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Old 22nd Sep 2008, 19:44
  #1962 (permalink)  
Join Date: Jan 2007
Location: Italy
Posts: 37
Clearifications of MD 80 systems

I Have seen that people are specutaling in how the Flap /systems mechanicly are working on the MD80 aircraft. I just wanted to clearify that neither the flap or the slat systems are actuated with so called screw jacks, they are fully hydraulical. Like posted earlier the slat is controlled by an dual actuator oval drum located in the mid section of center wing box.Wires on both sides of that oval drum will pull the flap either in or out. Due to the type of constuction and pure gravity rules it will stay as selected even is hydraulical failure accures or if left up during night.So that actuator positon would may tell you if slats were actually selected out. However the flap is contolled by hydraulical actuators at each end of the flap and they will just follow command from lever in cockpit via hydraulical/mechanical followup system to get to position selected. However the flap WILL fall down if left unattended (with hydraulic off) i.e during night stop. That is just pure gravity versas hygraulic internal leak slowly letteing fluid pass the actuators. When coming in the morning to the aircraft the flap will be anywere from 8-25 deg down until hydraulics applied again. That is normal. And there is no real time limits for how fast the flap is allowed to fall down with hydraulics off, I have asked. Generally the older the aircraft the faster they will fall down.Thats why I would not belive so much how the actuators are found since they could have moved easily when hydraulics failed during crash.
Also several people seems to ask about beacon light etc etc. Only light on the MD 80 that is controlled by WOW is strobelight and that IS controled by the L/H GND ctrl relay C/B and which if im not wrong is from main gear wow.But some functions like ( avionic cooling fan) will also be actuated by only nose wow-that is noted when taxying light and the nose oleo straights out and then for a moment it becomes quiet in the cockpit dur to avionic cooling gets off).
Then how to test the T/O warning system is done before engine start by just advancing the throttles verifying brakes ON first and stab NOT set and flaps UP then by advancing the throttles all the appropriate warning will come on auraly one by one.Also when advancing the throttle the outflowvalve starts closing and the yellow wheel on center pedestal starts turning fwd indication towards closing and also that the system is in automatic mode since it is always in manual mode (and closed ) during night stop or if the aircraft is left for a longer time.severar things to check with just throttle movement( and ofcourse free full movement)
That must obviously have been missed.



Last edited by wings1011; 22nd Sep 2008 at 20:26.
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