History of Flight
On August 6, 2015, about 2350 Alaska daylight time, a tailwheel-equipped Piper PA-18-150 airplane, N3675P, sustained substantial damage during impact with the ocean waters of Knik Arm, about 4 miles northwest of Chugiak, Alaska. The private pilot and sole passenger were fatally injured. The airplane was operated by the pilot as a visual flight rules (VFR) cross-country personal flight under 14 CFR Part 91. Visual meteorological conditions prevailed, and no flight plan was filed. The flight departed McGrath Airport, McGrath, Alaska, at 2111, en route to Birchwood Airport, Chugiak.
According to family members, the pilot resided in McGrath, and the purpose of the flight was to attend a family function in Anchorage. At 2354, a distress call was received by the Alaska State Troopers from the pilot reporting that he had crashed in Knik Arm, was too far to swim, and requested immediate rescue. At 0003, the 11th Air Force's Rescue Coordination Center diverted two C-17 Globemaster airplanes to search. By 0016, they were on scene. Search personnel included Alaska State Troopers, Civil Air Patrol, U.S. Coast Guard, and volunteers.
On August 7, about 0610, the Alaska Air National Guard located the wreckage about 1.8 miles northwest of Birchwood Airport. The airplane was inverted and mostly submerged, with the bottom of the fuselage, wing strut attach points, landing gear, and a portion of the propeller above water. No survivors were found.
Personnel Information
The pilot, age 29, held a private pilot certificate with an airplane single engine land rating. His most recent third-class medical certificate was issued on June 13, 2015, with no limitations. No personal logbooks were located. According to family members, he had accumulated about 360 total flight hours and had recently completed an emergency maneuvers training course.
Aircraft Information
The airplane was a Piper PA18-150, manufactured in 1955, equipped with a Lycoming O-320 series engine. The tachometer at the time of the accident displayed 995.08 hours. The last annual inspection was completed on January 16, 2015, at which time the tachometer read 897.58 hours and total time in service was 4473.58 hours.
Meteorological Information
The closest weather reporting facility was Birchwood Airport, about 2 miles southeast of the accident site. At 2336, a METAR reported wind from 120 degrees at 3 knots, clear sky, visibility 10 statute miles, temperature 63°F, dew point 52°F, altimeter 29.85 inHg.
Wreckage and Impact Information
On August 8, 2015, recovery crews recovered the wreckage from the ocean floor and transported it to Birchwood Airport. The wreckage had been subject to several tide cycles, partially filling it with organic material. During extraction, the airframe could not support the additional weight. Both wings fractured at the forward spar attach points and folded aft. The fuselage fractured about 3 feet forward of the horizontal stabilizer and remained attached by control cables. The carburetor heat control was found in the "off" or "cold" position.
Visual examination of the engine revealed no evidence of pre-impact catastrophic mechanical malfunction or fire. Both propeller blades remained attached; there was no conclusive evidence of rotational energy absorption at impact. All primary flight control surfaces remained connected, and control continuity was verified. The fuel selector valve was found in an intermediate position between the right fuel tank and off; it could not be determined if this was pre-impact or due to evacuation. The trim jackscrew indicated a slight nose-down trim. Left and right wing fuel tanks, gascolator bowl, and carburetor bowl contained a fluid consistent with salt water and fuel, all emitting an odor of automotive gasoline. No evidence of mechanical malfunctions or failures that would have precluded normal operation was found.
Additional Information
A Garmin 196 handheld GPS was mounted on the instrument panel. The NTSB Vehicle Recorders Laboratory extracted data including time, latitude, longitude, and GPS altitude. At 2340, the airplane climbed from 1156 feet msl; at 2345, it reached a peak of 1549 feet msl and began descending. Over the next 2:08, it descended 317 feet at about 176 feet per minute. At 2347, the rate of descent increased to a peak vertical velocity of about 947 feet per minute, averaging about 890 feet per minute until the last data point at 2349 when the airplane was 29 feet msl. During the final 1:17, the heading changed from east-southeast to south-southeasterly toward the nearest land.
When the temperature and dew point were entered into a carburetor icing probability chart, the result was in the "moderate icing – cruise power or serious icing – glide power" category.
Communications
A postaccident review of FAA radio communications showed that at 2109, the pilot reported taxiing for departure from McGrath Airport. At 2111, he reported taking off from runway 16. No further radio communications were received.
Medical and Pathological Information
The pilot's remains have not been located; no pathological or toxicology information exists. At his last medical examination, no concerns were reported. On August 29, the passenger's remains were recovered from the shore of Cook Inlet. A postmortem examination attributed the cause of death to drowning. No lifejacket or other personal flotation device was found with the passenger.
Survival Aspects
At 2354, the pilot called Alaska State Troopers, stating he was standing on top of his airplane. Air assets were on scene searching at 0016 but, due to rising tide, did not locate the airplane until about 0610 on August 7. When recovered, no occupants were present. The area consisted of fast-moving salt water with glacier-fed rivers, turbidity reducing visibility to less than 1 foot, and strong tidal currents. Water temperature at 2354 was 61.3°F. The airplane was equipped with an ACK Technologies E-04 406MHz ELT, but the Alaska Rescue Coordination Center never received a signal. ELTs are not certified for operation during or after submersion.
Tests and Research
On August 13, 2015, an engine examination by Lycoming Engines found no anomalies or evidence of malfunction in accessories. Internal components showed no anomaly except for a worn camshaft lobe for cylinders 3 and 4. The lobe was worn at the lifting area, with burnished edges and spalled surface on the tappet face.