Provincetown, MA, USA
N6249C
PIPER PA-28-181
The non-instrument-rated pilot of the single-engine airplane was departing on a dark night from an airport located at the tip of a peninsula. Analysis of global positioning system data showed that the pilot initiated a takeoff from the runway and prior to reaching an altitude of 100 feet, he began turning the airplane on course to the destination airport. After crossing over the left boundary of the runway and with the airplane oriented toward a non-lighted area of the landmass and water below, the airplane ceased climbing and impacted trees about 900 feet beyond the left boundary of the runway. The wreckage path orientation and length were consistent with a shallow, powered descent, and signatures observed on the wreckage were consistent with a relatively level impact attitude. Examination of the wreckage revealed no evidence of any preimpact mechanical failures or malfunctions of the airframe or engine. Toxicological analysis detected elevated levels of ethanol in postmortem samples of the pilot’s blood, urine, and brain tissue, the distribution of which was consistent with ingestion. The levels of ethanol present in the pilot’s samples were present in levels known to degrade psychomotor performance. Toxicological testing also detected an inactive metabolite of cocaine in postmortem samples of the pilot’s urine, but not in samples of blood. This was a likely indication that the pilot had used cocaine, but neither the drug nor its metabolite was active at the time of the accident. The circumstances of the accident are consistent with the pilot experiencing a form of spatial disorientation known as the somatogravic illusion, in which a pilot misperceives acceleration cues as increasing pitch and makes corrective nose-down inputs. These circumstances include the accelerating phase of flight during takeoff, the dark night lighting conditions associated with an early turn on course, and a non-instrument-rated pilot whose judgment and psychomotor performance were degraded by alcohol consumption. The airplane subsequently impacted the trees and terrain below in a shallow, un-arrested descent.
HISTORY OF FLIGHT On August 31, 2011, about 2240 eastern daylight time, a Piper PA-28-181, N6249C, was destroyed when it impacted trees and terrain shortly after departure from Provincetown Municipal Airport (PVC), Provincetown, Massachusetts. The certificated private pilot was fatally injured and the passenger was seriously injured. Dark night visual meteorological conditions prevailed, and no flight plan was filed for the flight, which was presumed to be destined for Falmouth Airpark (5B6), Falmouth, Massachusetts. The personal flight was operated under the provisions of Title 14 Code of Federal Regulations Part 91. Several flight crew members of a U.S. Coast Guard helicopter witnessed the accident and recounted a similar series of events during separate telephone interviews. According to the flight crew, they were returning from a mission when, while passing PVC, they heard a faint radio transmission from an aircraft “departing to the west.” Even though the radio was tuned to the common traffic advisory frequency at PVC, they were uncertain if the transmission originated from PVC as another nearby airport utilized the same radio frequency. The crew subsequently announced that they were about 3 miles northwest of the airport, and shortly thereafter observed an alert on the traffic collision avoidance system (TCAS). The TCAS target's altitude was not reported, but shortly thereafter one pilot of the crew observed the accident airplane on runway 25 at PVC. The other pilot visually acquired the accident airplane as it was taking off from runway 25. He initially saw the airplane at the mid-point of the runway, and noted that the airplane's strobe lights were operating. He looked inside the helicopter, and next saw the accident airplane in a left turn, which it had initiated prior to reaching the departure end of the runway. Due to his night vision goggles, he could not distinguish the airplane’s altitude as it flew over trees located on the south side of the runway. He further recalled that one moment he could see the airplane, and then it was gone. Shortly after, he observed smoke and flames on the ground, and then realized that the airplane had crashed. The flight crew subsequently contacted local first responders through their operations base, assisted them in locating the accident site, and assisted in extricating the passenger from the scene. PERSONNEL INFORMATION According to records maintained by the Federal Aviation Administration (FAA), the pilot held a private pilot certificate with a rating for airplane single engine land, and did not hold an instrument rating. The pilot’s most recent third-class medical certificate was issued on November 22, 2002, at which time he reported 340 total hours of flight experience. None of the pilot’s personal flight records or log books could be located. AIRCRAFT INFORMATION According to FAA airworthiness and registration records, the airplane was manufactured in 1978 and registered to the pilot in 1999. No airframe, engine, or propeller maintenance logs could be located. An aircraft maintenance provider located in Plymouth, Massachusetts provided an invoice for maintenance and an annual inspection performed on the accident airplane and billed to the pilot on July 21, 2010. The invoice indicated that on that date, the airplane had accumulated 1,630 total hours of operation. Review of fueling records at 5B6, where the accident airplane was based, showed that the pilot serviced the airplane with 8 gallons of 100LL aviation fuel on August 30, 2011 at 