N87SF

Part: GROUND WIRE — DETACHED (ZONE 400) · airframe 7,083 hrs · 5,896 cycles

APPROXIMATELY 1 HOUR INTO FLIGHT BOTH LT ITT INDICATORS AGAIN BEGAN TO FLUCTUATE WITH NO ENGINE COMPUTER ANNUNCIATION. THE AIRCRAFT CONTINUED ON TO SCHEDULED DESTINATION WHERE AN UNEVENTFUL LANDING WAS MADE. THIS WAS 4 LANDINGS AND APPROXIMATELY 6 HOURS SINCE THE PREVIOUS ITT ISSUE WHERE THE INDICATOR WAS REPLACED. TROUBLESHOOTING REVEALED A GROUND WIRE HAD BECOME DETACHED FROM THE WIRE SHIELDING AT THE ITT CONNECTOR IN THE L/H ENGINE PYLON. THE CONNECTOR WAS INSPECTED AND CLEANED AND THE GROUND WIRE REATTACHED. GROUND OPERATIONAL CHECK OF THE ITT SYSTEM WAS OK. THE AIRCRAFT HAS SINCE FLOWN 13 HOURS WITHOUT THIS FAILURE. IT IS BELIEVED THE LOSS OF SHIELDING GROUND ALLOWED ELECTROMAGNETIC OR STATIC INTERFERENCE TO BE INDUCED INTO THE WIRE HARNESS AFFECTING THE SIGNAL GOING TO THE INDICATOR.

Part: INDICATOR — MALFUNCTIONED (ITT) · airframe 7,278 hrs · 5,891 cycles

APPROXIMATELY 10 MINUTES INTO FLIGHT BOTH LT ITT INDICATORS BEGAN TO FLUCTUATE APPROXIMATELY 200 DEGREES. NO ENGINE COMPUTER ANNUNCIATION WAS NOTED. THE AIRCRAFT RETURNED TO HOME BASE WHERE AN UNEVENTFUL LANDING WAS MADE. THE ITT INDICATOR WAS REPLACED AND GROUND OPERATION AT MULTIPLE SUSTAINED POWER SETTINGS WAS PERFORMED WITH NO FAULTS AND THE AIRCRAFT WAS RETURNED TO SERVICE.

Part: COMPUTER — FAILED (STALL WARNING) · airframe 7,192 hrs · 5,807 cycles

AT CRUISE FLIGHT MULTIPLE AMBER ANNUNCIATIONS ILLUMINATED, AOA PROBE, FLAP SPEEDBRAKE AND STALL WARNING, OFF FLAGS ALSO CAME INTO VIEW ON THE AOA INDICATOR AND BOTH FAST/SLOW INDICATORS. CREW FOLLOWED AFM PROCEDURES AND A SAFE LANDING WAS MADE AT DESTINATION AIRPORT. INVESTIGATION REVEALED THAT THE ANGLE OF ATTACK COMPUTER HAD FAILED. THE COMPUTER WAS REPLACED WITH AN O/H UNIT AND ALL SYSTEM CHECKS WERE NORMAL. TIME 13 YEARS AND 2936 HRS SINCE LAST INSTALLATION AND FATIGUE ARE SUSPECTED CAUSES OF FAILURE.

Part: FLIGHT DIR — INTERMITTENT (ZONE 100) · airframe 6,746 hrs · 5,366 cycles

FLIGHT DIRECTOR SYS NOTED INOPERATIVE DURING TAXI FOR TAKEOFF. AVIONICS WERE SHUTDOWN & TURNED BACK ON WHICH DID NOT CORRECT THE PROBLEM. AVIONICS HAD BEEN ON FOR CLOSE TO AN HOUR PRIOR TO TAXI. AVIONIC BAY DOORS WERE OPENED TO COOL SUSPECTED OVERHEATED UNITS WHICH DID CORRECT THE PROBLEM. ACFT FLEW TO TWO DESTINATIONS WITH NO ISSUES. AFTER ACFT RETURNED TO HOME BASE AVIONICS WERE DETERMINED TO BE OPERATING NORMALLY. FLIGHT GUIDANCE COMPUTERS, AVIONICS J BOXES & SYMBOL GENERATORS WERE REMOVED, PINS CLEANED & RE-INSTALLED. SATISFACTORILY OPERATED AVIONICS FOR OVER 1 HOUR. IT IS BELIEVED HEAT, ALONG WITH RESIDUE ON PINS CREATED THIS INCIDENT. CREWS ARE REQUESTED NOT TO OPERATE AVIONICS UNNECESSARILY ON THE GND FOR PROLONGED PERIODS.

Part: FIRE LOOP — CHAFED (RT ENGINE) · airframe 6,593 hrs · 5,228 cycles

AFTER LANDING CREW NOTED RT ENG FIRE DETECT SYS FAILURE. ACFT WAS FERRIED BACK TO HOME BASE. INVESTIGATION REVEALED ENG FIRE DETECTOR LOOP CHAFFED THROUGH UNDER THE AFT ENG HEAT SHIELD, GREEN SHEETS AT INBD END. CAUSE WAS DUE TO IMPROPER ROUTING AT LAST ENG CHANGE. DETECTOR WAS REPLACED WITH NEW PART & ACFT RETURNED TO SERVICE.

