Narrative:

Light twin. Left engine failure (termed catastrophic). Safe landing. No aircraft damage. No injuries. Engine essentially brand new; in fact; factory new; less than 50 hours (ttsn). We departed ZZZ on pre-filed IFR flight plan to ZZZ1. VMC conditions. Run-up went perfectly; no indication of any engine difficulty. Takeoff went perfectly. Proceeded southwest bound; climbing; and called center. Perhaps 5-10 minutes after takeoff; we experienced a substantial vibration. Vibration came on suddenly but did not increase; it stayed steady but quite evident. Later; on the ground; the vibration on the left side had developed to the point (perhaps due to much lower RPM) that a rivet popped out of the control panel. At no time was the plane uncontrollable. There was no immediate asymmetrical thrust. In the process of troubleshooting; I noted that the engine monitor showed cylinders 1; 3; 5 on the left engine were not recording data. Adjusted mixture; no change or reduction in vibration. Unable to make any change that relieved the vibration. Some clacking sound from left engine. Told center that we had a problem and were returning to ZZZ; requested that center stay with us. Did not declare emergency. Returned to ZZZ and landed without incident; without damage to plane and with no injuries. Right engine functioning well at all times. Left engine providing partial power (no drag); left engine was not shut down until after landing. Subsequently; it would not restart. Called ZZZ2 flight service to report safe landing; got message back that center had received information and cancelled IFR flight plan. Upon opening the engine cowl; we noted that there was a patina of oil in the vicinity of the #1 cylinder. Upon compression and other checks by mechanic; found that left engine #1 cylinder had; in mechanic's terminology; thrown a rod. No compression in #1 cylinder and piston did not appear to move when propeller was hand-cranked. Engine has not been torn down as of this date. Lack of engine monitor indication of #3 and #5 may have been due to failure of em probes due to vibration. Left engine (and right engine; too) had less than 50 hours on them since new (ttsn) at time of left engine malfunction. Previous engines were replaced with factory new (not remanufactured; but factory new) continental io-470l21b engines. All instructions followed for break-in of engine. No previous sign of difficulty. This situation is remarkable for the youth virtually brand new and; in fact; factory new condition of the engine which failed. According to the mechanic; it should be termed a catastrophic failure. According to local mechanic; we could have expected that the engine would seize in a relatively short time span had we not returned to land. Mechanic noted that similar model engine on a light aircraft was in his hangar having failed for similar reason with less than 50 hours on the engine. Believe this may well be due to a manufacturing materials defect or to an assembly line process malfunction at manufacturer. Review should be made as soon as possible regarding procedures and other engines with similar component batches or similar process or inspection procedures.

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Original NASA ASRS Text

Title: ENGINE WITH LESS THAN 50 HRS TTSN ON A LIGHT TWIN ACFT FAILS DUE TO CONNECTING ROD FAILURE. INSPECTING MECHANIC DESCRIBES NEARLY IDENTICAL FAILURE ON ANOTHER ACFT AT THE SAME APPROX FLT HOURS IN SVC.

