Narrative:

When on the ground in ZZZZ; during loading; number one pack selected for ground operations. The noise on the upper deck; coming from the number one pack was extremely loud and best described as a high velocity air noise. We were unable to carry on normal level of conversation and be heard. Turned number one pack selector off then turned number two pack selector to norm. Pack operation returned to normal level. Station loadmaster asked us to set the temperature requirements for forward and aft lower cargo compartments and the main deck forward and aft; to be set to 7 degrees C. We positioned the lower lobe conditioned air flow rate (llcafr) selector to both; and selected the desired temperature of 7 degrees C in the compartments. Then turned pack number two off then selected pack number one selector to norm for start. Pushback; startup; takeoff; and initial climb out all normal. Passing through FL100; crew noticed temperature in cockpit extremely cold and uncontrollable. Further investigation revealed; high velocity cold air coming from around all screens. Captain's pfd; nd; upper EICAS; MCP; first officer nd; pfd. The crew selected the ecs display synopic. All compartments lower forward and lower aft cargo compartments; and main deck forward and aft cargo compartment; temperatures were at 7 degrees C for the perishables. Crew discussed course of action; and decided to turn off the llcafr selector and monitor temperature while passing through FL350. At this time all crew members heard loud bang noise coming from duct system followed by a short burst of visible moisture cloud that filled the cockpit coming from around all the screens. Captain's pfd; nd; upper EICAS; MCP; first officer's nd; pfd. At TOC cockpit filled with a noticeable odor. This odor smelled like overheated electrical equipment. The 1ST observer got out of the seat to try to determine the source and location of smell. The crew determined the odor to be localized in the flight deck. At this point; the captain's pfd became blurry; followed by blackout screen failure. At the same time the first officer's pfd followed captain's failing to a blackout screen. The captain called center declared an emergency and requested radar vectors for immediate return back to ZZZZ. Center gave us right turn direct to ZZZZ and a descent to FL100. At this point the PNF (captain) had programmed the FMC to return back to ZZZZ for the ILS with approach speeds. At present time the captain's nd and upper EICAS had blackout; and failed. 1ST observer pulled QRH out for a checklist. The 2ND observer heard another loud bang noise coming from the air conditioning duct system in the upper deck cabin area. He went to investigate. When he returned to the flight deck the captain directed him to monitor standby airspeed indicator. The first officer was flying the aircraft.callback conversation with reporter revealed the following information: reporter stated that they lost all but one of the five CRT displays on the front panel. The rightmost display on the first officer's side was available intermittently during the return to the departure airport. The lower middle CRT remained available throughout. Using the CRT selectors they were able to alternately display necessary navigation and system data sufficient for an ILS to visual conditions. Reporter was not complimentary regarding the standby instruments stating that when the one front panel CRT was not available to display the pfd; flying by the standby instruments was particularly difficult; noting especially the lack of an ivsi while attempting to fly a glideslope; particularly with the lack of a full time engine instrument display. The left and right autoplts remained functional throughout although the right autoplt was intermittent. Reporter's understanding is that the aircraft remained at the departure airport for maintenance. It was determined that a combination of an aircraft system temperature sensor failure and a malfunctioning pack controller resulted in the induction of massive amounts of AC air at -17C. This appeared to have frozen moisture in the AC ducting which eventually blew out causing the 'booming noise.' a combination of the extreme cold air and possibly ice being blown into the right&east compartment resulted in the failure of the crts. Maintenance advised that the flight crew's decision to place the equipment cooling selector switch in override -- which reverses the normal flow of cooling air -- might have been what allowed the two crts which didn't fail completely to remain available. Reporter emphasized that most of his information regarding the maintenance diagnosis and repair was second hand from a pilot who later flew the aircraft after the repairs.

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Original NASA ASRS Text

Title: B747-400 FLT CREW SUFFERS LOSS OF NEARLY ALL COCKPIT CRT DISPLAYS DUE TO MALFUNCTIONING AIR CONDITIONING SYSTEM. FLT CREW DECLARES AN EMERGENCY AND RETURNS TO DEP ARPT.

