History of Flight
On August 28, 2022, at approximately 1734 central daylight time, a Sea & Sky, Inc., Krucker Cygnet amphibious weight-shift-control aircraft, registration N505DB, sustained substantial damage during an accident near Emily, Minnesota. The flight instructor and a passenger were fatally injured. The aircraft was being operated as a personal flight under Title 14 Code of Federal Regulations Part 91. The purpose of the flight was for the passenger to aerially distribute cremated remains.
The pilot's wife reported that her husband initiated takeoff to the south, and the aircraft did not become airborne at the usual location, but rather became airborne when the flight was abeam a dock near the south end and west edge of the lake. Tall trees, estimated up to 70 ft, bordered the southern end of the lake. She reported hearing a "pop" sound when the aircraft was just above the trees, but did not witness nor perceive the aircraft had crashed.
After the flight did not arrive at its intended destination, the pilot's wife reported the overdue flight to law enforcement. An initial search by a medivac helicopter did not locate the wreckage, which was found later that evening by a homeowner near the accident site.
A Go-Pro camera mounted on the right wing strut, facing the cockpit, captured the flight. Review of the video showed the aircraft became airborne about 16 seconds after initiating takeoff, then slowly gained altitude flying south over the lake. Near the southern edge, the aircraft was not gaining altitude and was just above the trees. The pilot moved the control bar in a counterclockwise direction forward, left, back, and right. The flight crossed the southern edge just above the treetops. While continuing south without gaining altitude, the pilot moved the control bar forward and backward abruptly. The aircraft began to descend and enter a shallow left bank. The left wing clipped the top of a tree, and the aircraft entered a left downward spiral, impacting the tree canopy and the ground.
Personnel Information
The pilot held a private pilot certificate with a rating for airplane single-engine land and a sport endorsement for weight-shift-control aircraft. He also held a flight instructor certificate with a sport rating.
Aircraft Information
The aircraft's empty weight was 626 lbs, and its gross weight was 1,060 lbs. Density altitude at the time of the accident was approximately 2,950 ft. According to the takeoff distance chart, under calm wind conditions at 3,000 ft density altitude, the takeoff distance from water to climb to 50 ft was 1,345 ft. The engine operator's manual specified a takeoff rpm of 5,800 and a maximum continuous rpm of 5,500.
The mechanic who performed condition inspections in 2021 and on June 28, 2022, did not adjust the propeller blade angle during the last inspection. No flight test was performed after the 2022 inspection, but the owner (who assisted with the inspection) operated the engine; the mechanic did not know if a full-power static run-up was conducted.
Weight and Loading
Weight calculations using the aircraft's empty weight, pilot weight (186 lbs) and passenger weight (240 lbs) per autopsy reports, and drained fuel (6.5 gallons minus 0.4 gallons unusable) revealed the aircraft was a minimum of 29 lbs over design gross weight at the time of the accident. An unknown amount of fuel leaked from the impact-damaged tank, and the weight of tools and a PVC pipe holding the remains were not determined. The pilot's wife reported her husband routinely kept the fuel tank full to avoid condensation.
Engine and Propeller Examination
Engine rpm calculations from the accident flight and a previous takeoff recorded by the GoPro camera indicated the engine operated at or near its published maximum continuous power setting (5,500 rpm), rather than the takeoff power setting (5,800 rpm).
Postaccident examination of the engine revealed no evidence of preimpact failure or malfunction. Operational testing using an exemplar propeller with blade angles set to 11.5°, 9.0°, and 7.0° yielded maximum engine speeds of 4,800 rpm, 5,100 rpm, and 5,500 rpm, respectively.
The three-blade ground-adjustable propeller remained attached to the engine. All blades were impact damaged; one blade exhibited a semi-circular gouge consistent with contact by the right wing cable. Non-rotated blades had angles of 11.7° and 11.9°, and the rotated blade was positioned at 11.5° at impact.
According to the propeller manual, it is typical for peak rpm in flight to be higher than static rpm, and it is recommended to set static rpm 400-500 rpm below maximum engine rpm. A propeller manufacturer representative stated that for the accident engine and propeller combination, achieving 5,800 rpm during takeoff would likely require a static rpm setting of about 5,600, and that some operators set the blade angle higher to reduce engine rpm (de-rating).
Wreckage and Impact
The aircraft crashed in a densely wooded area about 1,075 ft southwest of the southern edge of the lake. There was no fire. The wreckage came to rest upright on a magnetic heading of about 270°, listing about 45° to the right. Cut damage to trees was consistent with propeller contact. The main landing gear were retracted (water landing position). About 6.5 gallons of automotive fuel were drained from the impact-damaged tank, which was leaking. No water was found in the fuel lines. The fuel shutoff valve was open. Both leading edge tubes exhibited overload fracture. Control cables showed no preimpact failure or malfunction.