What was found
DURING APPROACH, HYD PRESSURE OF BOTH HYD SYSTEMS DECREASED TO 0 PSI. UNEVENTFUL LANDING. BOTH SYSTEMS HAD BEEN SELECTED TO HIGH, AUXILIARY PUMP & PTU. DUE TO LANDING WITH OPEN LANDING GEAR DOORS, DOOR BUMPERS & DOOR STRUCTURE DAMAGED. AFTER LANDING, PTU WAS SELECTED OFF, HYD PRESSURE RECOVERED. WHEN PTU WAS SELECTED TO ON, HYD PRESSURE DECREASED AGAIN. INSPECTION OF PTU, P/N 4100310-6, S/N 707C, REVEALED DRAIN PORT HOUSING, P/N 4102202-1, CRACKED. PTU HAD ACCUMULATED 9,532 HRS & 6,724 CYCLES. AUSTRIAN AIRLINES/SR TECH ACCOMPLISHED FAILURE INVESTIGATION, FORWARDED FAILED DRAIN PORT HOUSING TO FRISBY AEROSPACE FOR ANALYSIS. PTU & DRAIN PORT HOUSING SUBJECT OF PREVIOUS S/B 4100310-29-0031 (AD 94-22-03).