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P-63 (?) Airacobra/Kingcobra power question
A question for the physics-minded among us, or for anyone who just has
the answer. I have heard the Airacobra was underpowered and that got me to thinking; Does having an engine at the middle of the fuselage (in any plane for that matter, like the XP-58) and connected by a long shaft contribute to a loss of power delivered to the propeller? In other words; would there be more power delivered the closer the engine is to the prop? Does the shaft "eat up" power in any way? I am a mechanic and pilot and fairly knowlegable about a/c physics & aerodynamics but this has me stumped. Thanks in advance for your ponderings and/or solution! Ricky |
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P-63 (?) Airacobra/Kingcobra power question
"Ricky" wrote in message ... Does having an engine at the middle of the fuselage (in any plane for that matter, like the XP-58) and connected by a long shaft contribute to a loss of power delivered to the propeller? In other words; would there be more power delivered the closer the engine is to the prop? As its name "rec.aviation.piloting" implies, this group is more for airplane drivers than for aircraft designers or aviation historians. You will get better answers at rec.aviation.military, and perhaps some very interesting answers at rec.aviation.homebuilt. Regards Vaughn |
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P-63 (?) Airacobra/Kingcobra power question
On Nov 3, 9:13*am, Ricky wrote:
A question for the physics-minded among us, or for anyone who just has the answer. I have heard the Airacobra was underpowered and that got me to thinking; Does having an engine at the middle of the fuselage (in any plane for that matter, like the XP-58) and connected by a long shaft contribute to a loss of power delivered to the propeller? In other words; would there be more power delivered the closer the engine is to the prop? Does the shaft "eat up" power in any way? I am a mechanic and pilot and fairly knowlegable about a/c physics & aerodynamics but this has me stumped. Thanks in advance for your ponderings and/or solution! Ricky Ricky, the question you'd have to ask is, if the energy is put into the shaft at the engine end, where could it go? One answer is heat, the the other sound energy, but really most of it is delivered to the prop. Long shafts do cause vibration problems, but those can be overcome. As it happens, there are other reasons for putting engines close to the front of a single engine airplane. The middle is a good place to park passengers, you avoid the weight/space issues with the shaft. My aerodynamic question had always been why there are fewer pusher props. In a puller some of the wind energy is used up against the airplane. In fact one of the things that made the Mooney 201 better than the Executive is the windscreen and cowling were redesigned to more effectively deflect the wind. In the case of the Mooney, the wind against the airplane is airspeed plus that contributed by the prop, and losses go up like something of the square of wind velocity. This could be a long thread, and some posters may actually contribute to the discussion. |
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P-63 (?) Airacobra/Kingcobra power question
Ricky wrote:
A question for the physics-minded among us, or for anyone who just has the answer. I have heard the Airacobra was underpowered and that got me to thinking; Does having an engine at the middle of the fuselage (in any plane for that matter, like the XP-58) and connected by a long shaft contribute to a loss of power delivered to the propeller? In other words; would there be more power delivered the closer the engine is to the prop? Does the shaft "eat up" power in any way? I am a mechanic and pilot and fairly knowlegable about a/c physics & aerodynamics but this has me stumped. The shaft itself won't eat up power, but the various gearboxes and shaft supports required will. Every bearing has a bit of friction; every gearbox has a bit of drag. A long drive shaft, and the gearbox required to let the cannon shoot through the hub, would cost more power than the straight installation. Whether it was enough to matter, in the case of the P-39, is another thing. ISTR the P-39's problem was the lack of a turbocharger rather than overall low power... the Airacobra started losing oommmmph above 12,000 feet, and it turned out that most of the combat was higher than that. Remember, Tex Johnston won the Thompson Trophy in a P-39, and set a speed record, besides. Ron Wanttaja |
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P-63 (?) Airacobra/Kingcobra power question
a wrote:
My aerodynamic question had always been why there are fewer pusher props. In a puller some of the wind energy is used up against the airplane. In a pusher, the prop has to operate in turbulent air stirred up by the structure in front. Depending on the design of the airplane, the prop also has to be stronger (e.g., heavier) to withstand the cycling loads if there's a wing or something blocking part of the prop disk from the slipstream (think Long-EZ). Ron Wanttaja |
