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pdf GFA AD 684 Issue 2 Popular

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GFA AD 684 Issue 2

INSPECTION, REPLACEMENT AND LIFE LIMITATIONS OF ON / OFF FUEL VALVES FITTED TO POWERED SAILPLANES

There have been reported cases of Fuel Shut Off Valves failing, resulting in in-flight engine power loss. In most cases the valve partially restricts flow when selected in the “ON” position, causing a reduction of power. Subsequent ground runs may not reveal the problem. On returning the powered sailplane to service; the power loss in flight is repeated. Additionally, there have also been reports of external fuel leaks from the valve spindle. See “Defects.” This fuel shut off valve in the Dimona H36 and the Scheibe Falke series has a sailplane manufacturer’s 5 year life limitation, based on deterioration of the internal sealing. All other installations in other types have no life limitations. The restriction of fuel flow has been found to be caused by failure of the control knob to turn the shaft through full travel in the ON direction. The result of the rectangular slot in the knob, (engaging over the rectangular shoulder on the top of the shaft) becoming rounded as illustrated. The Truma fuel valve is limited by this AD to 5 years service, in all powered sailplanes from the date of installation. This limitation is based on deterioration of the internal sealing.