Aviation Accident Summaries

Aviation Accident Summary NYC94LA037

CHRISTIANBURG, VA, USA

Aircraft #1

N49215

CESSNA 152

Analysis

WHILE CRUISING AT 6500 FT, THE PILOT SAID THE ENGINE STARTED TO SURGE AND LOSE RPM. USE OF CARBURETOR HEAT STOPPED THE SURGING, BUT DID NOT STOP THE POWER LOSS. THE PILOT SET UP FOR A FORCED LANDING ON ROLLING TERRAIN. AFTER TOUCHDOWN, THE AIRPLANE BECAME MOMENTARILY AIRBORNE AND THEN STRUCK AN EMBANKMENT, AND FLIPPED OVER. THE ENGINE WAS TEST RUN SATISFACTORILY AFTER THE ACCIDENT. ACCORDING TO THE FAA CARBURETOR ICING PROBABILITY CHART, THE TEMPERATURE OF 56F AND DEWPOINT OF 34F FELL INTO AN AREA OF SERIOUS ICING, GLIDE POWER. THE FAA SAID THERE WERE NO SUITABLE FORCED LANDING AREAS.

Factual Information

On December 9, 1993, at 1530 eastern standard time, a Cessna 152, N49215, operated by the College of West Virginia, in Buckley, West Virginia, experienced a partial power loss and nosed over during a forced landing in Christianburg, Virginia. The airplane received substantial damage. The student pilot was not injured. Visual meteorological conditions prevailed and the flight was operating on a VFR flight plan under 14 CFR Part 91. The pilot said he climbed to 6500 feet and leaned the mixture. In the NTSB Accident Report, he stated: ...I noticed the engine RPM drop from 2450 rpm to 2200 rpm,. It then increased back to 2450 rpm. My first reaction was enrichen the mixture, which seemed to help momentarily. Again the engine became rough, and the rpm's varied between 2200 - 2400 rpm. At this time I turned on carburetor heat. This also helped for awhile, but when I turned the carb heat off, the engine roughness returned. I then tried switching magnetos, which made the problem worse. I then switched the magnetos back to "both",...While enroute I continued to go through emergency procedures, which did not correct the problem. I found the carburetor heat made the engine run smoother, so I left it on for the duration of the flight. As I approached Christenburg the engine RPM continued to drop...At full throttle the engine could only maintain between 1900 - 2000 rpm. I did not feel I could make it to the airport, so I turned away from the city, and picked a field for landing...The field sloped uphill, and I adjusted my flare accordingly. The main gear touched down and I began braking. It was then that the plane came over the hill and became airborne again. I saw the embankment on the on the other side. I immediately applied full elevator up, which had little effect. The plane then hit the embankment, causing it to flip over onto the roof. The airplane and engine were taken to Hagerstown, Maryland, where the engine was test run. In a written statement, Mr. Douglas Schwab, an airworthiness inspector for the Baltimore Flight Standards District Office stated, "...Engine ran well, attained full RPM and mag ck [magneto check] was satisfactory...." In a telephone interview, Mr. John Phelps, of the Richmond Flight Standards District Office, said there were no suitable landing areas available to the pilot. The reported temperature and dewpoint at Roanoke, Virginia, which was 23 miles east of the accident site was 56 degrees F and 34 degrees F respectively. According to the DOT/FAA Carburetor Icing Probability Chart, these temperatures fell into an area of serious icing with glide power. Based on the chart, the relative humidity was approximately 45 percent.

Probable Cause and Findings

The pilot's improper use of carburetor heat which prevented the accumulation of carburetor ice and resulted in the loss of engine power. A factor was unsuitable terrain.

 

Source: NTSB Aviation Accident Database

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