Rough engine requires emergency landing.

Attributes
ACN	311292
Time
Date	199507
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : mdw
State Reference	IL
Altitude	msl bound lower : 9000 msl bound upper : 9000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : ord
Operator	general aviation : instructional
Make Model Name	Skylane 182/RG Turbo Skylane/RG
Operating Under FAR Part	Part 91
Flight Phase	cruise other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : private
Experience	flight time last 90 days : 20 flight time total : 500 flight time type : 40
ASRS Report	311292
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	other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

I experienced intermittent power loss while cruising at 9000 ft MSL. I notified ATC immediately about the problem, and requested vectors back to pwk. After checking all system aboard, I noticed the engine running rougher as I reduced power setting. I then asked for vectors into mdw which I got. After landing I ran the engine up, did a pre-takeoff static check and runup. Found 1 magneto inoperative. A mechanic from the FBO where I rented came down to mdw, confirmed the inoperative magneto and found water in the fuel. When I got back to the FBO at pwk, I was told that the fuel cap was left off last night and it rained. During my preflight there was not any indications of water in the fuel. Bag fuel tanks have ridges and can hold water. The water can come loose and start to flow. The reason for the cap being left off, I will take care of. ATC was great.

Original NASA ASRS Text

Title: ROUGH ENG REQUIRES EMER LNDG.

Narrative: I EXPERIENCED INTERMITTENT PWR LOSS WHILE CRUISING AT 9000 FT MSL. I NOTIFIED ATC IMMEDIATELY ABOUT THE PROB, AND REQUESTED VECTORS BACK TO PWK. AFTER CHKING ALL SYS ABOARD, I NOTICED THE ENG RUNNING ROUGHER AS I REDUCED PWR SETTING. I THEN ASKED FOR VECTORS INTO MDW WHICH I GOT. AFTER LNDG I RAN THE ENG UP, DID A PRE-TKOF STATIC CHK AND RUNUP. FOUND 1 MAGNETO INOP. A MECH FROM THE FBO WHERE I RENTED CAME DOWN TO MDW, CONFIRMED THE INOP MAGNETO AND FOUND WATER IN THE FUEL. WHEN I GOT BACK TO THE FBO AT PWK, I WAS TOLD THAT THE FUEL CAP WAS LEFT OFF LAST NIGHT AND IT RAINED. DURING MY PREFLT THERE WAS NOT ANY INDICATIONS OF WATER IN THE FUEL. BAG FUEL TANKS HAVE RIDGES AND CAN HOLD WATER. THE WATER CAN COME LOOSE AND START TO FLOW. THE REASON FOR THE CAP BEING LEFT OFF, I WILL TAKE CARE OF. ATC WAS GREAT.

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.