Accident Summary
On October 26, 2024, at about 13:50 JST, an Alexander Schleicher ASK21 glider (registration JA21YP) sustained damage to the outer skin of the fuselage and other parts while landing in a grassy area near Naganoshi Glider Site in Nagano City, Nagano Prefecture. The glider was occupied by an instructor pilot and a trainee; neither was injured.
Flight History
The glider was launched from Runway 04L for emergency operations training simulating a loss of winch towing force at low altitude. Shortly after becoming airborne, the trainee realized the winch had lost towing force, restored the glider to horizontal, and released the tow line at an indicated speed of about 90 km/h and altitude of about 90 m AGL. The trainee extended dive brakes to land on the runway, but the instructor judged that dive brakes alone would not allow a landing within the runway and took over control. The instructor added a forward slip to increase descent rate.
After the forward slip, the predicted touchdown point was about 100 m short of the runway end. The instructor calculated that about 150 m would be needed to stop after touchdown, and that continuing to land would require a ground loop to stay on the runway, risking collision with ground structures, or an overrun off a pavement step-down. The instructor aborted the runway landing and aimed for a grassy area about 70 m northeast of the runway.
The glider turned left to avoid trees and an elevated bridge, but the left wing contacted vegetation during the turn, causing the glider to touch down while rotating left. After skidding right, the right nose collided with vegetation and the glider stopped.
Glider Damage
The accident caused cracks in the left fuselage outer skin (requiring major repair), cracks in the left wing leading edge, and breakage of the rear seat canopy.
Training and Winch Operations
The training was organized by Nagano Gliding Association to maintain pilot skills, simulating abnormal conditions during tows. The association had conducted similar training twice before but did not specify safe operating conditions; methods were left to instructors. During pre-flight briefing, the instructor instructed the trainee to land straight ahead. The winch operator was told to stop winding once climb speed stabilized, but to prevent stalling, stopped at a higher altitude. The operator had not previously stopped the winch at such a low altitude.
Analysis
According to the Japan Transport Safety Board (JTSB), the glider likely skidded right after left-turn touchdown, and the right nose collision with vegetation caused the fuselage damage. The tow line release probably occurred near the parachute's falling point (about 450 m from runway end). Despite prompt descent using dive brakes and forward slip, the required runway length (976 m under accident conditions) exceeded the valid runway length (969 m), making a runway landing infeasible.