Hawker: Unexplained Hydraulic Pressure & Overheating

January 2010

Ungvarsky, Dave - Airframe Tech Rep - Lincoln, NE (LNK). Aviation professional since 1978.

Airframes: Hawker

Direct: 402.430.8668

We recently serviced a Hawker 900XP experiencing recurring hydraulic pressure and a hydraulic overheat issue that could not be readily duplicated on the ground. Troubleshooting revealed the Manual Pressure Release Valve for the emergency system would occasionally remain in the "Dump" position. When the release valve remains in this position, hydraulic pressure is slow to build and the aircraft can experience hydraulic overheat in flight, due to the excessive amount of fluid being introduced into the return system. These valves are installed on the Hawker 750, 850XP and 900XP aircraft.

Hawker 700 & 800 Series

Hawker 700 and 800 series operators need to be aware that excessive seepage to the return system from components can also create a hydraulic overheat condition. Follow the Aircraft Maintenance Manual for proper troubleshooting steps to determine the source of the excessive seepage.

For questions about Hawker technical issues, contact your Hawker Tech Rep.