What happened
Following its landing, a Vickers Viscount was maneuvering on the runway when it experienced a sudden loss of pressure within its hydraulic system. This mechanical failure rendered both the nosewheel steering and the wheel brakes non-functional. As a result, the aircraft drifted off the paved surface and began rolling down an adjacent downslope.
During the excursion, the crew attempted to retract the landing gear; however, this maneuver could not be completed due to the ongoing lack of hydraulic pressure. The sequence ended when the aircraft collided with the airport control tower.
Findings
An investigation into the incident identified a broken pipeline as a primary component of the failure. Additionally, investigators determined that a non-return valve, which was designed to maintain system pressure during a leak, failed to operate correctly. The loss of hydraulic system pressure was the critical factor that prevented the pilot from maintaining control of the aircraft's direction and stopping distance.