Glider ground strike during low-level pass at Alzate Brianza

Casualties unknown • Aeroporto di Alzate Brianza (CO), IT

An Alexander Schleicher ASK 21 glider struck the ground during a high-speed low pass at an Italian airfield, resulting in a shallow furrow in the grass.

What happened

On November 23, 2014, an Alexander Schleicher ASK 21 glider, registration I-LVIG, was conducting aerobatic training maneuvers at the Alzate Brianza airport. The flight involved two experienced pilots, including a flight instructor, performing recovery maneuvers from unusual attitudes.

During the flight, the instructor took control of the aircraft with the intention of performing a double low pass. The first pass was planned from South to North, followed by a second pass from North to South, ending with a landing on runway 03. While executing the second pass, the instructor became momentarily distracted by the low sun position while checking the airspeed indicator. This distraction led to a delayed pull-up maneuver. Due to the insufficient altitude, the glider's main wheels made contact with the grass area west of the runway, creating an 8-meter long and 3-centimeter deep furrow. Despite the contact, the aircraft maintained its speed, recovered altitude, and completed a smooth landing on the asphalt runway.

The investigation

The ANSV investigation examined the flight sequence, the cockpit communications, and the local aerodrome regulations. The investigation established that the decision to perform the double low pass was made in-flight at an altitude of 400 m QFE, rather than being planned and discussed during the pre-flight briefing.

Furthermore, the investigators reviewed the specific regulations of the local Aero Club, which govern low-level passes at Alzate Brianza. These regulations require specific authorization, a minimum altitude of 500 m QFE for the start of the maneuver, and strict adherence to flight paths and speed limits. Witnesses at the airfield also noted that the maneuver performed was not in accordance with the club's established procedures.

Findings

  • The primary cause of the event was human error, specifically the failure of the instructor pilot to adhere to established safety parameters regarding minimum altitude during the maneuver.
  • The instructor's momentary distraction, caused by the low sun and the need to monitor airspeed, contributed to the delayed recovery.
  • The maneuver was not properly coordinated or briefed prior to takeoff.
  • The flight did not comply with the local aerodrome's specific regulatory requirements for low-level passes.

Probable cause

The incident was caused by the instructor pilot's failure to maintain the required safety altitude during a low-level pass, exacerbated by a momentary distraction due to the sun's position and a lack of pre-flight planning for the maneuver.

Frequently asked questions

What happened in the 2014-11-23 ASK 21 accident near Aeroporto di Alzate Brianza (CO), IT?

An Alexander Schleicher ASK 21 glider struck the ground during a high-speed low pass at an Italian airfield, resulting in a shallow furrow in the grass.

What aircraft was involved and where did it happen?

The accident on 2014-11-23 involved a ASK 21, registration I-LVIG, at Aeroporto di Alzate Brianza (CO), IT.

What was the probable cause of the accident?

The incident was caused by the instructor pilot's failure to maintain the required safety altitude during a low-level pass, exacerbated by a momentary distraction due to the sun's position and a lack of pre-flight planning for the maneuver.

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