A B757 had a dual pegasus FMC fault on takeoff with no warning although they were properly programme...

Narrative:

Both fmcs dumped on takeoff; or shortly after rotation. Not alerted in any way. As pilot monitoring; I noticed the legs page was blank on climb out; as was the route page. FMC route and legs had been checked at the gate in accordance with our procedures; and takeoff data was updated upon receipt of the load closeout. We notified ATC (departure) that we would require radar vectors as we were without FMC navigation; and were vectored accordingly. All data in FMC was dumped with 'standby one' displayed in both fmcs. There was no nav data; nor was there any performance data. About 15 minutes into flight; as we were referencing the pegasus FMC lockup procedure; the FMC scratch pad displayed 'timed out'; and we regained control of the FMC. We loaded the remainder of the route; notified ATC that we could now navigate normally; and proceeded to our destination uneventfully.

Original NASA ASRS Text

Title: A B757 had a dual Pegasus FMC fault on takeoff with no warning although they were properly programmed during preflight. In cruise flight the FMC's became available and were reprogrammed for the remainder of the flight.

Narrative: Both FMCs dumped on takeoff; or shortly after rotation. Not alerted in any way. As pilot monitoring; I noticed the legs page was blank on climb out; as was the route page. FMC route and legs had been checked at the gate in accordance with our procedures; and takeoff data was updated upon receipt of the load closeout. We notified ATC (departure) that we would require radar vectors as we were without FMC navigation; and were vectored accordingly. All data in FMC was dumped with 'Standby One' displayed in both FMCs. There was no Nav data; nor was there any performance data. About 15 minutes into flight; as we were referencing the Pegasus FMC Lockup procedure; the FMC scratch pad displayed 'Timed Out'; and we regained control of the FMC. We loaded the remainder of the route; notified ATC that we could now navigate normally; and proceeded to our destination uneventfully.

Data retrieved from NASA's ASRS site as of April 2012 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.

Attributes
ACN	927645
Time
Date	201101
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	B757-200
Operating Under FAR Part	Part 121
Flight Phase	Climb
Flight Plan	IFR
Component
Aircraft Component	FMS/FMC
Person 1
Function	First Officer Pilot Not Flying
Person 2
Function	Pilot Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Less Severe

A B757 had a dual pegasus FMC fault on takeoff with no warning although they were properly programmed during preflight. In cruise flight the FMC's became available and were reprogrammed for the remainder of the flight.