ERA23FA033

Improper maintenance of the fuel injector nozzles and the pilots’ failure to abort the takeoff during the takeoff roll. Contributing to the accident was the mechanic’s decision to return the airplane to service with the engine unable to attain its full rated power.

A mechanic reported that the maximum engine rpm attained during a postmaintenance full-power engine run earlier on the day of the accident was between 2,300 and 2,375 rpm; he approved the airplane to return to service. (A maximum continuous power setting of 2,650 to 2,700 rpm was required.) The airplane had not flown in about 14 months. A postmaintenance check flight was not performed after the annual inspection. A flight instructor and a pilot under instruction were initiating a personal flight, which was the airplane’s first flight after the annual inspection was completed. Coincidentally, it was also their first flight in the same airplane in which they experienced poor takeoff and climb performance during a flight nearly 14 months earlier. Witnesses reported that during the accident takeoff roll, the engine did not sound normal, with one reporting that it never sounded smooth the entire time the airplane was on the runway or while airborne. The airplane became airborne about 3,311 ft down the 6,201-ft runway, which was about 2,087 ft more takeoff distance than the calculated value for the environmental conditions that day. After becoming airborne, the airplane leveled off at 25 ft followed by a momentary power reduction and then a power advance. The flight continued in a shallow climb, climbing no higher than about 50 to 200 ft when the flight was about 5,200 ft down the runway with about 1,000 ft of runway remaining. The flight continued off the airport where the “poor” engine sound continued. While maintaining controlled flight, the airplane impacted a storage structure attached to an apartment building, resulting in a postimpact fire that nearly consumed the airplane. Postaccident examination of the engine revealed that none of the two-piece fuel injector nozzles had inserts or restrictors installed The mechanic reported that the fuel injector nozzles were cleaned as part of the annual inspection. It is likely that at some point after removing the inserts or restrictors for cleaning, they were not reinstalled. Operational testing of the fuel injector nozzles without inserts or restrictors revealed extensive leakage. Operational testing of a four-cylinder engine of the same manufacturer revealed that without inserts or restrictors installed in any cylinder, the engine produced about 7% less horsepower at full power when compared to a baseline run of the same engine with all inserts or restrictors installed. There were no other engine or engine systems discrepancies noted. Acoustic analysis of the engine indicated that, as the airplane became airborne and immediately before impact, the engine was operating about 2,400 rpm, which was about 11% less than the maximum continuous power setting of 2,700 rpm. Although the engine rpm at the start of the takeoff could not be determined from the available evidence, based on the postaccident engine testing and the extended ground roll distance, it was likely at a significantly decreased value, consistent with the 2,400 rpm recorded during two separate points later during the flight. The mechanic likely incorrectly identified the maximum rpm value obtained during the post-maintenance engine run as falling within the normal operating range, and he did not recognize that with a constant-speed propeller installed the maximum full-power static rpm was specified to be within 50 rpm of the full-power value of 2,700 rpm. As such, the airplane should not have been returned to service. The flight instructor and the pilot under instruction likely did not recognize during the takeoff roll that the engine was producing about 2,400 rpm instead of the normal 2,700 rpm. They also should have recognized that the ground run was excessive and aborted the takeoff while still on the runway. A witness reported that shortly after takeoff, when the airplane was about 25 ft above the runway, he heard a power reduction followed by a power advance. It is possible that the pilots initiated a rejected takeoff but chose to continue the flight, likely due to the limited remaining runway available for landing.

