Why the ATSB did this research
This is the second in a series of research investigations looking at technical failures reported to the ATSB. This report reviews power plant problems affecting turboprop‑powered aircraft between 2012 and 2016.
By summarising power plant-related occurrences, this report provides an opportunity for operators to compare their own experiences with others flying the same or similar aircraft types, or aircraft using the same engines. By doing so, the ATSB hopes that the wider aviation industry will be able to learn from the experience of others.
What the ATSB found
A review of power plant‑related occurrences reported to the ATSB showed that there were 417 occurrences involving turboprop-powered aircraft between 2012 and 2016 (83 per year on average). The subset of occurrences involving operators whose flight hours were known consisted of 314 occurrences in the four years between 2012 and 2015 (79 per year on average). With a combined total of just over 1.4 million flight hours for these aircraft in this timeframe, this subset equates to approximately 2.2 occurrences every 10,000 flight hours.
The vast majority of all the 417 occurrences (96%) were classified as ‘low-risk rating’ occurrences with a low or no accident outcome, however, there were four classified as ‘medium-risk’ and three as ‘high-risk’. The three occurrences classified as high-risk occurrences all involved engine failures or malfunctions with forced/precautionary landings in single‑engine Cessna 208 (Caravan) aircraft. There were no occurrences classified as ‘very high-risk’.
The two occurrences in the set that resulted in any injury (both minor) were the result of engine failure or malfunctions and collision with terrain occurrences in aerial agricultural operations. The five occurrences classified as ‘accidents’ all involved aerial work operations, four in aerial agriculture and one in emergency medical services operations.
One aircraft type was found to have a rate of 13.9 power plant-related occurrences per 10,000 hours flown, more than double the rate of any other aircraft type. However, with only four occurrences between 2012 and 2015, the high rate is due to relatively very low flight hours for this aircraft. All four of these occurrences were classified as incidents (rather than accidents or serious incidents) and classified as low risk rating occurrences. Additionally, the sole operator of this aircraft type in Australia advised the ATSB that the fleet was retired in 2017 and replaced with a newer turbofan alternative.
Timely and vigilant reporting of all technical problems is encouraged to ensure as much information as possible is collected so as to enable a better understanding of the failures. Of particular importance in technical occurrences are the follow-up reports from engineering inspections provided to the ATSB. These are often the only way that the root cause of the problem can be determined.