A B737-300 on takeoff at 400 ft the flight control computer failed and flew beyond initial FMC turn ...

Attributes
ACN	525075
Time
Date	200109
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : bos.airport
State Reference	MA
Altitude	msl bound lower : 0 msl bound upper : 3000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time total : 9000
ASRS Report	525075
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : critical non adherence : clearance non adherence : published procedure other spatial deviation
Independent Detector	aircraft equipment other aircraft equipment : flt ctl computer other flight crewa other flight crewb
Resolutory Action	aircraft : equipment problem dissipated controller : issued advisory flight crew : became reoriented flight crew : overcame equipment problem flight crew : regained aircraft control flight crew : took precautionary avoidance action
Consequence	faa : reviewed incident with flight crew other
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

Flight (bos to den) takeoff from runway 27 at kbos, on a wylyy three departure. At 400 ft, the LNAV was selected as required by the SID. At this point, the flight director coupling with the FMC failed and I was left with no FMC/FD guidance on this (an FMS) departure procedure. During attempts to bring system back online; and due to heavy pilot work load in first min after takeoff, aircraft may have flown beyond initial FMC turn point on SID. DME could not be confirmed immediately as automatic/manual function on navigation radio head had been selected as required, and DME display had blanked out. Priority was on aircraft control and gaining altitude. Due to no lateral flight director guidance and questionable DME, a quick glance outside showed the noise sensitive area slightly left of center ahead. A decision to turn slightly right was made for the following reasons: 1) metropolitan area better avoided (being cognizant of current events especially), 2) map display indicated a sweeping right turn which we would join, 3) lack of FMS coupled flight director guidance to the contrary, 4) being unable to divert attention from flying to the fine print on the SID for further guidance/interpretation in event of FMC/FD failure. ATC noticed our problem, queried heading and gave helpful vectors to increase rate of interception. Remainder of flight uneventful, FMS/FD functions normal thereafter.

Original NASA ASRS Text

Title: A B737-300 ON TKOF AT 400 FT THE FLT CTL COMPUTER FAILED AND FLEW BEYOND INITIAL FMC TURN POINT ON SID. CAUSED BY A FAILED FLT CTL COMPUTER.

Narrative: FLT (BOS TO DEN) TKOF FROM RWY 27 AT KBOS, ON A WYLYY THREE DEP. AT 400 FT, THE LNAV WAS SELECTED AS REQUIRED BY THE SID. AT THIS POINT, THE FLT DIRECTOR COUPLING WITH THE FMC FAILED AND I WAS LEFT WITH NO FMC/FD GUIDANCE ON THIS (AN FMS) DEP PROCEDURE. DURING ATTEMPTS TO BRING SYS BACK ONLINE; AND DUE TO HVY PLT WORK LOAD IN FIRST MIN AFTER TKOF, ACFT MAY HAVE FLOWN BEYOND INITIAL FMC TURN POINT ON SID. DME COULD NOT BE CONFIRMED IMMEDIATELY AS AUTO/MANUAL FUNCTION ON NAV RADIO HEAD HAD BEEN SELECTED AS REQUIRED, AND DME DISPLAY HAD BLANKED OUT. PRIORITY WAS ON ACFT CTL AND GAINING ALT. DUE TO NO LATERAL FLT DIRECTOR GUIDANCE AND QUESTIONABLE DME, A QUICK GLANCE OUTSIDE SHOWED THE NOISE SENSITIVE AREA SLIGHTLY LEFT OF CENTER AHEAD. A DECISION TO TURN SLIGHTLY RIGHT WAS MADE FOR THE FOLLOWING REASONS: 1) METROPOLITAN AREA BETTER AVOIDED (BEING COGNIZANT OF CURRENT EVENTS ESPECIALLY), 2) MAP DISPLAY INDICATED A SWEEPING RIGHT TURN WHICH WE WOULD JOIN, 3) LACK OF FMS COUPLED FLT DIRECTOR GUIDANCE TO THE CONTRARY, 4) BEING UNABLE TO DIVERT ATTENTION FROM FLYING TO THE FINE PRINT ON THE SID FOR FURTHER GUIDANCE/INTERPRETATION IN EVENT OF FMC/FD FAILURE. ATC NOTICED OUR PROBLEM, QUERIED HEADING AND GAVE HELPFUL VECTORS TO INCREASE RATE OF INTERCEPTION. REMAINDER OF FLT UNEVENTFUL, FMS/FD FUNCTIONS NORMAL THEREAFTER.

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.

A B737-300 on takeoff at 400 ft the flight control computer failed and flew beyond initial FMC turn point on SID. Caused by a failed flight control computer.