Narrative:

I went over to ZZZ1 to refuel and was on my way back to ZZZ. Approximately 2 miles off the end of the northwest runway; the manifold pressure started decaying suddenly and the oil pressure started to fluctuate with the pressure stabilizing at the bottom of the green band. Oil pressure was never fully lost. Continued to climb to approximately 3000 ft AGL and glided on over to the airport. Upon landing the folks on the ground reported a lot of smoke coming from the engine area. This aircraft is a motorglider with a full feathering propeller and 28 to 1 glide ratio with a turbo charged rotax 914 engine. Upon checking the remaining oil left in the reservoir; there was approximately one quart left and the remainder had been blown out of the bearings in the turbo. There was apparently much smoke coming from the exhaust canister while this process went on. I was under power approximately 5 minutes or less. It is quite clear that if I had remained under power a few minutes longer that the oil would have gone to zero and the engine would have frozen up. As I started to track this problem down; it became apparent that this has happened to many other operators of the rotax 914 engine; at least 5 such events are known by the two persons I have contacted. One was where the pilot declared an emergency; feathered the propeller; and landed under emergency conditions. And 4 more are known by a representative. Upon contacting the manufacturer; they knew what the problem was immediately. So; I am quite sure that there are many more; all of which have gone unreported to any aviation authority. Manufacturer denied there was a problem at first; but the aircraft rep stated forcefully that he had informed them of the 4 events he knew about. In these emails; engine distributors admit to the return line coking/blowing out the oil being a known problem; they admit to there being nothing in any of their manuals for the pilots or maintenance people pertaining to signs of the line clogging up or procedures for ensuring that the line remains open. If the return line cokes up; all of the oil is forced on a one way trip out of the turbo through the bearings into the exhaust canister and up through the intake plenum. The very least that needs to be done is for the people operating with this engine to be advised of this potential problem and due to the potential disaster if the engine does this in an inhospitable area; a permanent solution should be found to stop this from happening. Turbos are not new to aviation or autos and there should be a straight forward and efficient solution to this issue.callback conversation with reporter revealed the following information: reporter advised the mfg is not available to users and their sales/service reps are unable to provide definitive answers to the means to avoid the failures. Reps have advised only certain types of oil are appropriate but in the next bulletin would state that the previously recommended oil should not be used. Many of the oils they do recommend are not available in the united states. Identical rotax 914 engine/turbo combinations are also installed in other aircraft. Reporter believes the same failure modes would exist in those installations which are much more numerous than for his aircraft models.

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Original NASA ASRS Text

Title: PLT OF POWERED SAILPLANE REPORTS ENGINE OIL SYSTEM FAILURE. LATER LEARNS OF OTHER; SIMILAR FAILURES. RPTR STATES THE CONDITION IS KNOWN TO THE ENGINE MFG; BUT NO SOLUTION HAS BEEN FORTHCOMING.

