Narrative:

I was the PF from ZZZ to ZZZ1. We were descending out of approximately FL250 to 12000 ft in VMC conditions with ZZZ1 airport in sight; with the autoplt engaged; the power levers at flight idle thrust; and the thrust reverser arm switches in the disarmed/off position; when the EICAS displayed an amber 'right rev unlocked' message; a single chime and an amber 'rev' icon on the right engine N1 display. The captain reached for the QRH and I began to slow the aircraft from approximately 300 KTS to 250 KTS by arresting our vertical descent from 2500 FPM to 500 FPM. I informed ATC that we were working a problem and that we could no longer make the assigned speed and crossing restriction previously given. Center requested to keep him advised if we needed assistance. The captain began to read out the immediate action items per the QRH such as 'affected thrust lever confirm at idle' (flight idle was the position that both thrust levers were already at); the QRH then directs the pilot to proceed to the emergency procedures section and 'affected thrust reverser emergency stow;' then the captain depressed the emergency stow switch. The QRH then asks 'affected thrust reverser is stowed (stow indicated by improved airplane handling and normal operation of affected thrust lever). I stated to the captain that I saw no adverse yaw or felt any type of abnormal aircraft buffet. Since we did not see a change to the EICAS or the amber 'rev' icon on the N1 gauge; the captain proceeded to the 'no' section. The QRH called for the 'airspeed not more than 200 KTS;' I advised ATC and continued to slow the aircraft in a gradual descent of less than 500 FPM to our assigned altitude of 12000 ft. The QRH called for 'affected thrust reverser off/do not arm' (which was the position of both thrust reverser switches prior to the beginning of the problem). The QRH continued 'APU start' and 'APU gen on' which the captain completed. The QRH then stated 'single engine procedures accomplish;' at this point the captain paused and stated that he did not want to shut the engine down. I agreed and I expressed that it was not my desire to needlessly shut the engine down. I suggested that we call maintenance control as I had done at other acrs I had worked for; he felt that we did not have time for that course and I did not press the issue since I was busy monitoring the radio and the autoplt. The captain began to read the QRH again to verify that there wasn't something he had missed in the process. When he got to the statement; 'affected thrust reverser is stowed (stow indicated by improved airplane handling and normal operation of affected thrust lever) he read it twice and stated that he did not see how the thrust reverser was in normal operation now. I agree that I did not see how the thrust reverser was normal since we still had an amber 'rev' icon and an amber 'right rev unlocked.' still at this point the thrust levers were at idle and we were in a slow speed descent to 12000 ft. Again the captain stated that he did not want to shut down the engine but he felt the QRH was only leading us to that course of action. The captain was not sure what the problem exactly was. Was the problem really going to get worse at a low altitude if we did not shut the engine