Part: DOOR SEAL — CONTAMINATED (CABIN) · airframe 14,498 hrs · 15,929 cycles

DURING CLIMB TO CRUISE ALTITUDE THE AIRCRAFT PRESSURIZATION SYSTEM DID NOT APPEAR TO BE MAINTAINING PRESSURIZATION PROPERLY AS THE AIRCRAFT CONTINUED TO CLIMB AS THE CABIN SEEMED TO RISE FURTHER AND BY 17,000FT A DECISION WAS MADE TO DESCEND AND RETURN TO HOME BASE WHERE AN UNEVENTFUL LANDING WAS MADE. DOOR SEAL/DOOR FRAME AREA REVEALED A POSSIBLE LEAK IN THE UPPER AFT CORNER. THE AREA OF THE SUSPECTED LEAK FELT SLIPPERY AND IS BELIEVED THAT A POOR SEAL WAS MADE DUE TO THIS, AND THE ADDED LUBRICATION FROM RAIN WATER THAT DAY. THE AREA WAS MILDLY SCUFFED AND BOTH THE DOOR FRAME AND SEAL WERE CLEANED. A GROUND CHECK WITH ENGINES RUNNING WAS SATISFACTORY.

Part: PRINTED CKT BOARD — FAULTY (COCKPIT) · airframe 7,139 hrs · 9,151 cycles

AFTER TAKEOFF CREW WENT TO SELECT GEAR UP & NOTICED THAT THE GEAR DOWNLOCK LIGHTS WERE INOPERATIVE. CREW CYCLED GEAR WITH NO AFFECT AND NOTED THE GEAR UNLOCK LIGHT ILLUMINATED AND EXTINGUISHED AS THOUGH A NORMAL CYCLE HAD BEEN COMPLETED. GEAR ALSO FELT NORMAL DURING THE RETRACT/EXTEND CYCLE. CREW PERFORMED A LIGHT TEST AND LIGHTS STILL WOULD NOT ILLUMINATE. AFTER A FLY BY CONFIRMING GEAR APPEARED TO BE FULLY DOWN, AND A REVIEW OF THE GEAR SCHEMATIC DIAGRAMS, IT WAS DETERMINED THAT ONLY AN INDICATION FAULT WAS OCCURRING AND A SAFE LANDING COULD BE MADE. THE EMERGENCY GEAR SYSTEM WAS ACTUATED AND A SAFE LANDING WAS MADE AT DEPARTURE AIRPORT. TROUBLESHOOTING REVEALED A FAULT IN THE LIGHT DIMMING CIRCUITRY (COMMON TO ALL THREE LIGHTS) AND A FAULTY SOLDER JOINT WAS FOUND AND REPAIRED ON THE CONTROL PRINTED CIRCUIT BOARD (PCB101). EMERGENCY SYSTEM WAS RESET AND SEVERAL NORMAL GEAR CYCLES MADE. AIRCRAFT WAS RETURNED TO SERVICE.

Part: SWITCH — INTERMITTENT (ACTUATOR) · airframe 13,097 hrs · 14,609 cycles

UPON APPROACH TO DESTINATION AIRPORT THE GEAR WAS SELECTED DOWN. THE PILOT NOTED THAT THE LT GEAR DOWN & LOCKED ANNUNCIATOR WAS NOT ILLUMINATED. THE PILOT RECYCLED THE GEAR BUT THE LIGHT STILL WOULD NOT ILLUMINATE. FOLLOWING PROCEDURES, THE EMERGENCY GEAR EXTENSION SYSTEM WAS ENGAGED AND A SAFE LANDING WAS MADE. AFTER TAXI TO THE RAMP, IT WAS NOTED THAT THE DOWN AND LOCKED ANNUNCIATOR HAD ILLUMINATED. A FERRY PERMIT WAS OBTAINED AND THE AIRCRAFT WAS FLOWN TO HOME BASE GEAR DOWN, WHERE AN UNEVENTFUL LANDING WAS MADE. INVESTIGATION INTO THE PROBLEM REVEALED THAT THE LT GEAR DOWNLOCK SWITCH HAD FAILED. THE SWITCH WAS REPLACED, THE EMERGENCY GEAR SYSTEM WAS RESET, AND THE GEAR WAS CYCLED NUMEROUS TIMES WITHOUT ANY PROBLEMS. THE AIRCRAFT WAS RETURNED TO SERVICE.

Part: RELAY — STICKING (RT STARTER) · airframe 12,642 hrs · 14,067 cycles

AFTER STARTING RT ENGINE THE START BUTTON LIGHT COULD NOT BE EXTINGUISHED. AFTER SHUTDOWN THE RT ENGINE REMAINED SPOOLING AS THE STARTER WAS STILL ENGAGED AND THE BATTERY HAD TO BE DISCONNECTED TO TERMINATE THE STARTER. THE RT START RELAY WAS REPLACED AND OPERATIONAL CHECK OF THE START SYSTEM WAS SATISFACTORY.

