WPR17LA148

A partial loss of engine power for reasons that could not be determined due to a lack of available evidence.

The private pilot, who was the builder and owner of the experimental, single-engine airplane, reported that the purpose of the flight was to assess recent changes to the propeller pitch and wing incidence angles. The engine started normally, and after some minor engine temperature anomalies, the pilot conducted a normal takeoff and climb. The pilot leveled off temporarily at 2,500 ft, then increased the engine rpm to climb to a higher altitude. He noted that the engine "did not feel as if it were operating smoothly" and switched the fuel selector from the left tank to the right tank. As the airplane was climbing through about 5,980 ft, he felt a loss of power, and the engine speed decreased to about 1,450 rpm. Throttle manipulation did not result in any rpm changes, so the pilot leveled off and initiated a turn toward the nearest airport. After determining that he would be unable to reach the airport, he began searching for a suitable off-airport landing site. He slowed to the airplane's best glide speed and verified that the ignition switch was properly set but did not conduct any other checks or restart attempts after the rpm further decreased and the engine lost power. The pilot initially set up for one landing location, but the airplane was traveling too fast, so he selected a second location, where he was able to land the airplane. The airplane sustained substantial damage when the landing gear collapsed, and the propeller struck the rough terrain. Postaccident examination of the airframe and engine did not reveal any evidence of preimpact mechanical malfunctions or failures that would have precluded normal operation. Because the pilot had previous problems with the engine-driven fuel pump, that pump and the carburetor were removed for testing on an exemplar engine of a test airplane, both of which were the same make and model as the accident engine and airplane. Although the accident airplane installation included an aftermarket mixture control device, that device was not installed on the test airplane because the pilot reported that he did not use that device during the accident flight. The test engine performed normally through its entire power range with the accident fuel pump, but at high power settings, it ran more roughly with the accident carburetor installed. An airplane and engine representative reported that this was likely due to the accident carburetor being improperly jetted for the application on the test engine/airplane. However, despite the roughness, the test personnel reported that, at all times, the test engine performance (and therefore that of the accident fuel pump and carburetor) was within the normal performance specifications. The test results indicated that the loss of engine power that the pilot experienced was not due to any mechanical malfunction of the engine-driven fuel pump or the carburetor. The pilot did not use carburetor heat, and weather conditions were conducive to the formation of carburetor ice at glide and cruise power. The power loss could have been due to carburetor icing, but there was insufficient evidence to make that determination. The pilot stated that the engine power loss might have been the result of his improper positioning of the fuel selector valve during his attempt to address the engine problem. However, because neither the in-flight nor postaccident position of the fuel selector was documented, that scenario could not be confirmed as the cause of the engine power loss.