1615. METEOROLOGICAL INFORMATION The weather conditions reported at PVC, at 2235, included clear skies, 10 statute miles visibility, calm winds, a temperature of 16 degrees Celsius (C), a dewpoint of 13 degrees C, and an altimeter setting of 30.21 inches of mercury. According to sun and moon data provided by the U.S. Naval Observatory, sunset occurred at 1917 and the end of civil twilight occurred at 1945. The moon (waxing crescent with 9-percent of the visible disk illuminated) had set at 2021. AIRPORT INFORMATION The Provincetown Municipal Airport was comprised of a single runway that was 3,502 feet long by 100 feet wide, and was oriented in a 07/25 configuration. The airport was located on the northwestern tip of the Cape Cod Peninsula, and was surrounded by the Cape Cod Bay to the south and west. The closest populated landmasses to the south and west were located between 15 and 20 nautical miles from the airport. WRECKAGE AND IMPACT INFORMATION The accident site was located about 860 feet southeast of the runway 7 displaced threshold at PVC. Several freshly broken tree branches, at a height of about 25 feet above the ground, identified the initial impact point. The wreckage path continued on a 190-degree magnetic heading, and was roughly 125 feet long. Numerous freshly cut tree branches, which varied in diameter from 1 to 3 inches, displayed approximate 45-degree-angle cuts and black paint transfer. All major portions of the airframe were accounted for at the scene. The right wing was located about 60 feet from the initial impact point, and had separated from the fuselage at its root. A concave depression, oriented roughly perpendicular to the chord line of the wing, was located about 12 inches outboard of the left wing fuel tank. The fuel tank remained intact, and was filled to roughly 3/4 of its total capacity with fuel that displayed a color and odor consistent with 100LL aviation fuel. The rudder remained attached to the upper portion of the vertical stabilizer and was separated from the remainder of the empennage. The rudder and vertical stabilizer were located near the right wing, while the remainder of the empennage was entangled with a tree about 15 feet forward, along the wreckage path. The empennage displayed significant fire damage. The stabilator trim jack screw was extended to a position that correlated roughly to a neutral trim tab deflection. The right wing was located about 20 feet forward of the empennage. The wing displayed a large concave depression, about 12 inches in diameter, about 18 inches inboard of the wing tip. The right wing fuel tank was significantly impact-and fire-damaged. The fuselage came to rest inverted, adjacent to and separated from the right wing, and was oriented roughly in the direction of the wreckage path. The cockpit and cabin areas were destroyed by impact forces and post-impact fire. Control continuity was traced from the cockpit controls to all primary flight control surfaces through cable separations that exhibited signatures consistent with overload. The flap actuator was observed in the 10-degree position. The fuel selector valve was recovered, but its internal components were melted. The engine displayed varying degrees of impact and post-impact fire-related damage. The propeller spinner was absent and not recovered. The propeller blades were bent aft at roughly half their span, and displayed chord-wise scratching and small nicks in the blade leading edges. One blade displayed 2 small gouges on the trailing edge; the opposite blade displayed slight inward curling at its tip. The starter bendix was engaged to the starter ring, however the engine crankshaft was free to rotate. The valve covers and top spark plugs were removed, and the crankshaft was rotated by hand at the propeller. Valvetrain and drivetrain continuity were confirmed from the propeller to the vacuum pump drive pad. Thumb compression was obtained on all cylinders. The removed spark plugs’ electrodes exhibited normal wear, and were light-to-dark gray in color. The carburetor was removed from the engine and disassembled. The carburetor bowl was absent of fuel and the floats were intact. The solder attaching the floats to their respective arms was melted. The engine oil filter was cut open, and the paper filter element was charred and disintegrated. The oil suction screen was removed and was absent of debris. A small quantity of oil drained from the suction screen attachment. The engine-driven fuel pump and both magnetos displayed extensive fire damage, and could not be removed from the engine. The vacuum pump was removed and its rotor and vanes were intact, while the plastic drive coupling was melted and absent. The engine exhaust baffling was intact. The electric fuel boost pump was disassembled, and its internal filter was disintegrated. MEDICAL AND PATHOLOGICAL INFORMATION An autopsy was performed on the pilot by the Commonwealth of Massachusetts, Office of the Chief Medical Examiner. The cause of death listed was “blunt trauma.” Toxicological testing performed by the University of Massachusetts Medical Center was positive for the presence of ethanol in blood, urine, and vitreous humor. The FAA's Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma, performed toxicological testing on the pilot. Ethanol was detected in samples of urine, blood, and brain tissue in quantities of 81, 76, and 61 milligrams/deciliter (mg/dl). Methanol was also detected in samples of brain tissue in a quantity of 5 mg/dl. Ecgonine Methyl Ester was detected in samples of urine, but not in samples of blood. ADDITIONAL INFORMATION Global Positioning System (GPS) Device Data A Garmin GPSMAP 296 portable GPS device was recovered from the