Inadvertent autopilot activation involving a Cessna 172R, Stanthorpe, Queensland, on 14 March 2023

What happened

On 14 March 2023, overhead Stanthorpe, Queensland, a student pilot was conducting a solo navigation flight in a Cessna 172R. The student was accumulating solo hours for the issue of a private pilot licence.

During cruise, the student reported difficulty controlling the aircraft. The student was unfamiliar with the operation of the Bendix/King KAP140 autopilot system and had inadvertently activated it. They reported that full aileron deflection was required to maintain wings level flight.

Upon realising the aircraft was not responding as expected, the student established communications with the flight school and air traffic control. An instructor tried to diagnose the problem over the phone however, after the student explained they had not activated the autopilot (because the activation was inadvertent and they were unaware this had occurred), it could not be confirmed exactly what the problem was.

After conducting further checks of the aircraft systems, the pilot reported the control column became easier to control and landed the aircraft safely at Stanthorpe aerodrome.

Bendix/King KAP140 autopilot

The Bendix/King KAP 140 autopilot fitted in the Cessna 172R on this flight was a single-axis system. The single-axis system requires the ‘AP’ button to be depressed for 0.25 seconds to engage, and defaults to ‘ROL’ (roll) mode. The aircraft is not fitted with a wing’s leveller function and therefore, when the autopilot is engaged in roll mode, it will attempt to maintain the current position from the turn and balance co-ordinator instrument. The autopilot will not automatically disengage when the controls are manually manipulated by the pilot.  

Position of autopilot

It is common practice for pilots to place a finger on the dashboard to support and assist with small changes to the throttle position as shown in Figure 1. The placement of the autopilot system made it very easy to engage by accident.

Figure 1: Autopilot position

Source: Operator, annotated by the ATSB

Safety action

As a result of this incident the operator has implemented aircraft differences training to ensure students have knowledge over all aircraft systems and varying avionics. This training includes troubleshooting techniques specific to autopilots.

Furthermore, the operator has added an ‘In-flight controllability issues’ checklist to assist pilots during solo flight exercises.

Safety message

When acting as pilot in command, the pilot should be familiar with all the systems of the aircraft. An understanding of the autopilot system can be a useful tool for inexperienced pilots in many situations including inadvertent activation. The autopilot can also assist competently trained pilots that inadvertently enter instrument meteorological conditions (IMC) when flying under the visual flight rules (VFR). The in-flight emergency response checklist ATC IFER checklist used by Air Services Australia suggests activation of the autopilot for VFR pilots that enter IMC where the aircraft is equipped, and the pilot has been trained to use it appropriately.

This incident has many similarities to a previous investigation conducted by the ATSB, Collision with terrain involving Cessna 172, VH-ZEW, near Millbrook, Victoria on 8 September 2015 | ATSB (AO-2015-105).

The aircraft’s pilot operating handbook can also be a valuable source of information to assist pilots in understanding or recalling vital information when required.

About this report

Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.