Structural Failure Leads to Loss of Control in PT-19 Flight Test

Casualties unknown • VILA VELHA, ES, BR

A PT-19 aircraft entered an unrecoverable spin and subsequent inverted flight during a test flight, resulting in the total destruction of the aircraft and the pilot's emergency parachute deployment.

What happened

On July 29, 1995, a PT-19 aircraft, registration PP-HNT, operated by Aeroclube do Espírito Santo, departed from the Barra do Jucú aerodrome for a flight test. The aircraft had been grounded for nearly two years due to engine issues. After approximately 30 minutes of flight, the pilot initiated a dive to reach 135 knots, followed by a recovery maneuver. During the pull-up, the aircraft entered an inverted position, followed by a dive and a spin. The pilot found the controls locked and was unable to recover the aircraft from the spin. The pilot successfully deployed a parachute and exited the aircraft; however, the aircraft struck the ground and was destroyed by fire.

The investigation

CENIPA investigators examined the structural integrity of the aircraft and the maintenance history of the airframe. The investigation focused on the condition of the wooden structural components and recent modifications made to the aircraft. Investigators also reviewed the pilot's training, medical certification, and the maintenance records regarding the replacement of a structural component.

Findings

  • The investigation identified that a structural modification had been performed, replacing the original pilot tube with a different part that required an adaptation to the wing structure. This modification was not accompanied by oversight from aviation authorities.
  • The area where the new tube was installed had not received the necessary fungicide treatment, leaving the wood in direct contact with the atmosphere.
  • Testing of the structural wood revealed that the moisture content had fallen below the minimum acceptable level of 11%. This low moisture content reduced the flexibility of the material, making it prone to brittle failure when subjected to flight stresses.
  • The aircraft's two-year period of inactivity contributed to the natural deterioration of the components.
  • The primary contributing factor was deficient maintenance, characterized by a structural modification that did not follow manufacturer specifications and the failure to properly prepare the installation area for the new component.
  • Inadequate supervision regarding the monitoring of natural wear in the wooden components contributed to the accident.

Probable cause

The accident was caused by improper maintenance involving an unauthorized structural modification to the wing, which, combined with inadequate fungicide treatment and low wood moisture levels, led to structural failure and loss of control.

Frequently asked questions

What happened in the 1995-07-29 aircraft accident near VILA VELHA, ES, BR?

A PT-19 aircraft entered an unrecoverable spin and subsequent inverted flight during a test flight, resulting in the total destruction of the aircraft and the pilot's emergency parachute deployment.

What aircraft was involved and where did it happen?

The accident on 1995-07-29 involved a aircraft, registration PPHNT, at VILA VELHA, ES, BR.

What was the probable cause of the accident?

The accident was caused by improper maintenance involving an unauthorized structural modification to the wing, which, combined with inadequate fungicide treatment and low wood moisture levels, led to structural failure and loss of control.

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