THE US NATIONAL Transportation Safety Board (NTSB) is conducting wake-vortex flight-tests as part of its continuing probe of the fatal crash of a Boeing 737 on 8 September 1994, outside Pittsburgh, Pennsylvania.
The USAir aircraft had passed through an area where a wake vortex created by a Boeing 727 would have existed. NTSB investigators had previously concluded through simulations that a wake vortex could not have produced an unrecoverable loss of aircraft control. The team is uncertain of the data, however, and it is now collecting more information.
The wake-vortex flight-tests involve a Boeing 737 operated by USAir and a Boeing 727 owned by the US Federal Aviation Administration. The NTSB expects to conduct a 20h flight evaluation over two weeks at the FAA's technical centre at Atlantic City, New Jersey.
The test is not designed to replicate the accident. Data gathered will be used to analyse the possible role of a wake-vortex such as encountered in the accident, which claimed 132 lives.
Smoke generators have been mounted on the wingtips of the FAA aircraft to feed smoke into the vortices for visual identification. The USAir aircraft is being flown into the smoke trails. Instrumentation in the 737 is recording the effects of the encounter. The data will be entered into Boeing engineering simulations.
A probable cause for the crash of USAir Flight 427 will not be issued before early 1996, says Jim Hall, NTSB chairman.
Source: Flight International
