Accident Details
On July 10, 2011, about 1315 Alaska daylight time, a float-equipped Cessna U206 airplane, registration N2186F, and a Piper PA-31-350 airplane, registration N76RA, collided in midair over Lake Clark Pass, approximately 37 miles northeast of Port Alsworth, Alaska. The Cessna was operated as a VFR personal cross-country flight under 14 CFR Part 91, departing Lake Hood Seaplane Base in Anchorage about 1300 en route to Brooks Camp, Alaska. A VFR flight plan was active. The Piper was operated by Lake Clark Air as a VFR passenger cross-country flight under 14 CFR Part 135, departing Kokhanok, Alaska, about 1254 with company flight following procedures in effect, en route to Anchorage via Lake Clark Pass. None of the four occupants in the Cessna or nine in the Piper were injured.
Location and Conditions
Lake Clark Pass is primarily a river valley between mountains. At the collision point, the valley floor is about half a mile wide at an elevation of approximately 1,000 feet above sea level, with mountain peaks exceeding 5,000 feet on both sides. Visual meteorological conditions prevailed.
Pilot Accounts
Both pilots reported to the NTSB investigator-in-charge that they did not see the opposing airplane until moments before impact, and neither took evasive action. The Cessna pilot stated he was westbound on the north side of the pass at 2,300 feet msl when he saw a tail pass under his left front and heard a loud thump. He transmitted on the CTAF, assessed his airplane, and performed right-hand turns searching for the other aircraft before returning to Lake Hood. He noted that the other airplane could have avoided the collision by staying to the right side of the pass. He reported giving position reports on and listening to the CTAF frequency recommended in the FAA's Alaska Supplement but heard no radio traffic from the Piper.
The Piper pilot said he was eastbound when he spotted the floatplane 200-300 feet away but lacked time to avoid it. He felt the top of his tail strike the floats and continued to Merrill Field, Anchorage, landing without incident. He contacted dispatch by radio and reported the collision. During an interview, the pilot stated he had been listening to XM Satellite Radio, not the CTAF frequency.
Examination Findings
Examination by the NTSB revealed that the Piper's vertical stabilizer top impacted the Cessna's forward float spreader bar, and the Cessna's left float inside chine sliced through the Piper's vertical stabilizer and rudder about 18 inches from the top. The rudder remained attached and functional. The Cessna sustained minor damage to its left float; after landing at Lake Hood, the left float began taking on water, and the pilot beached the airplane to prevent sinking. The Piper received substantial damage to its vertical stabilizer and rudder.
GPS tracking data from the Cessna was overlaid on a topographical map, showing its westbound entry and track along the north side of the pass. The approximate collision point was determined by the pilot's right-hand turns after the collision.
Radio and Lighting
The FAA's Alaska Supplement includes a graphic representation of Lake Clark Pass with a CTAF of 122.9 MHz. Generally accepted "rules of the road" advise flying on the right side of passes, rivers, and waterways, as reflected in FAA agreements and publications. Both publications also recommend using aircraft anti-collision lights when possible. The Cessna was equipped with a forward-facing landing/taxi light, tail and wingtip strobes; its pilot stated the strobes were on but could not recall if the landing light was operating. The Piper had no forward-facing lights; its landing light retracts with the nose wheel.
Recommendations from the Pilots
In written reports to the NTSB, the Cessna pilot recommended: (1) transiting aircraft stay to the right of center in confined airspace; (2) adhere to hemispheric altitude rules even below 3,000 feet agl; (3) use anti-collision lighting; (4) announce on and listen to CTAF; (5) add CTAF frequencies to sectional charts. The Piper pilot recommended: (1) add and always use anti-collision lighting; (2) have the FAA publish reporting points and frequencies in high traffic areas.