Narrative:

In the course of completing the normal preflight of our B737-300, as well as the required paperwork, our release and all other paperwork indicated that this aircraft was equipped with CFM26-B2 engines. During the cockpit setup, information displayed in the control display unit indicated that the software was for B1-pwred engines. Given the preponderance of data which told us to expect B2 engines, this one entry on the computer display could easily be missed by crews operating this aircraft. As I assume it was by the crew who brought this aircraft to mex. Our maintenance department indicates that some portion of our fleet has been equipped with a switch, which they can change from one engine rating to the other without having to complete extensive, time consuming procedures should a derating or engine replacement be necessary. Their supposition in this case is that this switch might have been inadvertently bumped and switched to the incorrect position. This situation highlights the problems faced by today's airline crews utilizing advanced technology equipment which provides access to almost unlimited information, but can, on occasion, provide incorrect data which affects safety of flight. The perceived infallibility of this equipment (computers) leads to a complacency which could be fatal.

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Original NASA ASRS Text

Title: CAPT OF A B737-300 FOUND THE CTL DISPLAY UNIT (CDU) SET TO THE WRONG ENG. PROB CAUSED BY A SWITCH USED BY MAINT WHEN A SLIGHTLY DIFFERENT MODEL ENG IS INSTALLED.

Narrative: IN THE COURSE OF COMPLETING THE NORMAL PREFLT OF OUR B737-300, AS WELL AS THE REQUIRED PAPERWORK, OUR RELEASE AND ALL OTHER PAPERWORK INDICATED THAT THIS ACFT WAS EQUIPPED WITH CFM26-B2 ENGS. DURING THE COCKPIT SETUP, INFO DISPLAYED IN THE CTL DISPLAY UNIT INDICATED THAT THE SOFTWARE WAS FOR B1-PWRED ENGS. GIVEN THE PREPONDERANCE OF DATA WHICH TOLD US TO EXPECT B2 ENGS, THIS ONE ENTRY ON THE COMPUTER DISPLAY COULD EASILY BE MISSED BY CREWS OPERATING THIS ACFT. AS I ASSUME IT WAS BY THE CREW WHO BROUGHT THIS ACFT TO MEX. OUR MAINT DEPT INDICATES THAT SOME PORTION OF OUR FLEET HAS BEEN EQUIPPED WITH A SWITCH, WHICH THEY CAN CHANGE FROM ONE ENG RATING TO THE OTHER WITHOUT HAVING TO COMPLETE EXTENSIVE, TIME CONSUMING PROCS SHOULD A DERATING OR ENG REPLACEMENT BE NECESSARY. THEIR SUPPOSITION IN THIS CASE IS THAT THIS SWITCH MIGHT HAVE BEEN INADVERTENTLY BUMPED AND SWITCHED TO THE INCORRECT POS. THIS SIT HIGHLIGHTS THE PROBS FACED BY TODAY'S AIRLINE CREWS UTILIZING ADVANCED TECHNOLOGY EQUIP WHICH PROVIDES ACCESS TO ALMOST UNLIMITED INFO, BUT CAN, ON OCCASION, PROVIDE INCORRECT DATA WHICH AFFECTS SAFETY OF FLT. THE PERCEIVED INFALLIBILITY OF THIS EQUIP (COMPUTERS) LEADS TO A COMPLACENCY WHICH COULD BE FATAL.

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.