Narrative:

Air carrier X was scheduled at the maintenance facility for right&right of the l-hand and r-hand hydraulic reservoir over-temperature switches the night of nov/sat/06; by production control. This particular task had not been done before at this location or by this mechanic. We initially did not have the switches in stock. The aircraft with switches arrived at XA00. Review of the task card showed a manual reference of only chapter 29; no other detail was given. The mechanic working with me looked in the chapter index and did not see specific instructions for right&right of this switch. This happened because it had been added on a temporary revision to the manual that is not placed in the normal index. It was decided to proceed using normal standard practices. Initial inspection showed access to be limited; and a 1 1/8 inch deep well socket was thought to be required. A box end wrench was found that would work with difficulty. The l-hand side was removed and replaced first; and a significant amount of fluid was lost when the switch was removed from the reservoir. The r-hand side was then removed and replaced; and a greater quantity of fluid spilled. I would estimate this to be 1 1/2 quarts. The quantity indicators were still within the safe to operate range; and a ground run to leak check was performed. No indications of hydraulic malfunction or air in the system were noted. After shutdown; fluid was added to the #1 system. The #2 system had been full enough to not require any additional fluid. On takeoff; the nose gear forward doors failed to close; followed by a #2 engine hydraulic caution light with #2 pressure dropping to zero. The crew re-extended the gear using alternate gear extension procedures. During this time; #2 pressure returned/caution light extinguished; followed by a normal landing. No emergency was declared. After closing the bypass door/levers; the nose gear doors were closed by hand spinning the #2 propeller. Air in the #2 system was suspected. On re-examination of the manuals; the temporary revision specific to right&right of the switch was found; which specified bleeding of the system after removal. 2 methods of bleeding are given in chapter 12; hand pump or hydraulic mule. Maintenance is not equipped with a mule; so the hand pump method was then used to bleed #1 and #2 system. Gear door operation then checked satisfactory during a ground run using an override switch. Subsequent repair of the aircraft entailed right&right of the #2 hydraulic pump; (ran under cavitated condition); case drain filter; re-bleed of the #1 and #2 system using hand pump method and bleed of the #2 rudder hydraulic actuator to remove trapped air causing a pressure drop on engine start. Note that during this time several bleeding cycles using the hand pump method were required to remove the air. Factors were: 1) new task. 2) hard to find manual reference. 3) failed to initially bleed system after switch replacement. 4) tooling; it is this mechanic's opinion that the hand pump method should not be used when a great quantity of fluid is lost; and may not have totally removed the air in the system in this case even if done previous to the flight. Corrections: 1) temporary revisions in main index in manuals. 2) hydraulic mule required for system bleeding after major maintenance. 3) research by production control of tooling; test equipment; parts etc; required before task is scheduled. 4) task card containing complete manual reference. A side note would be that too many tasks that were originally scheduled for compliance at c-chk inspections are being pushed to outstations where support is not adequate and overnight ron time may be insufficient.

Related reports:

Google
 

Original NASA ASRS Text

Title: A D8-200 ON CLBOUT NOSE GEAR DOORS FAILED TO CLOSE. #2 ENG HYD CAUTION LIGHT AND #2 SYS PRESSURE DROPPING TO ZERO. CAUSED BY POOR MAINT PROCS.

