Overview
On January 31, 2015, about 1305 Alaska standard time, a wheel/ski-equipped Piper PA-18 airplane, registration N82735, and a ski-equipped Piper PA-18 airplane, registration N78NR, collided midair near South Hollywood Airport, approximately 5 miles southwest of Wasilla, Alaska. N82735 was operated by the State of Alaska Department of Public Safety, Alaska State Troopers, as a VFR cross-country public-use flight. N78NR was operated by its pilot as a VFR cross-country flight. Both pilots, the sole occupants, sustained serious injuries. After the collision, both aircraft descended uncontrolled into densely populated birch and spruce trees and sustained substantial damage. Visual meteorological conditions prevailed.
Flight History
N82735 departed Wasilla Airport about 1300 bound for Beluga, Alaska, with company flight following procedures in effect. N78NR departed Birchwood Airport, Chugiak, Alaska, about 1250 destined for an off-airport landing site near Johnson Creek with no flight plan on file. Witnesses reported observing one PA-18 traveling southwesterly and the other northwesterly. One witness observed the airplanes converge at approximately a 90-degree angle; neither airplane changed altitude or direction as they approached, and they subsequently collided.
The pilot of N82735 stated that after departure he climbed to approximately 1,500 to 2,000 feet MSL and configured for cruise. While in level cruise on a southwesterly heading, with the sun at his 1130 to 1200 o'clock position, he saw a momentary flash in the upper left corner of his windscreen, instantly followed by the collision. After the collision, his airplane entered an uncontrollable dive with no elevator control; he pushed the control stick forward and regained limited elevator authority, but the airplane continued descending nose-low into the trees.
Aircraft Information
N82735 was a Piper PA-18-150, manufactured in 1977, equipped with a Lycoming O-320 series engine. Its colors were white with red accent lines, red wings, and a red propeller spinner. At its last annual inspection on October 14, 2014, it had 7,851 hours in service.
N78NR was a Piper PA-18-150, manufactured in 1956, equipped with a Lycoming O-320 series engine. Its colors were white with red accent lines, white wings, and a red propeller spinner. No airplane or engine logbooks were found.
Personnel Information
The pilot of N82735, age 35, held a commercial pilot certificate with ratings for airplane single-engine land, single-engine sea, and instrument airplane. His most recent second-class medical certificate was issued on September 4, 2014, with the limitation that he must wear corrective lenses. He had logged about 543 hours of flight experience at the time of the accident.
The pilot of N78NR, age 52, held a commercial pilot certificate with an airplane single-engine land rating, with the limitation restricting carriage of passengers for hire on cross-country flights over 50 nautical miles or at night. His most recent third-class medical certificate was issued on March 7, 2013, with the limitation that he must wear corrective lenses. On his last medical application, he indicated total aeronautical experience of about 1,400 hours.
Meteorological Information
The closest weather reporting facility was Wasilla Airport, about 5 miles northeast. At 1256, the METAR reported: wind 250 at 4 knots; visibility 10 statute miles; sky clear; temperature 12°F; dew point 1°F; altimeter 30.37 inHg.
Communications
Both airplanes' transceivers were recovered and tested. N82735 had a primary active frequency of 122.80 MHz and a non-active secondary of 135.25 MHz. N78NR had a primary active frequency of 122.80 MHz and a non-active secondary of 123.00 MHz. The CTAF for the area was 122.80 MHz. Both airplanes were operating in Class G airspace, with no regulatory requirement for two-way radio communications.
Wreckage and Impact
N82735 came to rest on its left side at about 335 feet MSL, nose on a 225° heading. The cockpit was extensively damaged; the throttle was near closed, mixture full rich, carburetor heat off. The left wing separated near its attach points and was found intertwined with N78NR's right wing. The right wing was severed and inverted. No mechanical malfunctions were found.
N78NR came to rest inverted at about 355 feet MSL, nose on a 240° heading. The right wing separated and fragmented; the outboard section was intertwined with N82735's left wing. The tail separated just forward of the vertical stabilizer. Control continuity could not be established due to fractures, all consistent with tension overload. No mechanical malfunctions were found.
Medical and Pathological Information
Toxicology tests for the pilot of N82735 were negative for alcohol and drugs. For the pilot of N78NR, tests were negative for ethanol but revealed etomidate in serum and ketamine in blood. Etomidate is a short-acting intravenous anesthetic used by first responders for induction of general anesthesia and sedation. Ketamine is an anesthetic used as a dissociative sedative in emergency medicine.
Survival Aspects
The pilot of N82735 used a 4-point safety harness, which remained secure and was cut by first responders. He wore a Kevlar protective vest and a David Clark Series K10 helmet; pieces of the fractured helmet were found. An Artex ME406 ELT was installed and transmitting upon first responders' arrival. N78NR was equipped with a 4-point safety harness; it is unknown if it was in use. A 121.5 MHz ELT activated on impact. Both ELTs did not aid search and rescue due to rapid witness response.
Tests and Research
A Garmin GPS 176 from N78NR provided data for the accident flight. The airplane departed Birchwood at about 1250, proceeded northeast then northwest around Knik Arm. Just prior to the collision, it climbed to a GPS altitude of 1,648 feet and was continuing northwest at 90 knots groundspeed. No abrupt course or altitude change was observed.
Examination of strobe lights from N82735 could not determine if they were illuminated. Landing, taxi, and left navigation lights from N78NR showed no clear indication of filament stretch or contact.