A PIPER PA23-250 ON LNDG ROLLOUT HAD THE ACFT SUDDENLY DIP FORWARD INCURRING DAMAGE TO BOTH PROPS. RPTR SUSPECTS CAUSE OF DIP WAS IMPROPER NOSE GEAR WORK ACCOMPLISHED 3 DAYS PRIOR TO FLT.

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SHORTLY AFTER LNDG (200 FT) ON RWY 5 AT NORTH LITTLE ROCK ARPT; WHILE STILL ROLLING ON CTRLINE THE ACFT SUDDENLY DIPPED FORWARD AND TO THE R. MY IMMEDIATE REACTION WAS TO PULL THE NOSE UP AND ADD PWR. THESE ACTIONS BROUGHT THE ACFT BACK INTO THE AIR AND WAS NOW OVER THE GRASSY AREA TO THE R (E) OF THE RWY HEADED FOR A HILL LINED WITH TREES. AT THIS POINT I ASKED XYZ 'WHICH ENG IS IT?' BEING PRETTY SURE IT WAS THE L ONE BECAUSE OF THE R DIP AND THE AMOUNT OF L RUDDER REQUIRED TO KEEP THE ACFT RIGHT SIDE UP. SIMULTANEOUSLY I REACHED FOR AND RAISED THE GEAR LEVER NOTING THAT I STILL HAD 3 GREEN LIGHTS AND THEN RAISED THE FLAPS. XYZ SAID THAT BOTH ENGS WERE INDICATING FULL PWR WHICH I CONFIRMED FROM THE INSTS. AT THIS TIME WE ARE FLYING PARALLEL TO RWY 5 AND 150 FT AGL. I ASKED XYZ ONCE AGAIN 'WHICH ENG IS IT?; IT FEELS LIKE THE R ONE.' HE LOOKED OVER HIS SHOULDER AND NOTED SMOKE FROM THE R ENG. I IMMEDIATELY FEATHERED THE R ENG AND CUT OFF THE MIXTURE. AT THAT TIME WE WERE ABOVE BLUE LINE AND CLBING AT 500-600 FPM. I INSTRUCTED XYZ SEVERAL TIMES WHILE FLYING A L HAND PATTERN TO ANNOUNCE TO EVERYONE THAT WE HAD AN EMER AND WOULD BE LNDG BACK ON RWY 5. WHILE TURNING BASE I LOWERED THE GEAR BELIEVING THAT I WOULDN'T GET 3 GREEN AGAIN BECAUSE WE DIDN'T HAVE A R MAIN LNDG GEAR OR TIRE. I TURNED FINAL AND DID HAVE 3 GREEN WHICH WAS CONFIRMED BY XYZ AND AN INSTRUCTOR ON THE GND WHO ANNOUNCED THAT WE HAD THREE DOWN. I LANDED THE ACFT WITHOUT FURTHER INCIDENT AND TAXIED TO THE RAMP ON THE L ENG. AFTER EXITING THE ACFT AND LOOKING AT THE R ENG SOMEONE SAID ALOUD 'LOOK AT THE L PROP' AT WHICH TIME I WALKED TO THE L SIDE OF THE ACFT AND NOTICED THAT THE L PROP WAS ALSO Q-TIPPED; I WAS SHOCKED SINCE I HAD NO INDICATION OF ANY PROB WITH THE L ENG OR PROP. FROM WHAT I CAN TELL IT APPEARS THAT THE NOSE GEAR MUST HAVE LOWERED FOR BOTH PROPS TO STRIKE. I BELIEVE THAT THE MAINT DONE THE 3 DAYS BEFORE INVOLVING REMOVING AND REPAIRING THE NOSE GEAR STRUT IS AT FAULT. I THINK THAT THE STRUT WAS NOT PUT BACK IN PROPERLY. CALLBACK INFO FROM RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE NOSE GEAR DOWNLOCK IS SUSPECT AS THE CAUSE OF THIS INCIDENT; HOWEVER THE ACFT WAS NOT JACKED AND THE GEAR RETRACTED TO CHK THE DOWNLOCK. THE RPTR SAID WHEN THE GEAR WAS REPAIRED RECENTLY THE MANUFACTURER'S MAINT MANUAL WAS NOT USED IN THE REPAIR. THE RPTR STATED THE FAA HAS LOOKED AT THE ACFT BUT HAS MADE NO COMMENT.