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Guest Ian_Riddell

Auto Slat and TE Flap RETRACT???

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This may be related to a previous problem regarding hydraulics and flaps...I was trying to see if the PMDG 737NG had an Autoslat System, a Hydraulic Power Transfer Unit and a Flap Load Relief System.The Autoslat system fully extends the slats if they are (already) partially extended and the aircraft is about to stall (Prerequisites: Airspeed has to be below 230kts, the flap lever has to be at 1, 2 or 5 units. Also, the Alternate Flaps should not be in use, the T/E flaps must not be up and the aircraft must be in the air). The logic crunching is done by the 2 Stall Management Yaw Damper Computers (SMYD's). The Stall Warning Yaw Damper Computers look at the airplane configuration and generate a LE Slat Full Extend signal when the aircraft reaches a critical Angle of Attack for that particular configuration).The Hydraulic Power Transfer Unit (PTU) is a hydraulic pump used to power the hydraulics of the Leading Edge Flap/Slat system if the (normal) System B hydraulic pressure (EDP output pressure) gets below a certain psi (2350 psi). The same system B hydraulic fluid is used, but System A Hydraulic pressure is used to run the PTU (i.e. no mixing of fluids).I was flying straight and level with flaps 5 selected. I then slowly pulled back on the throttles until the plane reached stall speed. No change in the LE flap/slat indicators/annunciators on the F/O's panel occured.... so, after hitting Pause, I went back to my notes and discovered that the F/O's "LE Flap Transit" indicator is inhibited for Autoslat operation (so far so good). I didn't think to look outside the aircraft to see what the flaps/slats were doing (maybe next time). Recovering from my stall, I levelled out again, flying with flaps 5 near stall speed, I then tried deselecting the B Hydraulic System pumps to check out the Power Transfer Unit. All the flaps & slats (LE's and TE's), immediately retracted.... and I fell out of the sky like the proverbial lead ballon.Next I tried the Flap Load Relief... also not modelled properly it seems (bits of flap seen floating in Sydney Harbour).Disappointing on one hand... but lots of fun on the other :-)Cheers.Ian.

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