Narrative: ACR X WAS SCHEDULED AT THE MAINT FACILITY FOR R&R OF THE L-HAND AND R-HAND HYD RESERVOIR OVER-TEMP SWITCHES THE NIGHT OF NOV/SAT/06; BY PRODUCTION CTL. THIS PARTICULAR TASK HAD NOT BEEN DONE BEFORE AT THIS LOCATION OR BY THIS MECH. WE INITIALLY DID NOT HAVE THE SWITCHES IN STOCK. THE ACFT WITH SWITCHES ARRIVED AT XA00. REVIEW OF THE TASK CARD SHOWED A MANUAL REF OF ONLY CHAPTER 29; NO OTHER DETAIL WAS GIVEN. THE MECH WORKING WITH ME LOOKED IN THE CHAPTER INDEX AND DID NOT SEE SPECIFIC INSTRUCTIONS FOR R&R OF THIS SWITCH. THIS HAPPENED BECAUSE IT HAD BEEN ADDED ON A TEMPORARY REVISION TO THE MANUAL THAT IS NOT PLACED IN THE NORMAL INDEX. IT WAS DECIDED TO PROCEED USING NORMAL STANDARD PRACTICES. INITIAL INSPECTION SHOWED ACCESS TO BE LIMITED; AND A 1 1/8 INCH DEEP WELL SOCKET WAS THOUGHT TO BE REQUIRED. A BOX END WRENCH WAS FOUND THAT WOULD WORK WITH DIFFICULTY. THE L-HAND SIDE WAS REMOVED AND REPLACED FIRST; AND A SIGNIFICANT AMOUNT OF FLUID WAS LOST WHEN THE SWITCH WAS REMOVED FROM THE RESERVOIR. THE R-HAND SIDE WAS THEN REMOVED AND REPLACED; AND A GREATER QUANTITY OF FLUID SPILLED. I WOULD ESTIMATE THIS TO BE 1 1/2 QUARTS. THE QUANTITY INDICATORS WERE STILL WITHIN THE SAFE TO OPERATE RANGE; AND A GND RUN TO LEAK CHK WAS PERFORMED. NO INDICATIONS OF HYD MALFUNCTION OR AIR IN THE SYS WERE NOTED. AFTER SHUTDOWN; FLUID WAS ADDED TO THE #1 SYS. THE #2 SYS HAD BEEN FULL ENOUGH TO NOT REQUIRE ANY ADDITIONAL FLUID. ON TKOF; THE NOSE GEAR FORWARD DOORS FAILED TO CLOSE; FOLLOWED BY A #2 ENG HYD CAUTION LIGHT WITH #2 PRESSURE DROPPING TO ZERO. THE CREW RE-EXTENDED THE GEAR USING ALTERNATE GEAR EXTENSION PROCS. DURING THIS TIME; #2 PRESSURE RETURNED/CAUTION LIGHT EXTINGUISHED; FOLLOWED BY A NORMAL LNDG. NO EMER WAS DECLARED. AFTER CLOSING THE BYPASS DOOR/LEVERS; THE NOSE GEAR DOORS WERE CLOSED BY HAND SPINNING THE #2 PROP. AIR IN THE #2 SYS WAS SUSPECTED. ON RE-EXAM OF THE MANUALS; THE TEMPORARY REVISION SPECIFIC TO R&R OF THE SWITCH WAS FOUND; WHICH SPECIFIED BLEEDING OF THE SYS AFTER REMOVAL. 2 METHODS OF BLEEDING ARE GIVEN IN CHAPTER 12; HAND PUMP OR HYD MULE. MAINT IS NOT EQUIPPED WITH A MULE; SO THE HAND PUMP METHOD WAS THEN USED TO BLEED #1 AND #2 SYS. GEAR DOOR OP THEN CHKED SATISFACTORY DURING A GND RUN USING AN OVERRIDE SWITCH. SUBSEQUENT REPAIR OF THE ACFT ENTAILED R&R OF THE #2 HYD PUMP; (RAN UNDER CAVITATED CONDITION); CASE DRAIN FILTER; RE-BLEED OF THE #1 AND #2 SYS USING HAND PUMP METHOD AND BLEED OF THE #2 RUDDER HYD ACTUATOR TO REMOVE TRAPPED AIR CAUSING A PRESSURE DROP ON ENG START. NOTE THAT DURING THIS TIME SEVERAL BLEEDING CYCLES USING THE HAND PUMP METHOD WERE REQUIRED TO REMOVE THE AIR. FACTORS WERE: 1) NEW TASK. 2) HARD TO FIND MANUAL REF. 3) FAILED TO INITIALLY BLEED SYS AFTER SWITCH REPLACEMENT. 4) TOOLING; IT IS THIS MECH'S OPINION THAT THE HAND PUMP METHOD SHOULD NOT BE USED WHEN A GREAT QUANTITY OF FLUID IS LOST; AND MAY NOT HAVE TOTALLY REMOVED THE AIR IN THE SYS IN THIS CASE EVEN IF DONE PREVIOUS TO THE FLT. CORRECTIONS: 1) TEMPORARY REVISIONS IN MAIN INDEX IN MANUALS. 2) HYD MULE REQUIRED FOR SYS BLEEDING AFTER MAJOR MAINT. 3) RESEARCH BY PRODUCTION CTL OF TOOLING; TEST EQUIP; PARTS ETC; REQUIRED BEFORE TASK IS SCHEDULED. 4) TASK CARD CONTAINING COMPLETE MANUAL REF. A SIDE NOTE WOULD BE THAT TOO MANY TASKS THAT WERE ORIGINALLY SCHEDULED FOR COMPLIANCE AT C-CHK INSPECTIONS ARE BEING PUSHED TO OUTSTATIONS WHERE SUPPORT IS NOT ADEQUATE AND OVERNIGHT RON TIME MAY BE INSUFFICIENT.

Data retrieved from NASA's ASRS site as of January 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.