On February 6, 2003, at 1645 eastern standard time, a Robinson R-44 helicopter, N7184M, was substantially damaged during a forced landing to Lake Malone, near Russellville, Kentucky. The certificated commercial pilot and two passengers were not injured. Instrument meteorological conditions prevailed, and no flight plan was filed for the flight. The flight originated at 1715, at Clarke County Airport (JVY), Jeffersonville, Indiana, and was destined for Outlaw Field (CKV), Clarksville, Tennessee. The business flight was conducted under 14 CFR Part 91.

According to the pilot, he was flying at an altitude of 1,000 feet, and the cloud bases were at an altitude of 1,100-1,200 feet. When he was approximately 30 miles from his destination, he decided to land the helicopter, due to deteriorating weather conditions and rising terrain. After landing, the pilot reassessed his route of flight, then prepared for another takeoff to continue the flight.

As the pilot initiated a hover, he applied full carburetor heat, and as he raised the collective for takeoff, the carburetor heat automatically dropped. He then lowered the collective, but "failed to get the carb heat needed to maintain power." The engine began to sputter, then lost power completely. The pilot then performed a full autorotation into the lake.

The pilot reported that the weather in the area included a visibility of 1-2 miles and light rain. He also reported 950 hours of total flight experience, 27 hours of which were in the R-44.

A passenger sitting in the left front seat reported that while en route, the intensity of the precipitation "picked up," and the pilot decided to land in a field. The passenger further stated that they remained on the ground for about 10 minutes, then the pilot decided to take off again and attempt another route. The pilot performed a "standard takeoff" and about 1-2 minutes later, at an altitude of 500 feet, the engine lost power, and the passenger "felt the lift cease." The pilot then performed an autorotation to the lake. Upon impact, the canopy burst, and the helicopter sank 10-15 feet underwater. All three occupants were able to unfasten their seatbelts and swim to the surface.

A Federal Aviation Administration (FAA) inspector performed an on-scene examination of the helicopter. According to the inspector, continuity was confirmed from the main rotor blades to the tail rotor. Engine continuity was also confirmed, and rotation of the magnetos revealed spark on all towers. Examination of the main fuel tank revealed a "significant amount" of fuel and the auxiliary fuel tank was observed empty. A functional test of the fuel system revealed fuel flow without obstruction from the fuel tank to the engine. The position of the carburetor heat control knob in the cockpit was extended approximately 2 inches, and the carburetor heat lock was unlatched.

Weather reported at Campbell Army Airfield (HOP), Fort Campbell, Kentucky, 25 miles to the southeast, at 1655, included wind from 010 degrees at 9 knots, 1 mile visibility with light snow and mist, overcast clouds at 500 feet, temperature 32 degrees Fahrenheit, dew point 32 degrees Fahrenheit, and barometric pressure 30.09 inches Hg.

Review of a FAA carburetor icing probability chart placed the reported temperature and dew point in the "serious icing at cruise power" area of the chart.

Examination of the Robinson R-44 Pilot's Operating Handbook described the carburetor heat assist system. According to the Handbook:

"The carb heat assist correlates application of carburetor heat with changes in collective setting to reduce pilot work load. Lowering collective mechanically adds heat and raising collective reduces heat...It is recommended that the control knob be unlatched (to activate carb heat assist) whenever OAT is between 80 degrees Fahrenheit and 25 degrees Fahrenheit and the difference between dew point and OAT is less than 20 degrees Fahrenheit.."

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