N111UA
AERO COMMANDER 680FL
AFTER A LOSS OF HYD PRESSURE, THE RGT MAIN GEAR WOULD NOT FULLY EXTD WHEN THE PLT TRIED TO LOWER THE GEAR FOR LNDG. ALL ATMTS TO LOCK IT INTO PLACE WERE UNSUCCESSFUL. WHEN THE ACFT TOUCHED DOWN DRG THE LNDG, THE RGT MAIN GEAR COLLAPSED.THE ACFT SLID TO A STOP & THE OCCUPANTS WERE EVACUATED. AN INSPN OF THE RGT MAIN GEAR ASSY REVEALED THE HYD ACTUATING CYL HAD FAILED AT THE SNAP RING GROOVE & THE PNEUMATIC ACTUATING CYL HAD FAILED AT THE ROD END. BOTH FAILED FM OVERLOAD.THIS WAS THE 2ND OVERLOAD FAILURE OF THE HYD ACTUATING CYL IN 26 FLT HRS OF OPN. ACCORDING TO A MECHANIC, WHO WAS FAMILIAR WITH THE ACFT, THIS FAILURE WAS CONSISTENT WITH EXCESSIVE PRESSURE IN THE SYS DUE TO A PRESSURE RELIEF/UNLOADERVALVE MALFUNCTION.
Source: NTSB Aviation Accident Database
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