Medium large transport misses crossing restr on arrival due to improper input in FMC.

Attributes
ACN	269948
Time
Date	199404
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : lga
State Reference	NY
Altitude	msl bound lower : 13000 msl bound upper : 14000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
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	arrival other enroute airway : zdc
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : atp pilot : cfi
Experience	flight time last 90 days : 120 flight time total : 10000 flight time type : 4000
ASRS Report	269948
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : commercial pilot : instrument
Events
Anomaly	altitude deviation : crossing restriction not met altitude deviation : undershoot non adherence : clearance
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	none taken : insufficient time
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

On nanci 5 arrival to lga. Flight plan to intercept arrival over dupont VORTAC (dqo) at 17000 ft. Received clearance to cross somto intersection at 13000 ft. Changed altitude in mode control panel to 13000 ft and crosschecked between captain and first officer. The intersection (somto) was entered on the FMC with the crossing restr. The aircraft was on autoplt in 'LNAV and VNAV' to provide the crossing at somto. ATC (washington center) then issued 'slow to 250 KTS,' which was entered in the speed window of the mode control panel. This disconnected the 'VNAV' and the aircraft did not begin to descend on schedule as programmed. (When speed change is entered, VNAV drops off and altitude hold is on.) we began descent too late to make the crossing restr of 13000 ft at somto. ATC asked altitude and I made a rapid descent to 13000 ft which came shortly after somto. ATC advised no traffic conflict and we continued to lga. When altitude and airspeed changes occur, it should be entered in the computer of the FMC, however the cockpit workload in northeast between washington and new york is extremely high. If the computer is being used for crossing restrictions, it must be rechked to be sure a modification has not removed the autoplt from the intended mode (VNAV or LNAV.)

Original NASA ASRS Text

Title: MLG MISSES XING RESTR ON ARR DUE TO IMPROPER INPUT IN FMC.

Narrative: ON NANCI 5 ARR TO LGA. FLT PLAN TO INTERCEPT ARR OVER DUPONT VORTAC (DQO) AT 17000 FT. RECEIVED CLRNC TO CROSS SOMTO INTXN AT 13000 FT. CHANGED ALT IN MODE CTL PANEL TO 13000 FT AND XCHKED BTWN CAPT AND FO. THE INTXN (SOMTO) WAS ENTERED ON THE FMC WITH THE XING RESTR. THE ACFT WAS ON AUTOPLT IN 'LNAV AND VNAV' TO PROVIDE THE XING AT SOMTO. ATC (WASHINGTON CTR) THEN ISSUED 'SLOW TO 250 KTS,' WHICH WAS ENTERED IN THE SPD WINDOW OF THE MODE CTL PANEL. THIS DISCONNECTED THE 'VNAV' AND THE ACFT DID NOT BEGIN TO DSND ON SCHEDULE AS PROGRAMMED. (WHEN SPD CHANGE IS ENTERED, VNAV DROPS OFF AND ALT HOLD IS ON.) WE BEGAN DSCNT TOO LATE TO MAKE THE XING RESTR OF 13000 FT AT SOMTO. ATC ASKED ALT AND I MADE A RAPID DSCNT TO 13000 FT WHICH CAME SHORTLY AFTER SOMTO. ATC ADVISED NO TFC CONFLICT AND WE CONTINUED TO LGA. WHEN ALT AND AIRSPD CHANGES OCCUR, IT SHOULD BE ENTERED IN THE COMPUTER OF THE FMC, HOWEVER THE COCKPIT WORKLOAD IN NE BTWN WASHINGTON AND NEW YORK IS EXTREMELY HIGH. IF THE COMPUTER IS BEING USED FOR XING RESTRICTIONS, IT MUST BE RECHKED TO BE SURE A MODIFICATION HAS NOT REMOVED THE AUTOPLT FROM THE INTENDED MODE (VNAV OR LNAV.)

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.