Narrative: WHEN ON THE GROUND IN ZZZZ; DURING LOADING; NUMBER ONE PACK SELECTED FOR GROUND OPERATIONS. THE NOISE ON THE UPPER DECK; COMING FROM THE NUMBER ONE PACK WAS EXTREMELY LOUD AND BEST DESCRIBED AS A HIGH VELOCITY AIR NOISE. WE WERE UNABLE TO CARRY ON NORMAL LEVEL OF CONVERSATION AND BE HEARD. TURNED NUMBER ONE PACK SELECTOR OFF THEN TURNED NUMBER TWO PACK SELECTOR TO NORM. PACK OPERATION RETURNED TO NORMAL LEVEL. STATION LOADMASTER ASKED US TO SET THE TEMPERATURE REQUIREMENTS FOR FORWARD AND AFT LOWER CARGO COMPARTMENTS AND THE MAIN DECK FORWARD AND AFT; TO BE SET TO 7 DEGREES C. WE POSITIONED THE LOWER LOBE CONDITIONED AIR FLOW RATE (LLCAFR) SELECTOR TO BOTH; AND SELECTED THE DESIRED TEMPERATURE OF 7 DEGREES C IN THE COMPARTMENTS. THEN TURNED PACK NUMBER TWO OFF THEN SELECTED PACK NUMBER ONE SELECTOR TO NORM FOR START. PUSHBACK; STARTUP; TAKEOFF; AND INITIAL CLIMB OUT ALL NORMAL. PASSING THROUGH FL100; CREW NOTICED TEMPERATURE IN COCKPIT EXTREMELY COLD AND UNCONTROLLABLE. FURTHER INVESTIGATION REVEALED; HIGH VELOCITY COLD AIR COMING FROM AROUND ALL SCREENS. CAPT'S PFD; ND; UPPER EICAS; MCP; FO ND; PFD. THE CREW SELECTED THE ECS DISPLAY SYNOPIC. ALL COMPARTMENTS LOWER FORWARD AND LOWER AFT CARGO COMPARTMENTS; AND MAIN DECK FORWARD AND AFT CARGO COMPARTMENT; TEMPERATURES WERE AT 7 DEGREES C FOR THE PERISHABLES. CREW DISCUSSED COURSE OF ACTION; AND DECIDED TO TURN OFF THE LLCAFR SELECTOR AND MONITOR TEMPERATURE WHILE PASSING THROUGH FL350. AT THIS TIME ALL CREW MEMBERS HEARD LOUD BANG NOISE COMING FROM DUCT SYSTEM FOLLOWED BY A SHORT BURST OF VISIBLE MOISTURE CLOUD THAT FILLED THE COCKPIT COMING FROM AROUND ALL THE SCREENS. CAPTAIN'S PFD; ND; UPPER EICAS; MCP; FO'S ND; PFD. AT TOC COCKPIT FILLED WITH A NOTICEABLE ODOR. THIS ODOR SMELLED LIKE OVERHEATED ELECTRICAL EQUIPMENT. THE 1ST OBSERVER GOT OUT OF THE SEAT TO TRY TO DETERMINE THE SOURCE AND LOCATION OF SMELL. THE CREW DETERMINED THE ODOR TO BE LOCALIZED IN THE FLIGHT DECK. AT THIS POINT; THE CAPT'S PFD BECAME BLURRY; FOLLOWED BY BLACKOUT SCREEN FAILURE. AT THE SAME TIME THE FO'S PFD FOLLOWED CAPTAIN'S FAILING TO A BLACKOUT SCREEN. THE CAPT CALLED CENTER DECLARED AN EMERGENCY AND REQUESTED RADAR VECTORS FOR IMMEDIATE RETURN BACK TO ZZZZ. CENTER GAVE US RIGHT TURN DIRECT TO ZZZZ AND A DESCENT TO FL100. AT THIS POINT THE PNF (CAPT) HAD PROGRAMMED THE FMC TO RETURN BACK TO ZZZZ FOR THE ILS WITH APPROACH SPEEDS. AT PRESENT TIME THE CAPT'S ND AND UPPER EICAS HAD BLACKOUT; AND FAILED. 