Altitude crossing restr - the captain miscalculates and the first officer misenters the crossing point in the FMC and between them they cross 1000 ft high.

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Attributes
ACN	301891
Time
Date	199504
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : slc
State Reference	UT
Altitude	msl bound lower : 16000 msl bound upper : 17000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zlc
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent other
Route In Use	enroute airway : zlc
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 10100 flight time type : 7000
ASRS Report	301891
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	altitude deviation : crossing restriction not met non adherence : clearance other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	none taken : unable
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

A clearance to cross 40 mi south of slc VOR was given by slc ATC and acknowledged. During the descent I discovered that I had miscalculated my top of descent point for the crossing. I use the FMC on the aircraft to compute a top of descent as well and then use the most conservative of the two, mine or the machine. The gotcha on this day was bad ole luck. The first officer had entered the waypoint crossing wrong and by chance it showed the same top of descent as my mental calculations. I didn't notice the error until it was too late. Even though I had increased our descent rate to almost 5000 FPM we still missed the crossing by about 1000 ft. Center did not indicate a problem in separation and slc approach control did not voice any concern. From now on I double check the first officer's use of the FMC more closely and my own arithmetic.

Original NASA ASRS Text

Title: ALT XING RESTR - THE CAPT MISCALCULATES AND THE FO MISENTERS THE XING POINT IN THE FMC AND BTWN THEM THEY CROSS 1000 FT HIGH.

Narrative: A CLRNC TO CROSS 40 MI S OF SLC VOR WAS GIVEN BY SLC ATC AND ACKNOWLEDGED. DURING THE DSCNT I DISCOVERED THAT I HAD MISCALCULATED MY TOP OF DSCNT POINT FOR THE XING. I USE THE FMC ON THE ACFT TO COMPUTE A TOP OF DSCNT AS WELL AND THEN USE THE MOST CONSERVATIVE OF THE TWO, MINE OR THE MACHINE. THE GOTCHA ON THIS DAY WAS BAD OLE LUCK. THE FO HAD ENTERED THE WAYPOINT XING WRONG AND BY CHANCE IT SHOWED THE SAME TOP OF DSCNT AS MY MENTAL CALCULATIONS. I DIDN'T NOTICE THE ERROR UNTIL IT WAS TOO LATE. EVEN THOUGH I HAD INCREASED OUR DSCNT RATE TO ALMOST 5000 FPM WE STILL MISSED THE XING BY ABOUT 1000 FT. CTR DID NOT INDICATE A PROB IN SEPARATION AND SLC APCH CTL DID NOT VOICE ANY CONCERN. FROM NOW ON I DOUBLE CHK THE FO'S USE OF THE FMC MORE CLOSELY AND MY OWN ARITHMETIC.

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.