Structural damage to horizontal stabiliser during student training flight

Casualties unknown • 34 km east-south-east of Archerfield Airport, Queensland

A training flight experienced a sudden nose-down dive after a student pilot released control pressure, leading to asymmetric loads and structural deformation of the horizontal stabiliser.

What happened

During a student pilot's initial training flight, an instructor was conducting an 'effects of control' lesson. During the exercise, the student suddenly released backpressure on the control wheel. Because the aircraft's elevator trim had been set to approximately two-thirds nose-down travel, this release triggered an abrupt and powerful nose-down pitch, forcing the aircraft into a sudden dive.

In an attempt to recover from the dive, the instructor tried to regain control of the aircraft before neutralizing the elevator trim. This sequence caused aerodynamic forces to concentrate on the right horizontal stabiliser rather than being distributed across both sides. The resulting asymmetric flight loads caused the forward outboard tip of the right stabiliser to twist approximately 30 mm downwards.

The investigation

Investigators examined the instructor's positioning and the aircraft's trim configuration. It was noted that the instructor's right hand was resting on the glareshield rather than in a position to immediately guard the controls. This positioning, combined with the unexpected nature of the dive, likely delayed the instructor's ability to react and execute an effective recovery technique.

Furthermore, the investigation looked into the flight school's training protocols. The operator's instructor guide lacked specific limits regarding the amount of trim that could be utilized during 'effects of control' lessons. This lack of standardization meant that instructors could use varying levels of trim, such as the significant nose-down setting used during this occurrence, which intensified the aircraft's response to the student's input.

Findings

  • The student pilot's sudden release of control wheel backpressure initiated the pitch change.
  • The use of excessive nose-down elevator trim increased the intensity of the nose-down response.
  • The instructor's hand position on the glareshield was not optimal for reacting to adverse student inputs.
  • Asymmetric flight loads during the recovery attempt caused the bending and buckling of the right horizontal stabiliser structure.

Probable cause

The sudden nose-down pitch and subsequent dive were caused by the student pilot releasing control pressure while the aircraft was configured with significant nose-down elevator trim. The structural damage resulted from asymmetric aerodynamic loads placed on the right horizontal stabiliser during the recovery attempt.

Frequently asked questions

What happened in the 2019-05-28 Cessna Aircraft Company 152 accident near 34 km east-south-east of Archerfield Airport, Queensland?

A training flight experienced a sudden nose-down dive after a student pilot released control pressure, leading to asymmetric loads and structural deformation of the horizontal stabiliser.

What aircraft was involved and where did it happen?

The accident on 2019-05-28 involved a Cessna Aircraft Company 152, registration VH-JIW, operated by Basair Aviation College, at 34 km east-south-east of Archerfield Airport, Queensland.

What was the probable cause of the accident?

The sudden nose-down pitch and subsequent dive were caused by the student pilot releasing control pressure while the aircraft was configured with significant nose-down elevator trim. The structural damage resulted from asymmetric aerodynamic loads placed on the right horizontal stabiliser during the recovery attempt.

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