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X key logic (runway heading to MCP HDG)

Started by Hardy Heinlin, Mon, 28 Oct 2019 08:37

Hardy Heinlin

Hello, this is the complete logic of the X key function in PSX.


If aircraft on ground and FMC contains an active origin runway:

    X key copies FMC origin runway heading to MCP HDG

Else if FMC contains an active destination runway:

    If difference between aircraft track and runway heading is < 90°:
        X key copies FMC destination runway heading to MCP HDG
    Else:
        X key copies FMC destination runway reciprocal heading to MCP HDG
    End.


    In PSX version 10.92 the red part is now replaced by this blue part:

    If difference between MCP HDG and runway heading is < 90°:
        X key copies FMC destination runway reciprocal heading to MCP HDG
    Else:
        X key copies FMC destination runway heading to MCP HDG
    End.


Else:

    X key copies heading of EGPWS predicted runway to MCP HDG

End.


The X key is particularly useful on a circle-to-land when you quickly need to set the MCP HDG to the reciprocal heading of the active runway. In older PSX versions this only worked when you are on the base turn within 90° of the opposite runway. I always wanted to get this function in an earlier flight phase. So since version 10.92 you can now toggle between front heading and reciprocal at any time. The first keypress usually sets the front heading.

This is also useful on non-precision approaches that include a long turn before the short final, e.g. on the KJFK Rwy 13 VOR approaches; the final turn is greater than 90°, and therefore in previous PSX versions the MCP unfortunately got the reciprocal runway heading when you hit the X key before that turn. In version 10.92 you just hit the X key a second time and you'll get the front heading.


Regards,

|-|ardy


(Note: This is an assistant function for solo sim sessions; there's no such function on the real aircraft.)

Jeroen Hoppenbrouwers

Quote from: Hardy Heinlin on Mon, 28 Oct 2019 08:37
(Note: This is an assistant function for solo sim sessions; there's no such function on the real aircraft.)

... yet.     :-D