Alisport SILENT 2 ELECTRO N321AD

Summary

On 7 September 2023 at about 21:25 local time, a Alisport SILENT 2 ELECTRO registered N321AD was involved in an accident near Giddings, 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

7 September 2023 at 21:25

Classification

Accident

Location

Giddings, Texas, United States

Coordinates

30.1813, -96.9374

Aircraft

Alisport SILENT 2 ELECTRO

Registration

N321AD

Category

Glider

Year built

2016

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

Waller → Waller

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

CEN23LA405

Nobody was injured.

The glider’s encounter with flutter during cruise flight that resulted in structural damage to the fuselage.

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

Read the full NTSB narrative

The pilot stated that the glider was in cruise flight at approximately 81 kts and 4,800 ft when the cockpit began to shake violently and noisily side-to-side. When the glider slowed to about 60 kts, the shaking ceased. The pilot landed the glider without further incident. The side-to-side shaking described by the pilot was consistent with a vibration event associated with flutter in straight and level flight. The vibrations dissipated as the airplane slowed, also consistent with flutter. The damage pattern in the aft portion of the fuselage showed multiple cracks oriented at ±45° relative to the horizontal plane, which was consistent with damage from torsion loading in both clockwise and counterclockwise rotation directions. Thus, the flutter likely produced high alternating torsion loads on the fuselage. The observed damage likely resulted from these high alternating torsion loads. Flutter could occur due to operation outside the design flight envelope, loose flight controls, changes in control surface mass, or reduced stiffness in control panel, wing, stabilizer, or fuselage structure. As discussed in more detail below, the examination found no clear evidence of preexisting damage or weakness that could have led to reduced stiffness of the fuselage structure. The glider manufacturer was no longer in business and information received by the investigative staff was limited. The glider had unbalanced horizonal and vertical control surfaces. The ailerons were balanced. A verification of proper flight control cable rigging, elevator trim tab free play, static balance of the control surfaces was not performed due to the lack of available instructions for continued airworthiness.

Quoted verbatim from the NTSB record.