N377YGEvektor-Aerotechnik A S HARMONY LSA · 2020

On February 11, 2024, about 1035 Pacific standard time, an Evektor-Aerotechnik Harmony light sport airplane, N377YG, was substantially damaged when it was involved in an accident near Santa Ana, California. The flight instructor sustained serious injuries and the student pilot sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight.

The flight instructor providing instruction in the accident airplane declined to communicate with the Investigator-in-charge regarding the facts, circumstances, and conditions that led to the accident sequence. According to a flight instructor that witnessed the accident sequence, he was following the accident airplane and was next to land on runway 20L. He reported that a narrow-body airliner had touched down on runway 20R about 30 seconds before the accident airplane had descended over the airport property just north of runway 20L. During the airplane’s approach, the witness heard the tower controller communicating with the accident airplane and issued a caution for wake turbulence. The accident airplane acknowledged the tower controller by reading back the instructions to land and the caution for wake turbulence. He recalled that the accident airplane was about 40 ft agl and attempting to land on runway 20L; however, the accident airplane entered an aggressive right bank and impacted the ground. The distance between runway 20R and 20L was about 390 ft.

The narrow-body airliner landing on runway 20R was a Boeing 757, which according to NTSB Special Investigation Report 94/01 is known for its strong wake turbulence, often generating more than airplanes of similar size due to its wing design and slower approach speeds that create powerful, potentially hazardous wingtip vortices. Video from a security surveillance camera oriented toward the approach end of runway 20L and 20R showed a narrow-body airliner making an approach to runway 20R. About 41 seconds later, the accident airplane came into the camera’s view; video showed that it was on approach to the parallel runway, 20L. About 8 seconds later the accident airplane entered an aggressive roll to the right and descended rapidly. The airplane continued the right roll and the right wing and then lower right fuselage impacted the ground. The airplane sustained substantial damage to both wings and the fuselage.

According to the meteorological aerodrome report at 09:53 from a station located at the airport, the wind was from 240° at 3 knots. A special meteorological aerodrome report was issued at 10:44 and indicated that the wind was calm.

Audio recordings of the communications between the tower controller and the accident airplane were provided by airport operations. The tower controller could be heard issuing the accident airplane a caution for wake turbulence from the airliner landing on runway 20R, and the student pilot in the accident airplane acknowledged the tower controller, followed by continuation of the approach to land.

AC 90-23G, section 3, highlighted that the vortices from an aircraft can pose a hazard to encountering aircraft. Additionally, section 6 of the AC noted that the most likely encountered hazard is an induced rolling moment that can exceed the roll control capability of encountering aircraft. The capability of an aircraft to counteract the roll imposed by the wake vortex primarily depends on the wingspan and counter control responsiveness of the encountering aircraft.

A crosswind will decrease the lateral movement of the upwind vortex and increase the movement of the downwind vortex. Thus, a light wind with a cross-runway component of 1 to 5 knots (depending on conditions) could result in the upwind vortex remaining in the touchdown zone for a period of time and hasten the drift of the downwind vortex away from the runway (possibly toward an adjacent runway if one exists).

The AC identified vortex avoidance procedures (section 8), specifically when landing behind a larger aircraft on a parallel runway closer than 2,500 ft apart. This AC stated that, when landing behind a larger aircraft on a parallel runway closer than 2,500 feet apart, pilots need to consider the relationship between the runway threshold locations, the relative glideslope descent paths/locations and possible vortex drift onto your runway. If you have visual contact with the larger aircraft landing on the parallel runway, stay at or above the larger aircraft’s final approach flightpath.

Section 11 of the AC identified pilot responsibilities for vortex avoidance and indicated that the pilot must exercise the flight awareness necessary to ensure vortex avoidance during visual meteorological conditions (VMC). The pilot should exercise vortex visualization and avoidance procedures using the same degree of awareness as in collision avoidance.