B737 crew had altitude undershoot.

Attributes
ACN	448031
Time
Date	199908
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : flo.vortac
State Reference	SC
Altitude	msl bound lower : 24000 msl bound upper : 29000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zjx.artcc
Operator	common carrier : air carrier
Make Model Name	B737-400
Operating Under FAR Part	Part 121
Navigation In Use	other other vortac
Flight Phase	descent : intermediate altitude descent : vacating altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 150 flight time total : 20000 flight time type : 5000
ASRS Report	448031
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument pilot : multi engine
Events
Anomaly	altitude deviation : undershoot non adherence : company policies non adherence : published procedure non adherence : far non adherence : clearance
Independent Detector	other controllera
Resolutory Action	controller : issued alert flight crew : returned to assigned altitude none taken : insufficient time
Supplementary
Problem Areas	Aircraft Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We were given a clearance to descend from FL290 to FL240 30 NM south of flo VOR. The first officer, who was the PF, entered the descent fix into the FMC. I monitored carefully as he entered the information because it can be confusing to place an altitude at a fix that is not initially on the FMC route and must therefore be built on the FMC route page. Also, because some of our company aircraft have different software data updates, performing certain functions, eg, creating fixes, requires different methods (a definite shortfall). The first officer built the altitude crossing restr 30 NM north of flo instead of 30 NM south and I did not recognize the mistake. Center noticed we had not started a descent and alerted us. We realized our error and began an immediate descent, but failed to make FL240 at the assigned point. No conflict with other aircraft occurred and the center controller did not express concern. Apparently the altitude restr has more to do with airspace jurisdiction than traffic. This situation emphasizes that as helpful as automation can be, a pilot must always be wary. An over reliance on computers without a little bit of skepticism can lead to complacency.

Original NASA ASRS Text

Title: B737 CREW HAD ALT UNDERSHOOT.

Narrative: WE WERE GIVEN A CLRNC TO DSND FROM FL290 TO FL240 30 NM S OF FLO VOR. THE FO, WHO WAS THE PF, ENTERED THE DSCNT FIX INTO THE FMC. I MONITORED CAREFULLY AS HE ENTERED THE INFO BECAUSE IT CAN BE CONFUSING TO PLACE AN ALT AT A FIX THAT IS NOT INITIALLY ON THE FMC RTE AND MUST THEREFORE BE BUILT ON THE FMC RTE PAGE. ALSO, BECAUSE SOME OF OUR COMPANY ACFT HAVE DIFFERENT SOFTWARE DATA UPDATES, PERFORMING CERTAIN FUNCTIONS, EG, CREATING FIXES, REQUIRES DIFFERENT METHODS (A DEFINITE SHORTFALL). THE FO BUILT THE ALT XING RESTR 30 NM N OF FLO INSTEAD OF 30 NM S AND I DID NOT RECOGNIZE THE MISTAKE. CTR NOTICED WE HAD NOT STARTED A DSCNT AND ALERTED US. WE REALIZED OUR ERROR AND BEGAN AN IMMEDIATE DSCNT, BUT FAILED TO MAKE FL240 AT THE ASSIGNED POINT. NO CONFLICT WITH OTHER ACFT OCCURRED AND THE CTR CTLR DID NOT EXPRESS CONCERN. APPARENTLY THE ALT RESTR HAS MORE TO DO WITH AIRSPACE JURISDICTION THAN TFC. THIS SIT EMPHASIZES THAT AS HELPFUL AS AUTOMATION CAN BE, A PLT MUST ALWAYS BE WARY. AN OVER RELIANCE ON COMPUTERS WITHOUT A LITTLE BIT OF SKEPTICISM CAN LEAD TO COMPLACENCY.

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.