-knock index, and is the arithmetic mean of RON and MON. In the United States, the octane ratings posted by automotive fuel vendors are AKI values. Predominant US AKI values range from 87 to 93. A ULPower representative stated that the 93 AKI fuel in the US is acceptable for use in the engine. Finally, the OM also stated that "AVGAS 100 LL and/ or AVGAS UL91 may be used if regular fuel is not available." The pilot did not specifically report the fuel(s), or the octane rating(s) of those fuel(s), that he used in the engine.

Logbook Information

The pilot-provided maintenance records were neither current nor in compliance with applicable FAA regulations. The records lacked the FAA-required documentation that certified the completion of the FAA-required Phase 1 flight test period. The airframe log only contained a single entry, dated 2014, which appeared to be the original post-build airworthiness signoff for the airplane. Although the pilot reported that he had an engine logbook, he did not provide one to the investigation. The records that were provided by the pilot did not include any entries that documented any maintenance activities.

Maintenance Information

According to pilot-provided information, the most recent "100 hour" inspection was completed on April 1, 2017, and that at that time both the airplane and engine total time in service was 200.5 hours. The pilot reported to an FAA inspector that he had previously had "low compression problems" with the engine, and that he had sent the engine back to the manufacturer for replacement of several components, including all four cylinder heads, one cylinder, and all piston rings. The pilot did not provide any documentation or other substantiation of that assertion. The incomplete maintenance records precluded evaluation of the maintenance history of the engine.

Engine Oil Changes

Regular oil changes that include examination of the oil filter and oil sample analyses are common practices that are proven to provide early detection of unusual engine wear or deterioration. The pilot-provided records did not include any entries that documented any oil changes, oil filter examinations, or oil sample analyses.

Pilot's Accident Accounts

In his initial communications with the NTSB about the accident, the pilot reported that he believed that the high pitch attitude during the demonstration flight had caused the oil to be vented overboard via the oil breather assembly. In his subsequent written accident report to the NTSB, the pilot reported that "something broke in the engine and dumped oil into the muffler from the no.1 exhaust." METEOROLOGICAL INFORMATIONThe 1054 APC automated weather observation included winds from 220° at 11 knots, visibility 10 miles, clear skies, temperature 23°C, dew point 14°C, and an altimeter setting of 29.98 inches of mercury. AIRPORT INFORMATIONGeneral

FAA records indicated that the airplane was built by the pilot, and received its initial airworthiness approval in 2014. The airplane was equipped with a Belgian ULPower brand 350iS series piston engine that was rated at 130 horsepower.

Engine Fuel

The ULPower Operating Manual (OM) for the engine stated that "regular unleaded automotive fuel…should be used to operate" the engine. The OM specified minimum octane rating values of 98 RON, 90 MON, or 94 AKI. "RON" and "MON" are two different methods and indices for determining the octane value. "AKI" stands for anti-knock index, and is the arithmetic mean of RON and MON. In the United States, the octane ratings posted by automotive fuel vendors are AKI values. Predominant US AKI values range from 87 to 93. A ULPower representative stated that the 93 AKI fuel in the US is acceptable for use in the engine. Finally, the OM also stated that "AVGAS 100 LL and/ or AVGAS UL91 may be used if regular fuel is not available." The pilot did not specifically report the fuel(s), or the octane rating(s) of those fuel(s), that he used in the engine.

Logbook Information

The pilot-provided maintenance records were neither current nor in compliance with applicable FAA regulations. The records lacked the FAA-required documentation that certified the completion of the FAA-required Phase 1 flight test period. The airframe log only contained a single entry, dated 2014, which appeared to be the original post-build airworthiness signoff for the airplane. Although the pilot reported that he had an engine logbook, he did not provide one to the investigation. The records that were provided by the pilot did not include any entries that documented any maintenance activities.

Maintenance Information

According to pilot-provided information, the most recent "100 hour" inspection was completed on April 1, 2017, and that at that time both the airplane and engine total time in service was 200.5 hours. The pilot reported to an FAA inspector that he had previously had "low compression problems" with the engine, and that he had sent the engine back to the manufacturer for replacement of several components, including all four cylinder heads, one cylinder, and all piston rings. The pilot did not provide any documentation or other substantiation of that assertion. The incomplete maintenance records precluded evaluation of the maintenance history of the engine.

Engine Oil Changes

Regular oil changes that include examination of the oil filter and oil sample analyses are common practices that are proven to provide early detection of unusual engine wear or deterioration. The pilot-provided records did not include any entries that documented any oil changes, oil filter examinations, or oil sample analyses.

Pilot's Accident Accounts

In his initial communications with the NTSB about the accident, the pilot reported that he believed that the high pitch attitude during the demonstration flight had caused the oil to be vented overboard via the oil breather assembly. In his subsequent written accident report to the NTSB, the pilot reported that "something broke in the engine and dumped oil into the muffler from the no.1 exhaust." WRECKAGE AND IMPACT IN...