Aviation occurrence briefs

Incorrect configuration involving SAAB 340A, near Mackay, Qld, on 15 May 2018

Status: Completed
Investigation completed


Occurrence Briefs are concise reports that detail the facts surrounding a transport safety occurrence, as received in the initial notification and any follow-up enquiries. They provide an opportunity to share safety messages in the absence of an investigation.

What happened

On the morning of 15 May 2018, the crew of a SAAB 340A were conducting a cargo flight from Rockhampton, Queensland (Qld) to Mackay, Qld. At approximately 0545 Eastern Standard Time, the aircraft was on descent into Mackay passing 10,000 ft.

During descent, the left engine surged from 50 per cent torque to over 70 per cent with an increase in interstage turbine temperature[1]. The crew retarded the power lever and all other indications appeared normal. The aircraft levelled off at 5,000 ft and failure management was carried out. The crew subsequently conducted a normal approach and landing.

Following the incident, the crew were interviewed and an analysis of the flight data recordings occurred. Engineers were notified of the incident and conducted inspections. No faults were found with the engine or controls. It was determined that the constant torque on take-off (CTOT) was inadvertently not de-selected during the climb phase of the flight, resulting in the abnormal engine surge.

Safety action

As a result of this occurrence, the operator has advised the ATSB that they have taken the following safety actions:

Refresher training was provided to the crew specific to the use and operation of the CTOT system.

The crew conducted a competency-based training refresher course on operations failure management.

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.



  1. The interstage turbine temperature (ITT) is the temperature of the exhaust gasses between the high pressure and low-pressure turbines.
General details
Date: 15 May 2018   Investigation status: Completed  
Time: 0545 EST    
Location   (show map): 30 NM SE of Mackay    
State: Queensland    
Release Date: 02 November 2018   Occurrence category: Incident  
Report status: Final   Highest injury level: None  

Aircraft details

Aircraft details
Aircraft manufacturer Saab Aircraft Co.  
Aircraft model 340A  
Type of operation Air Transport Low Capacity  
Sector Turboprop  
Damage to aircraft Nil  
Departure point Rockhampton, Qld  
Destination Mackay, Qld  
Last update 12 December 2018