Kekaha, HI, USA
N98EV
EVOLUTION TRIKES REVO
The instructor was taking the student on an introductory instructional flight in a special light-sport weight-shift-control aircraft (trike). After departure, the instructor maneuvered the trike over the ocean and along the coast at an altitude of about 1,000 ft above ground level. About 20 minutes into the flight, the trike descended into terrain, impacted in a near vertical attitude, and was consumed by fire. Although the pilot was in radio communication with another trike, he did not report that he was having any difficulties. The pilot had recently experienced a problem with the trike's fuel system: during a previous flight, fuel was streaming out of the vent line due to suction created by its position in the airstream. Although the airframe manufacturer explained that this can be normal, the pilot decided to reposition the vent line. Before the accident flight, the pilot had re-routed the clear plastic vent line so that it ran up the mast and aft along the keel (inside the keel pocket) and then bent 180-degrees upward and around to face into the airstream. The severe impact and fire damage to the trike precluded determination of the events that led to the departure from controlled flight. However, the rerouted vent line may have become constricted due to the rerouted configuration, either by the tie wraps securing it to the keel or by the keel tube riding tightly against the keel pocket in flight. Such a constriction would lead to the fuel system becoming fully depressurized and the engine experiencing a loss of power due to fuel starvation. It is likely that the pilot became distracted by the loss of power and subsequently lost control of the trike.
HISTORY OF FLIGHTOn March 11, 2014, about 0910 Hawaiian standard time, a special light-sport Revo Evolution Trikes weight-shift-control aircraft (trike), N98EV, impacted terrain and was consumed by fire near Kekaha, Hawaii. Birds in Paradise, LLC, owned by the accident pilot, was operating the trike under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The certified light sport instructor and student pilot sustained fatal injuries; the trike was destroyed. Visual meteorological conditions prevailed, and no flight plan was filed for the instructional flight. The trike departed Port Allen Airport, Hanapepe, Hawaii, about 0850, and the introductory flight was intended to take 60 minutes before returning to the airport. A second Birds in Paradise certified flight instructor (CFI) was giving instruction in another trike while flying in close proximity with the accident trike. He stated that about 0615 that morning he met up with the accident pilot at the company's facilities. They wheeled the trikes over to the staging area and greeted their student pilots shortly thereafter. After fitting the students with flight suits and helmets, the pilots gave them a briefing and departed around 0850. After departure, the accident pilot told the second pilot that he was going "on company," meaning that they would communicate to one another on the company frequency, 123.450; this was the last transmission the CFI heard from the accident pilot. Approaching the Barking Sands class D airspace, the second pilot transmitted over the company frequency that he was switching to the Barking Sands frequency to receive a clearance from the control tower, to transition through their airspace as a flight of two. As the CFI's trike was approaching the northwest side of Polihale Beach, he descended to about 600 feet above ground level (agl) and observed the accident trike about 1,000 feet agl and 75 feet away horizontally at his 1-o'clock position; that was the last time he saw the accident trike flying around 0910. The CFI and his student performed two near-360 degree turns over the ocean and attempted to contact the accident pilot over the radio. They noticed smoke on the base of the ridgeline and maneuvered over to the area. The accident trike was engulfed in flames. PERSONNEL INFORMATIONA review of Federal Aviation Administration (FAA) airman records revealed that the 54 year-old-pilot held a certified flight instructor sport-pilot certificate. The pilot's partner reported that he had amassed 19,000 flight hours and was renowned in the trike community. The pilot never had a medical certificate and was not required to have a medical certificate to be a Sport Pilot or a Sport Flight Instructor pilot. He held a light-sport repairman certificate. The pilot's partner reported that the pilot had flown four flights on March 8, 2014, totaling 5.5 hours of flight time. On March 10, the day before the accident, the pilot awoke early and made several flights before coming back home at 1600. The pilot received his normal 7-8 hours of sleep and arrived at the flight school about 0600. Customers would usually arrive about 0645, with the first flight starting at 0700. The flights were either 60 or 90 minutes long and would always be conducted as a tandem flight for a safety precaution, with both pilots staying in radio communication with one another. AIRCRAFT INFORMATIONThe trike was a special light sport (SLSA) weight-shift-control Evolution Trikes, Revo, serial number 000551, and equipped with a Rotax, 912ULS, serial number 6775546. A review of the trike's maintenance logbooks revealed that the last airframe conditional inspection was dated December 19, 2013, with an airframe total time of 1,427 hours. The last engine conditional inspection was dated January 03, 2014, with an engine total time of 1,442 hours. The same trike and pilot were involved in an accident in April 2010 (NTSB number WPR10CA224) where a loss of engine power resulted from fuel exhaustion due to the pilot's improper decision to continue the flight after the low fuel warning. The trike had 24 hours of total flight time when the accident occurred and was rebuilt shortly thereafter. Recent History The pilot had recently experienced problems with the trike's fuel system. He reported to the second pilot that during flight, he had noticed that fuel