If you watch the slats and flaps deploy on a swept wing, transport category aircraft, and you mentally draw a chord line, you'll notice that it's changing through the slats/flaps deployment schedule. Center of gravity (CG) on these aircraft is usually defined in percentage of mean aerodynamic chord (%MAC). If the chord is changing, is the %MAC referencing a clean configuration? Is the aircraft designed to tolerate the %MAC that exists in other flap configurations? Or is the %MAC constant throughout slat/flap deployment?

  • $\begingroup$ In what context is CG measured from %MAC?? I typically see it measured from a datum point at the nose of the A/C. $\endgroup$
    – Jim
    May 4, 2022 at 2:26
  • $\begingroup$ This question gives you a bit of background on %MAC. In larger aircraft we generally use %MAC as an expression of the CG rather than from a datum point. $\endgroup$
    – ryan1618
    May 4, 2022 at 10:11
  • $\begingroup$ I can add more detail for why I ask. I fly a CRJ-900. If you look a the wing configured to flaps 8 you have slats at 20 degress and flaps at 8. The wing chord is obviously different and it's noticable in the airplane when you deploy it. The chord and therefore the %MAC must be affected, and I am wondering how manufacturers approach this. $\endgroup$
    – ryan1618
    May 4, 2022 at 10:13
  • $\begingroup$ Ok. Shows my lack of experience in Transport-size a/c. All my experience is just in helicopters and light GA. $\endgroup$
    – Jim
    May 4, 2022 at 16:40
  • $\begingroup$ The great thing about this site is that there are people with different education and experience that can share insights. $\endgroup$
    – ryan1618
    May 6, 2022 at 23:16


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