Narrative:

When we arrived the aircraft was covered in a thick covering of snow and ice. The aircraft had not flown the day before and accumulated a large amount of contaminates on the aircraft surfaces. There was no contaminates in the engines and the fan section turned freely. After engine start we were directed to taxi to the deice pad. Two vehicles arrived and began to deice the aircraft which were joined by another two vehicles after twenty minutes. This process took about two hours to complete before the deice coordinator declared the aircraft free of contaminates. After the engines were started; we taxied the aircraft for departure when we received a radio call from the deice coordinator that he spotted some contaminates still on the aircraft. We returned to the deice pad; configured the aircraft for deicing; and had the deice truck remove any contaminates they found. This deice process took another twenty minutes. We were cleared for takeoff and after V1; when the first officer made the rotate call; I noticed we were about five knots slow. This got my attention as I waited about one second and starting rotating the aircraft. The aircraft nose was off the ground and I got multiple warnings on the pfd for airspeed and altitude disagreement along with a momentary stick shaker. I noticed the airspeed was rolling back to 45 knots and the altitude was remaining on field elevation. A buffet alert was displayed on the CDU as well. A quick glance and the first officer's pfd showed normal indications and; after we retracted the gear; I gave him the aircraft. We got an immediate call from ATC wanting to know our altitude which I gave off the first officer's altimeter. I quickly selected the number two position on the transponder to avoid further ATC interruptions. We climbed to 6000 feet and informed ATC that we needed to return but needed radar vectors to troubleshoot the problem and prepare for an approach. I ran the QRH checklist while the first officer flew the aircraft; but we did not recover the captain's airspeed or altitude indications. We elected to burn down fuel to landing limits. We received a clearance for a visual approach and on short final in visual conditions; a one-second windshear warning was received with no external indications or indications on the first officer's instruments. Considering the circumstances and the very real possibility the system was getting inaccurate information from the captain's altimeter and airspeed; the first officer stated his intention to continue to land. I concurred and a normal flaps 30 landing was flown by the first officer . After returning to the gate; contract maintenance found ice contaminates in both the left and right pitot static systems.in severe ground icing conditions; a cover should be placed over the static ports to prevent introduction of contaminants into the -700 pitot static system. Ground deicing crews should be trained repeatedly about the dangers of getting deice fluid in pitot static ports during deice and anti-ice operations.

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Original NASA ASRS Text

Title: B737-700 Flight Crew experiences Captain's pitot static instrument failure at rotation. The aircraft had been on the ground for 36 hours in a snow and ice storm before this departure. Maintenance found ice in the plumbing of both pitot static systems.

Narrative: When we arrived the aircraft was covered in a thick covering of snow and ice. The aircraft had not flown the day before and accumulated a large amount of contaminates on the aircraft surfaces. There was no contaminates in the engines and the fan section turned freely. After engine start we were directed to taxi to the deice pad. Two vehicles arrived and began to deice the aircraft which were joined by another two vehicles after twenty minutes. This process took about two hours to complete before the Deice Coordinator declared the aircraft free of contaminates. After the engines were started; we taxied the aircraft for departure when we received a radio call from the Deice Coordinator that he spotted some contaminates still on the aircraft. We returned to the deice pad; configured the aircraft for deicing; and had the deice truck remove any contaminates they found. This deice process took another twenty minutes. We were cleared for takeoff and after V1; when the First Officer made the rotate call; I noticed we were about five knots slow. This got my attention as I waited about one second and starting rotating the aircraft. The aircraft nose was off the ground and I got multiple warnings on the PFD for airspeed and altitude disagreement along with a momentary stick shaker. I noticed the airspeed was rolling back to 45 knots and the altitude was remaining on field elevation. A buffet alert was displayed on the CDU as well. A quick glance and the First Officer's PFD showed normal indications and; after we retracted the gear; I gave him the aircraft. We got an immediate call from ATC wanting to know our altitude which I gave off the First Officer's altimeter. I quickly selected the number two position on the transponder to avoid further ATC interruptions. We climbed to 6000 feet and informed ATC that we needed to return but needed radar vectors to troubleshoot the problem and prepare for an approach. I ran the QRH checklist while the First Officer flew the aircraft; but we did not recover the Captain's airspeed or altitude indications. We elected to burn down fuel to landing limits. We received a clearance for a visual approach and on short final in visual conditions; a one-second windshear warning was received with no external indications or indications on the First Officer's instruments. Considering the circumstances and the very real possibility the system was getting inaccurate information from the Captain's altimeter and airspeed; the First Officer stated his intention to continue to land. I concurred and a normal flaps 30 landing was flown by the First Officer . After returning to the gate; Contract Maintenance found ice contaminates in both the left and right pitot static systems.In severe ground icing conditions; a cover should be placed over the static ports to prevent introduction of contaminants into the -700 pitot static system. Ground Deicing Crews should be trained repeatedly about the dangers of getting deice fluid in pitot static ports during deice and anti-ice operations.

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.