Emily, MN, USA
N505DB
SEA & SKY INC KRUCKER CYGNET
The pilot and one passenger were departing from a lake for a local flight in the weight-shift-control aircraft. The pilot’s wife reported that the aircraft did not become airborne at the usual location. Video captured by an onboard camera revealed that, after becoming airborne with the engine operating about 300 rpm below the takeoff rpm setting, the aircraft began a slow climb while flying toward the south edge of the lake. Near the south end of the lake, with the engine operating at the same rpm, the climb stopped and the pilot abruptly manipulated the controls, likely to avoid trees ahead and prevent an aerodynamic stall. Around this time, the pilot’s wife heard a “pop” sound. The aircraft then entered a left descending spiral, impacting the tree canopy then the ground. Examination of the flight controls revealed no evidence of preimpact failure or malfunction. Damage signatures observed on one propeller blade indicated that the pop sound heard by the witness was likely the sound of the propeller blade impacting a control cable during the impact sequence. Examination and postaccident operational testing of the engine and propeller revealed that the propeller blade angle was set higher than optimal for the propeller/engine combination, preventing the engine from attaining the published takeoff power setting of 5,800 rpm. Additionally, calculations of the engine rpm during both the accident flight and one previous takeoff recorded by the onboard camera revealed the rpm to be consistent with the engine operating at or near its published maximum continuous power setting (5,500 rpm), rather than the takeoff power setting (5,800 rpm). Given the weights of the occupants and the fuel found onboard after the accident, the aircraft was a minimum of 29 lbs over design gross weight at the time of the accident, but could have been as much as 62 lbs, or about 5.8%, over the design gross weight at the start of the flight. The density altitude at the time of the accident was about 2,950 ft mean sea level. It is likely that the combined effects of the pilot’s operation of the aircraft in an overweight condition, the engine operating at less than the specified takeoff rpm throughout the flight, and the increased density altitude reduced the aircraft’s climb performance, resulting in impact with trees and terrain.
HISTORY OF FLIGHTOn August 28, 2022, about 1734 central daylight time, a Sea & Sky, Inc., Krucker Cygnet amphibious weight-shift-control aircraft, N505DB, was substantially damaged when it was involved in an accident near Emily, Minnesota. The flight instructor and a passenger were fatally injured. The aircraft was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The purpose of the flight was for the passenger to aerially distribute cremated remains. The pilot’s wife stated her husband initiated the takeoff to the south and the aircraft did not become airborne at the usual location; rather, it became airborne when the flight was abeam a dock near the south end and west edge of the lake. Bordering the southern end of the lake were trees, the tallest of which was estimated to be about 70 ft tall. The pilot’s wife reported hearing a “pop” sound when the aircraft was just above the trees, but she did not witness nor perceive the aircraft had crashed. After receiving a report that the flight had not arrived at the intended destination, the pilot’s wife reported the overdue flight to law enforcement. An initial search by a medivac helicopter failed to locate the wreckage, which was located later that evening by a homeowner who lived near the accident site. To capture the flight, a Go-Pro camera facing the cockpit was mounted on a bracket attached to the right wing strut. The camera, which remained attached to its mount during the accident sequence, was retained by the NTSB. Review of the video revealed that the aircraft became airborne about 16 seconds after initiating takeoff, then slowly gained altitude while flying in a southerly direction over the lake. When the flight was near the southern edge of the lake the aircraft was not gaining altitude and was just above the trees. During this time the pilot was moving the control bar in a counterclockwise direction forward, left, back and right. The flight continued in a southerly direction and crossed over the southern edge of the lake at an altitude that was just above the top of the trees. While continuing in a southerly direction the aircraft was not gaining altitude and the pilot was moving the control bar forward and backward abruptly. The pilot continued to make abrupt control bar inputs and the aircraft started 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. The aircraft then impacted the tree canopy and the ground. PERSONNEL INFORMATIONThe 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 sport rating. AIRCRAFT INFORMATIONThe aircraft’s empty and gross weights were 626 lbs and 1,060 lbs, respectively. Based on the altimeter setting, field elevation, and temperature about the time of the accident, the density altitude was about 2,950 ft. According to the takeoff distance chart in the aircraft operating instructions, under calm wind conditions at 3,000 ft density altitude, the takeoff distance from water to climb to 50 ft was 1,345 ft. According to the engine operator’s manual, the takeoff and maximum continuous rpm were 5,800 rpm and 5,500 rpm, respectively. According to the mechanic who performed the aircraft’s condition inspections in 2021 and then on June 28, 2022, he did not adjust the propeller blade angle during the last inspection. No flight test was performed at the conclusion of the 2022 inspection, but the owner who helped with the condition inspection operated the engine, though he (mechanic) did not know if the owner did a full-power static run-up. Weight calculations using the aircraft’s empty weight, the weights of the pilot and passenger per the autopsy reports (186 lbs and 240 lbs, respectively), and the amount of drained fuel (6.5 gallons) minus the unusable value of 0.4 gallon (the weight of which