Colville, WA, USA
N707PH
RANS S12
The owner of the airplane, who was not a pilot, was selling the airplane to his friend, who was a pilot. The two spent the winter rebuilding the airplane, which had previously been involved in an accident and had been in storage, in pieces, for the previous 5 years. On the day of the accident, the pilot announced to an acquaintance that the airplane’s maintenance issues had been corrected and they were going to take the airplane on a test flight. A witness who saw the airplane’s takeoff and initial climb reported that the airplane’s climb rate was “not impressive” and that it was only “slightly climbing.” Two witnesses who saw the airplane before the accident stated that the engine was “sputtering” and that the airplane was “losing altitude quickly.” Photos of the airplane just before the accident showed the airplane flying toward a set of power distribution lines before entering a steep bank away from the lines, after which the airplane impacted terrain. The airplane came to rest in a nose-down attitude in an open field adjacent to the power distribution lines. Examination of the wreckage revealed that both carburetors’ float brackets were not adjusted in accordance with the manufacturer’s maintenance manual, which likely restricted the amount of fuel in the carburetor bowls. Multiple people stated that the owner and pilot had been troubleshooting a carburetor issue before the accident flight. One person described it as, “over-producing fuel, and the fuel was running out of the back [of the airplane].” The repair work on the airplane was overseen by a mechanic with inspection authorization who advised the two as they went and gave the two general maintenance advice. The mechanic was aware that neither the owner nor the pilot were certificated mechanics or light sport repairmen; however, he described the owner as a competent mechanic. About 1 month before the accident, the mechanic completed an entry in the airplane’s maintenance logbook stating that the condition inspection had been completed and that the airplane was “found to be in an airworthy condition” and “approved for return to service.” The mechanic was aware of the carburetor issue but did not know who worked on the carburetors and thought that the carburetors had been sent away for repair. After the carburetors were reinstalled, the mechanic observed the pilot conduct ground runs and thought that the engine “sounded fine.” It is likely that the engine was not producing full power as a result of the improperly adjusted carburetor float brackets, which resulted in degraded climb performance or the airplane’s inability to climb. Based on the witness statements and photos, it is likely that the pilot was maneuvering to avoid powerlines when he exceeded the airplane’s critical angle of attack and the airplane entered an aerodynamic stall.
HISTORY OF FLIGHTOn April 17, 2021, about 1048 Pacific daylight time, an experimental, amateur-built Rans S-12 light sport airplane, N707PH, was substantially damaged when it was involved in an accident near Colville, Washington. The pilot and passenger were fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 test flight. Multiple witnesses observed the takeoff. One described the airplane’s climbout as “not impressive,” and another stated that, “it was slightly climbing but the engine sounded OK.” Multiple witnesses observed the airplane in flight. Two witnesses saw the airplane overfly their property, which was located about 1/8 mile from the accident site and reported that they could tell something “wasn’t right” because the engine sounded like it was “sputtering” and the airplane was losing altitude quickly. Neither saw the airplane impact the ground. Two other witnesses, located in a car on a highway, saw the airplane at a low altitude and getting lower. Neither heard the airplane’s engine, but both watched the airplane approach a set of power distribution lines, turn hard to its right, then descend straight down to a field. One witness stated that it looked like the pilot was flying straight to the power distribution lines then turned away from them, and if he did not turn, the airplane would have hit them. Another witness took multiple photos of the airplane as it approached the set of power distribution lines. The last photo revealed the airplane in a steep bank angle (see figure 1). Figure 1. The accident airplane in a steep bank moments before the accident. (Source: Witness) Note: The power distribution lines are in the foreground. The manager of the airport where the airplane was stored stated that he knew both occupants. He understood that the passenger was selling the airplane to the pilot. The airplane had been in the passenger’s hangar, in pieces, for about 5 years and the pilot and passenger spent the winter putting it back together. An acquaintance who spoke to the passenger and the pilot on the day of the accident reported that the two informed him that they had corrected some maintenance problems and were going to take the airplane on a test flight. The acquaintance was aware of several small problems that the two were correcting, one of which was a carburetor that was “over-producing fuel, and the fuel was running out of the back [of the airplane].” PERSONNEL INFORMATIONThe passenger was not a certificated pilot, and neither the pilot nor the passenger were certificated mechanics or light sport repairmen. AIRCRAFT INFORMATIONThe wife of the passenger stated that he bought it from a neighbor after it had been involved in an accident. He did not fly it. He recently sold the airplane to his friend, who was the accident pilot and the two worked on the airplane to get it ready to fly. AIRPORT INFORMATIONThe wife of the passenger stated that he bought it from a neighbor after it had been involved in an accident. He did not fly it. He recently sold the airplane to his friend, who was the accident pilot and the two worked on the airplane to get it ready to fly. WRECKAGE AND IMPACT INFORMATIONA Federal Aviation Administration (FAA) inspector examined the wreckage at the accident site. The airplane impacted terrain in an approximate 45° nose-down attitude and came to rest on an open, sloping field, adjacent to a large set of power distribution lines. The cabin area and floor area were heavily damaged, but the tail section was intact. Flight control continuity was established for all flight controls. Fuel and electrical systems appeared to be correctly installed. Fuel was observed draining from the airplane at the accident site. The engine oil and coolant had sufficient levels. When the FAA inspector visited the hangar where maintenance on the airplane was performed, he found two disassembled carburetors on a shelf that were the same as the carburetors on the airplane. Examination of the engine by a manufacturer’s representative revealed that one carburetor had a piece of blue tape attached to it with the word “leaks” written on it. The float brackets for both carburetors were out of adjustment, as shown in figure 2. According to the BRP-Rotax Heavy Maintenance Manual, the carburetor float brackets are to be parallel to the float chamber, as shown in figure 3. According to the manufacturer, the way the brackets were adjusted on the carburetors limited the amount of fuel in the carburetor bowl, and depending on the power demands, the engine may run perfectly fine while at idle, start to lean out, resulting in less power while at mid-range, or the engine may stumble and quit at full throttle. No other anomalies were noted with the engine that would have precluded normal operation. The last entry in the airplane’s maintenance logbook, dated March 20, 2021, stated, in part, “Condition inspection, airframe, engine, prop. Ops check systems OK. This aircraft was inspected and found to be in airworthy condition and approved for return to service.” The mechanic who completed the entry stated that he knew the two occupants, and they had approached him to ask if he could oversee their work on the airplane. The mechanic stated that he acted as an advisor and gave them general maintenance advice. He knew that neither were certificated repairmen but knew that the passenger was a good mechanic and was not worried about his mechanical skills. He stated that he was aware of a carburetor issue but did not know who worked on the carburetors. He thought that the two had sent the carburetors out for repair. When the carburetors were reinstalled, the mechanic noticed that the vacuum lines were incorrect. After the vacuum lines were corrected, the engine ran normally from idle to full power. After the reinstallation, he had seen the pilot conducting ground runs in the airplane and thought that the engine sounded fine. Figure 2. Photo showing one of two carburetors. Both exhibited incorrectly adjusted float brackets. Note: The green parallel lines indicate the correct position for the float bracket. The red line indicates the actual position of the float bracket. Figure 3. Excerpt from the BRP-Rotax Heavy Maintenance Manual explaining the float bracket adjustment procedure
The pilot’s exceedance of the airplane’s critical angle of attack while maneuvering to avoid powerlines, which resulted in an aerodynamic stall and a loss of control. Contributing to the accident was the partial loss of engine power due to improper maintenance of the carburetors.
Source: NTSB Aviation Accident Database
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