ERA23FA078

The pilot’s improper yaw control during the takeoff initial climb, which resulted in an excessive sideslip and a subsequent loss of aircraft control.

The sport pilot, who was also the owner of the gyroplane, had about 120 total hours of flight experience, all of which was in the accident gyroplane. During the three months before the accident flight, the gyroplane was in maintenance and the pilot had not flown. Surveillance video captured the accident sequence, and showed the aircraft in the initial climb. It leveled off briefly before resuming its climb while displaying a significant left yaw. Shortly thereafter, the aircraft rolled to the right about 360° and impacted the runway. Recorded data from onboard avionics, as well as postaccident examination of the aircraft, did not reveal any evidence of mechanical malfunction or anomalies that would have precluded normal operation. The rudder trim tab was found undamaged by impact and bent about 30° to the right (left rudder force). The aircraft manufacturer cautioned that extreme sideslip could result in a loss of control. With the aircraft flying sideways, the side of the aircraft faces the oncoming airflow, creating increased drag that tends to swing the fuselage away from the direction of flight. The rotor disc is subsequently pitched down on the side of the aircraft headed into the oncoming airflow. With the airflow above rather than below the rotor disc, the aircraft can rapidly roll over toward the side of the aircraft facing the direction of flight unless urgent corrective action is taken. The reason that the pilot did not take appropriate recovery action could not be determined. Toxicological testing indicated that the pilot had used cannabis, but the timing of his last cannabis use or whether he was impaired by cannabis effects at the time of the accident could not be determined. It is plausible that the pilot’s overcorrection of the aircraft’s yaw may have resulted, in some part, from impairing effects of delta-9-THC; however, the pilot also had not flown in the three months before the accident. Thus, whether the pilot’s use of cannabis contributed to the accident cannot be determined. Additionally, the pilot’s autopsy findings were consistent with high blood pressure’s effect on the heart muscle. The pilot’s disease put him at some increased risk for a sudden impairing or incapacitating cardiovascular event such as heart rhythm abnormality. Such an event cannot be ruled out; however, witness accounts and airport video were not consistent with a sudden medical event. Thus, it is unlikely that the pilot’s heart disease contributed to the accident.

