An overlooked propeller strap on a Link Airways Saab 340 that damaged the aircraft and hurt a passenger is an important reminder that everyone involved in an aircraft’s operation must remain vigilant, Australian investigators have stressed.
When opersting a flight on behalf of Virgin Australia on the Canberra-Sydney route on 10 November 2022, the twin-turboprop (VH-VEQ) took off with a strap still affixed to its left-side propeller, says the Australian Transport Safety Bureau (ATSB).
The strap – which Saab refers to as the ‘propeller restraining bridle’ – loops over a propeller blade and fixes it via two cables to a pair of pins on the underside of the engine cowling. The device prevents propeller movement when the aircraft is parked.
Normally an extension connects the propeller strap to the airstairs, so as to help guide boarding passengers.
On the day of if the incident – which the ATSB categorises as serious – the strap extension to the airstairs was not in place. Neither the flightcrew nor the dispatcher noticed the strap was still in place after boarding and during the final inspection.
“During the start-up sequence there was a delay between the commencement of engine start and the propeller spinning due to the pins securing the strap to the engine cowling,” says the ATSB.
“Once these failed, the propeller began turning normally and the aircraft was cleared to depart with the strap still attached to the left propeller but not visible due to the propeller’s rotation.”
It took around 33s from the propeller’s initial movement before it began to rotate freely, the ATSB says.
After the aircraft became airborne, there was a loud noise as the strap flew free of the blade and embedded itself in the fuselage. The two cowling pins, still attached to the strap, also penetrated the cabin with fragments hiting a passenger’s leg, resulting in bruising.
Approximately 25s after take-off, the cabin crew contacted the pilots – who were unaware of what had happened – and the aircraft returned to Canberra. Apart from the leg injury, all three crew and 29 passengers were unharmed.
Following the incident, Link updated its pre-flight checks, documentation, and training related to the propeller strap and strap extension.
“For those directly involved in aircraft operations, this occurrence highlights the importance of vigilance,” says the ATSB.
“When there are multiple risk controls in place and multiple responsible parties, it is easy to become complacent from an expectation that earlier checks have been done correctly and that future checks elsewhere in the system will likely catch anything missed.”
The aircraft was originally delivered to US regional carrier Mesaba Airlines in 1997. It was subsequently operated by PenAir before eventually being transferred to the Link Airways fleet in 2022.
