GalaxyFlyer wrote:Simple answer:: airliners are twins, tris or quads and each requires a powerful rudder for the OEI case. Imagine the Vmcg and Vmca for a V-tail B777?
26point2 wrote:GalaxyFlyer wrote:Simple answer:: airliners are twins, tris or quads and each requires a powerful rudder for the OEI case. Imagine the Vmcg and Vmca for a V-tail B777?
The Fouga CM 170 Magistar wasn’t an airliner but it was a twin jet with v tail.
GalaxyFlyer wrote:The conversation is technical by nature, how to design a certifiable, aerodynamically sound airliner. It’s subject to a rather clear cut answer, then what conversation are you looking for? I’m interested enough to provide an answer proven to be correct over the last 70 years.
WN732 wrote:V-Tails can be temperamental. It was found that fuselages had to be extended longer than the conventional airplane design normally allowed. Otherwise they could be subject to "snaking." It was found that the advantage/disadvantage was moot and the added cost of design plus the possible need for a more fortified and longer structure would outweigh any weight and parts savings.
The Bonanza proved that it was doable but it did come with abundant cost. V Tailed Bonanzas were more susceptible to inflight overstress breakups than their conventional partners.
crobak wrote:I’d guess that for the OEI case a v-tail will cause problems. Physically speaking with a v-tail you’ll always waste some chunk of energy through having the rudders also acting as elevators and vice versa. That’s offset by having to deal with less drag in straight and level flight but in case of one engine failing (on a conventional twin) you have will end up not only using the rudder for that but also constantly lose energy by unwanted elevator input that comes with it. That means losing energy by compensating unwanted pitching components while just trying to counter the yaw. Guess the required stronger (thus heavier) engines to counter that make it unworthy from an economical point of view
I see your mind working and it’s great but it really is not as much as you think. When a twin looses an engine or asymmetric thrust , you have to displace the rudder which creates drag. On a V tail, you will see one ruddervator displaced way more than the other. In fact the opposite ruddervator hardly looks out of place but it is. I have rigged the controls on a V tail a few times. Foga and Bonanza. You get the same area drag from the flight control displacement. It is best described as induced drag. Is V tail induced drag greater than rudder only induced drag? You would need lab work and each plane is different. My bet is they are different but not to far at all from each other. It’s a great discussion.
This is a cool way to look at fin area for a V tail. Look at a Side profile view of the plane. Measure the area from that flat side view and multiply x2. That’s your vertical area. You want horizontal area? Look at a view from the top.
F-18 uses the ruddervator to aid in pitch control and ultimately rudder control. Northrop/McDonnell Douglas thought it was worth the drag.
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