TWA Flight 553

Flight 553 departed from Greater Pittsburgh Airport en route to Dayton Municipal Airport. After passing Columbus, Ohio, Flight 553 had been cleared to descend from Flight Level (FL) 200 (about 20,000 feet (6,000 m) above sea level) to 3,000 feet (900 m). The flight was in uncontrolled airspace, but being handled by Dayton radar approach control, who advised them of uncontrolled VFR traffic ahead and slightly to the right, and one mile away, about 18 seconds before the collision. The crew acknowledged the traffic advisory. As the airliner descended through 4,500 feet (1,400 m) at a speed of 323 knots on a southwest heading, it collided with the smaller craft, a southbound Beechcraft Baron 55.[2] The front right side of the DC-9 hit the left side of the Beechcraft. Both aircraft fell to earth in Concord Township, a rural area northwest of the city of Urbana in Champaign County. The collision was just northeast of the intersection of Melody Lane and Woodville Pike.[1]

Visual flight rules (VFR) were in effect at the time of the accident, meaning it was the responsibility of the pilots on both aircraft to "see and avoid" each other. In addition, the radar controller stated that he did not see the Beechcraft on his radar scope until 22 seconds before the crash. Controllers testified that the zone near the crash site was a zone where small planes could be difficult to detect on radar, but flight checks in the area proved inconclusive.[1]

The National Transportation Safety Board investigated the accident and determined that due to the high rate of descent of the DC-9, its pilots were not able to see the other plane in time to avoid a collision. Weather conditions included widely scattered, thin clouds, with haze reducing visibility to 6 to 7 miles (10 to 11 km), twice the 3-mile (5 km) visibility required for VFR flight.[1]

Since 1961, FAR Part 91.85 had mandated speed restrictions below 10,000 feet (3,000 m) within 30 nautical miles of a destination airport (the result of a previous midair collision), but after this accident, all areas below 10,000 feet (3,000 m) were prohibited from exceeding 250 knots (460 km/h; 290 mph) IAS. It also contributed to the Federal Aviation Administration's decision to create terminal control areas or TCAs (now called Class B airspace) around the busiest airports in the country. The airspace around Dayton did not become a TCA, undergoing only minor changes until it was reclassified as Class C airspace in the late 1980s.

• Accident description at the Aviation Safety Network
• Airliners.net Flight 553 preparing for departure in a photo by Bob Garrard, 1967
• National Transportation Safety Board Report AAR68 on the crash (Archive)