The findings were that the flight penetrated a severe thunderstorm and the ingestion of intense rain and hail caused both engines to fail. The engines suffered internal damage and could not be restarted. The crew had no information on the storms west of Rome, and the captain initially decided, based on his airborne weather radar returns, that the storms were too severe to penetrate. For some reason or because of misinterpretation of the radar display, he changed his mind.
The Board determined the probable cause to be the "total and unique loss of thrust from both engines while the aircraft was penetrating an area of severe weather."
Board member Francis McAdams dissented, stating that the majority belief "was merely a statement of what happened rather than an explanation of why." His determination of probable cause is more likely much closer to the mark. "This accident involves the captain's critical decision to penetrate rather than avoid a known area of severe weather. . . . It is obvious that the captain flew a route or directed the FO to fly a route into an area which aircraft should not have entered. Southern Airways, and all air carriers, prohibit flying into convective storms because these types of storms are known to be serious hazards. The primary hazard relates to forces in these storms which can destroy an aircraft structurally; however, other hazards exist which are not well defined. . . . The loss of thrust . . . might have been unusual . . . but should not be considered entirely unexpected, given the multiple hazards associated with flight into severe convective storms."
There used to be more art than science when it came to reading airborne radar. The old monochromatic radars did not portray varying intensities as well as a modern color radar and were even more susceptible to attenuation. Without the proper training, pilots today can just as easily misread a clear spot on a radar scope to be a sign of clear skies when in fact it is the classic "blind alley." The lesson learned is never fly into a radar shadow. For more about this, refer to Radar Techniques..
Everything here is from the references shown below, with a few comments in an alternate color.
Figure: Dramatization, from Air Crash Investigations
About 1619 EST on April 4, 1977, a Southern Airways, Inc., DC-9, operating as Southern Flight 242, crashed in New Hope, Georgia. After losing both engines in flight, Flight 242 attempted an emergency landing on State Spur Highway 92, which bisected Hope. Of the 85 person aboard Flight 242, 62 were killed, 22 were seriously injured, and 1 was slightly injured. One passenger died on June 5, 1977. Additionally, eight persons on the ground were killed and one person was seriously injured; the injured person died about 1 month after the accident. The aircraft was destroyed.
Flight 242 entered a severe thunderstorm during flight between 17,000 and 14,000 feet near Rome, Georgia, while en route from Huntsville, Alabama, to Atlanta, Georgia. Both engines were damaged and all thrust was lost. The engines could not be restarted, and the flight crew was forced to make an emergency landing.
"Total and unique loss of thrust from both engines while the aircraft was penetrating an area of severe thunderstorms. The loss of thrust was caused by the ingestion of massive amounts of water and hail which, in combination with thrust lever movement, induced severe stalling in and major damage to the engine compressors. Major contributing factors include the failure of the company's dispatching system to provide the flight crew with up-to-date severe weather information pertaining to the aircraft's intended route of flight, the captain's reliance on airborne weather radar for penetration of thunderstorm areas, and limitations in the FAA's ATC system which precluded the timely dissemination of real-time hazardous weather information to the flight crew."
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