PA34-200 FLT CREW HAS COWLING DEPART ACFT WHILE INFLT.

Narrative

I DEPARTED HARTFORD; CT (HFD) ON AN IFR FLT PLAN TO PROVIDENCE; RI (PVD) WITH AN ATP/CFI RATED PLT ON BOARD. WE DEPARTED HFD AROUND XA05 LCL TIME; AND WERE UNDER POSITIVE CTL WITH BRADLEY APCH CTL. WE HAD REACHED OUR CRUISING ALT OF 5000 FT MSL AND HAD JUST COMPLETED THE CRUISE CHKLIST. WE WERE IN VMC CONDITIONS. SHORTLY BEFORE PASSING IJD; WE WERE HANDED OFF TO PROVIDENCE APCH. THE CRUISE CHKLIST HAS JUST BEEN COMPLETED WHEN I NOTICED THE UPPER R-HAND SIDE OF THE INNER COWLING PIECE ON THE L ENG FLAPPING IN THE RELATIVE WIND. IT HAD APPEARED TO ME THAT THE INTERIOR HINGE HAD FAILED; AS IT WAS THE ONLY PIECE THAT HAD BROKEN FREE. I ALERTED THE CFI/ATP ON BOARD OF THE ISSUE. NO SOONER THAN HE SAW THIS; WE BOTH NOTICED THAT THE RELATIVE WIND HAD CAUGHT ENOUGH OF THE COWLING PIECE TO RIP OFF THE FRONT HALF OF THE INNER COWLING PIECE; AND WITH THE FORCE OF THE RELATIVE WIND THE REMAINING PORTION WHICH DEPARTED THE ACFT IN ITS ENTIRETY. THE TIME FRAME FROM THE DISCOVERY OF THE PROB TO THE COWLING PIECE DEPARTING THE ACFT WAS APPROX 2-3 SECONDS. WINDHAM ARPT (IJD) WAS IN SIGHT OFF THE L WING AT THIS TIME. THE DECISION WAS MADE TO MAKE A PRECAUTIONARY LNDG AT WINDHAM ARPT (IJD) IN ORDER TO INSPECT THE ACFT FOR STRUCTURAL DAMAGE. I CANCELED OUR IFR FLT PLAN WITH PROVIDENCE APCH AND ALERTED THEM TO THE SITUATION WE WERE ENCOUNTERING; HOWEVER WE DID NOT DECLARE AN EMER. WE MADE A NORMAL DSCNT/LNDG VFR TO RWY 27 AT WINDHAM ARPT (IDG). DURING THE APCH/LNDG THERE WERE NO CONTROLLABILITY ISSUES OF ANY KIND WITH THE MANEUVERING OF THE ACFT. UPON ARR; BOTH MYSELF AND THE ATP/CFI MADE A VERY THOROUGH INSPECTION OF THE ACFT. NO DAMAGE OF ANY KIND WAS FOUND; AND THE REMAINING COWLING ON THE L ENG WAS STURDY AND VERY SECURE. A JOINT DECISION WAS MADE BTWN MYSELF; THE ATP/CFI ABOARD THE AIRPLANE WITH ME; AND THE OWNER OF FLT SCHOOL WHERE THE ACFT WAS RENTED FROM WHOM HAD A MAINT BACKGROUND ON THE GO/NO GO DECISION. WE DISCUSSED FACTORS SUCH AS ENG COOLING; STRUCTURAL SOUNDNESS; AND GENERAL SAFETY OF FLT ISSUES REGARDING THE SHORT FERRY TRIP TO HARTFORD. WE DETERMINED THAT SHOCK COOLING WOULD NOT BE AN ISSUE DUE TO WARM AMBIENT AIR TEMPS ALOFT; AND THE SHORT FLT TIME TO HARTFORD WITH REDUCED PWR SETTINGS ON THE L ENG. IT WAS AGREED TO MONITOR CLOSELY THE CYLINDER HEAD TEMPS AND OTHER ENG INDICATIONS WITH INCREASED SCRUTINY TO ENSURE ENG HEALTH AT ALL TIMES. THE FACT THAT THE ENG WAS STILL WARM FROM THE ATTEMPTED FLT TO PROVIDENCE WAS ALSO NOTED AS BEING HELPFUL IN PREVENTING A DRASTIC CHANGE IN ENG TEMP AFFECTING PERFORMANCE OR ENG HEALTH. IT WAS ALSO CLR THAT NO CONTROLLABILITY ISSUE EXISTED; AS WAS NOTICED FROM THE APCH INTO IJD. ALSO; THE PA34-200 IS AUTH FOR SKYDIVING ACTIVITIES WITH BOTH REAR DOORS REMOVED SO WITH THIS INFO WE ALSO CONCLUDED THAT THERE WOULD BE NO SIGNIFICANT ISSUE IN THE WAY OF DRAG; OR CONTROLLABILITY. WE ALSO LOOKED CLOSELY AT THE ISSUES OF WX AND DAYLIGHT CONDITIONS. THE WX FOR THE FERRY FLT WOULD BE VMC; IN DAYLIGHT CONDITIONS. FINALLY; WITH THE STRUCTURAL INTEGRITY OF THE ACFT NOT IN QUESTION WE HAD DEDUCED JOINTLY THAT THERE WERE NO INHERENT SAFETY RISKS WHATSOEVER TO COMPLETING THE FLT AS PLANNED. WE DEPARTED IJD FOR HFD; AND LANDED ON RWY 20 IN HARTFORD WITHOUT INCIDENT. AT ALL TIMES WE WERE IN VMC CONDITIONS OPERATING UNDER VFR; AND ALL ENG INDICATIONS ON THE L ENG WERE NORMAL. THE SITUATION WAS A GREAT LEARNING EXPERIENCE. IF I COULD MAKE ANY DECISIONS DIFFERENTLY; I WOULD HAVE OBTAINED A FERRY PERMIT FOR THE ACFT PRIOR TO FLYING IT BACK TO HARTFORD ON THE FERRY FLT. HOWEVER; I DO THINK WE MADE GOOD DECISIONS AS A CREW BTWN MYSELF; THE ATP/CFI; AND THE OWNER OF THE ACFT TO MAKE THE SAFEST DECISION POSSIBLE BASED UPON THE INFO AND KNOWLEDGE OF THE REGS THAT WE HAD AT THE TIME. AT NO TIME WAS SAFETY AT ALL COMPROMISED; AND IT WAS THE FIRST PRIORITY IN EVERY AND ALL DECISIONS MADE REGARDING THE INCIDENT. SUPPLEMENTAL INFO FROM ACN 720087: EVEN THOUGH THE PLANE WAS SAFE TO FLY BACK FROM IJD; IT WAS NOT AIRWORTHY. I SHOULD HAVE CONSULTED A MECH AS WELL AS THE WINDSOR LOCKS FSDO BEFORE WE DECIDED TO FLY IT BACK.