NYC98LA078

While in cruise flight, the airplane's engine experienced a decrease in RPM and began to run rough. The pilot added carburetor heat and the RPM increased. When the pilot removed the carburetor heat the engine began to run rough again, so he reapplied and maintained full carburetor heat. However, after a few moments, the engine began to run rough again. The pilot said he reached his destination airport at an altitude of about 2,500-2,600 feet and began a slow spiral to enter the traffic pattern at 1,400 feet. The engine began to run rougher while in the traffic pattern and the engine lost power during the final approach. The airplane crashed about 1/2 mile from the approach end of the runway. Examination of the wreckage did not reveal any pre-impact failures of the airframe or engine. The temperature and dewpoint reported at airports about 10 miles south, and about 45 miles east of the accident site, were 37 and 18 degrees F; and 43 and 21 degrees F, respectively . A carburetor icing probability chart was reviewed and revealed that the weather conditions were at the lower limit of the 'Icing- Glide and Cruise Power' area of the chart.

On March 17, 1998, about 1300 eastern standard time, a Cessna 150, N704GP, was substantially damaged during a forced landing, while on approach to the North Buffalo Suburban Airport (0G0), Lockport, New York. The certificated private pilot and passenger were not injured. Visual meteorological conditions prevailed and no flight plan had been filed for the personal flight conducted under 14 CFR Part 91.

In a telephone interview and written statements, the pilot said he was returning from a pleasure flight in the Rochester, New York, area. At 7,000 feet MSL, in the vicinity of the Genesse County Airport (GVQ), Batavia, New York, the airplane's engine experienced a decrease in RPM and began to run rough. The pilot added carburetor heat and the RPM increased. The pilot said removal of the carburetor heat caused a reoccurrence of the engine roughness, so he reapplied and maintained full carburetor heat. However, after a few moments the engine began to run rough again. The engine continued to run rough as the airplane passed over the Akron Airport (9G3), Akron, New York, at an altitude of about 5,000 feet. The pilot said he considered landing at 9G3, but based on his altitude and distance from 0G0, he elected to continue to his destination. He further stated:

"....Reached about 2500-2600 MSL North of [0G0] and began a slow spiral with full carburetor heat to enter a left downwind leg of the pattern at 1,400. Engine running rougher, so took base leg...Still running rough with full carburetor heat. Announced 'final.' Saw I couldn't clear trees at west end of runway. Banked gently to the left to land in adjacent field...total power failure at about 100 feet AGL. Apparently right wing caught high hedge, causing left wing tip to strike ground. Aircraft struck ground, buckling nose wheel...."

The wreckage was examined by a Federal Aviation Administration (FAA) Inspector. According to the FAA Inspector, the airplane came to rest approximately 1/2 mile west and slightly north of the extended center line of the runway. Examination of the wreckage did not revealed any pre-impact abnormalities of the airframe or engine.

The temperature and dewpoint reported at the Buffalo Niagara International Airport (BUF), about 10 miles south of 0G0, and the Greater Rochester International Airport, about 45 miles east of 0G0, were 37 and 18 degrees F; and 43 and 21 degrees F, respectively.

A carburetor icing probability chart was reviewed using the conditions reported at BUF and ROC. The chart revealed that the weather conditions were at the lower limit of the "Icing- Glide and Cruise Power" area of the chart.

FAA publication, AC 61-23C, Pilot's Handbook of Aeronautical Knowledge; Chapter 2 - Airplanes and Engines; Engine Operation; Carburetor System; Carburetor Icing, stated:

"...The vaporization of fuel, combined with the expansion of air as it flows through the carburetor, causes a sudden cooling of the [fuel/air] mixture. The temperature of the air passing through the carburetor may drop significantly within a fraction of a second. Water vapor in the air is 'squeezed out' by this cooling and, if the temperature in the carburetor reaches 0 degrees C (32 degrees F) or below, the moisture will be deposited as frost or ice inside the carburetor passages. Even a slight accumulation of this deposit will reduce power and may lead to complete engine failure..."