Date: 201209
Local time of day: 1801-2400
Location: ZZZZ.Airport, FO
Flight conditions: VMC
Weather elements / visibility: 5
Light: Night
Aircraft: B757-200
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Cargo / Freight / Delivery
Flight phase: Taxi
ATC / advisory: TRACON ZZZZ
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Workload; Troubleshooting; Time Pressure; Situational Awareness; Human-Machine Interface; Confusion; Distraction
Second reporter function: First Officer; Pilot Flying
Anomaly: Aircraft Equipment Problem Critical
Detector: Automation Aircraft Other Automation; Person Flight Crew
When detected: In-flight
Result: Flight Crew FLC complied w / Automation / Advisory; Flight Crew Returned To Departure Airport; Flight Crew Took Evasive Action; General Maintenance Action
Contributing factors: Aircraft; Procedure; Weather
Primary problem: Ambiguous

Narrative: On initial taxi First Officer airspeed and altimeter inoperative flags for a brief second and cleared. Later in the taxi Captain's Flight Data (FD) failed and alternate source was selected problem cleared. After takeoff First Officer flying at 800 FT AGL Captain's airspeed and altimeter failed seemingly all Captain's instruments went crazy with erroneous windshear and GPWS warnings. These warnings continued for several minutes. EICAS showed we had a Mach/SPD trim and rudder ratio failure. Center notified us they had a zero altitude readout from our transponder. Captain's instruments climbed and then descended warnings of TOO LOW TERRAIN...WHOOP WHOOP PULL UP...TERRAIN ...CLIMB...TOO SLOW...FLAPS...you name it. First Officer had good indications with autothrottles appearing to lag or inoperative. Initially leveling at 3;000 FT and then climbing to 6;000 FT running checklists with a very noisy and busy flight deck. The decision was made to divert back to the departure airport. ATC asked us if we wanted to declare emergency. We said no. Once setting up for approach and informing company we descended to 3;000 FT and were then cleared for LOC 30. With all the distractions horns and whistles we decided to not get an air return clearance from Dispatch. We talked about it but decided to just get airplane on ground. Leveling at 3;000 FT Captain's instruments appeared more normal. Gear down and flaps 30 was done early. Speed for flaps 30 was 128 plus 5...target speed 133. At one point all airspeeds showed 135 to 138 yet we had the ALPHA showing in the ADI. First Officer was getting Fast/Slow flashing both fast and slow in his ADI. Captain's side showed the ALPHA as well. I did not notice fast/slow on my side. Both landing and taxi in was normal. I'm not sure what we could have done different to prevent this.


Second narrative: We climbed as high as 6;000 FT while the Captain was running checklists and we were being vectored back to the airport. While on final the Captain's airspeed and altimeter came back and was functioning along with his flight director although occasionally sporadic; the indications were mostly good.

Second callback: The reporter stated that the aircraft had sat at an airport where rain had fallen for several days. During that time period; rain water had accumulated in the E and E compartment and at rotation during takeoff a large amount of water flowed onto several computers. He remembered there were five computers mentioned; the Air Data Computer and GPWS being two of those affected. Because the First Officer's instruments remained mostly functional the event was not as serious as it could have been had all flight instruments been damaged.

Synopsis: Rain water which accumulated in a B757 E and E compartment flowed onto several computers at rotation causing the loss of several Captain's flight instruments; so the crew returned to the departure airport.