1ST OBSERVER PULLED QRH OUT FOR A CHECKLIST. THE 2ND OBSERVER HEARD ANOTHER LOUD BANG NOISE COMING FROM THE AIR CONDITIONING DUCT SYSTEM IN THE UPPER DECK CABIN AREA. HE WENT TO INVESTIGATE. WHEN HE RETURNED TO THE FLIGHT DECK THE CAPT DIRECTED HIM TO MONITOR STANDBY AIRSPEED INDICATOR. THE FO WAS FLYING THE AIRCRAFT.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT THEY LOST ALL BUT ONE OF THE FIVE CRT DISPLAYS ON THE FRONT PANEL. THE RIGHTMOST DISPLAY ON THE FO'S SIDE WAS AVAILABLE INTERMITTENTLY DURING THE RETURN TO THE DEP ARPT. THE LOWER MIDDLE CRT REMAINED AVAILABLE THROUGHOUT. USING THE CRT SELECTORS THEY WERE ABLE TO ALTERNATELY DISPLAY NECESSARY NAV AND SYSTEM DATA SUFFICIENT FOR AN ILS TO VISUAL CONDITIONS. REPORTER WAS NOT COMPLIMENTARY REGARDING THE STANDBY INSTRUMENTS STATING THAT WHEN THE ONE FRONT PANEL CRT WAS NOT AVAILABLE TO DISPLAY THE PFD; FLYING BY THE STANDBY INSTRUMENTS WAS PARTICULARLY DIFFICULT; NOTING ESPECIALLY THE LACK OF AN IVSI WHILE ATTEMPTING TO FLY A GLIDESLOPE; PARTICULARLY WITH THE LACK OF A FULL TIME ENGINE INSTRUMENT DISPLAY. THE LEFT AND RIGHT AUTOPLTS REMAINED FUNCTIONAL THROUGHOUT ALTHOUGH THE RIGHT AUTOPLT WAS INTERMITTENT. REPORTER'S UNDERSTANDING IS THAT THE ACFT REMAINED AT THE DEP ARPT FOR MAINTENANCE. IT WAS DETERMINED THAT A COMBINATION OF AN ACFT SYS TEMPERATURE SENSOR FAILURE AND A MALFUNCTIONING PACK CONTROLLER RESULTED IN THE INDUCTION OF MASSIVE AMOUNTS OF AC AIR AT -17C. THIS APPEARED TO HAVE FROZEN MOISTURE IN THE AC DUCTING WHICH EVENTUALLY BLEW OUT CAUSING THE 'BOOMING NOISE.' A COMBINATION OF THE EXTREME COLD AIR AND POSSIBLY ICE BEING BLOWN INTO THE R&E COMPARTMENT RESULTED IN THE FAILURE OF THE CRTS. MAINT ADVISED THAT THE FLT CREW'S DECISION TO PLACE THE EQUIPMENT COOLING SELECTOR SWITCH IN OVERRIDE -- WHICH REVERSES THE NORMAL FLOW OF COOLING AIR -- MIGHT HAVE BEEN WHAT ALLOWED THE TWO CRTS WHICH DIDN'T FAIL COMPLETELY TO REMAIN AVAILABLE. REPORTER EMPHASIZED THAT MOST OF HIS INFORMATION REGARDING THE MAINT DIAGNOSIS AND REPAIR WAS SECOND HAND FROM A PLT WHO LATER FLEW THE ACFT AFTER THE REPAIRS.

Data retrieved from NASA's ASRS site as of May 2009 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.