The reason for the AD is
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In August 2008, a McDonnell Douglas DC-9-82 (MD-82) airplane crashed while attempting to take off from runway 36L at Madrid's Barajas International Airport.
Although the preliminary report issued by Spain’s Comisión de Investigación de Accidentes e Incidentes de Aviación Civil (CIAIAC) did not identify the probable causes of the accident, it states that the data recordings suggest the flaps/slats were not set for takeoff and the Take-Off Warning (TOW) did not occur.
After a similar accident in 1987 where it was concluded that the flaps/slats were not set for takeoff and the TOW did not occur, McDonnell Douglas recommended all MD-80 series operators conduct a check of the TOW system before engine start prior to every flight. It has been found that some operators’ procedures no longer reflect the initial intent of the recommendation made by McDonnell Douglas as the check is performed less frequently.
A defective TOW system could let an improper take-off configuration undetected to the flight crew and result in loss of control during the initial climb. As a consequence, to ensure that all operators of MD-80 series airplanes perform the TOW system check before every flight, this Airworthiness Directive requires an update of the Airplane Flight Manual (AFM) to make the frequency mandatory.
The AD also extends to the DC-9 and 717-200 aircraft as the design of the TOW system is common to all three types."