I had been reading in numerous articles (see this answer and this one) that there are advantages of using thick trailing edge flaps. In these articles it kept on coming up that Airbus uses thick trailing edge flaps also for certain reasons but I couldn't understand them. Could someone please explain?

My main question is about the aerodynamic aspect: Why do the flaps have to be made thicker?

  • $\begingroup$ @ymb1 sorry about that wasn't my intention. Added the other link to. $\endgroup$
    – Jai
    Commented Jan 26, 2018 at 17:04

1 Answer 1


enter image description here

The best flaps (aerodynamically, as you ask) will be complicated and elaborate. But complicated flaps add weight and maintenance cost. Airbus wanted to have a variable camber wing for the A340 (Flight), but they didn't pursue it to the end, due to the complexity.

As for the aerodynamic benefits of simple flaps, there aren't any, as the other post shows: slower MMO and smaller MTOW.

Slower MMO is because of the smaller wing sweep because of the simple flaps because of needing a good [slow] approach speed. MTOW is because simple flaps don't carry as much off the ground.

The simple flaps are thicker because:

  • The flaps are shorter chord-wise: the aerodynamic load (lift and drag) acts on a smaller surface area, compared to the complicated multi-slotted flaps.
  • Thin flaps would produce even less lift (thanks to @PeterKämpf).
  • The lack of a thrust gate: they need to be thicker to withstand the jet blast.

Also see comment by Peter Kämpf.

enter image description here
Comparing the A380 and 747-400 flaps. Note the thrust gate and the triple-slotted flaps of the 747.

  • 1
    $\begingroup$ The article linked in your other answer says that the thicker flap has a larger leading edge radius which will delay separation, allowing more lift. Also, it offers more torsional stiffness, which keeps the number of flap tracks low. $\endgroup$ Commented Jan 27, 2018 at 22:17
  • $\begingroup$ @PeterKämpf - Is there an example for the reduced torsion stiffness resulting in fewer tracks? The A380 has 5 tracks while the 747-400 has 4. Perhaps due to MTOW difference. I also checked the A320 and 737, and they have the same 3-track layout. $\endgroup$
    – user14897
    Commented Jan 27, 2018 at 23:50
  • $\begingroup$ No, the article only says the thicker flap has lower distortion. But a thinner flap would need more tracks eventually. $\endgroup$ Commented Jan 27, 2018 at 23:53

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