What happened
On 6 September 1999, a Fokker 50, registration G-UKTA, was performing a scheduled commercial flight from Stavanger Airport Sola to Aberdeen. Shortly after departing from runway 18, the crew issued a PAN-PAN urgency message to air traffic control, reporting hydraulic system issues and a potential leak.
During the initial climb and acceleration phase, the flight crew observed a flap asymmetry warning, which was immediately followed by a low hydraulic quantity alert. This was then accompanied by an indication of a double hydraulic pump failure. While the crew requested that air traffic controllers inspect the runway and taxiways for visible fluid, no leaks were detected on the ground while the aircraft was airborne. Due to the inability to confirm the location of the leak, the crew operated under the assumption that hydraulic fluid was being vented into the atmosphere.
Following the emergency declaration, the aircraft was instructed to hold in a safe area west of the aerodrome to allow the crew to assess the systems and prepare for a return landing. The airport emergency services were activated, and the aircraft was granted priority landing status. The aircraft landed normally on runway 18; however, because the nose wheel steering was inoperative, the aircraft could not exit the runway via taxiway A and had to be towed to a hangar. The runway was closed for approximately five minutes to facilitate the cleaning of a hydraulic oil spill.
The investigation
The investigation was conducted by the Norwegian Safety Investigation Authority (NSIA) based on information provided by Stavanger airport air traffic controllers and a summary from the KLM uk Flight Safety Manager. The inquiry focused on the mechanical failure of the hydraulic systems and the subsequent operational response.
Findings
- The primary mechanical cause of the incident was a ruptured hose associated with the left-hand gear up hydraulic pressure.
- The failure resulted in a loss of hydraulic fluid, leading to flap asymmetry warnings and indications of a double hydraulic pump failure.
- The investigation noted a significant delay in receiving information from the operator, as the NSIA only received a summary from the airline's safety manager approximately eight months after the event.
Safety action
- The investigation highlighted a lack of clarity regarding reporting procedures for foreign-registered aircraft operating within Norwegian airspace.
- To ensure timely and adequate reporting of incidents to the national investigative authority, the NSIA committed to improving the publication of information and establishing clearer reporting routines for international operators.