is included in the aircraft’s empty weight), revealed that the aircraft was a minimum of 29 pounds over design gross weight at the time of the accident. An unknown amount of fuel leaked from the impact-damaged fuel tank and the weight of a small amount of tools and the PVC pipe holding the remains for aerial dispersal were not determined. The pilot’s wife reported that her husband routinely kept the fuel tank full to avoid condensation. Engine rpm calculations of both the accident flight and one previous takeoff recorded by the GoPro camera revealed the rpm to be consistent with the engine operating at or near its published maximum continuous power setting (5,500 rpm), rather than the takeoff power setting (5,800 rpm). AIRPORT INFORMATIONThe aircraft’s empty and gross weights were 626 lbs and 1,060 lbs, respectively. Based on the altimeter setting, field elevation, and temperature about the time of the accident, the density altitude was about 2,950 ft. According to the takeoff distance chart in the aircraft operating instructions, under calm wind conditions at 3,000 ft density altitude, the takeoff distance from water to climb to 50 ft was 1,345 ft. According to the engine operator’s manual, the takeoff and maximum continuous rpm were 5,800 rpm and 5,500 rpm, respectively. According to the mechanic who performed the aircraft’s condition inspections in 2021 and then on June 28, 2022, he did not adjust the propeller blade angle during the last inspection. No flight test was performed at the conclusion of the 2022 inspection, but the owner who helped with the condition inspection operated the engine, though he (mechanic) did not know if the owner did a full-power static run-up. Weight calculations using the aircraft’s empty weight, the weights of the pilot and passenger per the autopsy reports (186 lbs and 240 lbs, respectively), and the amount of drained fuel (6.5 gallons) minus the unusable value of 0.4 gallon (the weight of which is included in the aircraft’s empty weight), revealed that the aircraft was a minimum of 29 pounds over design gross weight at the time of the accident. An unknown amount of fuel leaked from the impact-damaged fuel tank and the weight of a small amount of tools and the PVC pipe holding the remains for aerial dispersal were not determined. The pilot’s wife reported that her husband routinely kept the fuel tank full to avoid condensation. Engine rpm calculations of both the accident flight and one previous takeoff recorded by the GoPro camera revealed the rpm to be consistent with the engine operating at or near its published maximum continuous power setting (5,500 rpm), rather than the takeoff power setting (5,800 rpm). WRECKAGE AND IMPACT INFORMATIONThe aircraft crashed in a densely wooded area about 1,075 ft southwest of the southern edge of the lake. There was no evidence of a pre- or postimpact fire. The wreckage came to rest upright on a magnetic heading of about 270°, listing about 45° to the right. There was no evidence of bird remains found at the wreckage site or among the wreckage. Cut damage to trees of varying diameters was consistent with contact by the propeller. The main landing gear were in the retracted (also the water landing position). About 6.5 gallons of automotive fuel were drained from the fuel tank, which was impact damaged on the forward end and was leaking fuel. About 1 ounce of fuel was noted in the clear fuel line from the shutoff valve to the engine-driven fuel pump; no water was present. The fuel shutoff valve was in the open position and was free into the fuel tank. Fuel was also noted in the clear fuel filter; no water was noted. Both leading edge tubes exhibited overload fracture at varying lengths. Examination of the control cables revealed no evidence of preimpact failure or malfunction. Examination of the engine and its systems revealed no evidence of preimpact failure or malfunction. Postaccident operational testing of the engine using an exemplar propeller with each propeller blade angle set to 11.5° revealed that the maximum engine speed attained was 4,800 rpm. Changing each propeller blade angle to 9.0° and then 7.0° resulted in maximum engine speed of 5,100 rpm and 5,500 rpm, respectively. Examination of the three-blade composite ground-adjustable propeller, which remained attached to the engine, revealed that all blades remained installed in the hub, with one blade rotated from its original position. All propeller blades were impact damaged with one exhibiting a semi-circular gouge on the leading edge of the blade about 3 inches inboard from the tip, consistent with contact by the right wing cable that went from the control bar to the center forward attach point of the wing. The angle of the propeller blades that were not rotated in the hub were 11.7° and 11.9°. Correlating the impact mark on the rotated propeller blade with the propeller hub revealed that it was positioned at 11.5° at impact. According to the propeller Operation and Installation Manual, “It is typical for peak RPM while the vehicle is moving to be higher than static RPM. As a general rule, it is recommended to set the static RPM 400-500 RPM under the maximum engine RPM.” A representative of the propeller manufacturer indicated that, with the accident engine and propeller combination, if an owner/operator/pilot wanted to achieve 5,800 rpm during takeoff, the likely static rpm setting would be about 5,600. He further noted that some owner/operators choose to set the propeller blade angle at a higher setting, which reduces the engine rpm to a value lower than the specified takeoff value, as if de-rating the engine.
The pilot’s operation of the weight-shift control aircraft over its design gross weight and his decision to take off with the engine operating at less than the specified takeoff rpm, which resulted in degraded takeoff and climb performance. Contributing to the accident was the increased density altitude conditions, which further decreased the aircraft’s climb capability.
Source: NTSB Aviation Accident Database
Aviation Accidents App
In-Depth Access to Aviation Accident Reports
