A BEECH SIERRA LOSES OIL PRESSURE DURING FLT AND MAKES AN IMMEDIATE LNDG WITH NO OIL PRESSURE. NO ACFT DAMAGE.

Narrative

PREVIOUS FLT IN ACFT (BY ANOTHER PLT) HAD RESULTED IN LARGE AMOUNT OF OIL LOSS. CAUSE WAS DETERMINED BY A&P TO BE A LOOSE OIL FILLER NECK. AFTER TIGHTENING AND SAFETY WIRING; OIL WAS REPLENISHED AND ENG WAS GND RUN FOR SEVERAL MINS WITH NO LEAKS AND NORMAL OIL PRESSURE. I DEPARTED WITH A FLT INSTRUCTOR TO PRACTICE COMMERCIAL PLT MANEUVERS. MONITORED OIL PRESSURE; CHKED NORMAL. AFTER APPROX .6 HRS FLT; PROP OVERSPED. I CHKED OIL PRESSURE; IT WAS NOW ALMOST 0 PSI. INSTRUCTOR TOLD ME TO FLY TO NEAREST ARPT; WHERE A NORMAL (ALTHOUGH RUSHED) LNDG OCCURRED. AFTER REMOVING COWLING; ENG WAS AGAIN INSPECTED AND IT WAS DETERMINED THAT AN OIL HOSE TO THE OIL PRESSURE GAUGE WAS LOOSE AT THE FITTING; AND HAD PROBABLY ALLOWED OIL TO ESCAPE. THE OIL HAD BEEN CHANGED BY ANOTHER A&P 3 HRS PRIOR TO THE FLT; AND THE HOSE IN QUESTION IS IN A POS WHERE INSPECTION OF THE OIL SCREEN WOULD BE DIFFICULT WITHOUT ITS REMOVAL. IT APPEARS THAT AFTER SVCING THE SCREEN; THE HOSE WAS REPLACED BUT NOT TIGHTENED. LESSONS LEARNED: 1) FOLLOWING ANY MAINT; A TEST FLT IN THE VICINITY OF AN ARPT; VFR; IS A MUST. 2) DO NOT ASSUME THAT JUST BECAUSE A PROBABLE CAUSE OF SOME PROB IS DISCOVERED THAT IT IS THE ONLY CAUSE -- CAREFULLY INSPECT ALL COMPONENTS; SYS; ETC.