Narrative:

Daylight; clear weather; no clouds. During cruise at FL230 we received an amber left rev unlocked message; with associated rev icon in the left N1 gauge. I transferred control to the first officer and ran the QRH checklist; resulting in activation of the left emergency stow and shutdown of the left engine. We were directly over an airport and elected to divert there. We declared an emergency with ATC and completed the QRH single engine procedures. We notified dispatch both via ACARS and via relay through another flight; and then made the appropriate PA announcement; and landed without further incident. After landing I telephoned my dispatcher and I also spoke to maintenance control. The airplane was inspected by maintenance; the reverser was deferred; and we continued on our way. While on the ground I received a call from a chief pilot who wanted to know why we decided to shut down the engine. It was while reviewing the checklist with him that I realized I had misinterpreted a decision-tree step in the rev unlocked procedure. The checklist in the QRH begins with two boxed items; followed by a note. The very next action item after pressing the emergency stow switch is a bolded question -- or; more precisely; a true/false statement -- which is designed to determine whether the rev unlocked message might be a false indication. It is followed by a yes/no branch in the checklist flow. The 'question' essentially asks; 'is the reverser stowed?' unfortunately; I interpreted the question to be; 'did pressing the emergency stow improve the handling of the aircraft?' before proceeding I asked my first officer; who was now flying; whether he agreed that the aircraft handling did not change; which he did. As the answer in our case was therefore 'no;' I proceeded with the 'no' branch of the checklist; resulting in engine shutdown. I had further reason to expect to shut down the engine per the checklist (see below). It wasn't until my discussion with the chief pilot after landing that I became aware of my misinterpretation. In either case the diversion to the nearest suitable airport was the proper response. The difference was the decision to shut down the engine.I think there are two factors which contributed to my misinterpretation: (1) the wording of the bolded decision-tree statement. During my conversation with the chief pilot the grammar of the statement became clear; but in the heat of the moment it seemed to be asking the yes/no question from exactly the opposite direction. Further; it seems it would have been helpful had there been a specific step listed before the decision-tree statement directing the crew to attempt operation of the affected thrust lever out of idle. The checklist does not specifically say to do this; it only asks whether the operation of the thrust lever is affected; but that wording is toward the end; in the part I misread. (2) in my initial training for the crj our systems instructor made a very big deal about the fact that the activation of the emergency stow switch would; by design; crush and damage certain engine components in the process of forcibly re-stowing the reverser. I have spoken to other pilots who have been taught this as well. This is apparently incorrect; as I have now learned; but that memory from ground school was my primary thought as I pressed the emergency stow switch in response to the checklist. At that point; in my mind; the engine would no longer be usable once I pressed that button. I therefore had no reason to question the checklist's apparent resulting guidance to secure the engine. I now understand why the shutdown was unnecessary; but at the time I had no reason to suspect a mistake. While I don't blame the checklist for my decision; I would like to make two recommendations: (1) add an action item between the boxed items and the question; an item which specifically and clearly directs the crew to test the thrust lever for normal operation. Such as: 'affected thrust lever ....... Check for normal operation.' (2) the wording of the bolded decision-tree question could be re-written so as to make it clearer. As it stands now there isn't even a question mark. 'Is the thrust reverser now stowed?' would be short and simple; and would place the question mark in the correct place; instead of at the end of the line where I interpreted it to be. The existing 'symptom' text could then follow. This would more clearly match the yes or no decision in the checklist to the correct question. 'Is the thrust lever operating normally?' would be an improvement as well. I think either wording would have prevented my interpretation. (3) ensure that the system is being correctly taught during training. Based on a few brief conversations since this event there is an incorrect understanding in the minds of many of our pilots. A clarification email might be in order. I believe my initial crj ground school training led me to misinterpret the checklist -- or at least; led me not to suspect a misinterpretation on my part. It made perfect sense to shut down a damaged engine.

Related reports:

Google
 

Original NASA ASRS Text

Title: A CRJ200 L REV UNLOCKED message prompted the use of the QRH that was improperly interpreted resulting in an unnecessary shutdown of the affected engine and diversion.

