Washington

The single engine airplane departed Renton Airport with four people on board, apparently on a pre-delivery check flight. In unknown circumstances, it went out of control and crashed in a prairie located near Snohomish, bursting into flames. The aircraft was totally destroyed and all four occupants were killed. It is believed that the airplane suffered a wing failure in flight.

On approach, the crew apparently encountered technical problems with the landing gear that could not be lowered. The airplane landed on its belly on runway 03L and slid for few hundred metres before coming to rest, bursting into flames. All 10 occupants evacuated safely and the aircraft was destroyed by a post crash fire.

On September 4, 2022, about 1509 Pacific daylight time, a float-equipped de Havilland DHC-3 (Otter), N725TH, was destroyed when it impacted the water in Mutiny Bay, near Freeland, Washington, and sank. The pilot and nine passengers were fatally injured. The airplane was owned by Northwest Seaplanes, Inc., and operated as a Title 14 Code of Federal Regulations (CFR) Part 135 scheduled passenger flight by West Isle Air dba Friday Harbor Seaplanes. The flight originated at Friday Harbor Seaplane Base (W33), Friday Harbor, Washington, with an intended destination of Will Rogers Wiley Post Memorial Seaplane Base (W36), Renton, Washington. Visual meteorological conditions prevailed at the time of the accident. The accident pilot was scheduled to fly the accident airplane on three multiple leg roundtrips on the day of the accident. The first roundtrip flight was uneventful; it departed from W36 about 0930, made four stops, and returned about 1215. The accident occurred during the pilot’s second trip of the day. A review of recorded automatic dependent surveillance–broadcast (ADS-B) data revealed that the second roundtrip departed 36 about 1253 and arrived at Lopez Seaplane Base, (W81), Lopez Island, Washington, about 1328.2 The data showed that the flight then departed W81 and landed at Roche Harbor Seaplane Base (W39) about 1356. The airplane departed W39 about 1432, arrived at W33 about 1438, and departed about 1450. According to ADS-B data, after the airplane departed W33, it flew a southerly heading before turning south-southeast. The en route altitude was between 600 and 1,000 ft above mean sea level (msl), and the groundspeed was between 115 and 135 knots. At 1508:40, the altitude was 1,000 ft msl, and the groundspeed had decreased to 111 knots. Based on performance calculations, at 1508:43, the airplane pitched up about 8° and then abruptly pitched down about 58°. The data ended at 1508:51, when the airplane’s altitude was 600 ft msl and the estimated descent rate was more than 9,500 ft per minute (the flightpath of the airplane is depicted in figure. Witnesses near the accident site reported, and security camera video confirmed, the airplane was in level flight before it entered a slight climb and then pitched down. One witness described the descent as “near vertical” and estimated the airplane was in an 85° nose-down attitude before impact with the water. Several witnesses described the airplane as “spinning,” “rotating,” or “spiraling” during portions of the steep descent. One witness reported hearing the engine/propeller and noted that he did not hear any “pitch change” in the sounds. The airplane continued in a nose-low, near-vertical descent until it impacted water in Mutiny Bay.

On August 10, 2018, about 2043 Pacific daylight time, a De Havilland DHC-8-402, N449QX, was destroyed when it impacted trees on Ketron Island, near Steilacoom, WA. The noncertificated pilot was fatally injured. The airplane was registered to Horizon Air Industries, Inc,. and was being operated by the noncertificated pilot as an unauthorized flight. Visual meteorological conditions prevailed in the area at the time of the event, and no flight plan was filed. The airplane departed from the Seattle-Tacoma International Airport, Seattle, Washington, about 1932. Horizon Air personnel reported that the noncertificated pilot was employed as a ground service agent and had access to the airplanes on the ramp. The investigation of this event is being conducted under the jurisdiction of the Federal Bureau of Investigation (FBI). The NTSB provided requested technical assistance to the FBI, and any material generated by the NTSB is under the control of the FBI. The NTSB does not plan to issue an investigative report or open a public docket.

The pilot reported that, during the preflight, it was snowing, and he wiped the snow that had accumulated on the wings off "as best as [he] could." He added that, while taxiing to the runway, "snow was falling heavily," and he observed "light accumulation of wet snow" on the wings. During the takeoff roll, he observed the snow "sloughing off" the wings as the airspeed increased. Subsequently, during the climb to about 150 ft above the ground, the airplane yawed to the left, and he attempted to recover using right aileron. He reported that he "could see a stall forming," so he lowered the nose and reduced power to idle. The airplane impacted the general aviation ramp in a left-wing-down attitude and slid 500 to 600 ft. The pilot reported on the National Transportation Safety Board Aircraft Accident/ Incident Report 6120.1 form that the airplane stalled, and he recommended "better deicing" before takeoff. The airplane sustained substantial damage to the fuselage and left wing. The pilot reported that there were no preaccident mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation. A review of recorded data from the automated weather observation station located on the airport revealed that, about 27 minutes before the accident, the wind was 010° at 8 knots, 1/2-mile visibility, moderate snow, freezing fog, and sky condition broken at 500 ft above ground level (agl) and overcast at 1,500 ft agl. The airplane departed from runway 16. The Federal Aviation Administration (FAA) Aeronautical Information Manual stated, in part: "The presence of aircraft airframe icing during takeoff, typically caused by improper or no deicing of the aircraft being accomplished prior to flight has contributed to many recent accidents in turbine aircraft." The manual further stated, "Ensure that your aircraft's lift-generating surfaces are COMPLETELY free of contamination before flight through a tactile (hands on) check of the critical surfaces when feasible. Even when otherwise permitted, operators should avoid smooth or polished frost on lift-generating surfaces as an acceptable preflight condition." FAA Advisory Circular, AC 135-17, stated in part: "Test data indicate that ice, snow, or frost formations having thickness and surface roughness similar to medium or course sandpaper on the leading edge and upper surfaces of a wing can reduce wing lift by as much as 30 percent and increase drag by 40 percent." Included in the public docket for this report is a copy of a service bulletin from the airplane manufacturer, which describes deicing and anti-icing ground procedures. It stated, in part: During conditions conducive to aeroplane icing during ground operations, take-off shall not be attempted when ice, snow, slush or frost is present or adhering to the wings, propellers, control surfaces, engine inlets or other critical surfaces. This is known as the "Clean Aircraft Concept". Any deposit of ice, snow or frost on the external surfaces may drastically affect its performance due to reduced aerodynamic lift and increased drag resulting from the disturbed airflow.

While maneuvering at low altitude for a water landing, the commercial pilot of the float equipped airplane encountered low visibility due to ground fog. The pilot initiated a go-around, but the airplane impacted the water, bounced, and impacted the water a second time before coming to rest upright. The airplane subsequently sank, and all four occupants were later rescued. The pilot reported that there were no mechanical anomalies with the airplane that would have precluded normal operation. The operator further reported that other company pilots who were flying on the day of the accident stated that the low visibility conditions were easily avoided by a slight course deviation.