History of Flight
On May 17, 2008, about 1645 Pacific daylight time, a de Havilland DHC-2 MK I amphibious airplane, N9558Q, nosed over following a wheels-down landing on the waters of Lake Chelan, near Stehekin, Washington. The airplane sustained substantial damage. The airline transport pilot and two passengers received minor injuries, and the other two passengers were killed. The airplane was registered to, and being operated by, Lake Chelan Air Service, Inc., doing business as Chelan Airways. Visual meteorological conditions prevailed for the on-demand air taxi flight conducted under 14 Code of Federal Regulations Part 135. A company flight plan was filed for the flight that departed Lake Chelan Airport about 1615, with an intended destination of Stehekin.
The pilot reported performing a quick preflight and loading passengers' bags. He gave a safety briefing before boarding, but noted it was briefer than normal as the passengers had flown with him many times. He taxied to runway 20, performed an engine run-up, set flaps and trim, and announced departure on the CTAF. After a normal takeoff, he reduced throttle, propeller rpm, and raised flaps. He does not remember raising the landing gear. During the flight, the gear advisory warning activated multiple times in turbulent air; each time he canceled it before the aural warning completed. He eventually pulled the Gear Advisory circuit breaker to prevent the nuisance warnings, intending to reset it during descent, but does not recall doing so. The pilot noted that the airplane never accelerated beyond 95 mph, which he attributed to the warm day and load. He planned a landing to the north-northeast toward Stehekin Resort on flat glassy water. He slowed, adjusted mixture and propeller, lowered flaps halfway between cruise and takeoff, and set up a 150–200 ft/min rate of descent. Then water entered the cockpit. Witnesses observed a normal approach, but upon water contact, the airplane abruptly nosed over and came to rest inverted, suspended by the floats, with landing gear wheels protruding.
Personnel Information
The pilot, age 62, held an airline transport pilot certificate with airplane multiengine land rating, commercial privileges in single-engine land and sea airplanes, and a CE-500 type rating. He also held flight engineer and flight instructor certificates. His most recent second-class medical certificate was issued October 30, 2007, with a limitation for near vision. He reported 5,747 total flight hours, including 637 hours in the accident make and model. He had flown 69 hours in the previous 90 days and 30 hours in the previous 30 days, all in the accident airplane. On March 17, 2008, he passed an Airman Competency/Proficiency Check in the accident airplane. The accident date was his second consecutive duty day; his duty day began at 0900 and the accident flight was his third of the day. He had worked each day from May 1 to 14 with daily duty times of 10 hours (11 on May 12), and flight times ranging from 1.0 to 4.0 hours. He had a day off on May 15, then worked a 10-hour duty day on May 16. The pilot stated the accident was his nineteenth consecutive duty day, including office and flight duty, and felt the lack of days off was a contributing factor. He stated that using a checklist consistently would have prevented the accident; he did not use a written checklist on the accident flight.
Aircraft Information
The single-engine, high-wing, amphibious float-equipped airplane was manufactured in 1957, powered by a Pratt and Whitney R-985 radial engine with a three-bladed Hartzell constant-speed propeller. The most recent annual inspection was completed March 14, 2008, at a tachometer time of 411.8 hours and airframe total time of 12,069.9 hours. The engine had 411.8 hours since major overhaul. Tachometer time at the accident site was 479.36 hours. The airplane was equipped with Wipline 6100 amphibious floats; each float contained a main and nose landing gear, hydraulically actuated by two electric hydraulic pumps. Gear position was selected by a cockpit handle; blue lights indicated gear retracted, green lights extended, and red lights indicated pumps running (gear in transit). A Lake and Air Amphibian Landing Gear Position Advisory System provided visual (amber "GEAR ADVISORY" light) and aural advisories (e.g., "GEAR IS UP FOR WATER LANDING") when airspeed crossed a threshold. The system could be disabled by pulling the "Gear Adv" circuit breaker.
Meteorological Information
The pilot reported clear skies, visibility greater than 10 miles, calm winds, and an OAT of 92°F on the ground at Chelan Airport. The OAT at 2,000 feet was 90°F.
Wreckage and Impact Information
Examination revealed the airplane intact except for the missing engine cowling. The left wing was bent downwards about 30 degrees; the right wing bent about 20 degrees. Flaps were partially extended. The empennage was undamaged, and control surfaces were attached. The fuselage roof above the two forward seats was crushed and bent downwards; front windshields were fractured and mostly separated. The floats were attached except for the aft right fitting; no punctures or damage. Landing gear wheels were down and locked; the gear selector handle was in the down position. Water rudders were down. Flight control continuity was established. The flap indicator showed flaps between takeoff and cruise climb settings. The "Gear Adv" and "Yaw" circuit breakers were popped.
Tests and Research
A gear retraction/extension test on April 20, 2008, using a replacement battery, showed all gear retracted when the handle was placed UP (except right nose gear due to impact damage) and extended and locked when DOWN. The air data computer from the gear advisory system had a threshold setting corresponding to 75 knots; testing gave proper warnings at approximately 73 knots.
Survival Aspects
Water temperature at the accident site was measured at 47°F on July 18, 2008. The airplane had seven seats in three rows. The pilot occupied the left front; a male passenger the right front. Two female passengers occupied left and right middle row seats; the center middle seat was empty. A female passenger occupied the left rear seat; a box of plants was on the right rear seat. The pilot, right middle seat passenger, and left rear seat passenger survived; the right front and left middle seat passengers were killed. Seat belts and PFDs were found in various states. The pilot reported being disoriented after the nose-over; he released his belt, surfaced through the broken windshield, and attempted to assist passengers. Rescuers arrived within minutes. One trapped passenger had her seat belt cut by a rescuer about 15–20 minutes after the accident; the other passenger was recovered from the cabin. CPR was initiated but both were pronounced dead at the hospital.
Probable Cause
Not stated in the source.