Created Friday, Feb 21st 2025 10:14Z, last updated Friday, Feb 21st 2025 10:14Z
A Skippers Aviation Swearingen SA-227-DC, registration VH-WAJ performing charter flight PY-6002 from Forrestania,WA to Perth,WA (Australia) with 4 passengers and 2 crew, was enroute nearing the top of descent into Perth when the aircraft experienced a complete loss of hydraulics. The crew entered a hold to prepare for a manual gear extension and flapless landing. The crew requested a ground inspection after landing to check for any fluids leaking from the aircraft and requested a tow truck to pull them off the runway. The aircraft subsequently landed safely on Perth's runway 24 and vacated the runway onto taxiway A. Unable to establish communication with the tow truck and seeing, some hydraulic pressure was still available and testing of the brakes showed brake pressure was present, the captain decided to taxi the aircraft to the apron. Taxiing downslope due to a slight downhill gradient the aircraft accelerated, both crew applied brakes with no effect, the captain briefly applied reverse, but then feathered the propellers and shut the engines down just before the aircraft collided with a hangar. There were no injuries, the aircraft sustained minor damage.
The aircraft remained on the ground for 30 days and returned to service on Sep 11th 2024.
On Feb 21st 2025 the ATSB released their final report concluding the probable causes of the serious incident were:
- A crack in a hydraulic line in flight resulted in a loss of hydraulic pressure and required the crew to manage the emergency.
- Following the hydraulic system failure, the captain was required to take-on both the pilot flying and pilot monitoring roles. This reduced the ability to effectively manage the emergency.
- The first officer's inexperience limited their ability to contribute to managing the hydraulic system failure. This negatively impacted crew resource management and increased the captain's workload
- After stopping on the taxiway, the captain mistakenly assumed the brakes were functioning. Unable to locate or contact the tow tug and influenced by self-imposed pressure, continued the taxi to the apron. Approaching a hangar, the crew applied the brakes, but they were ineffective and resulted in the right wingtip and propellor colliding with the hangar.
The ATSB analysed:
During a non-scheduled air transport flight from Forrestania to Perth, the crew of VH-WAJ experienced a complete loss of pressure in the hydraulic system. Without the hydraulic system, the flaps, nose wheel steering, and landing gear were not functional, however limited braking was available from a reserve pressure accumulator. The captain conducted a flapless landing and after stopping on the taxiway for a short moment, opted to continue the taxi to the operator’s hangar, mistakenly believing the hydraulic pressure had returned and that the brakes were functioning. In close proximity to the operator’s hangar, the crew applied the brakes to stop the aircraft while on a slight slope, but they were ineffective and the aircraft collided with the hangar, damaging the right wingtip and right propellor.
The complete loss of hydraulic pressure was identified post-flight as a result of a fluid leak from a hydraulic pipe crack in the union flare in the left main landing gear wheel well.
The training captain ordinarily had an increased physical and cognitive workload due to oversight of the aircraft and providing guidance for the novice FO. However, their workload surged considerably when the illumination of both hydraulic system warning lights required immediate management of the in-flight emergency. In addition to conducting the checklist procedures, the captain had the added responsibilities of all the radio communications and guiding the FO through the emergency task of the manual extension of the landing gear. Additionally, the captain assumed the role of pilot flying from the FO for the approach and landing at Perth. This contributed to the captain’s decision to continue taxiing to the apron after exiting the runway, as the demands of the emergency likely disrupted the typical task prioritisation for post-landing procedures after this event, which would have been to have the aircraft towed.
The FO’s inexperience and low number of hours on the Metro, while completing supervised line-flying, reduced their capacity to contribute to decision-making, workload and task-sharing in the same manner as a more experienced FO during the emergency. The FO’s unfamiliarity with non-normal procedures outside of the simulator meant that they were unable to anticipate the needs of the captain to help distribute the workload after the hydraulic system had failed. As a result, this limited their ability to fully support the captain, which negatively impacted CRM and further increased the captain’s workload.
The captain reported that they did not check the brake accumulator gauge after landing. It was likely that after using the brakes during landing, the reserve accumulator pressure became depleted, although this was not obvious based on the feel of the brakes when tested after stopping.
Both the in-flight positive pressure indication observed on the main hydraulic pressure gauge (due to the manual extension of the landing gear) and the report of no fluid on the runway mistakenly supported the captain‘s understanding that the pressure had returned to the aircraft and that the brakes were functional. The absence of establishing contact with a tow vehicle and being aware of other traffic requiring access to the taxiway, it is likely that the captain felt self-imposed pressure to continue to move the aircraft. This likely influenced the captain’s decision to continue to taxi to the hangar.
