Washington

The pilot and three other crew members were performing flight testing for a new Supplemental Type Certificate (STC) for the single-engine turboprop-powered airplane. After departure, the pilot performed several maneuvers from the test card, then configured the airplane with the flaps extended for an intentional accelerated stall in a 30° left bank with the engine torque set to 930 ft-lb. Analysis of ADS-B data combined with a simulation matching the recorded trajectory of the accident maneuver revealed that, after the stall, the airplane rapidly rolled to the left, reaching a roll angle of 120° while the pitch angle decreased to 60° nose down. The airspeed rapidly increased, exceeding both the maximum flaps-extended speed (Vfe) and the airplane’s maximum operating speed (Vmo). Recorded engine data indicated that, after the stall, the engine torque increased. ADS-B data was lost at an altitude about 7,000 ft above ground level; the final track data indicated an approximate 8,700 ft/min rate of descent. Witnesses observed the airplane break up in flight and subsequently spiral to the ground. The wreckage was found in a rural field distributed over a distance of about 1,800 ft. Analysis of the aerodynamic loads in an overspeed condition showed that the wing design stress limit loads would be exceeded at high speeds with full flaps. The simulation of the stall maneuver indicated that reducing engine power to idle after the nose dropped could have reduced the rate at which the airspeed and associated aerodynamic loads increased, and would have likely given the pilot more time to recover. The airplane was equipped with an Electronic Stability and Protection (ESP) system, which was designed to deter attitude and airspeed exceedances during hand-flying and maintain stable flight by applying an opposite force to the direction of predetermined travel. It was designed to provide a light force that can be overcome by the pilot. To deactivate the ESP, the pilot needed to navigate to a specific page in the primary function display (PFD). Although the accident pilot was an experienced test pilot and qualified to operate the airplane, his experience with the accident airplane’s avionics system could not be determined. Videos of his previous flights in the airplane suggested that he was unfamiliar with the ESP system, as he did not deactivate it before the flight nor discuss the forces it was applying during the flight. Onboard video recording from a test flight the day before the accident indicated that, while performing a turning stall at idle power and 30° of left bank with the wing flaps extended, the airplane rapidly entered a left roll to a maximum of 83° before the pilot recovered to a wingslevel attitude. After recovery, the pilot pitched the airplane’s nose down about 25° in order to “get some airspeed back,” during which the ESP activated the autopilot to effect recovery to a level attitude. The airplane continued to gain airspeed, exceeding the Vmo of 175 knots and reaching 183 knots indicated airspeed, before pilot arrested the airplane’s acceleration and disconnected the autopilot. These two exceedances illustrated shortcomings in the test execution. First, although the 83° roll exceeded the allowable roll limit during this maneuver, the crew failed to identify this exceedance even though they discussed what angle had been reached and had a data acquisition system on board, which they could have consulted to determine the maximum roll angle reached during the maneuver. Correctly identifying the roll exceedance would have resulted in a “failed” test. In accordance with risk mitigation procedures for the test plan, the test buildup should have been stopped after roll limits were exceeded in order to determine the reasons for the exceedance and to implement corrective actions before proceeding with higher-risk conditions in the test plan. Secondly, after exceeding Vmo, the crew did not remark upon the exceedance, and even though the exceedance met the requirements for an overspeed inspection as described in the airplane’s maintenance manual, there was no indication that this inspection was completed. The accident flight simulation indicated that, during the stall immediately preceding the accident, it is likely that the ESP activated as the airplane pitched in excess of 19° nose-up. This would have required the pilot to apply more aft force on the control column in order to induce the stall. After the stall, the ESP would have activated at 45° bank, then deactivated as the airplane quickly exceeded 75°. The extent to which the control forces from the ESP, or the potential distraction due to the system’s engagement and disengagement, may have contributed to the pilot’s failure to recover from the nose-low attitude following the stall could not be determined. FAA guidance warns of the risks associated with upset events during stall maneuvers and advises against performing accelerated stalls with flaps deployed due to the increased risk of exceeding the airplane’s limitations in this configuration. Following a nose-low departure from controlled flight, reducing the power to idle immediately is crucial to avoid exceeding airspeed limitations and overstressing the airplane. The circumstances of the accident flight are consistent with the pilot’s improper recovery from a nose-low attitude following an intentional aerodynamic stall. Whether the increase in torque following the stall was the result of intentional application of power by the pilot could not be determined; however, the pilot’s failure to reduce engine power to idle following the airplane’s departure from controlled flight was contrary to published guidance as well as test flight hazard mitigation procedures. It is likely that this resulted in the airplane’s rapid exceedance of its airspeed limitations, and subsequently, a structural failure and inflight breakup.

After an uneventful flight, a jet airplane on a business flight was landing at its destination. The pilot reported to the tower controller that the airport was in sight and requested to land. The pilot further reported that, while on left base, he started to lower the flaps and extended the gear handle. He did not recall confirming whether the gear was down and locked but reported that there were no landing caution annunciations or aural warnings. Before making contact with the runway, the pilot noticed that the airplane floated longer than expected and upon touchdown realized that the landing gear was not extended. The airplane skidded down the runway and came to a stop just past the departure end of the runway. The pilot secured the engines and assisted the passengers out of the airplane. During the evacuation, the pilot reported that the airplane was on fire near the right engine. Shortly thereafter, the airplane was engulfed in flames. When the airplane was raised for recovery, all three-landing gear were free from their uplocks and dropped down to the extended position. Post accident examination confirmed the main landing gear uplocks were in the gear release (unlocked) position. In addition, the left main landing gear door was also partially extended on the airplane after it came to rest. The landing gear handle was observed in the down (extended) position during the examination. Accounting for the position of the landing gear uplocks, the landing gear door upon landing, and the witnesses’ observation of the airplane not having its landing gear extended, it is likely that the pilot positioned the landing gear handle to the down (extended) position just before or during landing. Nevertheless, the pilot failed to ensure that the landing gear was down and locked before landing. Examination of the landing gear handle and landing gear circuit cards revealed no anomalies. A review of the ADS-B data revealed that the airplane’s airspeed was fast on the approach and landing. The airplane’s ground speed was about 143 knots as it passed over the runway threshold, which was above the airspeed that the landing gear not extended warning system would activate (130 knots). Additionally, the airplane’s flaps were likely configured in the takeoff/approach setting (15°), which would not activate the landing gear not extended warning system. Stabilized approach criteria for airspeed and configuration were not maintained on the approach and landing.

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.