Narrative:

Preflight, start, and taxi out was normal for flight from mia to ZZZ. The WX was VFR and the winds out of east at approximately 10 KTS. It was my takeoff (captain). The power was advanced to takeoff power with normal indications. I was monitoring runway alignment and engine instruments, waiting for the 80 KTS call from the first officer when I sensed that the speed should have been close to 80 KTS I looked at my primary flight display and the airspeed was 30 KTS. I immediately looked at the first officer's primary flight display and it also said 30 KTS. I then looked at the standby airspeed and it was around 90 KTS and increasing. I looked back at my primary flight display and it had the same 30 KT indication. The standby airspeed was now over 100 KTS and I announced that I was continuing the takeoff. I determined that the standby instruments were correct and the WX was VFR, therefore, I could safely fly the aircraft. I did not want to risk a high speed abort. The takeoff was continued and we requested a holding pattern at 5000 ft from mia departure so we could assess our situation. The left primary flight display airspeed and altitude information came back after passing approximately 2000 ft on the climb out. The right primary flight display information never came back so it was bootstrapped to left primary flight display. The navigation data failure checklist was accomplished and I decided to dump fuel to maximum lnd weight and return to mia. An ILS was flown to runway 9R at mia. Taxi in and parking were normal. Callback conversation with reporter revealed the following information: the reporter stated the 80 knot callout was not received from the first officer and the left airspeed indication on the primary flight display was 30 knots. The reporter said the standby airspeed indicator was functioning normally and was used from takeoff to landing. The reporter stated this airplane was out of service for 36 hours and mud daubers had partially closed the left pitot tube and completely closed the right tube. The reporter said fortunately the mud daubers did not block the center pitot tube which supplied pitot pressure to the standby instruments. The reporter stated that any airplane laying overnight in miami should have the pitot tubes covered.

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Original NASA ASRS Text

Title: A B-777 ON TKOF ROLL EXPERIENCED LOSS OF L AND R AIRSPEED INDICATIONS ON THE PRIMARY FLT DISPLAYS. USED STANDBY AIRSPEED INDICATOR FOR TKOF AND RETURNED TO DEP ARPT.

Narrative: PREFLT, START, AND TAXI OUT WAS NORMAL FOR FLT FROM MIA TO ZZZ. THE WX WAS VFR AND THE WINDS OUT OF E AT APPROX 10 KTS. IT WAS MY TKOF (CAPT). THE POWER WAS ADVANCED TO TKOF POWER WITH NORMAL INDICATIONS. I WAS MONITORING RWY ALIGNMENT AND ENG INSTRUMENTS, WAITING FOR THE 80 KTS CALL FROM THE FO WHEN I SENSED THAT THE SPEED SHOULD HAVE BEEN CLOSE TO 80 KTS I LOOKED AT MY PRIMARY FLT DISPLAY AND THE AIRSPEED WAS 30 KTS. I IMMEDIATELY LOOKED AT THE FO'S PRIMARY FLT DISPLAY AND IT ALSO SAID 30 KTS. I THEN LOOKED AT THE STANDBY AIRSPEED AND IT WAS AROUND 90 KTS AND INCREASING. I LOOKED BACK AT MY PRIMARY FLT DISPLAY AND IT HAD THE SAME 30 KT INDICATION. THE STANDBY AIRSPEED WAS NOW OVER 100 KTS AND I ANNOUNCED THAT I WAS CONTINUING THE TKOF. I DETERMINED THAT THE STANDBY INSTRUMENTS WERE CORRECT AND THE WX WAS VFR, THEREFORE, I COULD SAFELY FLY THE ACFT. I DID NOT WANT TO RISK A HIGH SPEED ABORT. THE TKOF WAS CONTINUED AND WE REQUESTED A HOLDING PATTERN AT 5000 FT FROM MIA DEP SO WE COULD ASSESS OUR SIT. THE L PRIMARY FLT DISPLAY AIRSPEED AND ALTITUDE INFO CAME BACK AFTER PASSING APPROX 2000 FT ON THE CLBOUT. THE R PRIMARY FLT DISPLAY INFO NEVER CAME BACK SO IT WAS BOOTSTRAPPED TO L PRIMARY FLT DISPLAY. THE NAV DATA FAILURE CHKLIST WAS ACCOMPLISHED AND I DECIDED TO DUMP FUEL TO MAX LND WT AND RETURN TO MIA. AN ILS WAS FLOWN TO RWY 9R AT MIA. TAXI IN AND PARKING WERE NORMAL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE 80 KNOT CALLOUT WAS NOT RECEIVED FROM THE FO AND THE L AIRSPEED INDICATION ON THE PRIMARY FLT DISPLAY WAS 30 KNOTS. THE RPTR SAID THE STANDBY AIRSPEED INDICATOR WAS FUNCTIONING NORMALLY AND WAS USED FROM TKOF TO LNDG. THE RPTR STATED THIS AIRPLANE WAS OUT OF SVC FOR 36 HRS AND MUD DAUBERS HAD PARTIALLY CLOSED THE L PITOT TUBE AND COMPLETELY CLOSED THE R TUBE. THE RPTR SAID FORTUNATELY THE MUD DAUBERS DID NOT BLOCK THE CENTER PITOT TUBE WHICH SUPPLIED PITOT PRESSURE TO THE STANDBY INSTRUMENTS. THE RPTR STATED THAT ANY AIRPLANE LAYING OVERNIGHT IN MIAMI SHOULD HAVE THE PITOT TUBES COVERED.

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.