Data from the government’s weather radar in Mount Holly, N.J., first shows a signal at 11:01 a.m., centered around 28,000 feet. This is commensurate with the plane’s location at that point. These are the first signs of trouble, seconds after the engine explosion occurred. The debris had not begun to fan out at this point.
In the next sweep of the radar beam at 11:07 a.m., the metal debris from the torn engine casing can be seen tracing a path downward as it falls out of the skies. Given that the plane was moving 467 mph when the malfunction occurred, the spattering of shrapnel continued moving westward despite no longer being attached.
The radar beam makes passes at different beam elevations. In this case, we’re looking at the angles of 2.3, 1.4 and 0.4 degrees (see three images below). A higher angle means the radar beam probes higher into the skies. What we see is an image of engine fragments quickly falling in a west-northwesterly direction and appearing lower in the atmosphere as minutes pass.
Pieces would eventually be found in Bernville, Pa. Commercial airlines do not themselves appear on U.S. weather radar, because the radar is tuned to be most sensitive to precipitation — and precipitation does not move at the speed of a jet aircraft.
In each image above, the panel on the left shows the intensity of radar echoes from that location. Warmer colors represent a denser field of material. On the right, radar is discerning the shape of the particulates. Given the chaotic pattern of various colors, it stands to reason that the radar is sensing jagged or unusual shapes. This is supportive of the signals being a result of debris and not a weather target.
A 3-D slice through the atmosphere shows the pattern quite well, illustrating the path the debris took as it hurtled toward the ground.
A similar look into the atmosphere over rural Berks County, Pa., paints a sobering picture of the first airplane incident that led to a passenger fatality in the United States in nearly a decade.
At a news conference in Philadelphia on Wednesday, National Transportation Safety Board Chairman Robert L. Sumwalt confirmed the debris was detectable from weather radar.
“We have very talented meteorologists in Washington working [with the] NTSB as well as air traffic control specialists, and they noticed the ATC radar indications. They could see reflections of debris being painted on the radar, indicating there was debris flying into the atmosphere,” he said. They “plugged in winds, estimated where they thought the debris would land.”
“The debris landed in about the area where they anticipated.”
Washington Post transportation writer Faiz Siddiqui contributed to this report.