Narrative:

When I arrived at the aircraft prior to departure, I performed the usual preflight and walkaround inspection. After boarding and completing the necessary paperwork, we got underway. Shortly after takeoff we began to hear a loud whine in the cockpit. Moments after, the airspeed indicator began to fluctuate rapidly on both flight displays. The captain and I then decided to return to the airport without undue delay. We landed without incident. Upon returning to the gate, we discovered that the oxygen service door, located in front of the copilot's pitot tube, had come open shortly after takeoff. We later learned that the oxygen had been svced prior to the flight and that it had not been latched properly by the mechanic.

Related reports:

Google
 

Original NASA ASRS Text

Title: FLC OF LTT HEARS A LOUD WHINE IN THE COCKPIT AFTER TKOF AND THE AIRSPD INDICATOR BEGINS TO FLUCTUATE RAPIDLY. THEY RETURN LAND AND DISCOVER AN OXYGEN SVC DOOR IS OPEN. THIS HAD BEEN SVCED PRIOR TO DEP.

Narrative: WHEN I ARRIVED AT THE ACFT PRIOR TO DEP, I PERFORMED THE USUAL PREFLT AND WALKAROUND INSPECTION. AFTER BOARDING AND COMPLETING THE NECESSARY PAPERWORK, WE GOT UNDERWAY. SHORTLY AFTER TKOF WE BEGAN TO HEAR A LOUD WHINE IN THE COCKPIT. MOMENTS AFTER, THE AIRSPD INDICATOR BEGAN TO FLUCTUATE RAPIDLY ON BOTH FLT DISPLAYS. THE CAPT AND I THEN DECIDED TO RETURN TO THE ARPT WITHOUT UNDUE DELAY. WE LANDED WITHOUT INCIDENT. UPON RETURNING TO THE GATE, WE DISCOVERED THAT THE OXYGEN SVC DOOR, LOCATED IN FRONT OF THE COPLT'S PITOT TUBE, HAD COME OPEN SHORTLY AFTER TKOF. WE LATER LEARNED THAT THE OXYGEN HAD BEEN SVCED PRIOR TO THE FLT AND THAT IT HAD NOT BEEN LATCHED PROPERLY BY THE MECH.

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.