CHI94LA037

The pilot stated the airplane was in cruise flight at 2000 feet when the engine began to run rough and lose power. The pilot performed emergency procedures (applied carburetor heat, changed fuel tanks, and tried left and then right magnetos) to no avail. The engine lost power completely just as the pilot declared an emergency on radio frequency 121.5 mhz. The pilot prepared for a night forced landing when the aircraft impacted and became entangled in a group of 50 foot oak trees. Engine continuity, compression, ignition, induction and fuel systems were field tested. No defects were found. The spark plugs were all covered with black sooty deposits. A carburetor icing probability chart obtained from a DOT/FAA/CT-82/44 publication predicts serious icing at cruise power with the weather conditions existing at the time of the accident (temperature 40 degrees fahrenheit, dew point of 38 degrees fahrenheit).

On November 14, 1993, about 0150 hours central standard time, a Grumman AA-1B, N9896L, operated by the private pilot/registered owner, made a forced landing in treetops near Arcadia, Wisconsin, after a loss of engine power during cruise flight. The airplane sustained substantial damage. The pilot received serious injuries. The passenger received minor injuries. Visual meteorological conditions prevailed for the flight, no flight plan was filed. The flight operated under 14 CFR Part 91, and originated from Eau Claire, Wisconsin approximately 0110 hours. The intended destination was LaCrosse, Wisconsin.

The pilot stated that approximately 20 minutes after departure, the airplane was in cruise flight at 2000 feet and the engine began to run rough and lose power. The pilot reported he applied carburetor heat, changed fuel tanks, and tried left and then right magnetos in an attempt to regain engine power. The engine continued to lose power, and the pilot declared an emergency on radio frequency 121.5 MHz.

The radio transmission was received by Green Bay Air Traffic Control Tower at 0147 CST. The pilot stated the engine then lost total power. The pilot stated he "...left carb heat on...set up the glide at 80 miles per hour... ." With the landing light on, the pilot still was unable to see the ground, and had just spotted a clearing to use for landing when the airplane impacted and became entangled in a group of fifty foot oak trees.

The aircraft was located by a passing motorist approximately 0830 CST, and the pilot and passenger were removed from the aircraft at approximately 1000 CST.

The propeller was found on the ground, and had broken off at its attach bolts. Both prop blades were bent backwards.

Engine continuity, compression, ignition, induction and fuel systems were tested. The spark plugs were all covered with black soot. The carburetor was disassembled and found to be full of clean fuel. There was no evidence of preimpact mechanical malfunction.

A carburetor icing probability chart obtained from DOT/FAA/CT- 82/44 Publication: Light Aircraft Piston Engine Carburetor Ice Detector, predicts serious icing at cruise power for a condition of 40 degrees Fahrenheit with a dew point of 38 degrees Fahrenheit, the same as the morning of the accident flight.