down? Was the thrust reverser really deployed or not; or was this just an indication problem? The captain felt that shutting the engine down was the safest course of action given the fact that nothing had changed and we did not really know the true nature of the problem. ZZZ1 had VMC conditions; we were clear of all terrain and had the airport in sight. We both felt at the time that the checklist was ambiguous at best and that the checklist did not address this type of situation expressly. Our training on the aircraft for a left or right rev unlocked message was far different from this. In training we were given a takeoff scenario in which the problem occurred at a low altitude and the aircraft buffeted violently until the emergency stow was pushed and the buffeting went away; or if the buffeting continued; the engine was shut down as per the QRH. In either case; one was satisfied that the situation was under control once the QRH was completed.in our situation; neither the captain or myself could state with certainty that the right thrust reverser was contained to a safe and locked position and that at some point on approach and landing it could deploy further; causing loss of directional control. Therefore; the captain decided to shut the engine down and perform the single engine procedures QRH. We ran the single engine procedures QRH; I declared an emergency to ATC; the autoplt disengaged with a loss of the right generator. I transferred the autoplt to captain's side and I stated that it made more sense for him to take the controls and for me to complete the QRH; which we did. We completed all pertinent checklists. I informed the flight attendant and I made a PA announcement to the passenger that we had shut down the right engine for precautionary reasons and we were about 7 minutes from landing at ZZZ1; we would not have to evacuate the aircraft or brace for an emergency; but we would make a normal landing. I then advised company on operations frequency. The captain landed the aircraft at ZZZ1 without incident and we cleared the runway and taxied normally to the terminal where the passenger deplaned as normal. After all passenger had deplaned; maintenance came aboard the aircraft and informed us the right thrust reverser translating cowl was open approximately one inch. It is my personal opinion that QRH should be re-written to state that after depressing the emergency stow button and in any case that the amber 'rev' icon and the amber 'right rev unlocked' will or will not remain on the EICAS. This would give the crew a better understanding if the emergency stow switch has failed or operated correctly in a flight idle descent situation.callback conversation with reporter revealed the following information: the reporter stated they had all the indications the reverser was deployed with the EICAS 'right reverser unlock' message; the single chime and the rev icon in the right engine N1 display. The emergency stow switch was activated and did not change the reverser indications and the airplane flew the same as before the switch was activated. The only thing missing was the buffeting the QRH described. The decision was made to follow the book and shut down the engine and declare an emergency. A later meeting with the chief pilot about the incident revealed maintenance found the reverser out of rig.