Narrative: LIGHT TWIN. LEFT ENGINE FAILURE (TERMED CATASTROPHIC). SAFE LANDING. NO AIRCRAFT DAMAGE. NO INJURIES. ENGINE ESSENTIALLY BRAND NEW; IN FACT; FACTORY NEW; LESS THAN 50 HOURS (TTSN). WE DEPARTED ZZZ ON PRE-FILED IFR FLIGHT PLAN TO ZZZ1. VMC CONDITIONS. RUN-UP WENT PERFECTLY; NO INDICATION OF ANY ENGINE DIFFICULTY. TKOF WENT PERFECTLY. PROCEEDED SW BOUND; CLIMBING; AND CALLED CENTER. PERHAPS 5-10 MINUTES AFTER TKOF; WE EXPERIENCED A SUBSTANTIAL VIBRATION. VIBRATION CAME ON SUDDENLY BUT DID NOT INCREASE; IT STAYED STEADY BUT QUITE EVIDENT. LATER; ON THE GROUND; THE VIBRATION ON THE LEFT SIDE HAD DEVELOPED TO THE POINT (PERHAPS DUE TO MUCH LOWER RPM) THAT A RIVET POPPED OUT OF THE CONTROL PANEL. AT NO TIME WAS THE PLANE UNCONTROLLABLE. THERE WAS NO IMMEDIATE ASYMMETRICAL THRUST. IN THE PROCESS OF TROUBLESHOOTING; I NOTED THAT THE ENGINE MONITOR SHOWED CYLINDERS 1; 3; 5 ON THE LEFT ENGINE WERE NOT RECORDING DATA. ADJUSTED MIXTURE; NO CHANGE OR REDUCTION IN VIBRATION. UNABLE TO MAKE ANY CHANGE THAT RELIEVED THE VIBRATION. SOME CLACKING SOUND FROM LEFT ENGINE. TOLD CENTER THAT WE HAD A PROBLEM AND WERE RETURNING TO ZZZ; REQUESTED THAT CENTER STAY WITH US. DID NOT DECLARE EMERGENCY. RETURNED TO ZZZ AND LANDED WITHOUT INCIDENT; WITHOUT DAMAGE TO PLANE AND WITH NO INJURIES. RIGHT ENGINE FUNCTIONING WELL AT ALL TIMES. LEFT ENGINE PROVIDING PARTIAL POWER (NO DRAG); LEFT ENGINE WAS NOT SHUT DOWN UNTIL AFTER LANDING. SUBSEQUENTLY; IT WOULD NOT RESTART. CALLED ZZZ2 FLIGHT SVC TO REPORT SAFE LANDING; GOT MSG BACK THAT CENTER HAD RECEIVED INFORMATION AND CANCELLED IFR FLIGHT PLAN. UPON OPENING THE ENGINE COWL; WE NOTED THAT THERE WAS A PATINA OF OIL IN THE VICINITY OF THE #1 CYLINDER. UPON COMPRESSION AND OTHER CHECKS BY MECHANIC; FOUND THAT LEFT ENGINE #1 CYLINDER HAD; IN MECHANIC'S TERMINOLOGY; THROWN A ROD. NO COMPRESSION IN #1 CYLINDER AND PISTON DID NOT APPEAR TO MOVE WHEN PROPELLER WAS HAND-CRANKED. ENGINE HAS NOT BEEN TORN DOWN AS OF THIS DATE. LACK OF ENGINE MONITOR INDICATION OF #3 AND #5 MAY HAVE BEEN DUE TO FAILURE OF EM PROBES DUE TO VIBRATION. LEFT ENGINE (AND RIGHT ENGINE; TOO) HAD LESS THAN 50 HOURS ON THEM SINCE NEW (TTSN) AT TIME OF LEFT ENGINE MALFUNCTION. PREVIOUS ENGINES WERE REPLACED WITH FACTORY NEW (NOT REMANUFACTURED; BUT FACTORY NEW) CONTINENTAL IO-470L21B ENGINES. ALL INSTRUCTIONS FOLLOWED FOR BREAK-IN OF ENGINE. NO PREVIOUS SIGN OF DIFFICULTY. THIS SITUATION IS REMARKABLE FOR THE YOUTH VIRTUALLY BRAND NEW AND; IN FACT; FACTORY NEW CONDITION OF THE ENGINE WHICH FAILED. ACCORDING TO THE MECHANIC; IT SHOULD BE TERMED A CATASTROPHIC FAILURE. ACCORDING TO LOCAL MECHANIC; WE COULD HAVE EXPECTED THAT THE ENGINE WOULD SEIZE IN A RELATIVELY SHORT TIME SPAN HAD WE NOT RETURNED TO LAND. MECHANIC NOTED THAT SIMILAR MODEL ENGINE ON A LIGHT ACFT WAS IN HIS HANGAR HAVING FAILED FOR SIMILAR REASON WITH LESS THAN 50 HRS ON THE ENGINE. BELIEVE THIS MAY WELL BE DUE TO A MANUFACTURING MATERIALS DEFECT OR TO AN ASSEMBLY LINE PROCESS MALFUNCTION AT MANUFACTURER. REVIEW SHOULD BE MADE ASAP REGARDING PROCEDURES AND OTHER ENGINES WITH SIMILAR COMPONENT BATCHES OR SIMILAR PROCESS OR INSPECTION PROCEDURES.

Data retrieved from NASA's ASRS site as of January 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.