was being suctioned out of the main vent line located in the belly of the aircraft. On a recent flight, the pilot landed in Princeville, Kauai, to assess the problem and refuel. He determined that the fuel was streaming out of the vent line because of suction created due to its position in the airstream. This flight occurred about one month prior to the accident equating to about 25 flights and it is unknown when this began because the vent line position was not changed according to records. The accident pilot spoke with a representative from Evolution Trikes about a week prior to the accident expressing concern with fuel being syphoned out of the trike during flight. He stated that the fuel level was diminishing quickly and another pilot could see fuel streaming out. The representative told him that it was likely due to the fuel heating inside the tank due to the nature of its position adjacent to the radiator and exhaust. He explained to the pilot that the fuel will expand as it gets warmer which could result in about a half-gallon streaming out of the vent line. The pilot explained that he had re-run the vent line up the mast, and it was still leaking fuel even with the vent being higher than the tank. The representative stated that all of the fuel vent lines on the company's REVOs showed signs of fuel leakage. On the morning of the accident, the second pilot noticed as he was taking his trike out of the hangar, that the accident pilot was on a ladder routing compressed air into the accident-trike's fuel vent line. The second pilot commented to the accident pilot that the fuel cap was still affixed on the tank and removed it for him, which produced a "pop" sound as the compressed air escaped the system. The pilot had re-routed the clear plastic vent line so it was affixed up the mast, then routed aft along the keel (inside the keel pocket) and bent 180-degrees upward and around facing into the airstream (secured to the left side of the keel tube). The accident flight was the first flight with the fuel line in this position. A picture of the trike taken just prior to the accident departure revealed that the vent line was in this configuration for the flight; the clear vent line tubing can be seen bent 180-degrees forward and affixed to the keel tube with two tie-wraps and black tape. The pictures can be seen in the public docket for this accident. Fuel System The fuel system was designed with a single saddle-style aluminum fuel tank with a capacity of 14.5 gallons. There was a brass T-fitting threaded into the side of the tank about 2 inches in front of a large filler hose that led to the gas cap on the side of the aircraft. The two lower saddles of the tank were coupled utilizing a T-fitting and as series of 90-degree elbows. As originally installed, the vent tube went from the tee up about 4 inches over the filler tube and then made a 3 foot run out of the bottom of the aircraft. The mechanical fuel pump was located above the fuel tank, which, according to the airframe manufacturer, made it susceptible to vapor lock if there was low pressure (vacuum) in the tank. There was an electric fuel pump mounted below the fuel level, but it would not be able to force fuel to the engine if the vent line was plugged. According to the airframe manufacturer, although the vent line is at the top of the tank, filling up the tank to maximum capacity would result in the vent tube filling even with the fuel level lower in the filler tube. Since there are only a couple of inches of vent tube above the fuel level, when the aircraft makes a steep climb, the fuel would likely spill over the high point and then begin to draw a siphon until all of the fuel above the T-fitting was streamed out of the vent tube. The airframe manufacturer further stated that if compressed air was put into the fuel vent tube it would pressurize the fuel system. The pressure would further be exacerbated from expansion of the fuel by heating. The fuel tank, a thin-walled 5051 aluminum welded square-shaped tank, was pressure tested to 3 PSI. The airframe manufacturer further stated that while in flight, the keel tube rides tightly against the keel pocket, and he opined that pressure could have easily pinched off the vent line tubing. He stated that, if the vent line tubing was blocked (pinched off), the engine would operate for about 15 minutes before fuel starvation would occur due to a vacuum in the fuel tank. According to a representative from the engine manufacturer, if the fuel vent line was blocked, the fuel tank could pressurize with the fuel from the return line, which would be compounded by the electric boost pump and likely over pressurize the float bowl of the carburetor. He stated that there would be no way a fuel tank could become pressurized unless the fuel tank venting system was either blocked or nonexistent and something was simultaneously pressurizing the fuel tank over the suction value of what the engine fuel pump would produce. METEOROLOGICAL INFORMATIONThe closest aviation weather observation station was located at Barking Sands Pacific Missile Range Facility Airport, Kekaha, Kauai, about 2 nm south from the accident site. That facility issued an automated surface weather observation at 0856 (about 15 minutes prior to the accident) reporting the following: the wind was calm; 10 miles or greater visibility; sky conditions clear, temperature 21 degrees Celsius; dew point 19 degrees Celsius; and an altimeter setting of 30.05 inches of mercury. AIRPORT INFORMATIONThe trike was a special light sport (SLSA) weight-shift-control Evolution Trikes, Revo, serial number 000551, and equipped with a Rotax, 912ULS, serial number 6775546. A review of the trike's maintenance logbooks revealed that the last airframe conditional inspection was dated December 19, 2013, with an airframe total time of 1,427 hours. The last engine conditional inspection was dated January 03, 2014, with an engine total time of 1,442 hours. The same trike and pilot were involved in an accident in April 2010 (NTSB number WPR10CA224) where