AN SF340 DSNDING FOR LNDG EXPERIENCED GEAR EXTENSION PROBS. THE CREW DECLARED AN EMER; EXTENDED THE GEAR WITH THE ALTERNATE EXTENSION SYS; AND RETURNED TO DEP STATION.

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I WAS THE CAPT OF A FLT FROM ZZZ TO ZZZ1. I ARRIVED AT THE AIRPLANE APPROX 25 MINS PRIOR TO DEP. WE HAD FLOWN THE AIRPLANE SEVERAL LEGS EARLIER IN THE DAY. FO CONDUCTED A PREFLT AND ADVISED ME THAT IT WAS NORMAL. I CONDUCTED A REVIEW OF THE MAINT LOG AND ALL OTHER NORMAL PREPARATIONS AS REQUIRED BY THE FOM AND POM. CHKLISTS WERE USED IN THEIR ENTIRETY. THE FLT OPERATED NORMALLY UNTIL THE APCH PHASE WHEN THE FO CALLED FOR AND I SELECTED GEAR DOWN. AT THIS POINT I OBSERVED THE HYD PUMP TO BE RUNNING CONTINUOUSLY WITH THE GEAR UNSAFE INDICATOR ILLUMINATED AND NO GREEN DOWN LOCK INDICATION. I SHUT THE HYD PUMP OFF AND IMMEDIATELY CHKED FOR ABNORMAL HYD PRESSURE AND/OR QUANTITY INDICATIONS; THEY WERE NORMAL. WE HAD BEEN CLRED FOR A VISUAL APCH AT AN UNCTLED FIELD; AND HAD SWITCHED TO THE ADVISORY FREQ. WE HAD ONLY BEGUN OUR DSCNT SO WE IMMEDIATELY SWITCHED BACK TO CTR AND TOLD THEM WE NEEDED A PLACE TO HOLD. CTR CLRED US TO CLB BACK TO RADAR COVERAGE AND ALLOWED US TO HOLD OVER THE VOR. ADDITIONALLY; WE WERE WATCHING AN AREA OF CONVECTIVE ACTIVITY APPROX 10 MI TO THE SE AS WE HELD. THE FO THEN CALLED FOR 'QRH LNDG GEAR' AND I PROCEEDED TO WORK THROUGH THE QRH. ONE OF THE FIRST ITEMS THE QRH DIRECTED US TO DO WAS CHK THE F-7 CIRCUIT BREAKER. WE FOUND IT TO BE TRIPPED. WE QUESTIONED OUR ABILITY TO RESET THE CIRCUIT BREAKER AS THE QRH ONLY DIRECTED US TO 'CHK' THE BREAKER NOT 'CHK AND RESET.' AT THIS POINT WE CONTACTED MAINT CTL AND DISPATCH AND EXPLAINED THE SITUATION. MAINT WAS CONTACTED AND CONFIRMED THAT WE COULD IN FACT RESET THE BREAKER. I ATTEMPTED TO RESET THE BREAKER AND IT IMMEDIATELY TRIPPED AGAIN. I CONTINUED WITH THE QRH AND ULTIMATELY WAS SUCCESSFUL IN GETTING THE GEAR DOWN BY USING THE EMER GEAR EXTENSION HANDLE. THE F-7 CIRCUIT BREAKER REMAINED TRIPPED AND WE KNEW THAT WE WERE GOING TO HAVE ASSOCIATED FAILURES. WE DISCUSSED WITH MAINT THE EXPECTED FAILURES WITH THE F-7 BREAKER TRIPPED -- LACK OF NOSEWHEEL STEERING; LACK OF ANTI-LOCK BRAKING; AND FAILURE OF THE FLT IDLE STOP TO OPEN AND THE ASSOCIATED USE OF THE FLT IDLE STOP OVERRIDE. WE CHOSE TO RETURN TO ZZZ FOR THE FOLLOWING REASONS: 1) ZZZ1 BEING AN UNCTLED ARPT WOULD HAVE NO WAY OF PREVENTING ANOTHER ACFT FROM LNDG BEHIND US. OUR INTENTIONS WERE TO STOP THE ACFT ON THE RWY AND NOT ATTEMPT TO TAXI WITH NO NOSEWHEEL STEERING. ZZZ COULD PROVIDE THAT PROTECTION. 2) WITH THE APCHING CONVECTIVE ACTIVITY WE WERE CONCERNED ABOUT POSSIBLE GUST FRONT WINDS CAUSING US CTLABILITY PROBS ON LNDG. ZZZ WX WAS FAVORABLE. 3) BETTER ABILITY TO HAVE THE AIRPLANE TOWED IN ZZZ. 4) CFR RESOURCES ZZZ IN HIGHER NUMBERS. 5) SUFFICIENT FUEL TO RETURN ZZZ GIVEN WE WERE FUELED FOR THE ROUND TRIP. WE DECLARED AN EMER FOR THE LNDG IN ZZZ AND ADVISED DISPATCH OF OUR STATUS AND INTENTIONS. WE ASKED FOR BUT NEVER RECEIVED FUEL BURN CALCULATIONS WITH THE GEAR EXTENDED FOR THE RETURN TO ZZZ. ENRTE TO ZZZ WE DISCUSSED THE FOLLOWING: 1) CTLABILITY WITH NO NOSEWHEEL STEERING. 2) POSSIBLE LACK OF ANTI-LOCK BRAKING. 3) POSSIBLE USE OF THE FLT IDLE STOP OVERRIDE KNOB AND ASSOCIATED CALLS. 4) POSSIBLE GAR SCENARIOS AND PERFORMANCE WITH LNDG GEAR EXTENDED. LNDG WAS NORMAL AND THE AIRPLANE WAS STOPPED ON THE CTRLINE OF THE RWY. CFR IMMEDIATELY SURROUNDED US AND ESTABLISHED COM WITH US. I REQUESTED A BRAKE INSPECTION DUE TO UNKNOWN STATUS OF THE ANTI-LOCK BRAKES. BRAKE TEMPS WERE RPTED NORMAL AND THE AIRPLANE WAS SHUT DOWN AND SECURED USING ALL NORMAL CHKLISTS PER POM AND FOM. MAINT SECURED THE LNDG GEAR WITH PINS AND TOWED THE ACFT TO THE GATE WHERE PAX RETURNED TO THE TERMINAL USING THE STAIRS. BOTH THE F-7 CIRCUIT BREAKER AND USE OF THE EMER GEAR EXTENSION HANDLE WERE WRITTEN UP WITH REF TO THE PREVIOUS F-7 HISTORY.