Narrative:

Upon approach into ZZZ, first officer called for flaps 8 degrees. Flaps came down. First officer called for flaps 20 degrees. Flaps came down. First officer called for 'gear down, landing checklist.' gear would not come down, 3 red unsafe cond existed. Looked at hydraulic pressure gauge, pressure was low, and 'low hydraulic' light illuminated. Before captain lowered gear, full flaps were selected and flaps wouldn't move to full flaps. I used the auxiliary hydraulic pump to assist full flaps. The full flaps and gear down were selected simultaneously and flaps wouldn't move. Hydraulic pump moved full flaps down, and while I looked at checklist for appropriate action for 'low hydraulic' light on, the gear cycled to the down position. I looked at the checklist and step 1 is landing gear-extend with altitude extension. We never did make it to the altitude gear extend procedure, because the gear cycled down with the auxiliary hydraulic pump. We landed with no further problems and taxied to parking with auxiliary pump on for braking. Upon exterior inspection, in the aft equipment bay, it was discovered that a wire bundle had chafed a small hole in a hydraulic oil line supplying the right hand engine driven hydraulic pump. Callback conversation with reporter revealed the following information: the reporter stated the loss of the main hydraulic system pressure and quantity was due to a wire bundle located in the aft equipment bay chafing on the right engine driven pump supply line. The reporter said the wire bundle was properly clamped and displayed no damage to the insulation. The reporter said the aft equipment bay also contains the main hydraulic reservoir.

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Original NASA ASRS Text

Title: 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.

Narrative: 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.

Data retrieved from NASA's ASRS site as of July 2007 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.