interesting link!
i was brought to this thread by google when i typed in "stall warning logic"
there may be a point to uncover here.
in the Boeing Bible 737-800, in our version 3.20.7 it does say that the stall warning logic adjusts stickshaker and min maneuver speed bars on the IAS indication (tape) (we fly the 738's in STN that have a touch of blue)
it stays set when WAI is used in flight.
but there is a note that states that the FMC Vref speed is not adjusted!
so, perhaps, during the approach, if we use the FMC Vref speed plus 5 knots, then we might be slow enough to activate the underspeed blink.
the good book does not give us a clue as to what that adjustment is in knots that i can find. but i remember in the classics we used 10 knots to compensate for the fact that the stabilizer is not de-iced and there still might be ice on its leading edge reducing its effectiveness, hence the speed increase.
so, the instructor may actually be making a valid point, but the reduced books do not give us enough information to tell us how to compensate when the FMC Vref is not corrected.
there is that bit in the QRH in the single engine set up to change Vref 15.
that may be all we have at present!? that's 10 knots plus the 5 to fly. that matches what is in 4.20.21 (again-our version) Command speed limiting section.
and i have seen that underspeed many times! i suspect this is the cause.
chairs and rear guards.
Last edited by stator vane; 25th February 2012 at 05:53.