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H-tail / twin fin tail

What is an H-tail (twin tail) and why use one? · Standard part · basis: Design rules and figures from the cited sources; example geometry by Xem Studio

Also called: h-tail, h tail aircraft, twin tail, twin fin, twin vertical stabilizer, double tail plane, h-tail bomber, twin rudder rc plane, endplate fins stabilizer

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

sizes
2 in table

Notes

  • An H-tail puts two fins at the ends of the horizontal stabiliser. Bhattacharya et al. list redundancy and fins less affected by wing/fuselage downwash and fuselage turbulence as benefits, with propwash drag and boom weight as costs.
  • The stabiliser end-plates the fins in the same way a T-tail's stabiliser end-plates a single fin (Kitplanes T-Tails), and splitting the fin area keeps each fin short.
  • Arnedo describes twin (H) tails as 'much less common' than conventional, cruciform and T-tails.
  • Used on: Consolidated B-24, B-25 Mitchell, Avro Lancaster, Handley Page Halifax, Petlyakov Pe-2.
  • 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.

H-tail / twin fin tail size chart

parametervalue or rangesource
Fin area splittotal Sv shared by two fins (each 8,000 mm^2 in reference build)computed from Vv 0.04
Reference buildSh 40,000 mm^2, two fins 100 x 80 mmcomputed

Where the files are

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

engrXiv (Bhattacharya et al., ICMMM 2023)Design and Computational Analysis of Y-tail Configuration for Maritime UAVwebPublisher's page; dimensions are facts
LibreTexts (Arnedo, Fundamentals of Aerospace Engineering)2.2.3 EmpennagewebPublisher's page; dimensions are facts
Kitplanes (B. Wainfan)Design Process: T-Tails (2022)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

h-tail-twin-tail-tailh tail layout: horizontal span 400 × chord 100, vertical 100 × 80 mm on a 500 mm boom, NACA 0009 surfacesSTEP · STL
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Plain text: sheet.txt · JSON: /api/geometry?object=h-tail-twin-tail

H-tail / twin fin tail, isometric render of a generated part
Render of h-tail-twin-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
Cruciform tail (stabiliser part-way up the fin), isometric render of a generated part
Cruciform tail (stabiliser part-way up the fin)2 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

Questions

Why did WWII bombers use H-tails?

Twin fins give redundancy and sit outside fuselage turbulence (Bhattacharya et al.); examples include the B-24, B-25 and Lancaster.