ANC12FA066

The noninstrument-rated pilot's decision to continue visual flight into instrument meteorological conditions likely leading to spatial disorientation, which resulted in a loss of airplane control and in-flight structural failure.

The noninstrument-rated pilot and one passenger were flying as part of a group of three airplanes on a sightseeing tour. The accident airplane and one of the other airplanes in the group encountered deteriorating weather and made an unplanned stop at an airport along their route of flight. After receiving fuel and updated enroute weather, both pilots decided to depart for their original destination. During the second attempt to fly to the destination airport, the two airplanes again encountered deteriorating weather conditions. The pilot of the accident airplane decided to maintain visual flight rules, and the pilot of the other airplane requested an instrument flight rules clearance to the destination airport. A short time later, the pilot of the accident airplane contacted air traffic control and stated that he was having difficulty maintaining visual conditions and subsequently requested an instrument clearance. The pilot reported climbing through 6,800 feet for 7,000 feet, then no further communications were received. The wreckage was located on a brush- and tundra-covered hillside; the left wing had separated from the airplane inflight, followed by the separation of other airplane components before impact. Given the reported weather, the pilot's lack of an instrument rating, his request for an instrument clearance, the wreckage path, and the lack of any mechanical anomalies, it is likely that the pilot encountered instrument meteorological conditions and became spatially disoriented while attempting to climb to a higher altitude. It is also likely that the pilot then lost control of the airplane, and entered a steep spiraling dive from which he was unable to recover. During the dive, the aerodynamic forces increased to the point that the left wing separated from the airplane, which tightened the spiral, and led to the in-flight structural failure of other sections of the airplane.

