Narrative:

I was flying my aerobatic zlin 50 in mild aerobatics. As I came out of a hammerhead, I noticed that the propeller speed decreased markedly. I had been watching the oil pressure carefully, as I was new to this airplane, and had seen that the oil pressure was in the green arc, flickering into the yellow only occasionally when transitioning from upright to inverted. Also, I noticed that the oil pressure would drop off to zero at the top of the vertical line, but this is normal. After the incident where the propeller RPM dropped off to about 2000 RPM, I decided to end the aerobatic session and return to the airport. Just as I had pulled straight and level, and reduced the throttle, a large amount of oil came out of the engine and splattered on the windshield. Thinking that I had lost a front main crankshaft seal, I throttled back to 0.4 atmospheres and started a gentle climb directly for the airport, which was some 10 mi distance. At this point, the oil pressure had dropped to zero. I reduced the throttle to idle, and stopped the engine. I made a successful dead stick landing at the airport, with no damage to pilot or airframe. Disassembly of the engine revealed that the thrust bearing on the crankshaft had seized, even though the engine still contained 8 quarts of oil. Normal oil load for aerobatics in this airplane is only 10 quarts. In my emergency return to the airport, I entered and passed through class C airspace without contacting the appropriate ATC facility. Perhaps I should have contacted ATC, even given the nature of my emergency, however, I was kind of busy at the time.

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Original NASA ASRS Text

Title: AN ACROBATIC PLT IS CONCERNED THAT HE ENTERED CLASS C AIRSPACE WITHOUT CLRNC DURING AN EMER RETURN TO A NEARBY ARPT AFTER AN ENG FAILURE.

Narrative: I WAS FLYING MY AEROBATIC ZLIN 50 IN MILD AEROBATICS. AS I CAME OUT OF A HAMMERHEAD, I NOTICED THAT THE PROP SPD DECREASED MARKEDLY. I HAD BEEN WATCHING THE OIL PRESSURE CAREFULLY, AS I WAS NEW TO THIS AIRPLANE, AND HAD SEEN THAT THE OIL PRESSURE WAS IN THE GREEN ARC, FLICKERING INTO THE YELLOW ONLY OCCASIONALLY WHEN TRANSITIONING FROM UPRIGHT TO INVERTED. ALSO, I NOTICED THAT THE OIL PRESSURE WOULD DROP OFF TO ZERO AT THE TOP OF THE VERT LINE, BUT THIS IS NORMAL. AFTER THE INCIDENT WHERE THE PROP RPM DROPPED OFF TO ABOUT 2000 RPM, I DECIDED TO END THE AEROBATIC SESSION AND RETURN TO THE ARPT. JUST AS I HAD PULLED STRAIGHT AND LEVEL, AND REDUCED THE THROTTLE, A LARGE AMOUNT OF OIL CAME OUT OF THE ENG AND SPLATTERED ON THE WINDSHIELD. THINKING THAT I HAD LOST A FRONT MAIN CRANKSHAFT SEAL, I THROTTLED BACK TO 0.4 ATMOSPHERES AND STARTED A GENTLE CLB DIRECTLY FOR THE ARPT, WHICH WAS SOME 10 MI DISTANCE. AT THIS POINT, THE OIL PRESSURE HAD DROPPED TO ZERO. I REDUCED THE THROTTLE TO IDLE, AND STOPPED THE ENG. I MADE A SUCCESSFUL DEAD STICK LNDG AT THE ARPT, WITH NO DAMAGE TO PLT OR AIRFRAME. DISASSEMBLY OF THE ENG REVEALED THAT THE THRUST BEARING ON THE CRANKSHAFT HAD SEIZED, EVEN THOUGH THE ENG STILL CONTAINED 8 QUARTS OF OIL. NORMAL OIL LOAD FOR AEROBATICS IN THIS AIRPLANE IS ONLY 10 QUARTS. IN MY EMER RETURN TO THE ARPT, I ENTERED AND PASSED THROUGH CLASS C AIRSPACE WITHOUT CONTACTING THE APPROPRIATE ATC FACILITY. PERHAPS I SHOULD HAVE CONTACTED ATC, EVEN GIVEN THE NATURE OF MY EMER, HOWEVER, I WAS KIND OF BUSY AT THE TIME.

Data retrieved from NASA's ASRS site as of July 2007 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.