Narrative:

I am the owner/pilot of the C172 (1970 model). The event was a blown front crankshaft seal during a test flight causing loss of engine oil and resulting in zero oil pressure for a period of approximately 2 mins. The aircraft was kept under power till a safe airport landing could be made with no damage to the aircraft or other. Engine damage; if any; has not been determined at this time. The aircraft had been returned to the owner by ai/mechanic after annual inspection and test flight 4 days earlier. After 1.8 hours of additional flts; oil drips were noticed by the owner. Aircraft was returned to the ai/mechanic to check out. After further inspection and wash-down of the engine; the ai/mechanic said the source of the leak was not found and requested the owner take another test flight for further checking. During this test flight; the seal blew out as documented above. Immediately after the event; the ai/mechanic pulled the cowl; removed the propeller and discovered the blown seal. He then upon further inspection discovered a kinked vent tube hose; causing blockage and excessive engine internal pressure. The ai/mechanic said he had inadvertently caused this during the annual inspection. I feel this is an unusual error for this ai/mechanic. I continue to have confidence in his work.

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Original NASA ASRS Text

Title: A C172 AT 1000 FT DURING A TEST FLT LOST ALL ENG OIL. ENG OPERATED FOR 2 MINS TO REACH ARPT. OIL LOST THROUGH FRONT CRANKSHAFT SEAL.

Narrative: I AM THE OWNER/PLT OF THE C172 (1970 MODEL). THE EVENT WAS A BLOWN FRONT CRANKSHAFT SEAL DURING A TEST FLT CAUSING LOSS OF ENG OIL AND RESULTING IN ZERO OIL PRESSURE FOR A PERIOD OF APPROX 2 MINS. THE ACFT WAS KEPT UNDER PWR TILL A SAFE ARPT LNDG COULD BE MADE WITH NO DAMAGE TO THE ACFT OR OTHER. ENG DAMAGE; IF ANY; HAS NOT BEEN DETERMINED AT THIS TIME. THE ACFT HAD BEEN RETURNED TO THE OWNER BY AI/MECH AFTER ANNUAL INSPECTION AND TEST FLT 4 DAYS EARLIER. AFTER 1.8 HRS OF ADDITIONAL FLTS; OIL DRIPS WERE NOTICED BY THE OWNER. ACFT WAS RETURNED TO THE AI/MECH TO CHK OUT. AFTER FURTHER INSPECTION AND WASH-DOWN OF THE ENG; THE AI/MECH SAID THE SOURCE OF THE LEAK WAS NOT FOUND AND REQUESTED THE OWNER TAKE ANOTHER TEST FLT FOR FURTHER CHKING. DURING THIS TEST FLT; THE SEAL BLEW OUT AS DOCUMENTED ABOVE. IMMEDIATELY AFTER THE EVENT; THE AI/MECH PULLED THE COWL; REMOVED THE PROP AND DISCOVERED THE BLOWN SEAL. HE THEN UPON FURTHER INSPECTION DISCOVERED A KINKED VENT TUBE HOSE; CAUSING BLOCKAGE AND EXCESSIVE ENG INTERNAL PRESSURE. THE AI/MECH SAID HE HAD INADVERTENTLY CAUSED THIS DURING THE ANNUAL INSPECTION. I FEEL THIS IS AN UNUSUAL ERROR FOR THIS AI/MECH. I CONTINUE TO HAVE CONFIDENCE IN HIS WORK.

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.