What happened
During the approach phase, the flight crew experienced a loss of pressure within the main hydraulic system. In response, the pilots activated the auxiliary hydraulic system and utilized emergency procedures to extend the landing gear. As the aircraft reached the two-thirds mark of the runway during the landing roll, the crew observed that the braking system was not functioning as expected.
In an attempt to clear the active runway, the pilots turned onto a taxiway. However, the aircraft could not be steered or stopped, causing it to traverse a parallel runway and enter an adjacent field, where it collided with a metal beam. At the time of the incident, there were no reported fatalities or injuries.
Findings
An investigation into the aircraft's systems confirmed that the brake system remained continuous with the cockpit controls, and the hydraulic lines, tires, and brake assemblies were all undamaged. No leaks were found, and both hydraulic pumps were fully functional. The hydraulic fluid reservoir was approximately 25% full.
The investigation determined that the crew did not attempt to reset the electric hydraulic pump as prescribed by emergency protocols. Instead, they performed the emergency gear extension while the auxiliary hydraulic system was engaged. It is believed that failing to switch the auxiliary system to the off position during gear extension caused the hydraulic pressure to dissipate, leaving only the limited charge of the emergency brake accumulator available for use. Additionally, the crew opted to exit the runway at an intersection rather than utilizing the remaining 3,900 feet of runway to come to a complete stop, which contributed to the loss of directional control.