Narrative:

We were in cruise at FL260 with a pilot's discretion descent to FL240, assigned 280 KTS. The captain was flying with VNAV and LNAV engaged. ZMP told us to maintain 300 KTS. The captain deselected VNAV and set 300 KTS in the airspeed window. The throttles advanced and he assumed he was accelerating to 300 KTS in altitude hold. However, when VNAV is deselected and the altitude in the MCP window is not the same as on the cruise page (because we had a pilot's discretion to FL240) of the FMC, the autoplt reverts to control wheel steering pitch. When the throttles advanced, the airplane began a slow pitch up and climb. We climbed approximately 700 ft before the captain began a descent to FL240. This goes back to someone has to be flying the airplane. There were significant NOTAMS at msp international airport due to runway construction, and I was reviewing them and referring to the airport diagram. The captain was reviewing the arrival. The airplane did exactly what he told it to do, but not what he was expecting it to do. We learned that after you push buttons, make sure the airplane is doing what you intend it to do. This was a very unique situation, because you will not get an altitude deviation light or horn because the mode control panel altitude is set lower and you are climbing. Supplemental information from acn 407474: 4TH day of 4 day trip, slept poorly the night before. ZMP or approach changed stars and runways 60 mi east of airport. Told 'pilot discretion descend to maintain 24000 ft.' altitude window was set to 24000 ft. FMC pitch mode in altitude hold. Then told by ATC to increase speed to 300 KTS or greater. I hit VNAV button to open window of IAS/mach and selected 310 KTS. We were 280 KTS. After touching that VNAV button ADI-FMC pitch went blank and 'control wheel steering pitch' activated. Because of the thrust increasing, nose started climbing unbeknownst to me until 26700 ft. I descended back down. We were both busy getting out maps, charts, etc, and never noticed the climb or control wheel steering pitch. 'Classic over dependence on automation' doing what I expected but not familiar with the complexity of my request.

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Original NASA ASRS Text

Title: B737. ACFT FMC AUTOMATION DID NOT DO WHAT THE CAPT EXPECTED.

Narrative: WE WERE IN CRUISE AT FL260 WITH A PLT'S DISCRETION DSCNT TO FL240, ASSIGNED 280 KTS. THE CAPT WAS FLYING WITH VNAV AND LNAV ENGAGED. ZMP TOLD US TO MAINTAIN 300 KTS. THE CAPT DESELECTED VNAV AND SET 300 KTS IN THE AIRSPD WINDOW. THE THROTTLES ADVANCED AND HE ASSUMED HE WAS ACCELERATING TO 300 KTS IN ALT HOLD. HOWEVER, WHEN VNAV IS DESELECTED AND THE ALT IN THE MCP WINDOW IS NOT THE SAME AS ON THE CRUISE PAGE (BECAUSE WE HAD A PLT'S DISCRETION TO FL240) OF THE FMC, THE AUTOPLT REVERTS TO CTL WHEEL STEERING PITCH. WHEN THE THROTTLES ADVANCED, THE AIRPLANE BEGAN A SLOW PITCH UP AND CLB. WE CLBED APPROX 700 FT BEFORE THE CAPT BEGAN A DSCNT TO FL240. THIS GOES BACK TO SOMEONE HAS TO BE FLYING THE AIRPLANE. THERE WERE SIGNIFICANT NOTAMS AT MSP INTL ARPT DUE TO RWY CONSTRUCTION, AND I WAS REVIEWING THEM AND REFERRING TO THE ARPT DIAGRAM. THE CAPT WAS REVIEWING THE ARR. THE AIRPLANE DID EXACTLY WHAT HE TOLD IT TO DO, BUT NOT WHAT HE WAS EXPECTING IT TO DO. WE LEARNED THAT AFTER YOU PUSH BUTTONS, MAKE SURE THE AIRPLANE IS DOING WHAT YOU INTEND IT TO DO. THIS WAS A VERY UNIQUE SIT, BECAUSE YOU WILL NOT GET AN ALTDEV LIGHT OR HORN BECAUSE THE MODE CTL PANEL ALT IS SET LOWER AND YOU ARE CLBING. SUPPLEMENTAL INFO FROM ACN 407474: 4TH DAY OF 4 DAY TRIP, SLEPT POORLY THE NIGHT BEFORE. ZMP OR APCH CHANGED STARS AND RWYS 60 MI E OF ARPT. TOLD 'PLT DISCRETION DSND TO MAINTAIN 24000 FT.' ALT WINDOW WAS SET TO 24000 FT. FMC PITCH MODE IN ALT HOLD. THEN TOLD BY ATC TO INCREASE SPD TO 300 KTS OR GREATER. I HIT VNAV BUTTON TO OPEN WINDOW OF IAS/MACH AND SELECTED 310 KTS. WE WERE 280 KTS. AFTER TOUCHING THAT VNAV BUTTON ADI-FMC PITCH WENT BLANK AND 'CTL WHEEL STEERING PITCH' ACTIVATED. BECAUSE OF THE THRUST INCREASING, NOSE STARTED CLBING UNBEKNOWNST TO ME UNTIL 26700 FT. I DSNDED BACK DOWN. WE WERE BOTH BUSY GETTING OUT MAPS, CHARTS, ETC, AND NEVER NOTICED THE CLB OR CTL WHEEL STEERING PITCH. 'CLASSIC OVER DEPENDENCE ON AUTOMATION' DOING WHAT I EXPECTED BUT NOT FAMILIAR WITH THE COMPLEXITY OF MY REQUEST.

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.