The ATSB this week warned aircraft operators to consider their environment and take steps to combat corrosion after a brake disc on a Sling LSA fractured earlier this year.
VH-PPY was returning from a dual training flight at Moorabbin in February when the student and instructor heard a unusual sound coming from the right side of the aeroplane, and the brake effectiveness was reduced.
On inspection after parking, the instructor saw that the right-hand brake disc had fractured.
ATSB investigators attributed the fracture to corrosion, most likely caused by the aeroplane being parked outside at Moorabbin, which is only 3 km away from the salt-heavy environment of Port Phillip Bay.
“The ATSB’s examination of the brake disc identified severe corrosion had compromised its structural integrity to the point where it failed during normal braking after landing,” ATSB Director of Transport Safety Dr Stuart Godley said.
“This corrosion was not identified by those maintaining and operating the aircraft as having progressed to a point where failure of the brake disc was possible.”
Godley also said that corrosion was found on the brake discs of all seven of the operator's aircraft.
“Being parked outside and operated in the vicinity of a saltwater environment would have contributed to the corrosion development,” he noted.
“The effect of the environment was also demonstrated by the extent of corrosion observed on the brake disc assemblies of the other six aircraft in the operator's fleet.”
Investigators also found that VH-PPY had been fitted with unapproved aftermarket brake discs, which the operator has since replaced on all aircraft.
Godley said that the operator had had plenty of opportunity to detect the corrosion because the aircraft was inspected daily and about every two months by a maintenance organisation.
“As such aircraft operators and maintainers should take timely action to prevent the progression of corrosion, and replace parts before the serviceability of an aircraft is affected,” he said.
“Operators should also give consideration to their aircraft operating environments, and whether additional maintenance can be undertaken to limit corrosion development.”
The full Short Investigation report is on the ATSB website.