wreckage and forwarded to the NTSB Vehicle Recorders Laboratory. After applying power to the device, the startup was consistent with normal operation and data was downloaded. The data extracted included 24 total flight tracks, spanning a recorded flight time of nearly eight hours. The date and time stamps associated with 22 of the 24 records appeared to be inaccurate, indicating flights on dates between 1991 and 1992; however, the relative timing and position information of the final recorded flight strongly correlated with the known facts of the accident flight. The track data associated with the accident flight began in the vicinity of the parking ramp at PVC. The track then moved toward the approach end of runway 25, and taxied onto the runway. About 1.5 minutes after the track recording began, the track accelerated down runway 25. Two additional track points were recorded at a relatively constant GPS altitude, accelerating to a calculated groundspeed of 55 knots, covering a distance of about 900 feet. The next track point was recorded at a GPS altitude of 52 feet, a calculated groundspeed of 72 knots, and about 1,600 feet from where the track began the presumed takeoff. The next track point was recorded about 2,400 feet down the runway, and about 200 feet south of the runway extended centerline. The recorded GPS altitude was 112 feet and the calculated groundspeed was 72 knots. Another track point was recorded 4 seconds later, at a GPS altitude of 115 feet and a calculated groundspeed of 88 knots, about 500 feet south of the runway centerline and near the departure end of the runway. The initial impact point was located about 550 feet southwest of the final recorded track point, on a magnetic bearing of 220 degrees. Analysis of the track data showed that for the final ten seconds, and between the four final recorded track points, the track turned about 30 degrees left to the southwest, away from the previously established heading down the runway. A course line from the initial recorded position for the accident flight to 5B6 was superimposed onto a map. The resulting image showed that after becoming airborne, the track appeared to turn left directly toward the superimposed course line. The track data also recorded a flight that departed from PVC and terminated at 5B6 about 27 hours prior to the accident flight. Examination of the track data from that flight showed a departure from runway 25, with a left turn to the previously projected course line shortly after liftoff, but several seconds after and about 100 feet higher than the left turn initiated during the accident flight. Spatial Disorientation According to Spatial Disorientation in Aviation (F.H. Previc and W.R. Ercoline), the otoliths (tiny organs of the inner ear), sense the acceleration of gravity and the acceleration associated with translational motions. Because the otoliths cannot distinguish between these two types of acceleration, they can only sense a combination of these two forces, the gravitoinertial force (GIF) vector. During coordinated, unaccelerated flight, the GIF vector is directed straight down through the pilot’s seat. When an airplane accelerates rapidly, however, the GIF vector is displaced aft, causing a false sensation of pitching up. This misperception, known as the somatogravic illusion, is normally dispelled when the pilot views the external horizon and/or the flight instruments. If no external horizon is visible and the flight instruments are not continuously monitored or are not correctly interpreted, the somatogravic illusion can persist, leading to an inaccurate understanding of airplane orientation and direction of motion known as spatial disorientation, a condition that can lead to inappropriate pilot control inputs. Spatial disorientation illusions are described extensively in FAA pilot training literature. For example, the 2012 Aeronautical Information Manual states, “A rapid acceleration during takeoff can create the illusion of being in a nose up attitude.” Similarly, the FAA Instrument Flying Handbook states, “A rapid acceleration, such as experienced during takeoff, stimulates the otolith organs in the same way as tilting the head backwards. This action creates the somatogravic illusion of being in a nose-up attitude, especially in situations without good visual references.” The Manual and the Handbook warn that, “The disoriented pilot may push the aircraft into a nose-low or dive attitude.” Identical information is included in the FAA’s Pilot Handbook of Aeronautical Knowledge. This particular illusion is so well recognized that information about it is included in the FAA’s private pilot, instrument rating, and airline transport pilot knowledge test guides; and the FAA practical test standards for private pilots. According to FAA Advisory Circular AC 60-4A, “Pilot's Spatial Disorientation,” tests conducted with qualified instrument pilots indicated that it can take as long as 35 seconds to establish full control by instruments after a loss of visual reference of the earth's surface. AC 60-4A further states that surface references and the natural horizon may become obscured even though visibility may be above VFR minimums, and that an inability to perceive the natural horizon or surface references is common during flights over water, at night, in sparsely populated areas, and in low-visibility conditions.
The pilot’s failure to maintain adequate clearance from trees and terrain during the initial climb. Contributing was spatial disorientation due to a vestibular illusion and the pilot’s likely impairment due to alcohol consumption.
Source: NTSB Aviation Accident Database
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