Failed to make crossing restriction when FMC dropped the DME distance.

Attributes
ACN	87268
Time
Date	198805
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : sax airport : ewr
State Reference	NJ
Altitude	msl bound lower : 7000 msl bound upper : 10000
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Controlling Facilities	tracon : n90
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 15000
ASRS Report	87268
Person 2
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	altitude deviation : crossing restriction not met non adherence : clearance
Independent Detector	other controllera
Resolutory Action	none taken : detected after the fact other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We were cleared to cross 25 miles northeast sax VOR at 7000' MSL. Inserted downtrack fix in computer of medium large transport checked by both pilot and copilot for accuracy. We became involved in approach operation and did not notice computer fix change from 25 mi to 16 mi. We missed crossing restriction by 3000'. I did not realize we had missed restriction until approach control said he would like us to tell him the next time we couldn't make the crossing restriction. I learned not to have so much faith in computers.

Original NASA ASRS Text

Title: FAILED TO MAKE CROSSING RESTRICTION WHEN FMC DROPPED THE DME DISTANCE.

Narrative: WE WERE CLRED TO CROSS 25 MILES NE SAX VOR AT 7000' MSL. INSERTED DOWNTRACK FIX IN COMPUTER OF MLG CHKED BY BOTH PLT AND COPLT FOR ACCURACY. WE BECAME INVOLVED IN APCH OPERATION AND DID NOT NOTICE COMPUTER FIX CHANGE FROM 25 MI TO 16 MI. WE MISSED XING RESTRICTION BY 3000'. I DID NOT REALIZE WE HAD MISSED RESTRICTION UNTIL APCH CTL SAID HE WOULD LIKE US TO TELL HIM THE NEXT TIME WE COULDN'T MAKE THE XING RESTRICTION. I LEARNED NOT TO HAVE SO MUCH FAITH IN COMPUTERS.

Data retrieved from NASA's ASRS site as of August 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.