Improper FMC operation causes go around of large transport jet.

Attributes
ACN	432630
Time
Date	199903
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : dca.airport
State Reference	DC
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : dca.tracon tower : dca.tower
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : approach landing : go around
Route In Use	approach : visual
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : cfi pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 200 flight time total : 15000 flight time type : 1000
ASRS Report	432630
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument pilot : multi engine
Events
Anomaly	other anomaly
Independent Detector	other flight crewa other flight crewb
Resolutory Action	aircraft : automation overrode flight crew controller : issued new clearance flight crew : overrode automation flight crew : executed go around
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Flight Crew Human Performance

Narrative:

We were on final approach to runway 36 at dca. I selected 3500 ft in the altitude window, as this was the planned missed approach altitude. The airplane was below 3500 ft. Shortly thereafter, in an attempt to get the autothrottle to go to idle thrust so that we could start a descent down the GS, I pulled the altitude knob. Since the altitude in the altitude window was above the airplane altitude, the autoflt system commanded a climb and the autothrottle went to climb thrust. By the time we disconnected the autoflt system, the airplane was too high to land and a go around was performed. We were then vectored back around for another approach and landed normally. Contributing factors were fatigue (we had a short layover and an early wake-up the night before) and negative xfer of habit patterns when using the autoflt system. Often (but not always) when setting a new altitude in the altitude window, the altitude knob is pulled. This inadvertent pulling of the knob caused the autothrottle to go to climb thrust and resulted in a go around.

Original NASA ASRS Text

Title: IMPROPER FMC OP CAUSES GAR OF LGT JET.

Narrative: WE WERE ON FINAL APCH TO RWY 36 AT DCA. I SELECTED 3500 FT IN THE ALT WINDOW, AS THIS WAS THE PLANNED MISSED APCH ALT. THE AIRPLANE WAS BELOW 3500 FT. SHORTLY THEREAFTER, IN AN ATTEMPT TO GET THE AUTOTHROTTLE TO GO TO IDLE THRUST SO THAT WE COULD START A DSCNT DOWN THE GS, I PULLED THE ALT KNOB. SINCE THE ALT IN THE ALT WINDOW WAS ABOVE THE AIRPLANE ALT, THE AUTOFLT SYS COMMANDED A CLB AND THE AUTOTHROTTLE WENT TO CLB THRUST. BY THE TIME WE DISCONNECTED THE AUTOFLT SYS, THE AIRPLANE WAS TOO HIGH TO LAND AND A GAR WAS PERFORMED. WE WERE THEN VECTORED BACK AROUND FOR ANOTHER APCH AND LANDED NORMALLY. CONTRIBUTING FACTORS WERE FATIGUE (WE HAD A SHORT LAYOVER AND AN EARLY WAKE-UP THE NIGHT BEFORE) AND NEGATIVE XFER OF HABIT PATTERNS WHEN USING THE AUTOFLT SYS. OFTEN (BUT NOT ALWAYS) WHEN SETTING A NEW ALT IN THE ALT WINDOW, THE ALT KNOB IS PULLED. THIS INADVERTENT PULLING OF THE KNOB CAUSED THE AUTOTHROTTLE TO GO TO CLB THRUST AND RESULTED IN A GAR.

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.