Narrative:

On routine patrol; made turn toward ZZZ1 proceeded about 1 mi and experienced power loss that emulated water in fuel. Switched tanks to mains (from tips) and deployed electric fuel pumps; mixtures moved to full rich. Brief period 1-2 seconds of apparent improvement; then power loss returned accompanied by vibration and yaw to right (minor). Scan of gauges revealed reduced fuel flow right engine (12+ gph on left; 9+ gph on right side). Review of engine analyzer revealed 0 egt and cylinder head temperature on #1 cylinder right engine. Damage limited to issues with either 1 or 2 cylinders on right engine; 1 valve and its cylinder destroyed; possible damage to #2 cylinder (based on perceived increase of exhaust gas temperature noticed after power loss). No injuries or airframe damage. Right engine developing power so left online. Made immediate turn toward nearest suitable airport and notified ATC of situation (our company same at time). Air crew maintained communications with ATC and requested deployment of ready helicopter; while aircraft commander attempted communication with company then with approach. ATC advised probable unavailability of ready helicopter and we maintained course of ZZZ2. Aircraft and system stable at this time. Emergency declared with approach. Proceeded to ZZZ2 and landed without incident. This occurred quite suddenly and it is possible I had unnoticed warning from the engine monitor a few mins prior to the incident but did not notice due to concentration on navigation at that time (required turn). Such notice would not have made much difference since we were well offshore. Also; many times high cylinder head temperature and exhaust gas temperature readings are probe issues and confirmation by other means is necessary. There were no other such warnings; and the mechanic now working on the aircraft suggested there was probably not much warning here. Accordingly; this incident appears to be one that is always possible with piston engines and must be managed. No corrective action indicated according to this writer; except to continue the policy of using only multi-engine aircraft for missions similar to the instant case. Certainly; since diagnosis was made easier by use of the graphic engine monitor; installation of such devices in as many aircraft as possible is recommended; especially if operating in environments that can be dangerous; such as the offshore location of this incident. All aircraft occupants were wearing pfd's and a suitable raft was on board; as well as 2 epirbs; one with GPS; one without. Aircraft commander put one into flight suit; the air crew took the other.

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Original NASA ASRS Text

Title: A PA30 R ENG HAD TWO CYLINDERS AND VALVES DAMAGED INFLT. AN ENG ANALYZER USED TO CONFIRM THE POWER LOSS CAUSE. THE FLT DIVERTED TO A NEARBY ARPT.

Narrative: ON ROUTINE PATROL; MADE TURN TOWARD ZZZ1 PROCEEDED ABOUT 1 MI AND EXPERIENCED PWR LOSS THAT EMULATED WATER IN FUEL. SWITCHED TANKS TO MAINS (FROM TIPS) AND DEPLOYED ELECTRIC FUEL PUMPS; MIXTURES MOVED TO FULL RICH. BRIEF PERIOD 1-2 SECONDS OF APPARENT IMPROVEMENT; THEN PWR LOSS RETURNED ACCOMPANIED BY VIBRATION AND YAW TO R (MINOR). SCAN OF GAUGES REVEALED REDUCED FUEL FLOW R ENG (12+ GPH ON L; 9+ GPH ON R SIDE). REVIEW OF ENG ANALYZER REVEALED 0 EGT AND CYLINDER HEAD TEMP ON #1 CYLINDER R ENG. DAMAGE LIMITED TO ISSUES WITH EITHER 1 OR 2 CYLINDERS ON R ENG; 1 VALVE AND ITS CYLINDER DESTROYED; POSSIBLE DAMAGE TO #2 CYLINDER (BASED ON PERCEIVED INCREASE OF EXHAUST GAS TEMP NOTICED AFTER PWR LOSS). NO INJURIES OR AIRFRAME DAMAGE. R ENG DEVELOPING PWR SO LEFT ONLINE. MADE IMMEDIATE TURN TOWARD NEAREST SUITABLE ARPT AND NOTIFIED ATC OF SITUATION (OUR COMPANY SAME AT TIME). AIR CREW MAINTAINED COMS WITH ATC AND REQUESTED DEPLOYMENT OF READY HELI; WHILE ACFT COMMANDER ATTEMPTED COM WITH COMPANY THEN WITH APCH. ATC ADVISED PROBABLE UNAVAILABILITY OF READY HELI AND WE MAINTAINED COURSE OF ZZZ2. ACFT AND SYS STABLE AT THIS TIME. EMER DECLARED WITH APCH. PROCEEDED TO ZZZ2 AND LANDED WITHOUT INCIDENT. THIS OCCURRED QUITE SUDDENLY AND IT IS POSSIBLE I HAD UNNOTICED WARNING FROM THE ENG MONITOR A FEW MINS PRIOR TO THE INCIDENT BUT DID NOT NOTICE DUE TO CONCENTRATION ON NAV AT THAT TIME (REQUIRED TURN). SUCH NOTICE WOULD NOT HAVE MADE MUCH DIFFERENCE SINCE WE WERE WELL OFFSHORE. ALSO; MANY TIMES HIGH CYLINDER HEAD TEMP AND EXHAUST GAS TEMP READINGS ARE PROBE ISSUES AND CONFIRMATION BY OTHER MEANS IS NECESSARY. THERE WERE NO OTHER SUCH WARNINGS; AND THE MECH NOW WORKING ON THE ACFT SUGGESTED THERE WAS PROBABLY NOT MUCH WARNING HERE. ACCORDINGLY; THIS INCIDENT APPEARS TO BE ONE THAT IS ALWAYS POSSIBLE WITH PISTON ENGS AND MUST BE MANAGED. NO CORRECTIVE ACTION INDICATED ACCORDING TO THIS WRITER; EXCEPT TO CONTINUE THE POLICY OF USING ONLY MULTI-ENG ACFT FOR MISSIONS SIMILAR TO THE INSTANT CASE. CERTAINLY; SINCE DIAGNOSIS WAS MADE EASIER BY USE OF THE GRAPHIC ENG MONITOR; INSTALLATION OF SUCH DEVICES IN AS MANY ACFT AS POSSIBLE IS RECOMMENDED; ESPECIALLY IF OPERATING IN ENVIRONMENTS THAT CAN BE DANGEROUS; SUCH AS THE OFFSHORE LOCATION OF THIS INCIDENT. ALL ACFT OCCUPANTS WERE WEARING PFD'S AND A SUITABLE RAFT WAS ON BOARD; AS WELL AS 2 EPIRBS; ONE WITH GPS; ONE WITHOUT. ACFT COMMANDER PUT ONE INTO FLT SUIT; THE AIR CREW TOOK THE OTHER.

Data retrieved from NASA's ASRS site as of May 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.