Unsecured rear wing on Mignet HM 1100 leads to excursion at Royan

Casualties unknown • FR

A Mignet HM 1100 ultralight aircraft sustained heavy damage after its rear wings folded during takeoff due to an incomplete pre-flight inspection.

What happened

On Wednesday, August 12, 1998, at 18:35, a Mignet HM 1100 "Cordouan" ultralight, identified as 17-LN, was performing a local flight from AD Royan. Shortly after takeoff, the aircraft's rear semi-wings folded inward, causing the aircraft to enter a violent left-hand turn. The pilot attempted to recover the aircraft using rudder inputs, successfully countering the left turn with a sharp right-hand maneuver. While the pilot managed to reduce the bank angle, the aircraft ultimately landed in a grassy area adjacent to the runway, striking the left wing during the process. The aircraft was heavily damaged.

The investigation

The investigation focused on the mechanical state of the aircraft following the incident. It was determined that the rear wing locking mechanisms had not been engaged. This oversight occurred following recent exercises involving the folding and unfolding of the wings. The aircraft is a "Pou du ciel" type, featuring a staggered biplane configuration with wings designed to fold for road transport. The pilot stated that during the pre-flight inspection, the check was limited to verifying the connection and movement of the ailerons, and did not include a verification of the wing locks.

Findings

  • The primary cause of the accident was an incomplete pre-flight inspection.
  • The rear wing locks were left in the unlocked position following recent training maneuvers involving wing folding.
  • The pilot's inspection focused only on the aileron functionality rather than the structural integrity of the wing attachment points.

Probable cause

The accident was caused by the pilot's failure to verify that the rear wing locks were properly engaged during the pre-flight inspection, which allowed the wings to fold during the takeoff phase.

Frequently asked questions

What happened in the 1998-08-12 aircraft accident near FR?

A Mignet HM 1100 ultralight aircraft sustained heavy damage after its rear wings folded during takeoff due to an incomplete pre-flight inspection.

What aircraft was involved and where did it happen?

The accident on 1998-08-12 involved a aircraft, registration 17-LN, at FR.

What was the probable cause of the accident?

The accident was caused by the pilot's failure to verify that the rear wing locks were properly engaged during the pre-flight inspection, which allowed the wings to fold during the takeoff phase.

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