The 0753 automated weather observation at DVT, located about 17 miles south of the accident site, included variable winds at 3 knots, visibility 10 miles, clear skies, temperature 32o C, dew point 14o C, and an altimeter setting of 29.91 inches of mercury. The pilot held private and sport pilot certificates, with an instrument airplane rating. He had approximately 1,201 total hours of flight experience, including approximately 60 hours in the accident airplane make and model. His most recent flight review was completed in November 2016. At the time of the accident the pilot was operating the airplane under the medical provisions of his sport pilot certificate. The airplane was a 2-place low-wing monoplane constructed primarily of composite materials. Each wing was equipped with an integral fuel tank, each with a pilot-reported capacity of 20 gallons. According to pilot, he had purchased the airframe as a kit, and completed assembly of the airplane, including engine installation, at a dedicated build center near Phoenix in 2016. The pilot reported that the airplane and engine had accumulated about 63 hours total time (TT) in service at the time of the accident. The pilot reported that he had about 60 hours TT in the airplane. According to pilot, he had purchased a brand new, pre-assembled Jabiru model 3300A series engine. The engine was a 6 cylinder, horizontally opposed, normally aspirated, air-cooled engine, with a rated output of 120 hp. The pilot reported that in January 2017, when the airplane had a TT of about 33 hours, due to a rough-running engine, he replaced the engine-driven fuel pump that was found to be internally damaged. The damage was the result of the fuel pump actuation pushrod being about 2mm too long. The engine was purchased from Jabiru USA, with the fuel pump installed. Although the pilot queried Jabiru USA as to why the original pushrod was too long, he never received an explanation. The airplane came to rest upright in moderately flat area of desert terrain, about 17 miles north of DVT. Both wings remained attached, and sustained minor damage, primarily at their tips. The engine remained attached to its mount, and the mount to the firewall, but several of the engine mount tubes were bent, buckled, or fractured. The 2-blade composite propeller remained attached to the engine, and both blades were fracture-separated from the hub. The left fixed main landing gear remained intact, but the right strut was partially displaced, and wheel and tire assembly was liberated from the strut. The nose gear assembly and mount was crumpled, and folded aft and up. There was no indication of any fire or thermal damage to the airframe or engine. The FAA inspector who responded to the accident site reported that the two fuel tanks were not breached, and confirmed the presence of significant fuel in each tank. While at the accident site, the left and right seat bottoms were removed to access some fuel lines and the two transparent, in-line fuel filters (one per tank). Each tank was plumbed to an in-line filter in the fuselage, and both filters were observed to contain fuel. The inspector reported that the fuel in the tanks and filters was clean. The carburetor bowl was removed and contained very little (estimated ½ oz) fuel. The airframe and engine were examined in detail at the recovery facility. No evidence of any pre-impact mechanical failures was observed. Refer to the public docket for detailed documentation of the examination results. On July 10, 2017, about 0745 mountain standard time, an experimental light sport Arion Lightning airplane, N273DB, was substantially damaged in a forced off-airport landing near New River, Arizona. The private pilot was uninjured. The airplane was registered to and operated by the pilot as a Title 14 Code of Federal Regulations Part 91 personal flight. Visual meteorological conditions prevailed and no flight plan was filed. The local flight originated from Glendale Municipal Airport (GEU) Glendale, Arizona at 0730. The pilot was also the builder of the airplane and reported that he had changed the propeller pitch and right wing incidence on July 7, and the purpose of the flight was to assess those changes. The pilot fueled the airplane to a total quantity of about 30 gallons. The engine started normally, and after the engine temperatures reached appropriate values, the pilot conducted an engine runup before beginning his taxi out. That runup was normal. The pilot then taxied to runway 1, where he conducted a second runup, which again was normal. While awaiting takeoff clearance, the pilot noticed that the cylinder head temperature (CHT) on the No. 3 cylinder was higher than both normal and the other five cylinders, but still well below its maximum limit. When the airplane began its takeoff roll, the No. 3 cylinder CHT began decreasing, and aligned with the other CHT values during the climbout. The pilot reported that he conducted the climbout with an engine speed of 2,660 rpm, and leveled off temporarily at 2,500 ft. Shortly thereafter, the pilot increased the rpm to 2,800 for a climb to a higher altitude. He noticed that the engine "did not feel as if it were operating smoothly," and switched the fuel selector from the left tank to the right tank. As the airplane was passing through 5,980 ft, he felt a loss of power, and the rpm decreased to 1,450. An instrument scan indicated that the engine was still running, but manipulation of the throttle did not result in any rpm changes. The pilot leveled off and began a right turn back to the southwest, towards Deer Valley Airport (DVT) Deer Valley, Arizona. He unsuccessfully attempted to contact DVT air traffic control tower, changed his transponder code to 7700, and began searching for a suitable landing site. He also slowed to the airplane's best glide speed, and verified that the ignition switch was set to the 'BOTH' position. The pilot initially set up for a landing on a plateau, and during his turn from base to final, the engine rpm decreased to about 1,000. The airplane was going too fast to land on the plateau, so the pilot selected a new landing site just beyond the plateau. He added full flaps, turned off the fuel, and landed on undulating desert terrain. The landing gear collapsed, the propeller struck the ground, and the airplane slid to a stop. The pilot shut off all the switches, except for the emergency locator transmitter (ELT), which had activated. He exited the airplane, called his wife and then the owner of the local facility that he used to build the airplane, in order to begin the airplane recovery process. A local resident drove up to provide assistance. He and the pilot collected some debris, and then the pilot called the DVT manager to notify him of the accident, who then contacted the Federal Aviation Administration (FAA) and National Transportation Safety Board (NTSB). Several first responder ground vehicles, and then a Phoenix Police helicopter arrived, and during the discussions, the pilot was asked to shut off the ELT, which he did. The airplane was recovered later that day to a secure facility for future examination. About 25 gallons of fuel were obtained from the airplane fuel tanks during the recovery process. Fuel System Information The airplane fuel system was examined in detail, and several differences between the manufacturer's configuration guidance and the actual airplane were observed. No lines, fittings, or components of the fuel system exhibited any indications of fuel leakage, but the system was not able to be tested for integrity. According to the Jabiru Installation Manual (IM), "The fuel tank must be fitted with an outlet strainer of between 8 and 16 mesh per inch, with a minimum total mesh area of 5 cm2. Ensure the fuel tank is properly vented." The pilot reported that a mesh fuel screen was installed in each tank outlet. The FAA inspector did not observe any fuel screens in the fuel tanks. The