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What happened

At about 1410 Eastern Standard Time on 8 September 2015, the pilot of a Cessna Aircraft Company 172S, registered VH-ZEW, departed Point Cook Airfield, Victoria, on a solo navigational training flight via waypoints that included Ballarat Airport, Victoria. GPS data showed that the aircraft was on the third leg of the planned journey, cruising at about 3,000 ft above mean sea level when it started to descend rapidly. The aircraft impacted rising terrain at about 2,200 ft and was destroyed. The pilot who was the sole occupant, was fatally injured.

What the ATSB found

The site and wreckage inspection identified that the aircraft impacted terrain in a level, slight right‑wing low attitude. That indicated that the pilot likely stopped the aircraft’s descent and started to initiate a manoeuvre to avoid the terrain. It is likely that the pilot manually manipulated the controls while the autopilot was on and engaged in a vertical mode. As a consequence, the autopilot re-trimmed the aircraft against pilot inputs, inducing a nose-down mistrim situation, which led to a rapid descent. The aircraft’s low operating height above the ground, due to the extent and base of the cloud, along with rising terrain in front of the aircraft, gave the pilot limited time to diagnose, react, and recover before the ground impact.

There was no advice, limitation, or warning in the aircraft pilot operating handbook or avionics manual to indicate that if a force is applied to control column while the autopilot is engaged, that the aircraft’s autopilot system will trim against the control column force, and possibly lead to a significant out of trim situation. Training requirements for autopilot systems was rudimentary at the recreational pilot licence (RPL) level due to stipulated operational limitations for its use. At the time of the accident there was no regulatory requirement for pilots to demonstrate autopilot competency at the RPL level.

What's been done as a result

The ATSB issued safety recommendations to the aircraft and autopilot manufacturers about the provision of limitations, cautions and warnings for autopilot systems and audible pitch trim movement.

The flight training organisation updated their operations manual, as a result of flight testing they conducted, to include warnings about the operation and function of the autopilot system absent in the manufacturer’s documentation. The hazard of manual manipulation of the flight controls with the autopilot engaged was also emphasised to students.

Safety message

Technologically advanced avionics and autopilot systems are now often fitted to general aviation aircraft used for flight training, private and charter operations. It is essential for all pilots to develop a thorough understanding and operation of all systems fitted to the aircraft they are flying. It is also important that student pilots consolidate manual flight and navigation skills before using the advanced auto flight modes or extensively using autopilot systems. Avionics and aircraft manufacturers should increase pilot awareness of automated systems by providing written warnings surrounding known issues and including visual and aural alerts in auto flight systems to increase pilot awareness of non-standard inputs. Fundamentally, pilots should be aware that if the automation is not performing as expected, then the safest option under most circumstances is to disengage the system and manually fly the aircraft.

VH-ZEW main wreckage
VH-ZEW main wreckage. Source: ATSB
Source: ATSB

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The occurrence

Context

Safety analysis

Findings

Safety issues and actions

Sources and submissions

 
 
 

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Safety issues

AO-2015-105-SI-01 - AO-2015-105-SI-02 -  

Autopilot advice, limitations cautions and warnings (written and audible)

The lack of manufacturer written advice, limitations, cautions, or warnings (written or aural) about autopilot response to manual pilot control inputs meant that pilots may be unaware that their actions can lead to significant out of trim situations, and associated aircraft control issues.

Safety issue details
Issue number:AO-2015-105-SI-01
Who it affects:Aircraft owners and operators of aircraft fitted with the Garmin G1000 avionics system and GFC700 autopilot.
Status:Safety action pending


 

Autopilot advice, limitations cautions and warnings (written and audible)

The lack of manufacturer written advice, limitations, cautions, or warnings (written or aural) about autopilot response to manual pilot control inputs meant that pilots may be unaware that their actions can lead to significant out of trim situations, and associated aircraft control issues.

Safety issue details
Issue number:AO-2015-105-SI-02
Who it affects:Aircraft owners and operators of aircraft fitted with the Garmin G1000 avionics system and GFC700 autopilot.
Status:Safety action pending

 
General details
Date: 08 September 2015 Investigation status: Completed 
Time: 15:40 EST Investigation phase: Final Report: Dissemination 
Location   (show map):near Millbrook Investigation type: Occurrence Investigation 
State: Victoria Occurrence type: Collision with terrain 
Release date: 17 April 2018 Occurrence class: Operational 
Report status: Final Occurrence category: Accident 
 Highest injury level: Fatal 
 
Aircraft details
Aircraft manufacturer: Cessna Aircraft Company 
Aircraft model: 172S 
Aircraft registration: VH-ZEW 
Serial number: 172S11079 
Type of operation: Flying Training 
Sector: Piston 
Damage to aircraft: Destroyed 
Departure point:Point Cook, Vic
Destination:Point Cook, Vic
 
 
 
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Last update 17 April 2018