THE PLT OF AN ATX FREIGHTER PA60 HAD THE R ENG; A LYCOMING O-540; FAIL WHEN THE TOP OF THE ENG CRACKED AROUND THE OIL FILLER AREA. THE PLT MADE A SUCCESSFUL SINGLE ENG LNDG; BUT THE NOSE GEAR COLLAPSED DURING THE ROLLOUT. POSTFLT INSPECTION FOUND THAT THE NOSE GEAR OVER CTR SPRING HAD FAILED.

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WHILE BEING VECTORED FOR THE RWY 13R ILS INTO AUSTIN MUELLER ARPT; I SHUT DOWN THE R ENG DUE TO ENG GAUGES INDICATING A LOSS OF OIL PRESSURE. I WENT THROUGH THE EMER ENG FAILURE DURING FLT CHKLIST AND THE BEFORE LNDG CHKLIST AND LANDED. AFTER LNDG THE NOSEWHEEL COLLAPSED. I DID NOTE PRIOR TO LNDG NORMAL GEAR DOWN INDICATIONS AND THE GEAR WARNING HORN DID NOT SOUND BEFORE LNDG. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE PLT SAID THAT HE WAS ON A REGULAR FREIGHT RUN WHEN HE NOTICED A FLUCTUATION IN THE R ENG'S OIL PRESSURE. THE OIL PRESSURE THEN SUDDENLY WENT TO ZERO AND AS HE STARTED THE SHUTDOWN PROC THE ENG SEIZED. HE DECLARED AN EMER AND CONTINUED FOR A SINGLE ENG LNDG. AS HE WAS IN THE LNDG ROLL THE NOSE GEAR COLLAPSED AND HE SHUT DOWN THE L ENG; SECURED THE ACFT AND EXITED. THE ACFT WAS TOWED AFTER PINNING THE NOSE GEAR IN THE EXTENDED POS. MAINT FOUND THAT THE NOSE GEAR OVER CTR SPRING WAS HYPER-EXTENDED AND WOULD NOT DEVELOP MUCH PRESSURE TO HOLD THE MECHANISM IN THE DOWN AND LOCKED POS. THE LYCOMING ENG CASE HAD CRACKED AROUND THE OIL FILLER AREA ACCORDING TO THE RPTR. LATER; THE OWNER OF THE COMPANY; ALLEGEDLY; CALLED THE PIPER CUSTOMER SERVICE CTR AND THEY WERE FAMILIAR WITH THE PROBLEM WITH THE OVER CTR SPRING. ACCORDING TO THE PLT THIS SPRING HAD FAILED BEFORE; BUT HE DOES NOT KNOW IF THERE IS AN AVIATION DIRECTIVE CONCERNING THIS PROBLEM. THE ENG REPRESENTATIVE INSPECTED THE DAMAGE AND HAS BEEN IN CONTACT WITH THE OWNER; BUT THE PLT DOES NOT KNOW THE RESULTS OF THEIR DISCUSSIONS. THE R ENG WAS TOTALLY DESTROYED AND THE L ENG WAS DAMAGED WHEN ITS PROPELLER STRUCK THE RWY.