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Original NASA ASRS Text

Title: A CRJ200; IN DSCNT; DECLARED AN EMER AND SHUT DOWN THE R ENG DUE TO REVERSER UNLOCK LIGHT; SINGLE CHIME; AND REV ICON IN R ENG N1 DISPLAY.

Narrative: I WAS THE PF FROM ZZZ TO ZZZ1. WE WERE DSNDING OUT OF APPROX FL250 TO 12000 FT IN VMC CONDITIONS WITH ZZZ1 ARPT IN SIGHT; WITH THE AUTOPLT ENGAGED; THE POWER LEVERS AT FLIGHT IDLE THRUST; AND THE THRUST REVERSER ARM SWITCHES IN THE DISARMED/OFF POSITION; WHEN THE EICAS DISPLAYED AN AMBER 'R REV UNLOCKED' MESSAGE; A SINGLE CHIME AND AN AMBER 'REV' ICON ON THE R ENG N1 DISPLAY. THE CAPT REACHED FOR THE QRH AND I BEGAN TO SLOW THE ACFT FROM APPROX 300 KTS TO 250 KTS BY ARRESTING OUR VERT DSCNT FROM 2500 FPM TO 500 FPM. I INFORMED ATC THAT WE WERE WORKING A PROBLEM AND THAT WE COULD NO LONGER MAKE THE ASSIGNED SPD AND XING RESTRICTION PREVIOUSLY GIVEN. CTR REQUESTED TO KEEP HIM ADVISED IF WE NEEDED ASSISTANCE. THE CAPT BEGAN TO READ OUT THE IMMEDIATE ACTION ITEMS PER THE QRH SUCH AS 'AFFECTED THRUST LEVER CONFIRM AT IDLE' (FLT IDLE WAS THE POSITION THAT BOTH THRUST LEVERS WERE ALREADY AT); THE QRH THEN DIRECTS THE PLT TO PROCEED TO THE EMER PROCS SECTION AND 'AFFECTED THRUST REVERSER EMER STOW;' THEN THE CAPT DEPRESSED THE EMER STOW SWITCH. THE QRH THEN ASKS 'AFFECTED THRUST REVERSER IS STOWED (STOW INDICATED BY IMPROVED AIRPLANE HANDLING AND NORMAL OPERATION OF AFFECTED THRUST LEVER). I STATED TO THE CAPT THAT I SAW NO ADVERSE YAW OR FELT ANY TYPE OF ABNORMAL ACFT BUFFET. SINCE WE DID NOT SEE A CHANGE TO THE EICAS OR THE AMBER 'REV' ICON ON THE N1 GAUGE; THE CAPT PROCEEDED TO THE 'NO' SECTION. THE QRH CALLED FOR THE 'AIRSPD NOT MORE THAN 200 KTS;' I ADVISED ATC AND CONTINUED TO SLOW THE ACFT IN A GRADUAL DSCNT OF LESS THAN 500 FPM TO OUR ASSIGNED ALT OF 12000 FT. THE QRH CALLED FOR 'AFFECTED THRUST REVERSER OFF/DO NOT ARM' (WHICH WAS THE POSITION OF BOTH THRUST REVERSER SWITCHES PRIOR TO THE BEGINNING OF THE PROB). THE QRH CONTINUED 'APU START' AND 'APU GEN ON' WHICH THE CAPT COMPLETED. THE QRH THEN STATED 'SINGLE ENG PROCS ACCOMPLISH;' AT THIS POINT THE CAPT PAUSED AND STATED THAT HE DID NOT WANT TO SHUT THE ENG DOWN. I AGREED AND I EXPRESSED THAT IT WAS NOT MY DESIRE TO NEEDLESSLY SHUT THE ENG DOWN. I SUGGESTED THAT WE CALL MAINT CTL AS I HAD DONE AT OTHER ACRS I HAD WORKED FOR; HE FELT THAT WE DID NOT HAVE TIME FOR THAT COURSE AND I DID NOT PRESS THE ISSUE SINCE I WAS BUSY MONITORING THE RADIO AND THE AUTOPLT. THE CAPT BEGAN TO READ THE QRH AGAIN TO VERIFY THAT THERE WASN'T SOMETHING HE HAD MISSED IN THE PROCESS. WHEN HE GOT TO THE STATEMENT; 'AFFECTED THRUST REVERSER IS STOWED (STOW INDICATED BY IMPROVED AIRPLANE HANDLING AND NORMAL OPERATION OF AFFECTED THRUST LEVER) HE READ IT TWICE AND STATED THAT HE DID NOT SEE HOW THE THRUST REVERSER WAS IN NORMAL OPERATION NOW. I AGREE THAT I DID NOT SEE HOW THE THRUST REVERSER WAS NORMAL SINCE WE STILL HAD AN AMBER 'REV' ICON AND AN AMBER 'R REV UNLOCKED.' STILL AT THIS POINT THE THRUST LEVERS WERE AT IDLE AND WE WERE IN A SLOW SPD DSCNT TO 12000 FT. AGAIN THE CAPT STATED THAT HE DID NOT WANT TO SHUT DOWN THE ENG BUT HE FELT THE QRH WAS ONLY LEADING US TO THAT COURSE OF ACTION. THE CAPT WAS