Narrative:

Departed mia runway 9L. As PNF, I called V speeds for takeoff using my asi (airspeed indicator). First officer rotated slowly, but I didn't find out why until later. Shortly after departure, our air data computer, which supplies airspeed, altitude, and rate of vertical speed information to each pilot (2 computers), put out a message saying in effect that the first officer's computer data was invalid. The same message was received when we switched to the captain's side. Upon examination of the checklist, we determined that we should return to kmia. At this time, when ATC gave us an airspeed limit (170 KTS). We realized that there was a 20 KT difference between airspeed indicators (first officer's slower). After landing, the air data computer acted normally -- no invalid messages. Maintenance was notified. Upon further discussion and examination. Maintenance found what appeared to be fluff stuck on the first officer pitot tube, partially obstructing it. Later, one of the ramp persons showed me a large scrape on his arm. The ramp person was busy emptying the lavatory during our preflight of the aircraft and evidently hit his arm on the pitot tube, and that was what the 'fluff' was: his skin and hair held onto the tube by his quickly congealing blood. Lesson: ramp folks should be informed that if they cut themselves on aircraft equipment, they should tell either maintenance or the crew (we had already completed our preflight when this occurred).

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Original NASA ASRS Text

Title: RETURN LAND MANDATED BY FO'S AIRSPD INDICATOR BEING UNRELIABLE WITH FO'S AIR DATA COMPUTER BEING INVALID.

Narrative: DEPARTED MIA RWY 9L. AS PNF, I CALLED V SPDS FOR TKOF USING MY ASI (AIRSPD INDICATOR). FO ROTATED SLOWLY, BUT I DIDN'T FIND OUT WHY UNTIL LATER. SHORTLY AFTER DEP, OUR AIR DATA COMPUTER, WHICH SUPPLIES AIRSPD, ALT, AND RATE OF VERT SPD INFO TO EACH PLT (2 COMPUTERS), PUT OUT A MESSAGE SAYING IN EFFECT THAT THE FO'S COMPUTER DATA WAS INVALID. THE SAME MESSAGE WAS RECEIVED WHEN WE SWITCHED TO THE CAPT'S SIDE. UPON EXAMINATION OF THE CHKLIST, WE DETERMINED THAT WE SHOULD RETURN TO KMIA. AT THIS TIME, WHEN ATC GAVE US AN AIRSPD LIMIT (170 KTS). WE REALIZED THAT THERE WAS A 20 KT DIFFERENCE BTWN AIRSPD INDICATORS (FO'S SLOWER). AFTER LNDG, THE AIR DATA COMPUTER ACTED NORMALLY -- NO INVALID MESSAGES. MAINT WAS NOTIFIED. UPON FURTHER DISCUSSION AND EXAMINATION. MAINT FOUND WHAT APPEARED TO BE FLUFF STUCK ON THE FO PITOT TUBE, PARTIALLY OBSTRUCTING IT. LATER, ONE OF THE RAMP PERSONS SHOWED ME A LARGE SCRAPE ON HIS ARM. THE RAMP PERSON WAS BUSY EMPTYING THE LAVATORY DURING OUR PREFLT OF THE ACFT AND EVIDENTLY HIT HIS ARM ON THE PITOT TUBE, AND THAT WAS WHAT THE 'FLUFF' WAS: HIS SKIN AND HAIR HELD ONTO THE TUBE BY HIS QUICKLY CONGEALING BLOOD. LESSON: RAMP FOLKS SHOULD BE INFORMED THAT IF THEY CUT THEMSELVES ON ACFT EQUIP, THEY SHOULD TELL EITHER MAINT OR THE CREW (WE HAD ALREADY COMPLETED OUR PREFLT WHEN THIS OCCURRED).

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.