Engine sputters and stutters. Emergency off airport forced landing performed by instructor pilot.

Attributes
ACN	251018
Time
Date	199309
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : dsm
State Reference	IA
Altitude	msl bound lower : 2600 msl bound upper : 2600
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : dsm artcc : zdv
Operator	general aviation : instructional
Make Model Name	Small Aircraft
Flight Phase	cruise other cruise other descent : approach
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	Other
Function	instruction : instructor oversight : pic
Qualification	pilot : cfi pilot : instrument pilot : commercial
Experience	flight time last 90 days : 150 flight time total : 960
ASRS Report	251018
Person 2
Affiliation	Other
Function	flight crew : single pilot instruction : trainee
Qualification	pilot : private
Experience	flight time last 90 days : 43 flight time total : 88 flight time type : 15
ASRS Report	250837
Events
Anomaly	aircraft equipment problem : critical non adherence : published procedure other anomaly other
Independent Detector	other flight crewa
Resolutory Action	other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We experienced a rough running engine and loss of RPM. We had just been vectored onto the localizer for runway 13L. Immediately when the engine quit, I took control from my student and began emergency restart procedures. Both engine fuel gauges were showing plenty of fuel. Left tank full, right tank less than 3/4 tank. We were running on the left tank so I immediately switched to the right tank. When I did, the engine quit completely. At this point, I thought I would switch back to the left tank so I would have at least a rough running engine than no engine. When I switched back to the left tank, the engine sputtered and surged a little, but at least it was running. This gave us the ability to get to a sod farm and land without incident. After landing, we did a visual walkaround and at this time noticed the left tank was low on fuel, even though the tank showed full. When the mechanic came out he drained approximately 3/4 of a gallon out of the left tank and noticed lots of sediment in the sample. I feel that faulty instrument indications were a contributing factor in the incident, and as a result of full indications, the left tank was run low which caused the sediment to be pulled from the tank into the engine causing the engine problem. On preflight inspection, no sediment was drawn from the tank. This could have been prevented by timing fuel burnout of each tank. In the future I will keep a written tally of how long I flew on each tank. Supplemental information from acn 250837: the FAA people arrived and performed their inspection.

Original NASA ASRS Text

Title: ENG SPUTTERS AND STUTTERS. EMER OFF ARPT FORCED LNDG PERFORMED BY INSTRUCTOR PLT.

Narrative: WE EXPERIENCED A ROUGH RUNNING ENG AND LOSS OF RPM. WE HAD JUST BEEN VECTORED ONTO THE LOC FOR RWY 13L. IMMEDIATELY WHEN THE ENG QUIT, I TOOK CTL FROM MY STUDENT AND BEGAN EMER RESTART PROCS. BOTH ENG FUEL GAUGES WERE SHOWING PLENTY OF FUEL. L TANK FULL, R TANK LESS THAN 3/4 TANK. WE WERE RUNNING ON THE L TANK SO I IMMEDIATELY SWITCHED TO THE R TANK. WHEN I DID, THE ENG QUIT COMPLETELY. AT THIS POINT, I THOUGHT I WOULD SWITCH BACK TO THE L TANK SO I WOULD HAVE AT LEAST A ROUGH RUNNING ENG THAN NO ENG. WHEN I SWITCHED BACK TO THE L TANK, THE ENG SPUTTERED AND SURGED A LITTLE, BUT AT LEAST IT WAS RUNNING. THIS GAVE US THE ABILITY TO GET TO A SOD FARM AND LAND WITHOUT INCIDENT. AFTER LNDG, WE DID A VISUAL WALKAROUND AND AT THIS TIME NOTICED THE L TANK WAS LOW ON FUEL, EVEN THOUGH THE TANK SHOWED FULL. WHEN THE MECH CAME OUT HE DRAINED APPROX 3/4 OF A GALLON OUT OF THE L TANK AND NOTICED LOTS OF SEDIMENT IN THE SAMPLE. I FEEL THAT FAULTY INST INDICATIONS WERE A CONTRIBUTING FACTOR IN THE INCIDENT, AND AS A RESULT OF FULL INDICATIONS, THE L TANK WAS RUN LOW WHICH CAUSED THE SEDIMENT TO BE PULLED FROM THE TANK INTO THE ENG CAUSING THE ENG PROB. ON PREFLT INSPECTION, NO SEDIMENT WAS DRAWN FROM THE TANK. THIS COULD HAVE BEEN PREVENTED BY TIMING FUEL BURNOUT OF EACH TANK. IN THE FUTURE I WILL KEEP A WRITTEN TALLY OF HOW LONG I FLEW ON EACH TANK. SUPPLEMENTAL INFO FROM ACN 250837: THE FAA PEOPLE ARRIVED AND PERFORMED THEIR INSPECTION.

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.