NOT SURE WHAT THE PROB EXACTLY WAS. WAS THE PROB REALLY GOING TO GET WORSE AT A LOW ALT IF WE DID NOT SHUT THE ENG DOWN? WAS THE THRUST REVERSER REALLY DEPLOYED OR NOT; OR WAS THIS JUST AN INDICATION PROB? THE CAPT FELT THAT SHUTTING THE ENG DOWN WAS THE SAFEST COURSE OF ACTION GIVEN THE FACT THAT NOTHING HAD CHANGED AND WE DID NOT REALLY KNOW THE TRUE NATURE OF THE PROB. ZZZ1 HAD VMC CONDITIONS; WE WERE CLR OF ALL TERRAIN AND HAD THE ARPT IN SIGHT. WE BOTH FELT AT THE TIME THAT THE CHKLIST WAS AMBIGUOUS AT BEST AND THAT THE CHKLIST DID NOT ADDRESS THIS TYPE OF SITUATION EXPRESSLY. OUR TRAINING ON THE ACFT FOR A L OR R REV UNLOCKED MESSAGE WAS FAR DIFFERENT FROM THIS. IN TRAINING WE WERE GIVEN A TKOF SCENARIO IN WHICH THE PROB OCCURRED AT A LOW ALT AND THE ACFT BUFFETED VIOLENTLY UNTIL THE EMER STOW WAS PUSHED AND THE BUFFETING WENT AWAY; OR IF THE BUFFETING CONTINUED; THE ENG WAS SHUT DOWN AS PER THE QRH. IN EITHER CASE; ONE WAS SATISFIED THAT THE SITUATION WAS UNDER CTL ONCE THE QRH WAS COMPLETED.IN OUR SITUATION; NEITHER THE CAPT OR MYSELF COULD STATE WITH CERTAINTY THAT THE R THRUST REVERSER WAS CONTAINED TO A SAFE AND LOCKED POSITION AND THAT AT SOME POINT ON APCH AND LNDG IT COULD DEPLOY FURTHER; CAUSING LOSS OF DIRECTIONAL CTL. THEREFORE; THE CAPT DECIDED TO SHUT THE ENG DOWN AND PERFORM THE SINGLE ENG PROCS QRH. WE RAN THE SINGLE ENG PROCS QRH; I DECLARED AN EMER TO ATC; THE AUTOPLT DISENGAGED WITH A LOSS OF THE R GENERATOR. I TRANSFERRED THE AUTOPLT TO CAPT'S SIDE AND I STATED THAT IT MADE MORE SENSE FOR HIM TO TAKE THE CTLS AND FOR ME TO COMPLETE THE QRH; WHICH WE DID. WE COMPLETED ALL PERTINENT CHKLISTS. I INFORMED THE FLT ATTENDANT AND I MADE A PA ANNOUNCEMENT TO THE PAX THAT WE HAD SHUT DOWN THE R ENG FOR PRECAUTIONARY REASONS AND WE WERE ABOUT 7 MINUTES FROM LNDG AT ZZZ1; WE WOULD NOT HAVE TO EVACUATE THE ACFT OR BRACE FOR AN EMER; BUT WE WOULD MAKE A NORMAL LNDG. I THEN ADVISED COMPANY ON OPS FREQ. THE CAPT LANDED THE ACFT AT ZZZ1 WITHOUT INCIDENT AND WE CLRED THE RWY AND TAXIED NORMALLY TO THE TERMINAL WHERE THE PAX DEPLANED AS NORMAL. AFTER ALL PAX HAD DEPLANED; MAINT CAME ABOARD THE ACFT AND INFORMED US THE R THRUST REVERSER TRANSLATING COWL WAS OPEN APPROX ONE INCH. IT IS MY PERSONAL OPINION THAT QRH SHOULD BE RE-WRITTEN TO STATE THAT AFTER DEPRESSING THE EMER STOW BUTTON AND IN ANY CASE THAT THE AMBER 'REV' ICON AND THE AMBER 'R REV UNLOCKED' WILL OR WILL NOT REMAIN ON THE EICAS. THIS WOULD GIVE THE CREW A BETTER UNDERSTANDING IF THE EMER STOW SWITCH HAS FAILED OR OPERATED CORRECTLY IN A FLT IDLE DSCNT SITUATION.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THEY HAD ALL THE INDICATIONS THE REVERSER WAS DEPLOYED WITH THE EICAS 'R REVERSER UNLOCK' MESSAGE; THE SINGLE CHIME AND THE REV ICON IN THE R ENG N1 DISPLAY. THE EMER STOW SWITCH WAS ACTIVATED AND DID NOT CHANGE THE REVERSER INDICATIONS AND THE AIRPLANE FLEW THE SAME AS BEFORE THE SWITCH WAS ACTIVATED. THE ONLY THING MISSING WAS THE BUFFETING THE QRH DESCRIBED. THE DECISION WAS MADE TO FOLLOW THE BOOK AND SHUT DOWN THE ENG AND DECLARE AN EMER. A LATER MEETING WITH THE CHIEF PLT ABOUT THE INCIDENT REVEALED MAINT FOUND THE REVERSER OUT OF RIG.

Data retrieved from NASA's ASRS site as of January 2009 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.