ENG SHUTDOWN; THEN RESTART.

Narrative

THE CAPT AND I NOTICED THE OIL PRESSURE GAUGE ON THE R # 2 ENG SHOWED OIL PRESSURE SLOWLY DECREASING. IT FELL INTO THE YELLOW ARC ON THE GAUGE; YET ALL OTHER INDICATIONS REMAINED NORMAL. THE CAPT ASKED ZID FOR A DSCNT FROM 17000 FT TO 15000 FT; AND IN THE DSCNT HE PULLED THE TORQUE ON THE #2 ENG BACK TO ABOUT 25 PERCENT. THE OIL PRESSURE CONTINUED TO FALL TO THE LOW LIMIT; ILLUMINATING A RED WARNING LIGHT. WE RAN THROUGH THE CHKLIST IN ITS ENTIRETY. INITIALLY WE HAD TO SHUT DOWN THE ENG; WHICH PROVIDES FOR A WAY TO TEST A SECOND OIL PRESSURE WARNING SYS. SINCE THE SECOND SYS WAS OPERATIONAL; THE CHKLIST REQUIRED US TO RESTART ENG #2 AND CONSIDER THE OIL PRESSURE GAUGE UNRELIABLE. THE FLT THEN CONTINUED ON TO COLUMBUS WITHOUT INCIDENT. NO RPT OF A PRECAUTIONARY SHUTDOWN IN FLT WAS MADE TO ATC PER FAR 121.565 BECAUSE TO DO SO WE WOULD HAVE HAD TO INTERRUPT THE FLOW OF THE CHKLIST; AND WHEN THE CHKLIST WAS COMPLETED BOTH ENGS WERE OPERATING NORMALLY AND NO ABNORMAL SIT EXISTED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR CAN ADD NOTHING TO THE RPT ABOUT THE ENG SHUTDOWN. HE HAS BEEN FLYING THE ATR-72 FOR ONLY ABOUT 6 MONTHS. THIS WAS THE ONLY INCIDENT OF THIS TYPE THAT HE HAS SEEN. HE AGREES THAT THIS IS A STRANGE WAY TO CHK THE OIL PRESSURE SYS AT FIRST GLANCE; BUT THE PROC WORKS WELL. HIS COMPANY IS COMPLYING WITH THE AD REGARDING THE ATR-72; NO USE OF THE AUTOPLT WHILE IN ICING CONDITIONS. IN ADDITION; THE 'COMPANY LINE' IS TO LEAVE ICING CONDITIONS ASAP. SUPPLEMENTAL INFO FROM ACN 278728: (LCL ALERT ONLY) NO TCASII WARNING. THE CHKLIST CALLS FOR SHUTTING DOWN THE ENG; THEN PUTTING THE CONDITION LEVER TO FEATHER. AFTER 30 SECONDS YOU SHOULD NOW GET A ICAS WARNING THAT THERE IS NO OIL PRESSURE. IF YOU DO GET THE ICAS WARNING; YOU CAN RESTART THE ENG.