At 1408, the pilot contacted the Fairbanks Flight Service Station (FFS), and stated that he and one other pilot in his group were unable to make it to Fairbanks due to weather, and they were landing at the Fort Yukon Airport. The pilot received an updated weather briefing, and informed the FSS that they would file another flight plan if they were able to depart for Fairbanks. Radio recordings from the Anchorage Air Route Traffic Control Center (ARTCC) revealed that at 15:58:03, the pilot contacted Anchorage ARTCC stating that he had just departed Ft. Yukon, direct to Fairbanks and was "squawking 1155." At 13:58:51, ARTCC radar identified the airplane 10 miles south of the Ft. Yukon VOR. The pilot requested 5,000 feet as a final altitude, and ARTCC instructed the pilot to maintain VFR, and expect advisories. At 16:05:28, the ARTCC controller switches with another controller, and during the handoff he states that, "weather is IFR." At 16:14:48, ARTCC advises the pilot that if voice is lost, change to frequency 120.9 in 10 minutes, and the pilot confirms. At 16:25:45 ARTCC advised that radar contact was lost. At 16:26:35 ARTCC advised the pilot that the Fairbanks altimeter setting was 29.96 inHg. At 16:30:48, another aircraft relays to ARTCC that there are two aircraft trying to contact Fairbanks approach control. The relaying airplane says that one airplane is heading north. At 16:33:02 the accident airplane relays that he is "out in the open now, good VFR flying." At 16:37:05, the pilot relayed through another aircraft that he was requesting an IFR clearance to Fairbanks, and that his altitude was 2,800 feet with "reasonable VFR," but at 16:37:50, when asked if he could maintain his own terrain and obstruction clearance to 8,000 feet, the pilot said he could not maintain VFR to 8,000 feet and that he had "good VFR coming up," so he declined the IFR clearance and said he would remain VFR. At 16:38:04, the pilot of the other airplane in the group contacted ARTCC and requested an IFR clearance to Fairbanks. At 16:39:56, ATRCC asked the pilot if he was still in contact with N432LT, and the pilot responded that he was not in contact with him. At 16:41:00, ARTCC regained radar and voice contact with the accident airplane, and the pilot stated that he was "through 4,300 [feet]." At 16:41:29 the pilot stated to the controller that he required "IFR assistance." At 16:41:45, the pilot was issued an IFR clearance and was instructed to climb to 7,000 feet. AT 16:43:18 ARTCC requested that the pilot report reaching 7,000 feet, and the pilot responded stating that he was climbing through 6,800 feet for 7,000 feet. At 1643:28, ARTCC requested the airplane's equipment suffix, and the response of "Golf, Lima Tango" was given by the pilot of the accompanying airplane. No further communications were received. Radar contact with the airplane was lost at 16:44:55. A postmortem examination was conducted under the authority of the Alaska State Medical Examiner, Anchorage, Alaska, on July 20, 2012. The cause of death for the pilot was attributed to blunt force and thermal injuries. The FAA's Civil Aeromedical Institute performed toxicological examinations for the pilot on September 28, 2012, which was negative for alcohol and drugs. The toxicological examination revealed 10 mg/dl of Ethanol was detected in the muscle, which was attributed to sources other than ingestion. The wreckage was examined at the hangar of Alaska Claims Services, Wasilla, AK, on August 15, 2012. In attendance for the examination was the NTSB IIC, and investigators from Piper Aircraft Company. Control Continuity The rudder cables were attached at the rudder pedals, and at the control surface. The horizontal stabilator cables were attached at the cockpit and control surface. The aileron cables were attached at the cockpit controls and attached to the bell cranks in both wings. Horizontal Stabilator The left and right sections of the horizontal stabilator failed under positive loads. The signatures were consistent with the stabilator twisting as it separated from the empennage. The trim jack screw showed 16 threads, which corresponds to full nose up trim. The stop bolts appeared normal. Vertical Stabilizer The vertical stabilizer separated from the empennage at the rear attach bracket. The rudder remained attached at the top hinge. The rudder horn assembly remained attached, and both arms were bent. The stop bolts appeared normal. Left Wing The left wing separated from the airplane at the wing root under positive load. The left aileron separated during the accident sequence, although signatures on the control stops did not indicate a flutter event. The left aileron separated and tore at the outboard hinge point. The outboard 16 inches of aileron were not located. The aileron push rod fractured in overload. There was wing buckling on the top and bottom of the wing, 5 feet inboard of the tip. The loads appeared positive on the stringers on the top of the wing, and negative on the stringers on the bottom of the wing. Right Wing The inboard section of the right wing was severely damaged from postcrash fire. The aileron was still attached. The right flap separated at impact. The spar had positive load signatures, and a slight "S" bend in the spar, consistent with the wing "unloading" after the separation of the left wing. Engine/Fuel Selector There was extensive thermal damage to the engine. The bottom of the engine case was melted. The engine crankshaft appeared intact. The fuel selector valve was found, but thermal damage prevented the determination of its position at the time of the accident. Fuselage The fuselage had extensive thermal damage. No cockpit switch positions could be determined. Propeller The propeller remained attached to the engine. One blade was fractured at the shank, just outboard of the hub. The tip was broken off. There was leading edge gouging, slight "S" bending, and chordwise scratches. The other two blades remained in the hub, and both were bent slightly aft. The spinner was crushed upward and aft from the hub of the fractured blade. Fuel The fuel system consists of two interconnected tanks in each wing, having a combined capacity of 53.5 U.S. gallons per wing, for a total capacity of 107 U.S. gallons, of which 102 gallons are useable. Fuel consumption calculations completed by the NTSB IIC showed that approximate total fuel burn for the flight from Inuvik to Fairbanks was estimated at 46 gallons. Given that the airplane was properly fueled in Inuvik, the airplane would have had sufficient fuel to accomplish the flight. The left wing fuel tank cap was not located with the airplane wreckage, and was later found on the ramp at Fort Yukon. On-scene examination of the left wing revealed no evidence fuel siphoning, fuel staining, or leaking from the open left fuel tank filler port. A National Transportation Safety Board (NTSB) meteorologist did a comprehensive study of the weather conditions along the airplane's route of flight. The synoptic or large scale migratory weather systems influencing the area were documented using standard National Weather Service (NWS) charts issued by the National Center for Environmental Prediction (NCEP) located in Camp Springs, Maryland. These are the base products used in describing weather features and in the creation of forecasts and warnings. Reference to these charts can be found in the joint NWS and Federal Aviation Administration (FAA) Advisory Circular "Aviation Weather Services", AC 00-45. The NWS Surface Analysis Chart for 1600 ADT July 18, 2012 (0000Z on July 19, 2012) depicted a low pressure system at 1007-hectopascals (hPa) over the Gulf of Alaska with an associated occluded frontal system and a secondary trough of low pressure extending into southern Alaska over the Kenai Peninsula to the south of the accident site. Over northwe