Narrative: I WENT OVER TO ZZZ1 TO REFUEL AND WAS ON MY WAY BACK TO ZZZ. APPROXIMATELY 2 MILES OFF THE END OF THE NW RUNWAY; THE MANIFOLD PRESSURE STARTED DECAYING SUDDENLY AND THE OIL PRESSURE STARTED TO FLUCTUATE WITH THE PRESSURE STABILIZING AT THE BOTTOM OF THE GREEN BAND. OIL PRESSURE WAS NEVER FULLY LOST. CONTINUED TO CLIMB TO APPROXIMATELY 3000 FT AGL AND GLIDED ON OVER TO THE AIRPORT. UPON LANDING THE FOLKS ON THE GROUND REPORTED A LOT OF SMOKE COMING FROM THE ENGINE AREA. THIS ACFT IS A MOTORGLIDER WITH A FULL FEATHERING PROP AND 28 TO 1 GLIDE RATIO WITH A TURBO CHARGED ROTAX 914 ENGINE. UPON CHECKING THE REMAINING OIL LEFT IN THE RESERVOIR; THERE WAS APPROXIMATELY ONE QUART LEFT AND THE REMAINDER HAD BEEN BLOWN OUT OF THE BEARINGS IN THE TURBO. THERE WAS APPARENTLY MUCH SMOKE COMING FROM THE EXHAUST CANISTER WHILE THIS PROCESS WENT ON. I WAS UNDER POWER APPROXIMATELY 5 MINUTES OR LESS. IT IS QUITE CLEAR THAT IF I HAD REMAINED UNDER POWER A FEW MINUTES LONGER THAT THE OIL WOULD HAVE GONE TO ZERO AND THE ENGINE WOULD HAVE FROZEN UP. AS I STARTED TO TRACK THIS PROBLEM DOWN; IT BECAME APPARENT THAT THIS HAS HAPPENED TO MANY OTHER OPERATORS OF THE ROTAX 914 ENGINE; AT LEAST 5 SUCH EVENTS ARE KNOWN BY THE TWO PERSONS I HAVE CONTACTED. ONE WAS WHERE THE PILOT DECLARED AN EMERGENCY; FEATHERED THE PROP; AND LANDED UNDER EMERGENCY CONDITIONS. AND 4 MORE ARE KNOWN BY A REPRESENTATIVE. UPON CONTACTING THE MANUFACTURER; THEY KNEW WHAT THE PROBLEM WAS IMMEDIATELY. SO; I AM QUITE SURE THAT THERE ARE MANY MORE; ALL OF WHICH HAVE GONE UNREPORTED TO ANY AVIATION AUTHORITY. MANUFACTURER DENIED THERE WAS A PROBLEM AT FIRST; BUT THE ACFT REP STATED FORCEFULLY THAT HE HAD INFORMED THEM OF THE 4 EVENTS HE KNEW ABOUT. IN THESE EMAILS; ENGINE DISTRIBUTORS ADMIT TO THE RETURN LINE COKING/BLOWING OUT THE OIL BEING A KNOWN PROBLEM; THEY ADMIT TO THERE BEING NOTHING IN ANY OF THEIR MANUALS FOR THE PILOTS OR MAINTENANCE PEOPLE PERTAINING TO SIGNS OF THE LINE CLOGGING UP OR PROCEDURES FOR ENSURING THAT THE LINE REMAINS OPEN. IF THE RETURN LINE COKES UP; ALL OF THE OIL IS FORCED ON A ONE WAY TRIP OUT OF THE TURBO THROUGH THE BEARINGS INTO THE EXHAUST CANISTER AND UP THROUGH THE INTAKE PLENUM. THE VERY LEAST THAT NEEDS TO BE DONE IS FOR THE PEOPLE OPERATING WITH THIS ENGINE TO BE ADVISED OF THIS POTENTIAL PROBLEM AND DUE TO THE POTENTIAL DISASTER IF THE ENGINE DOES THIS IN AN INHOSPITABLE AREA; A PERMANENT SOLUTION SHOULD BE FOUND TO STOP THIS FROM HAPPENING. TURBOS ARE NOT NEW TO AVIATION OR AUTOS AND THERE SHOULD BE A STRAIGHT FORWARD AND EFFICIENT SOLUTION TO THIS ISSUE.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER ADVISED THE MFG IS NOT AVAILABLE TO USERS AND THEIR SALES/SERVICE REPS ARE UNABLE TO PROVIDE DEFINITIVE ANSWERS TO THE MEANS TO AVOID THE FAILURES. REPS HAVE ADVISED ONLY CERTAIN TYPES OF OIL ARE APPROPRIATE BUT IN THE NEXT BULLETIN WOULD STATE THAT THE PREVIOUSLY RECOMMENDED OIL SHOULD NOT BE USED. MANY OF THE OILS THEY DO RECOMMEND ARE NOT AVAILABLE IN THE UNITED STATES. IDENTICAL ROTAX 914 ENGINE/TURBO COMBINATIONS ARE ALSO INSTALLED IN OTHER ACFT. REPORTER BELIEVES THE SAME FAILURE MODES WOULD EXIST IN THOSE INSTALLATIONS WHICH ARE MUCH MORE NUMEROUS THAN FOR HIS ACFT MODELS.

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.