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twin tail questions
On Mon, 04 Aug 2003 18:13:25 +0000, Chris W wrote:
I got such a good answer on my question about flap design I thought I would ask another design question. why would a plane that has two engines have two vertical stabilizers. No in the case of the Aircoupe I always thought the reason for the twin tail was so that the helical prop wash wouldn't induce a yaw tendency from the prop wash hitting the vertical stabilizer/rudder. It is my understanding that the Aircoupe was designed so you wouldn't need rudder pedals, and the twin tail I think would have helped that. But on a twin engine, what's the point? having two vertical stabilizers and two rudders seems significantly more complicated both structurally and mechanically so why do it if there isn't some advantage? There must be one I don't know about. -- Chris Woodhouse Planes may have multiple vertical stabs for several different reasons. Some (e.g. the Lockheed Constellation) may have them to facilitate fitting them in existing hangars without hitting the top of the door opening. Some multiple engine designs have multiple vertical tails so that one portion is directly in the prop wash of the operating engine which may help reduce the minimum control speed following an engine failure. At least that is what Kelly Johnson says about the twin vertical tails of the first Lockheed Electra (More Than My Share of it All, Kelly Johnson, pg. 24). And he says that they also acted as end plates on the horizontal tail, which increased its effectiveness, and improved the static longitudinal stability - same book, same page). -- Kevin Horton RV-8 (finishing kit) Ottawa, Canada http://go.phpwebhosting.com/~khorton/rv8/ |
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"Chris W" wrote in message ... I got such a good answer on my question about flap design I thought I would ask another design question. why would a plane that has two engines have two vertical stabilizers. No in the case of the Aircoupe I always thought the reason for the twin tail was so that the helical prop wash wouldn't induce a yaw tendency from the prop wash hitting the vertical stabilizer/rudder. It is my understanding that the Aircoupe was designed so you wouldn't need rudder pedals, and the twin tail I think would have helped that. But on a twin engine, what's the point? having two vertical stabilizers and two rudders seems significantly more complicated both structurally and mechanically so why do it if there isn't some advantage? There must be one I don't know about. -- Chris Woodhouse There used to be an argument that, in the event of an engine failure, a twin-tail twin would have one fin and rudder directly behind the operating engine, in the prop wash, where it would be more effective. The more likely reason that the '30s and '40's saw a number of twin and triple tail aircraft had to do with the low vertical clearance of hangar doors. A multi-vertical tail aircraft would more likely be able to pass through the low door opening where a single tail would have to be much higher and have to be left outside. Bill Daniels |
#3
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So why did the P-38 have a twin tail. I think it is a pretty cool
looking bird. I think the bird the "Doolittle Raiders" flew had a twin tail too. Fred Chris W wrote: I got such a good answer on my question about flap design I thought I would ask another design question. why would a plane that has two engines have two vertical stabilizers. No in the case of the Aircoupe I always thought the reason for the twin tail was so that the helical prop wash wouldn't induce a yaw tendency from the prop wash hitting the vertical stabilizer/rudder. It is my understanding that the Aircoupe was designed so you wouldn't need rudder pedals, and the twin tail I think would have helped that. But on a twin engine, what's the point? having two vertical stabilizers and two rudders seems significantly more complicated both structurally and mechanically so why do it if there isn't some advantage? There must be one I don't know about. -- Chris Woodhouse 3147 SW 127th St. Oklahoma City, OK 73170 405-691-5206 N35° 20.492' W97° 34.342' "They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety." -- Benjamin Franklin, 1759 Historical Review of Pennsylvania |
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"Frederick Wilson" wrote in message et... So why did the P-38 have a twin tail. I think it is a pretty cool looking bird. I think the bird the "Doolittle Raiders" flew had a twin tail too. Fred The Doolittle raiders flew B-25's, and yes, they had twin tails. I was not in the head of the designers of the P-38, but as it ended up, there are a few reasons that they ended up with twin booms (different than most other twin tails of the time). In the P-38, everything went towards speed and low drag. They made as skinny frontal profile as possible. To get lots of HP, thery also wanted it turbo (or was it super) charged. They put the intercooler (and perhaps the turbocharger) back behind the engine, and it made it so long, they must have figured they were halfway back to the tailplane, so why not contine it, and connect to the tail, and leave off the fuselage. Works for me! G -- ---Jim in NC--- |
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On Mon, 04 Aug 2003 17:13:25 GMT, Chris W wrote:
I got such a good answer on my question about flap design I thought I would ask another design question. why would a plane that has two engines have two vertical stabilizers. No in the case of the Aircoupe I always thought the reason for the twin tail was so that the helical prop wash wouldn't induce a yaw tendency from the prop wash hitting the vertical stabilizer/rudder. It is my understanding that the Aircoupe was designed so you wouldn't need rudder pedals, and the twin tail I think would have helped that. But on a twin engine, what's the point? having two vertical stabilizers and two rudders seems significantly more complicated both structurally and mechanically so why do it if there isn't some advantage? There must be one I don't know about. So many smart answers to averything but the question. If the tail assembly is in the prop awsh, the low and no-speed response is much greater. ie ground and taxi. The tradeoff is the crosswind component induced by the spinning prop, which the Ercoup didn't want, so the put the rudders outboard of the prop and pu on a kickass main gear system to keep the thing straight. Mr Knowital. |
#6
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In the case of some Navy jets, the issue was one of space. The vertical
surface area desired on a plane like an F-14 would have required a single tail too tall to fit inside the hangar deck. Or so I have heard it explained by the "Aviator" types. Harry "first effective rudder" Frey Wright 1902 glider, etc. |
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