Engine fails while in traffic pattern resulting in an off airport landing.

Attributes
ACN	234076
Time
Date	199302
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : 47n
State Reference	NJ
Altitude	agl bound lower : 800 agl bound upper : 800
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	general aviation : instructional
Make Model Name	Small Aircraft, High Wing, 1 Eng, Fixed Gear
Flight Phase	other other
Flight Plan	None
Person 1
Affiliation	Other
Function	instruction : instructor
Qualification	pilot : cfi
Experience	flight time last 90 days : 44 flight time total : 825 flight time type : 29
ASRS Report	234076
Person 2
Affiliation	Other
Function	instruction : trainee
Qualification	pilot : student
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa
Resolutory Action	none taken : unable other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

Aircraft started vibrating on downwind. Student pilot continued to fly pattern as I troubleshot cause, with mixed success (vibration abated a bit). Continued pattern and power ok. On final at 800 ft, 1/2 mi, put in full flaps and all ok. Then propeller started to jerk (same look as a strobe light on propeller) and glide path altered greatly. The engine failed. At that time I took control of aircraft. With shred of doubt about gliding over wires and trees, I turned aircraft and landed on field safely. No damage to aircraft, occupants, field (frozen). Cause: carburetor ice. Lessons: #1 -- the engine will quit. Plan for this. Plan for worst case but realize idling propeller has different glide than stopped propeller! #2 -- don't worry about 'fixing' engine in air. Put it down then fix it. #3 -- as CFI (or PIC) decide when you will take over aircraft, under what conditions, etc, so that decision need not be made under or during emergency. This will differ from person to person and with experience of CFI/student. I'm writing this report for anyone who has not thought hypothetically about an incident such as above. I never had, and I lost such valuable time as I muddled through #1-3.

Original NASA ASRS Text

Title: ENG FAILS WHILE IN TFC PATTERN RESULTING IN AN OFF ARPT LNDG.

Narrative: ACFT STARTED VIBRATING ON DOWNWIND. STUDENT PLT CONTINUED TO FLY PATTERN AS I TROUBLESHOT CAUSE, WITH MIXED SUCCESS (VIBRATION ABATED A BIT). CONTINUED PATTERN AND PWR OK. ON FINAL AT 800 FT, 1/2 MI, PUT IN FULL FLAPS AND ALL OK. THEN PROP STARTED TO JERK (SAME LOOK AS A STROBE LIGHT ON PROP) AND GLIDE PATH ALTERED GREATLY. THE ENG FAILED. AT THAT TIME I TOOK CTL OF ACFT. WITH SHRED OF DOUBT ABOUT GLIDING OVER WIRES AND TREES, I TURNED ACFT AND LANDED ON FIELD SAFELY. NO DAMAGE TO ACFT, OCCUPANTS, FIELD (FROZEN). CAUSE: CARB ICE. LESSONS: #1 -- THE ENG WILL QUIT. PLAN FOR THIS. PLAN FOR WORST CASE BUT REALIZE IDLING PROP HAS DIFFERENT GLIDE THAN STOPPED PROP! #2 -- DON'T WORRY ABOUT 'FIXING' ENG IN AIR. PUT IT DOWN THEN FIX IT. #3 -- AS CFI (OR PIC) DECIDE WHEN YOU WILL TAKE OVER ACFT, UNDER WHAT CONDITIONS, ETC, SO THAT DECISION NEED NOT BE MADE UNDER OR DURING EMER. THIS WILL DIFFER FROM PERSON TO PERSON AND WITH EXPERIENCE OF CFI/STUDENT. I'M WRITING THIS RPT FOR ANYONE WHO HAS NOT THOUGHT HYPOTHETICALLY ABOUT AN INCIDENT SUCH AS ABOVE. I NEVER HAD, AND I LOST SUCH VALUABLE TIME AS I MUDDLED THROUGH #1-3.

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.