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P-63 (?) Airacobra/Kingcobra power question
On Nov 3, 9:09*am, "vaughn"
wrote: As its name "rec.aviation.piloting" implies, this group is more for airplane drivers than for aircraft designers or aviation historians...(rest snipped) * Regards Vaughn Hey, thanks for your suggestion. I've been in Usenet since the early 90s and am very careful (generally) about on-topic discussion. This is totally on topic and useful, interesting & beneficial to this particular community. I am an "airplane driver," and, I'm sure you know or will learn, drivers run the gamut of interest in airplanes in every aspect. I submit this topic with absolutely NO reservation that this is violating the traditions of an "airplane driver's" group. Thanks anyway, Ricky |
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P-63 (?) Airacobra/Kingcobra power question
On Tue, 3 Nov 2009 08:10:54 -0800 (PST), Ricky wrote:
On Nov 3, 9:09*am, "vaughn" wrote: As its name "rec.aviation.piloting" implies, this group is more for airplane drivers than for aircraft designers or aviation historians...(rest snipped) * Regards Vaughn Hey, thanks for your suggestion. I've been in Usenet since the early 90s and am very careful (generally) about on-topic discussion. This is totally on topic and useful, interesting & beneficial to this particular community. I am an "airplane driver," and, I'm sure you know or will learn, drivers run the gamut of interest in airplanes in every aspect. I submit this topic with absolutely NO reservation that this is violating the traditions of an "airplane driver's" group. Thanks anyway, Ricky This article should answer that for you. Good Luck! http://tinyurl.com/5gt7 |
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P-63 (?) Airacobra/Kingcobra power question
On Nov 3, 10:55*am, Ron Wanttaja wrote:
a wrote: My aerodynamic question had always been why there are fewer pusher props. In a puller some of the wind energy is used up against the airplane. In a pusher, the prop has to operate in turbulent air stirred up by the structure in front. *Depending on the design of the airplane, the prop also has to be stronger (e.g., heavier) to withstand the cycling loads if there's a wing or something blocking part of the prop disk from the slipstream (think Long-EZ). Ron Wanttaja Thanks! I seem to remember the pusher in the C310 was less effective too. |
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P-63 (?) Airacobra/Kingcobra power question
In article
, a wrote: On Nov 3, 10:55*am, Ron Wanttaja wrote: a wrote: My aerodynamic question had always been why there are fewer pusher props. In a puller some of the wind energy is used up against the airplane. In a pusher, the prop has to operate in turbulent air stirred up by the structure in front. *Depending on the design of the airplane, the prop also has to be stronger (e.g., heavier) to withstand the cycling loads if there's a wing or something blocking part of the prop disk from the slipstream (think Long-EZ). Ron Wanttaja Thanks! I seem to remember the pusher in the C310 was less effective too. Cessna? The C-336/337 turns out to perform slightly better in single-engine flight on the rear engine than the front. |
#10
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P-63 (?) Airacobra/Kingcobra power question
In article ,
Ron Wanttaja wrote: Ricky wrote: A question for the physics-minded among us, or for anyone who just has the answer. I have heard the Airacobra was underpowered and that got me to thinking; Does having an engine at the middle of the fuselage (in any plane for that matter, like the XP-58) and connected by a long shaft contribute to a loss of power delivered to the propeller? In other words; would there be more power delivered the closer the engine is to the prop? Does the shaft "eat up" power in any way? I am a mechanic and pilot and fairly knowlegable about a/c physics & aerodynamics but this has me stumped. [snip] Whether it was enough to matter, in the case of the P-39, is another thing. ISTR the P-39's problem was the lack of a turbocharger rather than overall low power... the Airacobra started losing oommmmph above 12,000 feet, and it turned out that most of the combat was higher than that. Combat in the ETO tended to be higher than other theaters, which, since the USAAC pulled the turbocharger from the P-39, hamstrung it in that arena. The Airacobra was also a small aircraft, with limited fuel, as it was designed as a point defense fighter, and lack of range hurt it, too. That said, the Russians liked it pretty well, since air combat on the eastern front tended to remain below 15,000', and it performed well down there against the Luftwaffe. (In spite of the 37mm cannon, the P-39 was used much more in the anti-air role, and not against German armor; the Il-2 was much better down in the mud.) The P-39/P-400 didn't exactly shine, not that it embarrassed itself, in the Pacific, partly due to the long distances that were common there. |
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