DELAY IN LNDG OCCURS AFTER LOSS OF A PORTION OF ATR-42'S HYD SYS IS EXPERIENCED.

Narrative

UPON CONFIGURING ACFT FOR LNDG MOMENTARY PWR LOSS OCCURRED WHEN MAIN LNDG GEAR LOWERED. BLUE HYD SYS AIR CONDITIONING 'WILD PWRED' HYD PUMP FAILED. ENTERED HOLDING PATTERN OVER FIELD; COMPLETED EMER CHKLIST; BROUGHT BACKUP SYS ON LINE AND NOTIFIED FLT ATTENDANT. NORMAL LNDG INITIATED. CAPT MADE LNDG. MADE USE OF COCKPIT RESOURCE TECHNICIANS AND EMER TRAINING. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR REVEALED THAT THE POST FLT INSPECTION SHOWED A FAILURE OF THE L SIDE HYD PUMP. THIS PUMP MALFUNCTIONED DURING THE LOWERING OF THE LNDG GEAR. SINCE IT IS AC PWRED BY THE 'AC WILD SYS' IT OVERLOADED THE AC WILD GENERATOR AND BLEW ITS CIRCUIT BREAKERS. THE CROSS TIE BUS RELAY THAT IS SUPPOSED TO CLOSE AT THIS POINT TO PWR THE HYD SYS FROM THE R (GREEN) SIDE FAILED TO OPERATE; NECESSITATING THE USE OF THE CHKLIST TO GET THE HYD AND ELECTRICAL PWR BACK INTO THE CORRECT SYS. THE 'WILD' AC GENERATOR IS ONLY PWRING THE HYD PUMPS WHEN THE PROPS ARE TURNING; PWRED THROUGH THE PROP REDUCTION GEAR BOX. THERE ARE 2 OTHER GENERATORS THAT RUN OFF THE ENGS BUT THEY DO NOT PWR THE AC WILD SYS PUMPS. THIS ACFT DOES NOT HAVE AN APU; IT HAS A PROP BRAKE ON THE R ENG AND THEREFORE CAN RUN THE R ENG AS AN APU WHILE 'BRAKING' THE PROP. RPTR FELT THAT THIS WAS AN ODD HAPPENING AND HAD NOT HAD ANY PRIOR EXPERIENCES LIKE THIS IN THE ATR-42.