What was found
AFTER MEL APU ELECTRICAL, TAXI OUT AND TAKEOFF NORMAL. JUST AFTER LIFTOFF MULTIPLE ELECTRICAL AND AVIONICS FAILURES. CAPTAIN AIRSPEED INDICATED 400 KNOTS ALTIMETER WENT TO 40,000 FEET ALL CAPTAIN FLIGHT INSTRUMENTS STOPPED WORKING. F/O AIRSPEED ALSO INDICATED OVER SPEED AND F/O FLIGHT DIRECTOR WAS GIVING FALSE INDICATIONS. STBY INSTRUMENT WORKED NORMALLY. F/O INSTRUMENTS RETURNED TO NORMAL. CAPTAINS INSTRUMENTS REMAINED FAILED. WE DECLARED AN EMERGENCY AND RETURNED TO RUNWAY 24 IN MANILA. SHGN 24JUN21 08:28 MNL U T/S FOUND ON BITE ON BPCU OVERBOLT TRIP ON RIGHT ELECTRICAL SYSTEM. REMOVED AND REPLACED R/H GCU PER AMM 24-22-02-4. COMPLETED. GCU PART N0.734284A SERIAL NO. 0604 RAN BOTH ENGINES BY FLT CREW SATIS. PERFORMED WATER ACCUMULATION CHECK PER AMM 05-51-99-6.COMPLETED. FACT 24JUN21 09:26 MNL U T/S FOUND ON BITE ON BPCU OVERBOLT TRIP ON RIGHT ELECTRICAL SYSTEM. REMOVED AND REPLACED R/H GCU PER AMM 24-22-02-4. COMPLETED. GCU PART N0.734284A SERIAL NO. 0604 RAN BOTH ENGINES BY FLT CREW SATIS. PERFORMED WATER ACCUMULATION CHECK PER AMM 05-51-99-6.COMPLETED. A/C OK FOR SVC. T/S FOUND ON BITE ON BPCU OVERBOLT TRIP ON RIGHT ELECTRICAL SYSTEM. REMOVED AND REPLACED R/H GCU PER AMM 24-22-02-4. GCU PART N0.OFF/ON 734284E/734284A S/N OFF/ON 3075/0604.