Port Alsworth, AK, USA
N2186F
CESSNA U206
N76RA
PIPER PA-31-350
Two airplanes, a Cessna and a Piper, collided midair in a mountain pass while traveling in opposite directions. The pass is a river valley, about 1/2-mile wide, with the floor about 1,000 feet mean sea level (msl), between mountains in excess of 5,000 feet msl. Neither pilot saw the other airplane in time to take evasive action. Both airplanes landed safely after the collision. The airplanes were operating in visual flight rules meteorological conditions, in uncontrolled airspace at about 2,300 feet msl, without any air traffic control services. The westbound Cessna sustained minor damage to its left float and the eastbound Piper sustained substantial damage to its vertical stabilizer and rudder. The Cessna pilot reported that he was monitoring the common traffic advisory frequency (CTAF) for the pass and making position reports. He saw the opposing airplane pass under his left front and heard a loud “thump.” The Cessna was equipped with wingtip- and tail-mounted strobe anticollision lights, which were operating at the time of collision. The Piper pilot reported that when he spotted the Cessna floatplane he did not have time to take evasive action. He was not monitoring the CTAF, and the airplane he was flying had no anticollision wingtip strobes or any forward-facing lights. A local Federal Aviation Administration publication contains a graphic representation of the pass, and includes remote communications outlets, weather cameras, reference points, and a CTAF for the pass.
On July 10, 2011, about 1315 Alaska daylight time, a float-equipped Cessna U206 airplane, N2186F, and a Piper PA-31-350 airplane, N76RA, collided midair in Lake Clark pass, about 37 miles northeast of Port Alsworth, Alaska. None of the occupants in either airplane, four in the Cessna and nine in the Piper, were injured. The Cessna was operated by the airline transport certificated pilot as a visual flight rules (VFR) personal cross-country flight under the provisions of 14 Code of Federal Regulations (CFR), Part 91, and was flying west en route to Brooks Camp, Alaska. It departed Lake Hood seaplane (PALH), Anchorage, Alaska, about 1300. A visual flight rules flight plan was in effect. The Piper was operated by Lake Clark Air, Port Alsworth, Alaska, and flown by an airline transport certificated pilot as a VFR passenger cross-country flight under the provisions of 14 CFR Part 135. The flight departed Kokhanok, Alaska, about 1254, and company flight following procedures were in effect. The airplane was flying east to Anchorage via Lake Clark Pass. The Cessna sustained minor damage to its left float, and the Piper received substantial damage to its vertical stabilizer and rudder. Visual meteorological conditions prevailed in Lake Clark Pass at the time of the accident. Lake Clark Pass is predominately a river valley between mountains. Near the point of collision, the floor of the valley is approximately one-half mile wide, and the elevation is approximately 1,000 feet above sea level. The valley has mountain peaks on both the north and south sides exceeding 5,000 feet in elevation. During separate conversations with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), both pilots said they did not see the opposing airplane until moments before the collision. Neither pilot took evasive action. The Piper continued to Merrill Field (MRI), Anchorage, and landed without incident. The Cessna returned to the Lake Hood Seaplane base, Anchorage, and landed. After landing, the pilot said the left float began taking on water, and he beached the airplane to keep it from sinking. An examination of both airplanes by the NTSB IIC revealed that the top of the vertical stabilizer of the Piper impacted the forward float spreader bar of the Cessna, and the left float inside chine of the Cessna sliced through the vertical stabilizer and rudder of the Piper, about 18 inches from the top. The rudder remained attached and functional. In a written report to the NTSB dated July 13, the pilot of the Cessna reported that he was westbound in Lake Clark Pass, at an altitude of 2300 feet above sea level (msl), and on the north side of the pass. He saw the tail of an airplane pass under his left front and heard a very loud thump. He transmitted a message to any aircraft in the area on the common traffic advisory frequency (CTAF), and assessed the condition of his airplane. After determining that his airplane was flyable, he did several right-hand turns flying east and west in the pass searching for the other airplane. Unable to locate the other airplane, or make contact with any other airplane, he returned to the departure airport to report the collision. The pilot of the Cessna reported that had the other airplane stayed to the right side of the pass/river, the collision could have been avoided. He further reported that he was giving position reports on, and listening to the CTAF frequency recommended in the FAA's Alaska Supplement. He did not hear any radio traffic from the second airplane. In a written statement to the NTSB dated July 20, the pilot of the Piper reported that he was eastbound in Lake Clark Pass when he spotted a floatplane going the opposite direction about 200-300 feet away, He said he did not have time to take evasive action, and that the top of the tail of his airplane struck the floats of the other airplane. Since his airplane continued to fly normally after the collision, he continued to his destination. He contacted his dispatch via radio, reported the collision, and requested an aircraft be dispatched to look for the other airplane. During an interview with the NTSB IIC, the pilot of the Piper said he had been listening to XM Satellite Radio, and not the CTAF frequency. Global positioning system (GPS) tracking data was obtained from a GPS unit operating on board the Cessna, and the data track was overlaid onto a topographical map. The track showed the airplane's westbound entry into the pass, and its track along the north side of the pass. The approximate collision point was determined by the right-hand turns made by the pilot following the collision. The Alaska Supplement, published by the FAA, contains a graphic representation of Lake Clark Pass. The information in the publication includes remote communications outlets, weather cameras, reference points, and a CTAF of 122.9 MHz. Although not a regulation, generally accepted "rules of the road" are, if possible, fly up the right side of a pass/canyon/waterway in anticipation of other aircraft flying in the opposite direction. The following language is contained in the FAA's Juneau (Alaska) Commercial Operators Letter of Agreement, dated May 1, 2007, and mirrors the generally accepted rules of the road; Except where noted in a Specific Area Procedure, or when confronted with weather, traffic or other conflicts, normal traffic will fly on the right side of rivers, valleys, mountain passes, shorelines, or waterways. Similar language is also used in the Denali National Park and Preserve, Aviation Information brochure, dated 2009. Both publications further suggest the use of aircraft anti-collision lights when possible. The Cessna was equipped with a forward facing landing/taxi light, and tail and wingtip strobes. The Cessna pilot said the strobes were turned on, but he did not recall if the landing light was operating at the time of the accident. The Piper was designed with no forward facing lights, anti-collision or otherwise. The landing light is retracted with the nose wheel. Recommendations from the Pilots In their written reports to the NTSB, in the section "Recommendation (How could this accident/incident have been prevented?") both pilots made suggestions on how to avoid a midair collision. The pilot of the Cessna made five recommendations, paraphrased here for brevity: (1) When possible, aircraft transiting confined airspace should remain to the right of center in the confined airspace (2) When possible, adhere to hemispheric altitude rules, even below 3,000 feet above ground level; (3)Use anti-collision lighting systems; (4) Announce on and listen to CTAF; (5) CTAF frequencies should be added to sectional charts. The pilot of the Piper airplane made two recommendations: (1) Add anti-collision lighting to the airplane and use it all the time; (2) Have the FAA publish reporting points and frequencies in high traffic areas.
The pilot’s failure to see and avoid the approaching airplane, which did not have any forward-facing lights.
Source: NTSB Aviation Accident Database
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