V-tail
Aircraft tail with two V-shaped surfaces combining rudder and elevator.
The V-tail, also called a vee-tail, butterfly tail, or Rudlicki's V-tail, is an aircraft tail configuration that replaces the conventional vertical and horizontal stabilizers with two surfaces arranged in a V shape. Each surface's trailing edge carries a hinged control surface known as a ruddervator, which combines the functions of a rudder and an elevator. This design is not widely used in aircraft.
Quick Facts
- Inventor
- Jerzy Rudlicki
- Year of invention
- 1930
- First test aircraft
- Hanriot HD.28 trainer
- First test year
- 1931
- Modifying manufacturer
- Plage and Laśkiewicz
Facts from the source article.
Variants
The experimental Lockheed XFV had an X-shaped tail that was basically a V-tail extending both above and below the body. The Beechcraft Bonanza Model 35, often called the V-tail Bonanza, is the most widely produced conventional V-tail aircraft. Other examples include the Lockheed F-117 Nighthawk, the Fouga CM.170 Magister trainer, and the newer Cirrus Vision SF50 jet. Some gliders, like the Lehtovaara PIK-16 Vasama, were originally designed with a V-tail, but the ones actually built used a cruciform tail. The Blohm & Voss P 213 Miniaturjäger was one of the earliest planes to use an inverted V-tail. Later, drones such as the LSI Amber, General Atomics Gnat, and MQ-1 Predator adopted this design. The Ultraflight Lazair, with over 2,000 units made, had an inverted V-tail that also supported the rear landing gear.
Advantages
A V-tail uses two angled surfaces instead of the usual three, which can reduce weight and drag. However, NACA research found that these surfaces must be larger than expected, so the total wetted area stays about the same. The main drag benefit comes from having only two intersections instead of three, cutting down on interference drag. In some light jets and larger aircraft, this design keeps the tail out of the engine exhaust, avoiding thrust loss and wear. For military planes, the V-tail's fewer right angles help with stealth.
Disadvantages
In the mid-1980s, the Federal Aviation Administration reassessed the V-tailed Beechcraft Bonanza due to a history of fatal mid-air breakups during extreme stress at a rate exceeding the accepted norm; the type was deemed airworthy after Beechcraft issued a structural modification as an Airworthiness Directive. V-tailed aircraft require longer rear fuselages than conventional empennages to prevent yawing, a tendency called 'snaking' that was apparent on the Fouga CM.170 Magister during takeoff and landing.
Ruddervators
Ruddervators are the control surfaces on a V-tailed airplane, located at the trailing edge of each of the two tail airfoils. The first use of ruddervators may have been on the Coandă-1910's X-tail, though there is no proof that aircraft ever flew; the later Coandă-1911 flew with ruddervators on its X-tail. Polish engineer Jerzy Rudlicki designed the first practical ruddervators in 1930, tested on a modified Hanriot HD.28 trainer in 1931. The name is a portmanteau of 'rudder' and 'elevator.' In a conventional tail, the rudder provides yaw control and the elevator provides pitch control. Ruddervators provide the same effects through a more complex control system that actuates the surfaces in unison. For an upright V tail, moving the pedals left deflects the left ruddervator down and left and the right ruddervator up and left, producing yaw to the left; the opposite produces yaw to the right. Moving the stick back deflects both ruddervators up, producing pitch nose up; moving it forward produces the opposite movements for pitch nose down.
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