The airplane was equipped with a three-bladed, constant-speed, single-acting McCauley propeller that was installed in accordance with Supplemental Type Certificate SA496CH. The Federal Aviation Administration (FAA) Approved Airplane Flight Manual Supplement associated with the propeller installation specified that there was no performance change as compared to the originally installed propeller, and that the rated full power rpm was 2,700 rpm. Section VIII, Handling, Service and Maintenance, of the Pilot’s Operating Handbook and FAA Approved Airplane Flight Manual (POH/AFM), specified the static rpm range during a power check to be between 2,650 and 2,700 rpm. The performance section of the POH/AFM indicated that from a paved, level, dry surface runway, based on the environmental conditions at the time, the approximate ground roll distance at 2,750 pounds was about 1,224 ft. A note in the chart specified that for each 100 pounds below 2,750 pounds, to subtract 8 percent from the distances. Before the accident flight, the accident airplane was last flown on September 4, 2021, over 13 months before the accident flight. The pilot in the left seat during that flight reported that he was interested in possibly purchasing a similar make and model airplane as the accident airplane. He, therefore, flew two flights in the accident airplane. Once on August 28, 2021, for 1.3 hours, and during the second flight on September 4, 2021, which lasted 1.2 hours. He reported that the airplane flew normally during the first flight and for the first 2 legs on September 4th. However, he reported that the airplane did not perform normally during the third leg of flight (The right front pilot during the September 4th flight was the accident flight instructor, and the passenger in one of the rear seats was the left seat pilot during the accident flight). During the taxi for takeoff on the third leg of flight, the engine sounded like it might have a fouled spark plug or bad magneto. During takeoff, the airplane did not accelerate as expected and the right seat pilot took the controls and aborted the takeoff. The right seat pilot did another run-up and magneto check and decided to attempt another takeoff. The left front pilot reported that the airplane did not get airborne until between 2,200 to 2,500 ft down the runway; the airplane was climbing about 100 ft per minute and nearly hit a tree on departure. The right seat pilot continued to climb by making “zig zag” turns up the valley until they cleared a ridgeline and landed uneventfully at the destination airport, EEN. The left front pilot described the flight as the “worst flight of my life.” The owner/operator of the airplane reported that before the accident flight the airplane had not been flown since the September 2021 event and had been stored in a hangar. She, and one of the operator’s mechanics, indicated that the issue associated with the September 2021 flight was a plugged fuel injector. The airplane’s last annual inspection was completed on October 19, 2022. The mechanic reported that the fuel injector nozzles were cleaned as part of the annual inspection. Additional engine work consisted of replacing five spark plugs and re-timing the magnetos. Each differential compression check was greater than 75 psi when checked at 80 psi. The mechanic who performed a full-power post-maintenance engine run earlier on the day of the accident reported the maximum rpm attained was between 2,300 and 2,375 rpm. A postmaintenance check flight was not performed after the annual inspection; the accident flight was the first flight flown after the annual inspection. Lycoming Service Bulletin No. 1414B, and Lycoming Service Instruction No. 1275C specified instructions for cleaning, and removing, cleaning, reassembly, and then testing of the fuel injector nozzles, respectively. Postmortem examinations of the pilot and commercial-rated pilot were performed by the New Hampshire Medical Examiner’s Office. The cause of death for both was inhalation of smoke and toxic products of combustion. Forensic toxicology was performed on specimens of the pilot and commercial-rated pilot by the FAA Forensic Sciences Laboratory, Oklahoma City, Oklahoma. The results of testing of specimens of the flight instructor revealed 14% carboxyhemoglobin and 1.09 ug/mL cyanide in the heart blood, respectively. The results of testing of specimens of the commercial-rated pilot revealed 47% carboxyhemoglobin and 1.05 ug/mL cyanide in the heart blood, respectively. The accident site was located about .54 nautical mile north-northeast from the departure end of the runway. Examination of the accident site revealed extensive heat and/or impact damage to the storage building and its contents, several of the apartments, and its roof. Inspection of the metal roof of the storage shed, which was displaced from its normal position, revealed it contained red paint transfer oriented on a magnetic heading of 021º. The red paint transfer was located to the right side of the energy path. Two parallel slash marks on the metal roof were oriented 66 inches apart, though the scars were not oriented in a direction consistent with the direction of flight. The aft portion of the aft empennage, heat-damaged sections of the left wing, pitot tube, and melted aluminum were found on top of the metal roof. Additional wreckage debris was found among the building debris. The engine with attached propeller was resting on its right side forward of the aft empennage. No bird remains were found among the wreckage. Examination of the wreckage revealed the cockpit, cabin, right wing, portion of the left wing, and forward portion of the aft empennage were nearly consumed by the postcrash fire to approximately fuselage station 250.00. One restraint buckle was found in the buckled position; the buckle released easily. Although the remains of several flight instruments were recovered, the readings could not be determined. Examination of the flight control cables for pitch and yaw revealed no evidence of preimpact failure or malfunction. Examination of separated direct aileron control cables from the control column to the bellcrank attachment hardware revealed cuts that were consistent with those typically made by first responders, and thermal damage with a fracture located about 45 inches from the bellcrank attach point. Examination of the fractured thermally damaged aileron control cable by the National Transportation Safety Board (NTSB) Materials Laboratory revealed the macro profile of the fractured cable was consistent with separation due to tensile overstress. The stabilator trim measurement was 0.875 inch, which correlated to near neutral with the stabilator in an approximate neutral position. The flap actuator was not located. Examination of the airframe fuel supply and vent systems revealed extensive heat damage. The fuel selector valve was not located. Examination of the engine, which sustained heavy fire damage, revealed crankshaft, camshaft, and valvetrain continuity. Thumb suction and compression were noted at each cylinder. Borescope inspection of each cylinder revealed no discrepancies to the cylinder walls, piston, intake, or exhaust valve faces. Although the engine and its systems sustained impact and heat damage, there was no evidence of preimpact failure or malfunction of the ignition, air induction, exhaust, and lubricating systems, as well as the engine-driven fuel pump, flow divider, fuel servo, and fuel injector lines. A slight amount of water expelled from the No. 4 fuel injector line during examination of it. Based on the circumstances of the accident and the postcrash firefighting efforts, the water was not tested to determine the source. Visual examination of each two-piece fuel injector nozzle revealed a clean/soot demarcation line along the length of the threads at the end where the fuel injector line attached. None of the fuel injector nozzles