Air carrier misses crossing altitude while trying to reprogram FMC.

Attributes
ACN	248996
Time
Date	199308
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : ekn
State Reference	WV
Altitude	msl bound lower : 27000 msl bound upper : 27000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zob tower : cps
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	248996
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	altitude deviation : undershoot altitude deviation : crossing restriction not met non adherence : clearance
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance none taken : detected after the fact none taken : insufficient time
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Had clearance to cross 35 mi south of elkins at FL240. We were level at FL270. I attempted to program FMC for the descent and became aware belatedly that I had misprogrammed. The FMC had initially accepted my input but then the first officer noticed a bypass situation. While we were trying to rectify, we flew overy 35 mi south of elkins at FL270 and simultaneously were issued direct to another fix further down line and descend to FL190. I was lulled into complacency because I thought the FMC was properly programmed. When the first officer saw that something was wrong, we did not immediately recognize our proximity to 35 mi south fix because of several intermediate short legs displayed in FMC. I should have backed up my programming of FMC with a check on the fix page to determine distance to elkins and done a mental calculation of time and distance to top of descent.

Original NASA ASRS Text

Title: ACR MISSES XING ALT WHILE TRYING TO REPROGRAM FMC.

Narrative: HAD CLRNC TO CROSS 35 MI S OF ELKINS AT FL240. WE WERE LEVEL AT FL270. I ATTEMPTED TO PROGRAM FMC FOR THE DSCNT AND BECAME AWARE BELATEDLY THAT I HAD MISPROGRAMMED. THE FMC HAD INITIALLY ACCEPTED MY INPUT BUT THEN THE FO NOTICED A BYPASS SIT. WHILE WE WERE TRYING TO RECTIFY, WE FLEW OVERY 35 MI S OF ELKINS AT FL270 AND SIMULTANEOUSLY WERE ISSUED DIRECT TO ANOTHER FIX FURTHER DOWN LINE AND DSND TO FL190. I WAS LULLED INTO COMPLACENCY BECAUSE I THOUGHT THE FMC WAS PROPERLY PROGRAMMED. WHEN THE FO SAW THAT SOMETHING WAS WRONG, WE DID NOT IMMEDIATELY RECOGNIZE OUR PROX TO 35 MI S FIX BECAUSE OF SEVERAL INTERMEDIATE SHORT LEGS DISPLAYED IN FMC. I SHOULD HAVE BACKED UP MY PROGRAMMING OF FMC WITH A CHK ON THE FIX PAGE TO DETERMINE DISTANCE TO ELKINS AND DONE A MENTAL CALCULATION OF TIME AND DISTANCE TO TOP OF DSCNT.

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.