Page:CAB Accident Report, American Airlines Flight 9 (1945).pdf/6

 CIVIL AERONAUTICS BOARD

ACCIDENT INVESTIGATION REPORT

The synoptic map issued prior to departure of the subject flight from New York shows a rather intense low pressure system covering the Great Lakes area eastward to New England and southward to Alabama and Georgia with the center in Ontario, Canada. A cold front moving eastward extended from the center through eastern New York to the Atlantic, thence southwestward just off and parallel to the coast as far as southeastern Georgia. A secondary cold front extended southward from near Buffalo, New York, through western Pennsylvania, West Virginia, extreme western Virginia, crossing the boundary of Tennessee and North Carolina and thence to Atlantic and Mobile. When the flight was ready to clear Washington the secondary cold front was located along the route between Pulaski and Roanoke, Virginia, and was rather diffuse and composed of a broad bend of decreasing temperature and local rain squalls. Light rain prevailed ahead of this front as far as Washington.

Observations available to American Airlines before departure from Washington indicated the following heights above sea level of broken or overcast cloud layers: Washington unlimited, Quantico 1900, Gordonsville 1800, Lynchburg 1500, Roanoke 6600, Pulaski 6600 and Tri-City 4900. The reports at 0130, while the flight was en route, showed the following heights above sea level of the bases of broken or overcast layers: Washington 1500, Quantico 1800, Gordonsville 1800, Lynchburg 1400, Roanoke 4600, Pulaski 4900 and Tri-City 4900. At 0230, five minutes after the accident, the following ceilings above sea level were reported: Lynchburg 1500, Roanoke 4500, Pulaski 3900 and Tri-City 4900. These observations show that ceilings existed below 4000 feet from Quantico to Lynchburg before the flight departed from Washington and that while en route the ceiling lowered between Lynchburg and Tri-City with Pulaski showing ceiling below 4000 feet near the time of the accident.

When the accident occurred the forward edge of the cold frontal zone was near and a little east of Roanoke at the surface. At 4000 feet the front was probably entered between Roanoke and Pulaski and the flight at that point went from winds estimated 240°- 250°, 35 to 40 miles per hour, into 270°, 23 - 28 miles per hour. The temperature also decreased as the flight progressed toward the point of the crash. It is believed that the temperature at the 4000-foot level at the time of the accident was approximately 32°.