Charter pilot has engine roughness then smoothed out.

Attributes
ACN	250527
Time
Date	199308
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : mqp
State Reference	TX
Altitude	msl bound lower : 4000 msl bound upper : 4000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air taxi
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other
Route In Use	enroute airway : dfw
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : atp
Experience	flight time last 90 days : 250 flight time total : 2200 flight time type : 600
ASRS Report	250527
Person 2
Affiliation	Other
Function	other personnel other
Qualification	other other : other
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa
Resolutory Action	flight crew : overcame equipment problem
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

I was near the western edge of the dfw TCA at 4000 ft. I was cruising at 24 inches manifold pressure, 2400 RPM, with the cowl flaps open, when the right engine seemed to miss some. I called flight operations to notify them that I would be returning to dal if the engine continued to run rough. At this time I noticed the manifold pressure on the right engine increase momentarily to 25 inches and return to 24 inches. The engine simultaneously smoothed out as before. After checking all engine instruments and finding them no different than before, I judged it safe to continue on to abi and notified flight operations to that effect. When I reduced the power to idle on touchdown at abi, I noticed that the right engine was at 21 inches versus 15 inches on the left for approximately 1000 RPM. Upon shutdown, I opened the right cowl to check for any obvious reasons that this was occurring and found that, what I am told is, the #4 cylinder on the right engine was cracked near the valves. I immediately grounded the aircraft and advised flight operations of the situation.

Original NASA ASRS Text

Title: CHARTER PLT HAS ENG ROUGHNESS THEN SMOOTHED OUT.

Narrative: I WAS NEAR THE WESTERN EDGE OF THE DFW TCA AT 4000 FT. I WAS CRUISING AT 24 INCHES MANIFOLD PRESSURE, 2400 RPM, WITH THE COWL FLAPS OPEN, WHEN THE R ENG SEEMED TO MISS SOME. I CALLED FLT OPS TO NOTIFY THEM THAT I WOULD BE RETURNING TO DAL IF THE ENG CONTINUED TO RUN ROUGH. AT THIS TIME I NOTICED THE MANIFOLD PRESSURE ON THE R ENG INCREASE MOMENTARILY TO 25 INCHES AND RETURN TO 24 INCHES. THE ENG SIMULTANEOUSLY SMOOTHED OUT AS BEFORE. AFTER CHKING ALL ENG INSTS AND FINDING THEM NO DIFFERENT THAN BEFORE, I JUDGED IT SAFE TO CONTINUE ON TO ABI AND NOTIFIED FLT OPS TO THAT EFFECT. WHEN I REDUCED THE PWR TO IDLE ON TOUCHDOWN AT ABI, I NOTICED THAT THE R ENG WAS AT 21 INCHES VERSUS 15 INCHES ON THE L FOR APPROX 1000 RPM. UPON SHUTDOWN, I OPENED THE R COWL TO CHK FOR ANY OBVIOUS REASONS THAT THIS WAS OCCURRING AND FOUND THAT, WHAT I AM TOLD IS, THE #4 CYLINDER ON THE R ENG WAS CRACKED NEAR THE VALVES. I IMMEDIATELY GNDED THE ACFT AND ADVISED FLT OPS OF THE SIT.

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.