Plain flap — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/plain-flap/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)
Basis: Design rules and figures from the cited sources; example geometry by Xem Studio
Catalog version: 2026-10-20

Sizes: see table below
- A plain flap is a hinged section of the trailing edge that increases camber and lift coefficient at a given angle of attack; it greatly increases drag and moves the centre of pressure aft, pitching the nose down (FAA PHAK ch.6).
- Its section CLmax increment is about 0.9 (Arnedo, data from Franchini et al.); on a NACA 0012, a 20% chord flap at 40 deg raises CLmax from just under 1.6 to 2.4 (Virginia Tech Appendix A, NACA data).
- Wing-level gain for plain flaps scales with flapped area ratio and cos^3 of quarter-chord sweep (Arnedo).
- The file is a reference example built by Xem Studio from the numbers above. Sizes the sources do not fix are illustrative; scale the example to your own vehicle.

parameter  value or range  source
Section delta-CLmax  0.9  Arnedo (Franchini)
NACA 0012 + 20% chord flap at 40 deg  CLmax ~1.6 -> 2.4 (Re 6e6)  Virginia Tech Appendix A
NACA 0012 zero-lift angle with that flap  about -12 deg  Virginia Tech Appendix A
Wing delta-CLmax  0.92 x dCl x (Sflapped/S) x cos^3(sweep)  Arnedo
Typical CLmax/cos(sweep), plain flap  1.4-1.6 takeoff (20 deg) / 1.7-2.0 landing (60 deg)  Arnedo (Franchini)
Reference build  chord 100, 25% flap, 300 span, 20 deg  Sadraey/Arnedo-range example

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- FAA: Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25), Ch. 6 Flight Controls — web — Publisher's page; dimensions are facts — https://www.faa.gov/sites/faa.gov/files/08_phak_ch6.pdf
- LibreTexts (Arnedo, Fundamentals of Aerospace Engineering; data from Franchini et al.): 3.4.3 Increase in CLmax (high-lift devices) — web — Publisher's page; dimensions are facts — https://eng.libretexts.org/Bookshelves/Aerospace_Engineering/Fundamentals_of_Aerospace_Engineering_(Arnedo)/03%3A_Aerodynamics/3.04%3A_High-lift_devices/3.4.03%3A_Increase_in_CLmax
- Virginia Tech Pressbooks (data from Abbott & von Doenhoff, NACA): Appendix A: Airfoil Data — web — Publisher's page; dimensions are facts — https://pressbooks.lib.vt.edu/aerodynamics/?p=52

Free files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/plain-flap/index.json
API: https://xemstudio.com/api/geometry?object=plain-flap