On December 4, 2022, about 1135 eastern standard time, a Rotorsport UK Cavalon gyroplane, N401GR, was substantially damaged when it was involved in an accident near Beverly, Massachusetts. The sport pilot was fatally injured. The gyroplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot, who was also the owner of the gyroplane, acquired his sport pilot certificate about 6 months before the accident and had about 120 total hours of flight experience, all of which were in the gyroplane. The pilot had just received the gyroplane back after about three months in maintenance, and according to witnesses, he had not flown during that period. On the day of the accident, the pilot was planning to conduct a local flight; after engine start, he taxied from his hangar to runway 34, where he was cleared for takeoff by a tower controller. Security video showed that, during the initial climb, the gyroplane climbed to about 40 ft above ground level, where it leveled off briefly, then resumed a shallow climb while in a left yaw. As the gyroplane continued to climb, it began to tilt to the right followed by a rapidly developing right roll. (see figure 1.) The aircraft completed one full 360° roll to the right as it descended out of control and impacted the runway on its right side. Figure 1. Security camera footage screen grabs showing the gyrocopter during climb as it entered a left yaw followed by a roll to the right. Two electronic flight displays with recording capability were retained and sent to the NTSB Recorders Laboratory for download. Review of nonvolatile memory revealed 27 parameters that were captured over a period of 20 minutes leading up to the accident. During the takeoff roll, all engine parameters, including but not limited to engine rpm, oil pressure, fuel flow, temperature, pitch, acceleration and airspeed were normal as the aircraft rolled down the runway. As the aircraft lifted off the runway surface, the airspeed was 53 kts with a vertical speed of 371 ft per minute (fpm) and a pitch of about 9.7°. As the aircraft climbed through 75 ft mean sea level (msl) and a GPS altitude of 150 ft, the airspeed was at 58 kts, the vertical speed was 782 fpm and the pitch was at 5.5° with a left roll of 10°. About 6 seconds later, while climbing through 150 ft msl, the aircraft yawed hard to the left and continued to do so until the loss of control. The pitch increased to 15° and over the next 3 seconds, the aircraft climbed through 193 ft msl and the vertical speed increased to 2,692 fpm as the aircraft rolled to the right and descended to impact. The aircraft impacted the paved runway surface and skidded off the right side of the runway into the grass. The wreckage path extended about 245 ft from the initial impact point to the main wreckage and was oriented on a 340° heading. During impact, the rotor head, containing the two aluminum-skinned rotor blades, hub bar, teeter bolt, and ring gear was impact-separated from the mast below the ring gear. All damage to the mast and rotor head was consistent with overstress due to impact. The rotor assembly was discovered about 170 ft south of the main wreckage. The rotor assembly was removed from the rotor blades, placed on top of the rotor mast, and attached with zip ties for examination. Pitch control continuity was confirmed from the flight controls in the cockpit to the rotor mast and head through an overload separation of the rotor head pitch pushrod and pitch control cable. Roll control continuity was confirmed from the cockpit control to the rotor mast and head through an overload separation at the rotor head connection point. Manual manipulation of the teetering function was normal and there was no evidence of rotor blade contact with any of the fuselage or control surfaces. The teetering stops were unremarkable with no bending or impact observed. The right side of the fuselage was crushed upwards into the cockpit. Control continuity was established through the airframe to all control surfaces; the rudder and vertical stabilizer remained intact and functional. The manual static rudder trim was in the 30° right position (left rudder deflection), was undamaged, and did not exhibit any damage features or witness marks. The engine remained intact and operated at nearly full power for about two minutes after impact, until fire rescue personnel were able to shut it down. The four-bladed composite pusher propeller was splintered and delaminated on the outer 6-inches of all four blades in a uniform pattern and remained attached to the flange and hub. Subsequent examination of the engine revealed crankshaft and valvetrain continuity. Examination of the engine and airframe revealed no evidence of any pre-impact anomalies that would have precluded normal operation. The Office of the Chief Medical Examiner (OCME), Commonwealth of Massachusetts, performed the pilot’s autopsy. According to the autopsy report, the pilot’s cause of death was blunt force injuries. The manner of death was accident. The autopsy revealed an enlarged heart with thickening of both cardiac ventricles. Mild atherosclerosis of the aorta and iliac arteries was also noted. Examination of the brain, lungs, and remainder of the heart revealed no evidence of other significant natural disease. At the request of the OCME, NMS Labs performed postmortem testing of the pilot’s femoral blood. Delta-9-THC was detected in femoral blood at 4.6 ng/mL. 11-hydroxy-delta-9-THC was detected at 1.1 ng/mL. Amlodipine and caffeine were presumptively detected. The Federal Aviation Administration Forensic Sciences Laboratory also performed toxicological testing of postmortem specimens from the pilot. Delta-9-THC was detected in two femoral blood specimens at 5 ng/mL and 5.5 ng/mL, respectively. Delta-9-THC was also detected in cavity blood at 4.1 ng/mL and in urine at 1.4 ng/mL. 11-hydroxy-THC was detected in urine at 27.1 ng/mL but was not detected in femoral or cavity blood. Carboxy-delta-9-THC was not detected in femoral blood but was detected in cavity blood. According to an excerpt from the Pilot Information Letter issued by the manufacturer, titled, “Gyroplane Yaw Management and Effects on Controls” (AG-PIL-2023-01-EN), “The effect of excessive sideslip on gyroplane pitch and roll control, is, in general, poorly understood, which can lead to a risk to safe gyroplane operation.” The letter stated, Excessive sideslip may be created in a gyroplane deliberately, typically using rudder pedal inputs, or as an aircraft’s reaction (secondary effect) to another input such as engine power changes. The result of either input is the same; the aircraft will yaw but the aircraft will initially continue in the original flight direction which creates sideslip. Although the aircraft’s directional stability, caused by airflow over the fin, will resist the creation of sideslip, the fin is ineffective at low airspeeds and can be overpowered. Further engine thrust can be used to overpower the fin. In extremis the aircraft could be turned as much as 90 degrees to the direction of flight. 1. Gyroplane stick pitch control stops typically range from a few degrees forward (‘nose down’) to around 20 degrees aft. During flight the stick/rotor is typically positioned around 10 degrees aft, with an in-flight stick movement of only a few degrees. The extra movement is required for take-off (stick fully back) or for stopping the rotor after landing (stick fully forward). 2. Gyroplane stick roll control stops range normally around 8-9 degrees either side of vertical. This amount of movement is never used in flight, it is only used on the ground for safe handling in side-winds. In-flight roll movement is only a few degrees. 3. These limit stops are always built into the rotor head, normally with secondary limit stops on the stick. Yaw as a result of an extreme pedal input It is important to