Narrative:

After departing rld in MVFR conditions (haze, visibility 3 mi, 900 scattered 1500 scattered to broken) on IFR flight plan, engine(south) began missing, running rough and surging. Immediately advised chinook departure controller (ATC) that I was making a 180 degree turn to return to airport because I had engine problems. ATC initiated calls to alert emergency vehicles to stand by at rld airport. Engine(south) continued to run rough throughout remainder of flight including landing. But, roughness and surging decreased in severity as power was reduced for descent from approximately 5000 ft MSL to approximately at 2000 ft MSL and subsequent landing. Fuel was added approximately 45 mins prior to flight and checked approximately 20-30 mins later with no contamination observed. However, after landing a mechanic checked fuel and said he saw tiny drops of water in main tank sample, but none in others (2 wing tanks and auxiliary tank that feeds main tank). He said that other aircraft had reported problems with fuel contamination (water) on several occasions. After several run-ups, fuel checks, taxies, fuel checks, etc, a test flight was made when all appeared normal. Flight was normal, no engine problems. Later, another IFR flight was attempted in VFR conditions and engine(south) started surging shortly after lift-off. An immediate return for and landing was made. Aircraft is now in shop being examined for fuel, turbo, induction, etc, problems. Aircraft recently had annual inspection by manufacturer (aerostar aircraft corp), including overhaul of one cylinder and engine wing deice upgrades to 'known icing certified.' all applicable manufacturer safety bulletins, and FAA airworthiness directives were complied with at that time (jan/xx/96 to feb/xx/96). Water in fuel contamination was ruled out as cause on this second flight. On subsequent flight, with mechanic on board, two very brief engine misses were noted after takeoff and at pattern altitude as power was being slowly reduced. Engines are lycoming 10-540's with machen upgrades to 350 hp (42 in map @ 2500 RPM) with approximately 550 hours since major over- hauls. Cause is under investigation. Callback conversation with reporter revealed the following information: this aircraft was a model 601T aerostar with modifications that brought it up to the superstar model 700 performance according to the reporter. After several unsuccessful test flts the mechanics contacted the engine modification corporation and they recommended that the injectors be cleaned or changed. The fault was found to be primarily in the left engine's injectors. There were 2 different styles of injectors and the ones on the left engine were the 1-PIECE type. This type cannot be disassembled for cleaning and inspection whereas the 2-PIECE type on the right engine can be examined. After the left engine's injectors were changed to new 2-PIECE type injectors it performed well.

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Original NASA ASRS Text

Title: A CORPORATE PLT EXPERIENCES ENG DIFFICULTIES SHORTLY AFTER TKOF AND RETURNS AND MAKES AN EMER LNDG.

Narrative: AFTER DEPARTING RLD IN MVFR CONDITIONS (HAZE, VISIBILITY 3 MI, 900 SCATTERED 1500 SCATTERED TO BROKEN) ON IFR FLT PLAN, ENG(S) BEGAN MISSING, RUNNING ROUGH AND SURGING. IMMEDIATELY ADVISED CHINOOK DEP CTLR (ATC) THAT I WAS MAKING A 180 DEG TURN TO RETURN TO ARPT BECAUSE I HAD ENG PROBS. ATC INITIATED CALLS TO ALERT EMER VEHICLES TO STAND BY AT RLD ARPT. ENG(S) CONTINUED TO RUN ROUGH THROUGHOUT REMAINDER OF FLT INCLUDING LNDG. BUT, ROUGHNESS AND SURGING DECREASED IN SEVERITY AS PWR WAS REDUCED FOR DSCNT FROM APPROX 5000 FT MSL TO APPROX AT 2000 FT MSL AND SUBSEQUENT LNDG. FUEL WAS ADDED APPROX 45 MINS PRIOR TO FLT AND CHKED APPROX 20-30 MINS LATER WITH NO CONTAMINATION OBSERVED. HOWEVER, AFTER LNDG A MECH CHKED FUEL AND SAID HE SAW TINY DROPS OF WATER IN MAIN TANK SAMPLE, BUT NONE IN OTHERS (2 WING TANKS AND AUX TANK THAT FEEDS MAIN TANK). HE SAID THAT OTHER ACFT HAD RPTED PROBS WITH FUEL CONTAMINATION (WATER) ON SEVERAL OCCASIONS. AFTER SEVERAL RUN-UPS, FUEL CHKS, TAXIES, FUEL CHKS, ETC, A TEST FLT WAS MADE WHEN ALL APPEARED NORMAL. FLT WAS NORMAL, NO ENG PROBS. LATER, ANOTHER IFR FLT WAS ATTEMPTED IN VFR CONDITIONS AND ENG(S) STARTED SURGING SHORTLY AFTER LIFT-OFF. AN IMMEDIATE RETURN FOR AND LNDG WAS MADE. ACFT IS NOW IN SHOP BEING EXAMINED FOR FUEL, TURBO, INDUCTION, ETC, PROBS. ACFT RECENTLY HAD ANNUAL INSPECTION BY MANUFACTURER (AEROSTAR ACFT CORP), INCLUDING OVERHAUL OF ONE CYLINDER AND ENG WING DEICE UPGRADES TO 'KNOWN ICING CERTIFIED.' ALL APPLICABLE MANUFACTURER SAFETY BULLETINS, AND FAA AIRWORTHINESS DIRECTIVES WERE COMPLIED WITH AT THAT TIME (JAN/XX/96 TO FEB/XX/96). WATER IN FUEL CONTAMINATION WAS RULED OUT AS CAUSE ON THIS SECOND FLT. ON SUBSEQUENT FLT, WITH MECH ON BOARD, TWO VERY BRIEF ENG MISSES WERE NOTED AFTER TKOF AND AT PATTERN ALT AS PWR WAS BEING SLOWLY REDUCED. ENGS ARE LYCOMING 10-540'S WITH MACHEN UPGRADES TO 350 HP (42 IN MAP @ 2500 RPM) WITH APPROX 550 HRS SINCE MAJOR OVER- HAULS. CAUSE IS UNDER INVESTIGATION. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THIS ACFT WAS A MODEL 601T AEROSTAR WITH MODIFICATIONS THAT BROUGHT IT UP TO THE SUPERSTAR MODEL 700 PERFORMANCE ACCORDING TO THE RPTR. AFTER SEVERAL UNSUCCESSFUL TEST FLTS THE MECHS CONTACTED THE ENG MODIFICATION CORPORATION AND THEY RECOMMENDED THAT THE INJECTORS BE CLEANED OR CHANGED. THE FAULT WAS FOUND TO BE PRIMARILY IN THE L ENG'S INJECTORS. THERE WERE 2 DIFFERENT STYLES OF INJECTORS AND THE ONES ON THE L ENG WERE THE 1-PIECE TYPE. THIS TYPE CANNOT BE DISASSEMBLED FOR CLEANING AND INSPECTION WHEREAS THE 2-PIECE TYPE ON THE R ENG CAN BE EXAMINED. AFTER THE L ENG'S INJECTORS WERE CHANGED TO NEW 2-PIECE TYPE INJECTORS IT PERFORMED WELL.

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.