Training aircraft enters steep dive during pitch trim demonstration


Cessna 152 right stabiliser damage

Key points:

  • Cessna 152 entered a steep dive after student pilot released control wheel during pitch trim demonstration
  • Instructor sustained minor injuries and aircraft sustained structural damage during recovery
  • Instructors need to account for the potential for students to carry out unexpected actions

A Cessna 152 abruptly pitched down and entered a steep dive when a student pilot released the aircraft’s control wheel during a demonstration of the effects of control and the use of trim, an ATSB investigation details.

The Basair Aviation College-operated Cessna 152 had departed Brisbane’s Archerfield Airport on 28 May 2019 with a student pilot on their first flight and an instructor on board to demonstrate manoeuvres from the effects of control flight training syllabus.

With the student flying, the aircraft was approaching overhead Lagoon Island south-east of Brisbane at about 2,000 feet above ground level when the instructor moved the pitch trim to about two-thirds travel nose down while the student maintained attitude with nose-up pressure on the control wheel.

“When returning the elevator trim to neutral, the student became confused about the correct procedure and suddenly released the control wheel and the aircraft rapidly pitched nose-down, rolled left, and entered into a dive,” said ATSB Director Transport Safety Dr Mike Walker.

“The instructor took control of the aircraft and arrested the descent 25 seconds later, at about 400 feet. Flight radar data showed the aircraft experienced an average descent rate of over 3,000 feet/minute.”

The instructor, who sustained minor injuries, then terminated the lesson and returned to Archerfield.

A post-flight examination of the aircraft identified significant structural damage with bending and buckling of the right horizontal stabiliser structure, likely due to excessive asymmetric flight loads from the dive recovery.

“The instructor’s use of a large amount of nose-down elevator trim for the lesson increased the effect when the student released backpressure on the elevator, leading to a sudden nose-down pitch change and subsequent entry into a dive,” Dr Walker said.

The investigation report notes that the flying school’s instructor guide did not specify a limit of trim input for such exercises.

“The ATSB also determined that the instructor’s hands were not in a ready position to take control in the event of any mishandling by the student pilot,” Dr Walker said.

“The recovery by the instructor was likely further delayed after sustaining a head injury during the in-flight upset, and initially being unsure about what had happened and how to then recover the aircraft.”

Following the incident the flying school operator revised its training procedures to include detailed instructor demonstrations prior to student practice of effects of control manoeuvres, and to ensure the use of a consistent moderate amount of trim following the incident.

“The first stages of flight training can be both exciting and daunting and this incident serves to remind student pilots to raise with their instructor any uncertainties they have over procedures,” Dr Walker stated.

“Conversely, instructors need to account for the potential for students to carry out unexpected actions. This means that lessons should be conducted under the lowest risk conditions that still impart the lesson intent.”

You can find here the investigation report: AO-2019-028: Loss of control involving Cessna 152, VH-JIW, near Archerfield, Queensland, on 28 May 2019

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