Narrative:

We were preparing for an ILS to runway 31C at mdw. We were on the goshen 2 arrival into mdw when we had a caution light for low oil pressure. I gave the controls to my first officer, took out the emergency checklist for that indication, reviewed it briefly, and handed the checklist to him. I took over the flight controls and my first officer performed the checklist. After completing the checklist, we elected to keep the engine running. We then reviewed the engine shutdown procedures and checklist. At this time, we discussed our options and agreed that mdw would be the best airport to land at due to our proximity to the approach courses at mdw and sbn. Gary, in, was ruled out because we were not familiar with the airport and the crash fire rescue provisions. At 15 DME on the localizer 31C, the engine speed began to decrease. We initiated the engine shutdown procedure, notified ATC, declared an emergency, and asked for crash fire rescue to stand by. We completed a single engine approach and landing without further incident. Enclosed you should find a copy of the cap 'oil' checklist. The checklist indicates an engine shutdown for various conditions, and provides the procedures at the bottom. One option is to shut down the engine, and the other is to keep the engine running and monitor the other indications. Both my first officer and I believe we followed the appropriate actions, however we see how the checklist can be ambiguous and interpreted in different ways, leading to confusion concerning the best course of action. In our case, for the question: below 23000 ft, is oil pressure less than 70 psi? The answer is yes. Then immediately following is the question: at any altitude, is there any other abnormal indication or vibration? The answer is no. At this point we have a yes or a no, so we follow the line down to the procedures boxes for yes or no, and we have conflicting actions. In our case, we elected to keep the engine running due to WX conditions, training procedures, and engine indications. We feel that the checklist could be better written to remove these ambiguities.

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Original NASA ASRS Text

Title: COMMUTER CAPT CITES PUB DEFICIENCY IN CHKLIST USE DURING INFLT ENG SHUTDOWN ON LTT.

Narrative: WE WERE PREPARING FOR AN ILS TO RWY 31C AT MDW. WE WERE ON THE GOSHEN 2 ARR INTO MDW WHEN WE HAD A CAUTION LIGHT FOR LOW OIL PRESSURE. I GAVE THE CTLS TO MY FO, TOOK OUT THE EMER CHKLIST FOR THAT INDICATION, REVIEWED IT BRIEFLY, AND HANDED THE CHKLIST TO HIM. I TOOK OVER THE FLT CTLS AND MY FO PERFORMED THE CHKLIST. AFTER COMPLETING THE CHKLIST, WE ELECTED TO KEEP THE ENG RUNNING. WE THEN REVIEWED THE ENG SHUTDOWN PROCS AND CHKLIST. AT THIS TIME, WE DISCUSSED OUR OPTIONS AND AGREED THAT MDW WOULD BE THE BEST ARPT TO LAND AT DUE TO OUR PROX TO THE APCH COURSES AT MDW AND SBN. GARY, IN, WAS RULED OUT BECAUSE WE WERE NOT FAMILIAR WITH THE ARPT AND THE CRASH FIRE RESCUE PROVISIONS. AT 15 DME ON THE LOC 31C, THE ENG SPD BEGAN TO DECREASE. WE INITIATED THE ENG SHUTDOWN PROC, NOTIFIED ATC, DECLARED AN EMER, AND ASKED FOR CRASH FIRE RESCUE TO STAND BY. WE COMPLETED A SINGLE ENG APCH AND LNDG WITHOUT FURTHER INCIDENT. ENCLOSED YOU SHOULD FIND A COPY OF THE CAP 'OIL' CHKLIST. THE CHKLIST INDICATES AN ENG SHUTDOWN FOR VARIOUS CONDITIONS, AND PROVIDES THE PROCS AT THE BOTTOM. ONE OPTION IS TO SHUT DOWN THE ENG, AND THE OTHER IS TO KEEP THE ENG RUNNING AND MONITOR THE OTHER INDICATIONS. BOTH MY FO AND I BELIEVE WE FOLLOWED THE APPROPRIATE ACTIONS, HOWEVER WE SEE HOW THE CHKLIST CAN BE AMBIGUOUS AND INTERPRETED IN DIFFERENT WAYS, LEADING TO CONFUSION CONCERNING THE BEST COURSE OF ACTION. IN OUR CASE, FOR THE QUESTION: BELOW 23000 FT, IS OIL PRESSURE LESS THAN 70 PSI? THE ANSWER IS YES. THEN IMMEDIATELY FOLLOWING IS THE QUESTION: AT ANY ALT, IS THERE ANY OTHER ABNORMAL INDICATION OR VIBRATION? THE ANSWER IS NO. AT THIS POINT WE HAVE A YES OR A NO, SO WE FOLLOW THE LINE DOWN TO THE PROCS BOXES FOR YES OR NO, AND WE HAVE CONFLICTING ACTIONS. IN OUR CASE, WE ELECTED TO KEEP THE ENG RUNNING DUE TO WX CONDITIONS, TRAINING PROCS, AND ENG INDICATIONS. WE FEEL THAT THE CHKLIST COULD BE BETTER WRITTEN TO REMOVE THESE AMBIGUITIES.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.