Thursday, October 30, 2008

Preflight Take-off Warning System check ordered for MD-80 and DC-9 series aircraft

The European Aviation Safety Association (EASA) has issued an Airworthiness Directive ordering a mandatory check of the Take-off Warning System (TOWS) on MD-80 series aircraft and related types before every flight. This action was taken following the crash of a Spanair MD-82 aircraft at Madrid this past August. A preliminary report about the Spanair accident issued earlier this month by Spain's Comisión de Investigación de Accidentes e Incidentes de Aviación Civil (CIAIAC) noted that the flaps/slats were not set for takeoff, but the Take-Off Warning did not sound.

EASA AD No.: 2008- 0197, issued today, October 29, 2008, applies to "All McDonnell Douglas Model DC-9-10, DC-9-20, DC-9-30, DC-9-40, and DC-9-50 airplanes; Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD-83), and DC-9-87 (MD-87) airplanes; Model MD-88 airplanes; Model MD-90-30 airplanes and Model 717-200 airplanes."

The AD states, in part:
...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.
The AD requires amendment of the PROCEDURES section of the applicable Airplane Flight Manual to incorporate the following check:

Note: This check is mandatory and must be carried out before the first engine start before every flight.

Before engine start, and with power on the aircraft:

Takeoff Warning/Throttles……..………………………..CHECK/IDLE

Move both throttles toward full forward position and observe takeoff warning sounds. Move throttles to idle and observe warning is silenced.

NOTE: If takeoff warning does not sound, maintenance action is required prior to takeoff. Confirmation of takeoff warning system operation does not ensure that correct takeoff values for stabilizer trim, centre of gravity, or flap/slats position have been set.
Here is the link to the complete AD: AD No.: 2008- 0197 - EASA Airworthiness Directive, Oct. 29, 2008 (2 page 'pdf' file)

...or visit the EASA Airworthiness Directives page.