a loss of engine power resulted from fuel exhaustion due to the pilot's improper decision to continue the flight after the low fuel warning. The trike had 24 hours of total flight time when the accident occurred and was rebuilt shortly thereafter. Recent History The pilot had recently experienced problems with the trike's fuel system. He reported to the second pilot that during flight, he had noticed that fuel was being suctioned out of the main vent line located in the belly of the aircraft. On a recent flight, the pilot landed in Princeville, Kauai, to assess the problem and refuel. He determined that the fuel was streaming out of the vent line because of suction created due to its position in the airstream. This flight occurred about one month prior to the accident equating to about 25 flights and it is unknown when this began because the vent line position was not changed according to records. The accident pilot spoke with a representative from Evolution Trikes about a week prior to the accident expressing concern with fuel being syphoned out of the trike during flight. He stated that the fuel level was diminishing quickly and another pilot could see fuel streaming out. The representative told him that it was likely due to the fuel heating inside the tank due to the nature of its position adjacent to the radiator and exhaust. He explained to the pilot that the fuel will expand as it gets warmer which could result in about a half-gallon streaming out of the vent line. The pilot explained that he had re-run the vent line up the mast, and it was still leaking fuel even with the vent being higher than the tank. The representative stated that all of the fuel vent lines on the company's REVOs showed signs of fuel leakage. On the morning of the accident, the second pilot noticed as he was taking his trike out of the hangar, that the accident pilot was on a ladder routing compressed air into the accident-trike's fuel vent line. The second pilot commented to the accident pilot that the fuel cap was still affixed on the tank and removed it for him, which produced a "pop" sound as the compressed air escaped the system. The pilot had re-routed the clear plastic vent line so it was affixed up the mast, then routed aft along the keel (inside the keel pocket) and bent 180-degrees upward and around facing into the airstream (secured to the left side of the keel tube). The accident flight was the first flight with the fuel line in this position. A picture of the trike taken just prior to the accident departure revealed that the vent line was in this configuration for the flight; the clear vent line tubing can be seen bent 180-degrees forward and affixed to the keel tube with two tie-wraps and black tape. The pictures can be seen in the public docket for this accident. Fuel System The fuel system was designed with a single saddle-style aluminum fuel tank with a capacity of 14.5 gallons. There was a brass T-fitting threaded into the side of the tank about 2 inches in front of a large filler hose that led to the gas cap on the side of the aircraft. The two lower saddles of the tank were coupled utilizing a T-fitting and as series of 90-degree elbows. As originally installed, the vent tube went from the tee up about 4 inches over the filler tube and then made a 3 foot run out of the bottom of the aircraft. The mechanical fuel pump was located above the fuel tank, which, according to the airframe manufacturer, made it susceptible to vapor lock if there was low pressure (vacuum) in the tank. There was an electric fuel pump mounted below the fuel level, but it would not be able to force fuel to the engine if the vent line was plugged. According to the airframe manufacturer, although the vent line is at the top of the tank, filling up the tank to maximum capacity would result in the vent tube filling even with the fuel level lower in the filler tube. Since there are only a couple of inches of vent tube above the fuel level, when the aircraft makes a steep climb, the fuel would likely spill over the high point and then begin to draw a siphon until all of the fuel above the T-fitting was streamed out of the vent tube. The airframe manufacturer further stated that if compressed air was put into the fuel vent tube it would pressurize the fuel system. The pressure would further be exacerbated from expansion of the fuel by heating. The fuel tank, a thin-walled 5051 aluminum welded square-shaped tank, was pressure tested to 3 PSI. The airframe manufacturer further stated that while in flight, the keel tube rides tightly against the keel pocket, and he opined that pressure could have easily pinched off the vent line tubing. He stated that, if the vent line tubing was blocked (pinched off), the engine would operate for about 15 minutes before fuel starvation would occur due to a vacuum in the fuel tank. According to a representative from the engine manufacturer, if the fuel vent line was blocked, the fuel tank could pressurize with the fuel from the return line, which would be compounded by the electric boost pump and likely over pressurize the float bowl of the carburetor. He stated that there would be no way a fuel tank could become pressurized unless the fuel tank venting system was either blocked or nonexistent and something was simultaneously pressurizing the fuel tank over the suction value of what the engine fuel pump would produce. ADDITIONAL INFORMATIONData Upon arrival at the NTSB Vehicle Recorder Laboratory, an exterior examination revealed that the GoPro Camera had sustained significant impact damage. The camera's glass element lens was shattered; the battery and memory card were not seated in the appropriate locations. A crack in the memory chip that corresponded to the crack in the card's external plastic casing was discovered. Despite numerous attem
The pilot's reconfiguration of the fuel venting system, which resulted in a loss of engine power and subsequent loss of aircraft control.
Source: NTSB Aviation Accident Database
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