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Cruciform tail (stabiliser part-way up the fin)

What is a cruciform tail? · Standard part · basis: Design rules and figures from the cited sources; example geometry by Xem Studio

Also called: cruciform tail, cross tail aircraft, mid tail, cruciform empennage, stabilizer mounted halfway up fin, cruciform vs t-tail, cruciform tail rc, cross shaped tail plane

Exact dimensions. True size, with no printing tolerance added.

sizes
2 in table

Notes

  • A cruciform tail mounts the horizontal stabiliser part-way up the fin, forming a cross when seen from behind (Arnedo).
  • It is used to keep the horizontal surfaces out of the engine wake while avoiding many of the T-tail's drawbacks (Arnedo), such as the heavy, flutter-prone fin needed to carry a stabiliser at its tip (FAA PHAK ch.6).
  • Because it is neither fully out of the wing wake nor carried at the fin tip, sizing sits between the conventional and T-tail cases; the published coefficients are for conventional tails and T-tails (Scholz 2021).
  • 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.

Cruciform tail size chart

parametervalue or rangesource
Tail volume basisuse conventional class values (e.g. homebuilt 0.50 / 0.04)HAW Hamburg Table 2.1
Reference buildsame areas as conventional example; stabiliser at mid-fincomputed

Where the files are

Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.

LibreTexts (Arnedo, Fundamentals of Aerospace Engineering)2.2.3 EmpennagewebPublisher's page; dimensions are facts
FAAPilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25), Ch. 6 Flight ControlswebPublisher's page; dimensions are facts
INCAS Bulletin / HAW Hamburg (D. Scholz)Empennage sizing with the tail volume complemented with a method for dorsal fin layout (2021)webPublisher's page; dimensions are facts
HAW Hamburg (Aircraft Design and Systems Group)Empennage sizing: tail lever arm as % of fuselage length (thesis; Table 2.1 typical tail volume coefficients)webPublisher's page; dimensions are facts

Free files

★ Free files 1 parts. Xem Studio design: free to use, print and sell things from; not to be republished as files. Xem Studio Design License. index.json

cruciform-tail-tailcruciform layout: horizontal span 400 × chord 100, vertical 140 × 114 mm on a 500 mm boom, NACA 0009 surfacesSTEP · STL
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Plain text: sheet.txt · JSON: /api/geometry?object=cruciform-tail

Cruciform tail (stabiliser part-way up the fin), isometric render of a generated part
Render of cruciform-tail-tail from the free STEP; not to scale.

Fits with

Tail volume coefficient (horizontal and vertical tail sizing), isometric render of a generated part
Tail volume coefficient (horizontal and vertical tail sizing)19 sizes★ 1 file
Tail moment arm (tail lever arm ratios), isometric render of a generated part
Tail moment arm (tail lever arm ratios)11 sizes★ 1 file
Conventional tail (low-mounted stabiliser and single fin), isometric render of a generated part
Conventional tail (low-mounted stabiliser and single fin)5 sizes★ 1 file
T-tail (stabiliser on top of the fin), isometric render of a generated part
T-tail (stabiliser on top of the fin)4 sizes★ 1 file
V-tail (butterfly tail with ruddervators), isometric render of a generated part
V-tail (butterfly tail with ruddervators)8 sizes★ 1 file
Inverted V-tail (anhedral V), isometric render of a generated part
Inverted V-tail (anhedral V)2 sizes★ 1 file

Questions

Why choose a cruciform tail?

To lift the stabiliser out of engine wake without the T-tail's structural and deep-stall penalties (Arnedo).