A M20K pilot experienced a rough running engine on a cross country flight. He declared an emergency ...

Attributes
ACN	824984
Time
Date	200902
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	M-20 K (231) / Encore
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Flight Plan	IFR
Component
Aircraft Component	Fuel System
Person 1
Function	Single Pilot Pilot Flying
Qualification	Flight Crew Instrument Flight Crew Private
Experience	Flight Crew Last 90 Days 50 Flight Crew Total 4400 Flight Crew Type 3900
Events
Anomaly	Aircraft Equipment Problem Critical

Narrative:

On an IFR flight from ZZZ1 to ZZZ2 at FL190; the engine began to run rough after approximately 1.5 hours of flight. Shortly before that event; I had switched from the left tank to the right. I was located approximately 20 miles from ZZZ airport. I started the low boost fuel pump; canceled IFR and began a slow descent to ZZZ airport. I was asked by center if I wanted to declare an emergency. I said yes. In my anxiety over the rough engine; I forgot to return to the left fuel tank. After landing at ZZZ; I discovered that there was water in the right fuel tank; as evidenced by some residual water in the sump drain cup. After warming the plane in the hangar; I checked the fuel sump and continued my flight VFR.

Original NASA ASRS Text

Title: A M20K pilot experienced a rough running engine on a cross country flight. He declared an emergency and diverted to the nearest airport; where he found water in the right fuel tank.

Narrative: On an IFR flight from ZZZ1 to ZZZ2 at FL190; the engine began to run rough after approximately 1.5 hours of flight. Shortly before that event; I had switched from the left tank to the right. I was located approximately 20 miles from ZZZ Airport. I started the low boost fuel pump; canceled IFR and began a slow descent to ZZZ Airport. I was asked by Center if I wanted to declare an emergency. I said yes. In my anxiety over the rough engine; I forgot to return to the left fuel tank. After landing at ZZZ; I discovered that there was water in the right fuel tank; as evidenced by some residual water in the sump drain cup. After warming the plane in the hangar; I checked the fuel sump and continued my flight VFR.

Data retrieved from NASA's ASRS site as of April 2012 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.