Aerobatic aircraft has rough running engine. Makes emergency landing.

Attributes
ACN	159936
Time
Date	199010
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : mem
State Reference	TN
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : mem
Operator	general aviation : personal
Make Model Name	Small Aircraft
Flight Phase	cruise other descent other landing other
Flight Plan	None
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : atp
Experience	flight time last 90 days : 250 flight time total : 10000 flight time type : 50
ASRS Report	159396
Person 2
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : declared emergency none taken : anomaly accepted
Consequence	Other
Supplementary
Primary Problem	Aircraft

Narrative:

Approximately 12 mi southwest of mem, while on a pleasure flight in my home built aerobatic aircraft, I experienced a severe vibration and missing in my engine. I turned toward mem and called approach control and told them my problem. At this point the engine seemed to get worse and I declared an emergency and was given immediate clearance to land on 36L rather than continue on around to runway 27, as they had first assigned. There were no conflicts as the traffic was nil at this point. Upon examination of the engine the #3 intake valve was found to be 'tuliped.' this came as a surprise. 2 weeks earlier the #1 intake valve was found in the same condition! The rest of the cylinders were removed and the #3 valve had started the same deformation. #4 appeared normal. The #1, 3 and 4 cylinders were sent back to the overhauler to try and determine what caused the valves to crater. The #2 cylinder had already been sent and repaired. The engine is an 180 hp at 260 since new, 50 smoh. It appears that a bad batch of intake valves were released some 3 yrs ago when this engine was overhauled. We are going to have the valves tested to find out if any defect occurred during their manufacture.

Original NASA ASRS Text

Title: AEROBATIC ACFT HAS ROUGH RUNNING ENGINE. MAKES EMERGENCY LNDG.

Narrative: APPROX 12 MI SW OF MEM, WHILE ON A PLEASURE FLT IN MY HOME BUILT AEROBATIC ACFT, I EXPERIENCED A SEVERE VIBRATION AND MISSING IN MY ENG. I TURNED TOWARD MEM AND CALLED APCH CTL AND TOLD THEM MY PROB. AT THIS POINT THE ENG SEEMED TO GET WORSE AND I DECLARED AN EMER AND WAS GIVEN IMMEDIATE CLRNC TO LAND ON 36L RATHER THAN CONTINUE ON AROUND TO RWY 27, AS THEY HAD FIRST ASSIGNED. THERE WERE NO CONFLICTS AS THE TFC WAS NIL AT THIS POINT. UPON EXAMINATION OF THE ENG THE #3 INTAKE VALVE WAS FOUND TO BE 'TULIPED.' THIS CAME AS A SURPRISE. 2 WKS EARLIER THE #1 INTAKE VALVE WAS FOUND IN THE SAME CONDITION! THE REST OF THE CYLINDERS WERE REMOVED AND THE #3 VALVE HAD STARTED THE SAME DEFORMATION. #4 APPEARED NORMAL. THE #1, 3 AND 4 CYLINDERS WERE SENT BACK TO THE OVERHAULER TO TRY AND DETERMINE WHAT CAUSED THE VALVES TO CRATER. THE #2 CYLINDER HAD ALREADY BEEN SENT AND REPAIRED. THE ENG IS AN 180 HP AT 260 SINCE NEW, 50 SMOH. IT APPEARS THAT A BAD BATCH OF INTAKE VALVES WERE RELEASED SOME 3 YRS AGO WHEN THIS ENG WAS OVERHAULED. WE ARE GOING TO HAVE THE VALVES TESTED TO FIND OUT IF ANY DEFECT OCCURRED DURING THEIR MANUFACTURE.

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.