Alisport SILENT 2 ELECTRO N64JG

Summary

On 22 July 2023 at about 21:00 local time, a Alisport SILENT 2 ELECTRO registered N64JG was involved in an accident near Wallis, Texas, United States. One person was on board and nobody was injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

22 July 2023 at 21:00

Classification

Accident

Location

Wallis, Texas, United States

Coordinates

29.6216, -96.0640

Aircraft

Alisport SILENT 2 ELECTRO

Registration

N64JG

Category

Glider

Year built

2014

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

CEN23LA319

Nobody was injured.

The failure of the tail boom structure due to cyclic torsion overloading as of a result of flutter in the empennage. The reason for the flutter could not be determined.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

After completing a cross-country flight, the pilot set up his final glide at 79 knots (kts), the top of the normal operating airspeed range, to descend from 6,000 ft. About 4,000 ft, the pilot experienced a severe vibration and shaking of the glider. The pilot stated that the glider did not sustain a bird strike or encounter severe turbulence. The pilot deployed the spoilers to slow the glider for possible elevator flutter and the vibration stopped when the glider reached about 60 kts. The pilot verified glider control and slowly increased the airspeed, at which time the vibration returned. The pilot slowed the glider again and proceeded to land. The straight-in landing was uneventful, and the glider rolled to a stop. After exiting the glider, the pilot noticed the composite tail boom structure was cracked in multiple locations. A materials examination of the tail boom structure revealed a damage pattern in the aft portion of the tail boom that contained multiple cracks orientated at ±45° relative to the transverse plane, consistent with torsion loading in both clockwise and counterclockwise rotation directions. Thus, a flutter event likely produced high alternating torsion loads on the fuselage and subsequent damage. The examination found no clear evidence of preexisting damage or weakness that would have led to reduced stiffness of the fuselage structure. The glider sustained a vibration event consistent with flutter while operating below the design maneuvering airspeed. The vibrations dissipated as the glider slowed, which also was consistent with flutter. Flutter could occur due to operation outside of the design flight envelope, loose flight controls, changes in control surface mass, or reduced stiffness in the control panel, wing, stabilizer, or fuselage. Based on the available evidence, the reason for the flutter event could not be determined.

Quoted verbatim from the NTSB record.