B737 crew mishandled the FMC VNAV descent system.

Attributes
ACN	457840
Time
Date	199912
Day	Thu
Local Time Of Day	0601 To 1200
Place
State Reference	PA
Altitude	msl bound lower : 23000 msl bound upper : 41000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zny.artcc
Operator	common carrier : air carrier
Make Model Name	B737-700
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : level descent : vacating altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 250 flight time total : 8000 flight time type : 4000
ASRS Report	457840
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial pilot : multi engine
Events
Anomaly	altitude deviation : crossing restriction not met non adherence : company policies non adherence : published procedure other anomaly other
Independent Detector	other flight crewa other flight crewb
Resolutory Action	controller : issued new clearance
Supplementary
Problem Areas	Flight Crew Human Performance FAA Company Aircraft
Primary Problem	Company

Narrative:

Cleared to cross 10 NM west of sfk VOR at FL230. We were in cruise flight at FL410 with approximately 100 KT tailwind. Had difficulty with aircraft FMC's where inputs were responded to after about 10-15 seconds delay. Reset FMC circuit breakers and discussed situation while allowing aircraft to pass the proper descent point. Therefore, started down late. Notified ZNY 'unable altitude clearance at 10 NM west of sfk,' and requested vectors or a 360 degree turn. ZNY said 'no traffic in your area, just descend and maintain FL230.' no conflicts with any traffic ensued. Recommendations: 1) always manually calculate a descent point immediately after receiving a clearance. 2) don't allow slow or malfunctioning avionics to distract pilots from starting the descent on time.

Original NASA ASRS Text

Title: B737 CREW MISHANDLED THE FMC VNAV DSCNT SYS.

Narrative: CLRED TO CROSS 10 NM W OF SFK VOR AT FL230. WE WERE IN CRUISE FLT AT FL410 WITH APPROX 100 KT TAILWIND. HAD DIFFICULTY WITH ACFT FMC'S WHERE INPUTS WERE RESPONDED TO AFTER ABOUT 10-15 SECONDS DELAY. RESET FMC CIRCUIT BREAKERS AND DISCUSSED SIT WHILE ALLOWING ACFT TO PASS THE PROPER DSCNT POINT. THEREFORE, STARTED DOWN LATE. NOTIFIED ZNY 'UNABLE ALT CLRNC AT 10 NM W OF SFK,' AND REQUESTED VECTORS OR A 360 DEG TURN. ZNY SAID 'NO TFC IN YOUR AREA, JUST DSND AND MAINTAIN FL230.' NO CONFLICTS WITH ANY TFC ENSUED. RECOMMENDATIONS: 1) ALWAYS MANUALLY CALCULATE A DSCNT POINT IMMEDIATELY AFTER RECEIVING A CLRNC. 2) DON'T ALLOW SLOW OR MALFUNCTIONING AVIONICS TO DISTRACT PLTS FROM STARTING THE DSCNT ON TIME.

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.