A LEAR 36 ON APCH AT 1500 FT REQUIRED USE OF THE AUX ELCETRIC HYD PUMP TO LOWER THE LNDG GEAR AND FLAPS CAUSED BY THE MAIN SYS LOSS OF PRESSURE AND QUANTITY.

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UPON APCH INTO ZZZ; FO CALLED FOR FLAPS 8 DEGS. FLAPS CAME DOWN. FO CALLED FOR FLAPS 20 DEGS. FLAPS CAME DOWN. FO CALLED FOR 'GEAR DOWN; LNDG CHKLIST.' GEAR WOULD NOT COME DOWN; 3 RED UNSAFE COND EXISTED. LOOKED AT HYD PRESSURE GAUGE; PRESSURE WAS LOW; AND 'LOW HYD' LIGHT ILLUMINATED. BEFORE CAPT LOWERED GEAR; FULL FLAPS WERE SELECTED AND FLAPS WOULDN'T MOVE TO FULL FLAPS. I USED THE AUX HYD PUMP TO ASSIST FULL FLAPS. THE FULL FLAPS AND GEAR DOWN WERE SELECTED SIMULTANEOUSLY AND FLAPS WOULDN'T MOVE. HYD PUMP MOVED FULL FLAPS DOWN; AND WHILE I LOOKED AT CHKLIST FOR APPROPRIATE ACTION FOR 'LOW HYD' LIGHT ON; THE GEAR CYCLED TO THE DOWN POS. I LOOKED AT THE CHKLIST AND STEP 1 IS LNDG GEAR-EXTEND WITH ALT EXTENSION. WE NEVER DID MAKE IT TO THE ALT GEAR EXTEND PROC; BECAUSE THE GEAR CYCLED DOWN WITH THE AUX HYD PUMP. WE LANDED WITH NO FURTHER PROBS AND TAXIED TO PARKING WITH AUX PUMP ON FOR BRAKING. UPON EXTERIOR INSPECTION; IN THE AFT EQUIP BAY; IT WAS DISCOVERED THAT A WIRE BUNDLE HAD CHAFED A SMALL HOLE IN A HYD OIL LINE SUPPLYING THE R HAND ENG DRIVEN HYD PUMP. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE LOSS OF THE MAIN HYDRAULIC SYS PRESSURE AND QUANTITY WAS DUE TO A WIRE BUNDLE LOCATED IN THE AFT EQUIP BAY CHAFING ON THE R ENG DRIVEN PUMP SUPPLY LINE. THE RPTR SAID THE WIRE BUNDLE WAS PROPERLY CLAMPED AND DISPLAYED NO DAMAGE TO THE INSULATION. THE RPTR SAID THE AFT EQUIP BAY ALSO CONTAINS THE MAIN HYD RESERVOIR.