Narrative:

I departed pou airport in a C152. The runup and departure from runway 24 were uneventful, with normal climb (70 KTS) and power indications. I continued a normal climb after turning onto a northbound crosswind to depart the pattern. Approximately 2 mi from pou, I contacted the tower and requested a l-hand 360 degree climbing turn to gain altitude prior to crossing the hudson river. After completing the 360 degree turn, I continued northbound, paralleling the hudson river. Approximately 1 mi later, at approximately 2000 ft MSL, I heard a loud 'bang' from the engine and noticed an immediate drop in RPM accompanied by the violent shaking of the engine. I immediately turned back toward pou and simultaneously notified the tower that I was inbound and reduced power to a point at which the engine vibrations subsided sufficiently to continue flight without the risk of damaging the engine mounts. While I did not notice what my RPM was, I believe it was in the 1200-1400 RPM range. Pou tower inquired if I required any assistance. Since I was well within gliding distance and had some power, I declined any assistance other than an expedited landing clearance. There was 1 other aircraft in contact with pou, a C182 agreed to allow me to land first. Since I was directly north of the airport, runway 15 was closest. However, since I had sufficient altitude and some power, I elected to land on runway 24, which was 2000 ft longer and had a visual approach slope indicator. Approach and landing were uneventful. The aircraft had sufficient power to taxi back to our tie-down. Subsequent investigation revealed that the #3 cylinder exhaust valve had broken, with the valve head becoming impaled in the face of the piston. The valve and piston required replacement. The lower engine suffered no damage. A critique of my performance leads me to these observations: 1) I did not declare an emergency since I believed throughout the incident that I had sufficient altitude to complete a power-off landing at pou. However, had the engine problem worsened, or had other complications developed, I might have required emergency services. Since seconds count in an emergency, I should have declared it 'just in case.' 2) my decision to perform a climbing 360 degree turn to gain altitude gave me a safety cushion. I now see the importance of best-performance (vy) departures. Every ft of altitude helps in an emergency. 3) during my return to pou, my airspeed occasionally deviated as much as 10 KTS from the best glide speed of 60 KTS. While this was not a factor in this incident, I need to be more focused on precisely maintaining the best glide speed to maximize my landing options.

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Original NASA ASRS Text

Title: PLT OF A C152 HEARS A LOUD BANG AND HAS LOSS OF RPM AND ENG VIBRATION. HE RETURNS TO ARPT FOR SAFE LNDG.

Narrative: I DEPARTED POU ARPT IN A C152. THE RUNUP AND DEP FROM RWY 24 WERE UNEVENTFUL, WITH NORMAL CLB (70 KTS) AND PWR INDICATIONS. I CONTINUED A NORMAL CLB AFTER TURNING ONTO A NBOUND XWIND TO DEPART THE PATTERN. APPROX 2 MI FROM POU, I CONTACTED THE TWR AND REQUESTED A L-HAND 360 DEG CLBING TURN TO GAIN ALT PRIOR TO XING THE HUDSON RIVER. AFTER COMPLETING THE 360 DEG TURN, I CONTINUED NBOUND, PARALLELING THE HUDSON RIVER. APPROX 1 MI LATER, AT APPROX 2000 FT MSL, I HEARD A LOUD 'BANG' FROM THE ENG AND NOTICED AN IMMEDIATE DROP IN RPM ACCOMPANIED BY THE VIOLENT SHAKING OF THE ENG. I IMMEDIATELY TURNED BACK TOWARD POU AND SIMULTANEOUSLY NOTIFIED THE TWR THAT I WAS INBOUND AND REDUCED PWR TO A POINT AT WHICH THE ENG VIBRATIONS SUBSIDED SUFFICIENTLY TO CONTINUE FLT WITHOUT THE RISK OF DAMAGING THE ENG MOUNTS. WHILE I DID NOT NOTICE WHAT MY RPM WAS, I BELIEVE IT WAS IN THE 1200-1400 RPM RANGE. POU TWR INQUIRED IF I REQUIRED ANY ASSISTANCE. SINCE I WAS WELL WITHIN GLIDING DISTANCE AND HAD SOME PWR, I DECLINED ANY ASSISTANCE OTHER THAN AN EXPEDITED LNDG CLRNC. THERE WAS 1 OTHER ACFT IN CONTACT WITH POU, A C182 AGREED TO ALLOW ME TO LAND FIRST. SINCE I WAS DIRECTLY N OF THE ARPT, RWY 15 WAS CLOSEST. HOWEVER, SINCE I HAD SUFFICIENT ALT AND SOME PWR, I ELECTED TO LAND ON RWY 24, WHICH WAS 2000 FT LONGER AND HAD A VISUAL APCH SLOPE INDICATOR. APCH AND LNDG WERE UNEVENTFUL. THE ACFT HAD SUFFICIENT PWR TO TAXI BACK TO OUR TIE-DOWN. SUBSEQUENT INVESTIGATION REVEALED THAT THE #3 CYLINDER EXHAUST VALVE HAD BROKEN, WITH THE VALVE HEAD BECOMING IMPALED IN THE FACE OF THE PISTON. THE VALVE AND PISTON REQUIRED REPLACEMENT. THE LOWER ENG SUFFERED NO DAMAGE. A CRITIQUE OF MY PERFORMANCE LEADS ME TO THESE OBSERVATIONS: 1) I DID NOT DECLARE AN EMER SINCE I BELIEVED THROUGHOUT THE INCIDENT THAT I HAD SUFFICIENT ALT TO COMPLETE A PWR-OFF LNDG AT POU. HOWEVER, HAD THE ENG PROB WORSENED, OR HAD OTHER COMPLICATIONS DEVELOPED, I MIGHT HAVE REQUIRED EMER SERVICES. SINCE SECONDS COUNT IN AN EMER, I SHOULD HAVE DECLARED IT 'JUST IN CASE.' 2) MY DECISION TO PERFORM A CLBING 360 DEG TURN TO GAIN ALT GAVE ME A SAFETY CUSHION. I NOW SEE THE IMPORTANCE OF BEST-PERFORMANCE (VY) DEPS. EVERY FT OF ALT HELPS IN AN EMER. 3) DURING MY RETURN TO POU, MY AIRSPD OCCASIONALLY DEVIATED AS MUCH AS 10 KTS FROM THE BEST GLIDE SPD OF 60 KTS. WHILE THIS WAS NOT A FACTOR IN THIS INCIDENT, I NEED TO BE MORE FOCUSED ON PRECISELY MAINTAINING THE BEST GLIDE SPD TO MAXIMIZE MY LNDG OPTIONS.

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.