Narrative:

On climb out at about 10;350 ft the EICAS displayed a cabin altitude caution message. The cabin altitude was approximately 8;250 ft and rising consistent with our vertical speed. The pressure differential was low. We ran the QRH procedures for a cabin altitude caution message. The cabin altitude was uncontrollable in both manual and automatic modes. We contacted ATC and requested a lower altitude and vectors back to the departure airport. After it was determined that the aircraft was unable to pressurize; we contacted the company via ACARS; declared our intentions to return to the departure airport; and landed without further incident. During a previous flight; prior to the event; we received an ovbd (overboard) cool caution and ovbd cool fail status message on the ground. We made an entry in the aircraft maintenance log book; contacted the dispatch; and waited on contract maintenance to arrive. The mechanic decided to defer the item; overboard exhaust sov. The (M) procedures; referencing a specific task in the amm; instruct the mechanic to deactivate the overboard exhaust sov in the closed position. When we completed the air return after the depressurization event and called the contract maintenance back out to the aircraft; it was determined that the sov had been improperly secured in the open position. The mechanic moved the manual override lever on the overboard exhaust sov to the closed position and we completed the flight without further incident. Flight crews do not have the same training and scope of knowledge about the inner mechanical details of the aircraft that our mechanics do. There is no way for us to determine through either a preflight inspection or close scrutiny of the deferred items that the maintenance (M) items have been complied with. The only things that we can rely upon are a proper entry into the aircraft maintenance log; the MEL book and the word of the mechanic that the procedures were accomplished in accordance with the MEL and the aircraft maintenance manual. Referencing the task card procedures in the amm instruct the mechanic step by step in deactivating and securing the overboard exhaust sov. The problem is the same task is referenced when securing the valve in the open or the closed position. Shouldn't there be separate tasks (with diagrams) for securing the sov in the open position and securing the sov in the closed position? This would provide another level of separation to help the mechanics ensure that the sov is secured in the correct position. Flight crews need to be extra vigilant when operating under deferrals. In the future it may help to review the MEL with the mechanic present to ensure that both the (M) and (O) procedures have been or will be complied with to ensure the safe completion of the flight.

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Original NASA ASRS Text

Title: A Contract Mechanic secured a CRJ200's failed OVERBOARD EXHAUST SOV in the open position but the MEL procedure indicated it should have been closed. The aircraft would not pressurize after takeoff and so the crew returned to land.

Narrative: On climb out at about 10;350 FT the EICAS displayed a CABIN ALT caution message. The cabin altitude was approximately 8;250 FT and rising consistent with our vertical speed. The pressure differential was low. We ran the QRH procedures for a CABIN ALT caution message. The cabin altitude was uncontrollable in both manual and automatic modes. We contacted ATC and requested a lower altitude and vectors back to the departure airport. After it was determined that the aircraft was unable to pressurize; we contacted the company via ACARS; declared our intentions to return to the departure airport; and landed without further incident. During a previous flight; prior to the event; we received an OVBD (overboard) COOL caution and OVBD COOL FAIL status message on the ground. We made an entry in the aircraft maintenance log book; contacted the Dispatch; and waited on Contract Maintenance to arrive. The Mechanic decided to defer the item; Overboard Exhaust SOV. The (M) procedures; referencing a specific task in the AMM; instruct the Mechanic to deactivate the Overboard Exhaust SOV in the CLOSED position. When we completed the air return after the depressurization event and called the Contract Maintenance back out to the aircraft; it was determined that the SOV had been improperly secured in the OPEN position. The Mechanic moved the manual override lever on the Overboard Exhaust SOV to the CLOSED position and we completed the flight without further incident. Flight crews do not have the same training and scope of knowledge about the inner mechanical details of the aircraft that our mechanics do. There is no way for us to determine through either a preflight inspection or close scrutiny of the deferred items that the maintenance (M) items have been complied with. The only things that we can rely upon are a proper entry into the aircraft maintenance log; the MEL book and the word of the mechanic that the procedures were accomplished in accordance with the MEL and the Aircraft Maintenance Manual. Referencing the task card procedures in the AMM instruct the mechanic step by step in deactivating and securing the Overboard Exhaust SOV. The problem is the same task is referenced when securing the valve in the OPEN or the CLOSED position. Shouldn't there be separate tasks (with diagrams) for securing the SOV in the OPEN position and securing the SOV in the CLOSED position? This would provide another level of separation to help the mechanics ensure that the SOV is secured in the correct position. Flight crews need to be extra vigilant when operating under deferrals. In the future it may help to review the MEL with the mechanic present to ensure that both the (M) and (O) procedures have been or will be complied with to ensure the safe completion of the flight.

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.