Narrative:

During a training flight originating at pao I was fling an aerobatic aircraft in the rear seat as CFI. During return to pao from training maneuvers by ocean (san gregorio beach) I experienced complete engine failure in level cruise flight at 2400' MSL over the stanford linear accelerator. After a descent over skyline blvd from 3000' from 3000' MSL, the aircraft was in level flight for approximately 3 mins at 2400' MSL at 2400' RPM (approximately 65% power). The student was flying from the front seat. I had received pao ATIS information with wind 360 degrees at 20 KTS. The engine began to run rough. Carburetor heat was applied with no rectification of problem. Engine continued rough. I took over control of aircraft. Adjustment of throttle (100-200 RPM) did not rectify. Engine came to complete stop with a metallic grinding sound within approximately 30 seconds. As I set (trimmed) for best glide speed (60-65 mph IAS). I radioed pao tower declaring an emergency with engine failure and would advise of selected landing site. Tower acknowledged. As I scanned and turned toward landing sites (cteta horse park off of sand hill road), we secured fuel shutoff, mixture off, mags off, seatbelts/harnesses tight and secure, no electrical except master, radio, transponder. There was no fire or visible front cowling damage. When I committed to landing site I radioed pao tower to advise. They acknowledged. Radios and transponder and master. We crossed overhead the field, made a downwind, high base and slipped base to final approach. As I transitioned from approach descent to roundout a strong gust of wind caused a momentary nose high attitude with 10 mph IAS decrease. I lowered the nose to recover airspeed, flared for an uphill (slight grade), direct headwind, tail first T/D on a soft/rough field at as slow an airspeed as possible. The landing was firm and run out about 25-50' in length. There were no injuries, no property damage and only very minor aircraft damage (the right main wheel caught a gopher hole and was slightly bent, 1-2'). An aircraft overhead relayed for us by radio that we were down and safe. Chp, fire, sheriff, FAA, news media, mechanics, club manager all arrived at various times. Engine failure was due to exhaust valve failure in #4 cylinder causing complete/instant disintegration of #4 cylinder and cracking of case on #3 side.

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Original NASA ASRS Text

Title: ENGINE FAILURE IN AEROBATIC SMA TYPE ACFT AT 2400' MSL OVER POPULATED AREA. PLT LANDED IN OPEN FIELD. SLIGHT DAMAGE TO ACFT. NO INJURIES.

Narrative: DURING A TRNING FLT ORIGINATING AT PAO I WAS FLING AN AEROBATIC ACFT IN THE REAR SEAT AS CFI. DURING RETURN TO PAO FROM TRNING MANEUVERS BY OCEAN (SAN GREGORIO BEACH) I EXPERIENCED COMPLETE ENG FAILURE IN LEVEL CRUISE FLT AT 2400' MSL OVER THE STANFORD LINEAR ACCELERATOR. AFTER A DSNT OVER SKYLINE BLVD FROM 3000' FROM 3000' MSL, THE ACFT WAS IN LEVEL FLT FOR APPROX 3 MINS AT 2400' MSL AT 2400' RPM (APPROX 65% PWR). THE STUDENT WAS FLYING FROM THE FRONT SEAT. I HAD RECEIVED PAO ATIS INFO WITH WIND 360 DEGS AT 20 KTS. THE ENG BEGAN TO RUN ROUGH. CARB HEAT WAS APPLIED WITH NO RECTIFICATION OF PROB. ENG CONTINUED ROUGH. I TOOK OVER CTL OF ACFT. ADJUSTMENT OF THROTTLE (100-200 RPM) DID NOT RECTIFY. ENG CAME TO COMPLETE STOP WITH A METALLIC GRINDING SOUND WITHIN APPROX 30 SECS. AS I SET (TRIMMED) FOR BEST GLIDE SPD (60-65 MPH IAS). I RADIOED PAO TWR DECLARING AN EMER WITH ENG FAILURE AND WOULD ADVISE OF SELECTED LNDG SITE. TWR ACKNOWLEDGED. AS I SCANNED AND TURNED TOWARD LNDG SITES (CTETA HORSE PARK OFF OF SAND HILL ROAD), WE SECURED FUEL SHUTOFF, MIXTURE OFF, MAGS OFF, SEATBELTS/HARNESSES TIGHT AND SECURE, NO ELECTRICAL EXCEPT MASTER, RADIO, XPONDER. THERE WAS NO FIRE OR VISIBLE FRONT COWLING DAMAGE. WHEN I COMMITTED TO LNDG SITE I RADIOED PAO TWR TO ADVISE. THEY ACKNOWLEDGED. RADIOS AND XPONDER AND MASTER. WE CROSSED OVERHEAD THE FIELD, MADE A DOWNWIND, HIGH BASE AND SLIPPED BASE TO FINAL APCH. AS I TRANSITIONED FROM APCH DSNT TO ROUNDOUT A STRONG GUST OF WIND CAUSED A MOMENTARY NOSE HIGH ATTITUDE WITH 10 MPH IAS DECREASE. I LOWERED THE NOSE TO RECOVER AIRSPD, FLARED FOR AN UPHILL (SLIGHT GRADE), DIRECT HEADWIND, TAIL FIRST T/D ON A SOFT/ROUGH FIELD AT AS SLOW AN AIRSPD AS POSSIBLE. THE LNDG WAS FIRM AND RUN OUT ABOUT 25-50' IN LENGTH. THERE WERE NO INJURIES, NO PROPERTY DAMAGE AND ONLY VERY MINOR ACFT DAMAGE (THE RIGHT MAIN WHEEL CAUGHT A GOPHER HOLE AND WAS SLIGHTLY BENT, 1-2'). AN ACFT OVERHEAD RELAYED FOR US BY RADIO THAT WE WERE DOWN AND SAFE. CHP, FIRE, SHERIFF, FAA, NEWS MEDIA, MECHS, CLUB MGR ALL ARRIVED AT VARIOUS TIMES. ENG FAILURE WAS DUE TO EXHAUST VALVE FAILURE IN #4 CYLINDER CAUSING COMPLETE/INSTANT DISINTEGRATION OF #4 CYLINDER AND CRACKING OF CASE ON #3 SIDE.

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.