Narrative:

Departing dca as flight X dca-ind, the B757 departing before us hit a fox on the runway so we were cleared into position runway 1 and held for several mins while vehicles swept for debris. Several aircraft on approach were sent around and told to intercept the dca 328 degree radial outbound. We were set up to fly the FMS guidance procedure and had briefed and quick-aligned the IRS's in accordance with company procedures. When cleared for takeoff, the captain flew the RNAV departure, starting the turn up-river towards tedie at 400 ft as we entered the overcast. For the next few seconds, I was occupied as I cut my thumb on the glareshield when raising the gear. It was bleeding profusely and by the time I grabbed a napkin and looked back up, I saw we were heading approximately 330 degrees but the flight directors were commanding a steep right turn. At this time potomac ap commanded an immediate right turn to 050 degrees. At the time we assumed this was for spacing behind the GA aircraft sent up the 320 degree radial while we were waiting on the runway. However, during the next couple of vectors we received the FMS alert message 'verify position.' when potomac approach cleared us direct ginya intersection, we were unable due to FMC failure (FMC annunciated in middle of blank screen). At this point, we notified ATC of our equipment failure, and requested to continue flight as '/a' (VOR only). Callback conversation with reporter revealed the following information: the reporter's callback included his research into the mechanical failure responsible for the deviation. One of the 2 FMC's experienced a hardware failure and began sending incorrect information to the opposite FMC. The good FMC shut down because the conflicting information created uncertainty in the computer logic about the validity of the good FMC. The crew initially thought the vectors were for traffic separation from preceding aircraft executing go around's following the runway closure for a dead fox on the runway. In fact the vectors were to keep them away from the naval observatory (vice president's residence) after they narrowly missed the president's quarters (P56) while following faulty FMC heading guidance. The crew has not had enforcement action initiated against them. The air carrier poi and pilot union reviewed the incident and the reporter believes the crew has been cleared of a violation because of the navigation hardware failure.

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Original NASA ASRS Text

Title: A B737-300 ON DEP FROM DCA PENETRATED P56 FOLLOWING DUAL FMC FAILURES.

Narrative: DEPARTING DCA AS FLT X DCA-IND, THE B757 DEPARTING BEFORE US HIT A FOX ON THE RWY SO WE WERE CLRED INTO POS RWY 1 AND HELD FOR SEVERAL MINS WHILE VEHICLES SWEPT FOR DEBRIS. SEVERAL ACFT ON APCH WERE SENT AROUND AND TOLD TO INTERCEPT THE DCA 328 DEG RADIAL OUTBOUND. WE WERE SET UP TO FLY THE FMS GUIDANCE PROC AND HAD BRIEFED AND QUICK-ALIGNED THE IRS'S IN ACCORDANCE WITH COMPANY PROCS. WHEN CLRED FOR TKOF, THE CAPT FLEW THE RNAV DEP, STARTING THE TURN UP-RIVER TOWARDS TEDIE AT 400 FT AS WE ENTERED THE OVCST. FOR THE NEXT FEW SECONDS, I WAS OCCUPIED AS I CUT MY THUMB ON THE GLARESHIELD WHEN RAISING THE GEAR. IT WAS BLEEDING PROFUSELY AND BY THE TIME I GRABBED A NAPKIN AND LOOKED BACK UP, I SAW WE WERE HEADING APPROX 330 DEGS BUT THE FLT DIRECTORS WERE COMMANDING A STEEP R TURN. AT THIS TIME POTOMAC AP COMMANDED AN IMMEDIATE R TURN TO 050 DEGS. AT THE TIME WE ASSUMED THIS WAS FOR SPACING BEHIND THE GA ACFT SENT UP THE 320 DEG RADIAL WHILE WE WERE WAITING ON THE RWY. HOWEVER, DURING THE NEXT COUPLE OF VECTORS WE RECEIVED THE FMS ALERT MESSAGE 'VERIFY POS.' WHEN POTOMAC APCH CLRED US DIRECT GINYA INTXN, WE WERE UNABLE DUE TO FMC FAILURE (FMC ANNUNCIATED IN MIDDLE OF BLANK SCREEN). AT THIS POINT, WE NOTIFIED ATC OF OUR EQUIP FAILURE, AND REQUESTED TO CONTINUE FLT AS '/A' (VOR ONLY). CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR'S CALLBACK INCLUDED HIS RESEARCH INTO THE MECHANICAL FAILURE RESPONSIBLE FOR THE DEV. ONE OF THE 2 FMC'S EXPERIENCED A HARDWARE FAILURE AND BEGAN SENDING INCORRECT INFO TO THE OPPOSITE FMC. THE GOOD FMC SHUT DOWN BECAUSE THE CONFLICTING INFO CREATED UNCERTAINTY IN THE COMPUTER LOGIC ABOUT THE VALIDITY OF THE GOOD FMC. THE CREW INITIALLY THOUGHT THE VECTORS WERE FOR TFC SEPARATION FROM PRECEDING ACFT EXECUTING GAR'S FOLLOWING THE RWY CLOSURE FOR A DEAD FOX ON THE RWY. IN FACT THE VECTORS WERE TO KEEP THEM AWAY FROM THE NAVAL OBSERVATORY (VICE PRESIDENT'S RESIDENCE) AFTER THEY NARROWLY MISSED THE PRESIDENT'S QUARTERS (P56) WHILE FOLLOWING FAULTY FMC HEADING GUIDANCE. THE CREW HAS NOT HAD ENFORCEMENT ACTION INITIATED AGAINST THEM. THE ACR POI AND PLT UNION REVIEWED THE INCIDENT AND THE RPTR BELIEVES THE CREW HAS BEEN CLRED OF A VIOLATION BECAUSE OF THE NAV HARDWARE FAILURE.

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.