Narrative: Daylight; clear weather; no clouds. During cruise at FL230 we received an amber L REV UNLOCKED message; with associated REV icon in the left N1 gauge. I transferred control to the First Officer and ran the QRH checklist; resulting in activation of the left EMER STOW and shutdown of the left engine. We were directly over an airport and elected to divert there. We declared an emergency with ATC and completed the QRH Single Engine Procedures. We notified Dispatch both via ACARS and via relay through another flight; and then made the appropriate PA announcement; and landed without further incident. After landing I telephoned my Dispatcher and I also spoke to Maintenance Control. The airplane was inspected by Maintenance; the reverser was deferred; and we continued on our way. While on the ground I received a call from a Chief Pilot who wanted to know why we decided to shut down the engine. It was while reviewing the checklist with him that I realized I had misinterpreted a decision-tree step in the REV UNLOCKED procedure. The checklist in the QRH begins with two boxed items; followed by a note. The very next action item after pressing the EMER STOW switch is a bolded question -- or; more precisely; a true/false statement -- which is designed to determine whether the REV UNLOCKED message might be a false indication. It is followed by a YES/NO branch in the checklist flow. The 'question' essentially asks; 'Is the reverser stowed?' Unfortunately; I interpreted the question to be; 'Did pressing the EMER STOW improve the handling of the aircraft?' Before proceeding I asked my First Officer; who was now flying; whether he agreed that the aircraft handling did NOT change; which he did. As the answer in our case was therefore 'no;' I proceeded with the 'No' branch of the checklist; resulting in engine shutdown. I had further reason to expect to shut down the engine per the checklist (see below). It wasn't until my discussion with the Chief Pilot after landing that I became aware of my misinterpretation. In either case the diversion to the nearest suitable airport was the proper response. The difference was the decision to shut down the engine.I think there are two factors which contributed to my misinterpretation: (1) The wording of the bolded decision-tree statement. During my conversation with the Chief Pilot the grammar of the statement became clear; but in the heat of the moment it seemed to be asking the yes/no question from exactly the opposite direction. Further; it seems it would have been helpful had there been a specific step listed before the decision-tree statement directing the crew to attempt operation of the affected thrust lever out of idle. The checklist does not specifically say to do this; it only asks whether the operation of the thrust lever is affected; but that wording is toward the end; in the part I misread. (2) In my initial training for the CRJ our Systems Instructor made a very big deal about the fact that the activation of the EMER STOW switch would; by design; crush and damage certain engine components in the process of forcibly re-stowing the reverser. I have spoken to other pilots who have been taught this as well. This is apparently incorrect; as I have now learned; but that memory from ground school was my primary thought as I pressed the EMER STOW switch in response to the checklist. At that point; in my mind; the engine would no longer be usable once I pressed that button. I therefore had no reason to question the checklist's apparent resulting guidance to secure the engine. I now understand why the shutdown was unnecessary; but at the time I had no reason to suspect a mistake. While I don't blame the checklist for my decision; I would like to make two recommendations: (1) Add an action item between the boxed items and the question; an item which specifically and clearly directs the crew to test the thrust lever for normal operation. Such as: 'Affected thrust lever ....... check for normal operation.' (2) The wording of the bolded decision-tree question could be re-written so as to make it clearer. As it stands now there isn't even a question mark. 'Is the thrust reverser now stowed?' would be short and simple; and would place the question mark in the correct place; instead of at the end of the line where I interpreted it to be. The existing 'symptom' text could then follow. This would more clearly match the YES or NO decision in the checklist to the correct question. 'Is the thrust lever operating normally?' would be an improvement as well. I think either wording would have prevented my interpretation. (3) Ensure that the system is being correctly taught during training. Based on a few brief conversations since this event there is an incorrect understanding in the minds of many of our pilots. A clarification email might be in order. I believe my initial CRJ ground school training led me to misinterpret the checklist -- or at least; led me not to suspect a misinterpretation on my part. It made perfect sense to shut down a damaged engine.

Data retrieved from NASA's ASRS site as of April 2012 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.