Part: TACH GENERATOR — FAILED (LT ENGINE) · airframe 12,464 hrs · 13,828 cycles

DURING CRUISE FLIGHT THE LT ENGINE N1(FAN) INDICATOR WENT TO ZERO, ALL OTHER ENGINE INDICATIONS WERE NORMAL. INVESTIGATION REVEALED THAT THE N1 TACH GENERATOR DRIVE SHAFT HAD SHEARED. REPLACED WITH OVERHAULED UNIT AND OPERATIONALLY CHECKED OK. CAUSE WAS EVIDENTLY METAL FATIGUE, GIVE THE TIME ON THE UNIT SINCE NEW.

Part: STUD — BROKEN (RT MLG STRUT) · airframe 11,013 hrs · 12,386 cycles

DURING SCHEDULED REPLACEMENT OF THE MLG STRUT CYLINDERS, THE HYD ACTUATOR ATTACH STUD WAS BEING REMOVED FOR RE-USE. UPON APPLYING A TENSION LOAD ON THE STUD TO REMOVE IT, PER MM, THE STUD SEPARATED ALONG THE THREADS WELL BELOW THE MAX TORQUE LIMIT, THE CRACK BEGAN APPROX 1 THREAD UP FROM THE BASE AND EXTENDED UP THREE THREADS, STOPPING APPROX 1 THREAD BEFORE THE COTTER PIN HOLE. EXAMINATION REVEALED THAT THE FRACTURE HAD EXISTED FOR SOME TIME AND THAT IT EXTENDED THROUGH APPROXIMATELY 80 PERCENT OF THE STUD. THE POINT AT WHICH THE FRACTURE BEGAN IS THE SAME POINT AT WHICH THE NUT CONTACTS THE ROD END.

Part: STRUCTURE — MISDRILLED (HORIZ STABILIZER)

DURING COURSE OF 10,000-HOUR INSPECTION, THE HORIZONTAL STABILIZER WAS FOUND TO HAVE NUMEROUS DOUBLE HOLES, HOLES DRILLED OFF-CENTER, HOLES DRILLED ON AN ANGLE AFTER REMOVAL OF THE HYLOCKS IN THE CENTER SECTION THROUGH ALL SPARS AND FITTINGS. SUBMITTER STATED IT IS VERY OBVIOUS A MANUFACTURING PROBLEM.

Part: BUMPER PAD — DEFECTIVE (THRUST REV)

PILOTS REPORTED LT REVERSER WOULD INTERMITTENTLY 'HANG UP' WHILE OPENING, BUT CLOSE AND LOCKING WERE NORMAL. 319.7 HRS, 490 CYCLES PRIOR TO THIS OCCURRENCE, ROHR SB CIT 78-8R1 WAS C/W WHICH INSTALLS NEW DOOR BUMPERS OVER OLD BUMPERS. THIS DECREASES CLEARANCE BETWEEN INBD UPPER STANG FAIRING SUPPORT AND DOOR BUMPER. OVER TIME, NEW BUMPER MUSHROOMED SLIGHTLY ALLOWING DOOR TO CATCH ON SUPPORT SKIN. INSPECTION OF RT SIDE SHOWED SIGNS OF SAME PROBLEM BEGINNING TO OCCUR. ROUTING OUT FORWARD SKIN OF BOTH SUPPORTS FOR EXTRA CLEARANCE RECTIFIED PROBLEM. SUBMITTER SUGGESTS SB BE REVISED TO INSPECT THIS AREA AND ALLOW A MINIMUM OF .25 INCH CLEARANCE.

Part: BUMPER PAD — DEFECTIVE (THRUST REV)

PILOTS REPORTED LT REVERSER WOULD INTERMITTENTLY 'HANG UP' WHILE OPENING, BUT CLOSE AND LOCKING WERE NORMAL. 319.7 HRS, 490 CYCLES PRIOR TO THIS OCCURRENCE, ROHR SB CIT 78-8R1 WAS C/W WHICH INSTALLS NEW DOOR BUMPERS OVER OLD BUMPERS. THIS DECREASES CLEARANCE BETWEEN INBD UPPER STANG FAIRING SUPPORT AND DOOR BUMPER. OVER TIME, NEW BUMPER MUSHROOMED SLIGHTLY ALLOWING DOOR TO CATCH ON SUPPORT SKIN. INSPECTION OF RT SIDE SHOWED SIGNS OF SAME PROBLEM BEGINNING TO OCCUR. ROUTING OUT FORWARD SKIN OF BOTH SUPPORTS FOR EXTRA CLEARANCE RECTIFIED PROBLEM. SUBMITTER SUGGESTS SB BE REVISED TO INSPECT THIS AREA AND ALLOW A MINIMUM OF .25 INCH CLEARANCE.