Narrative:

En route from pdk, atlanta to newport news, va. When the air data computer became erratic. It fluctuated on and off twice while still in the terminal area. At no time was it off long enough for us to do any trouble-shooting. Upon reaching 33000' our cruise altitude, it completely failed and would not reset itself like in the past. The pilot's F/D also became unusable at this time and altitude became hard to control. An 'emergency' was declared with ATC and we were given a descent back into the atlanta terminal area. We were about 50 mi from the airport when both systems began to operate properly again. We landed west/O any other problems. A second air data computer was delivered to us for use and it checked normal. Mr tech rep from radio arrived and did some tests. All checked normal. These test would require us to fly the aircraft. While passing through about 11000' my F/D failed once again. About 4 mins later technician came forward and told us that they had found the problem. Above the potty baggage compartment there is a small (approximately 1 gallon) water tank for washing your hands. This tank has the filler spout on the left end of it as it sits on the shelf. As the aircraft climbs, the tank is tilted to the spouts end and water is allowed to spill down into the radio storage area. Because it is so cramped in this area and there is such a heat problem, all of the radios have a perforated covering around each unit. Because of this the water pouring into this area was shorting out the flight guidance computer and air data computer. Callback conversation with revealed the following information. Aircraft has been modified to prevent any further incident of shorting FMC equipment. This was modified by the preparation for delivery people not an aircraft mfr item.

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Original NASA ASRS Text

Title: FMC AND FD FAILED AT FL330. REPLACED UNITS TWICE. MANY TESTS TO FINALLY DISCOVER WATER SPILLING INTO THE ELECTRONICS DURING CLIMB.

Narrative: ENRTE FROM PDK, ATLANTA TO NEWPORT NEWS, VA. WHEN THE AIR DATA COMPUTER BECAME ERRATIC. IT FLUCTUATED ON AND OFF TWICE WHILE STILL IN THE TERMINAL AREA. AT NO TIME WAS IT OFF LONG ENOUGH FOR US TO DO ANY TROUBLE-SHOOTING. UPON REACHING 33000' OUR CRUISE ALT, IT COMPLETELY FAILED AND WOULD NOT RESET ITSELF LIKE IN THE PAST. THE PLT'S F/D ALSO BECAME UNUSABLE AT THIS TIME AND ALT BECAME HARD TO CTL. AN 'EMER' WAS DECLARED WITH ATC AND WE WERE GIVEN A DSNT BACK INTO THE ATLANTA TERMINAL AREA. WE WERE ABOUT 50 MI FROM THE ARPT WHEN BOTH SYSTEMS BEGAN TO OPERATE PROPERLY AGAIN. WE LANDED W/O ANY OTHER PROBS. A SECOND ADC WAS DELIVERED TO US FOR USE AND IT CHKED NORMAL. MR TECH REP FROM RADIO ARRIVED AND DID SOME TESTS. ALL CHKED NORMAL. THESE TEST WOULD REQUIRE US TO FLY THE ACFT. WHILE PASSING THROUGH ABOUT 11000' MY F/D FAILED ONCE AGAIN. ABOUT 4 MINS LATER TECHNICIAN CAME FORWARD AND TOLD US THAT THEY HAD FOUND THE PROB. ABOVE THE POTTY BAGGAGE COMPARTMENT THERE IS A SMALL (APPROX 1 GALLON) WATER TANK FOR WASHING YOUR HANDS. THIS TANK HAS THE FILLER SPOUT ON THE LEFT END OF IT AS IT SITS ON THE SHELF. AS THE ACFT CLBS, THE TANK IS TILTED TO THE SPOUTS END AND WATER IS ALLOWED TO SPILL DOWN INTO THE RADIO STORAGE AREA. BECAUSE IT IS SO CRAMPED IN THIS AREA AND THERE IS SUCH A HEAT PROB, ALL OF THE RADIOS HAVE A PERFORATED COVERING AROUND EACH UNIT. BECAUSE OF THIS THE WATER POURING INTO THIS AREA WAS SHORTING OUT THE FLT GUIDANCE COMPUTER AND ADC. CALLBACK CONVERSATION WITH REVEALED THE FOLLOWING INFO. ACFT HAS BEEN MODIFIED TO PREVENT ANY FURTHER INCIDENT OF SHORTING FMC EQUIP. THIS WAS MODIFIED BY THE PREPARATION FOR DELIVERY PEOPLE NOT AN ACFT MFR ITEM.

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.