Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Slade on March 27, 2009, 09:16:48 PM
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Guys,
Which planes would you say have the best E (energy) retention?
Thanks,
Slade
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Depends on a couple of things.. e.g. speed range.
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E retention is not merely dependant upon airframe but also on how the airframe is handled.
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Two pilots making any same maneuver won't get different E retention. It's the airframe.
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Moot, I think Chalenge meant it depends on what type of maneuvers the airplane does, not that it varies from pilot to pilot.
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hope this helps,pretty much it boils down to wait/drag
Energy available
An aircraft in straight and level flight has:
* linear momentum — m × v [kg·m/s]
* kinetic energy (the energy of a body due to its motion) — ½mv² [joules or newton metres (N·m)]; remembering that 'm' in the ½mv² term represents mass
(Note: normally, the newton metre — the SI unit of moment of force — is not used as the measure of work or energy; however throughout this guide, it is more helpful to express the kinetic energy in the N·m form rather than joules — the N·m and the joule are dimensionally equivalent)
* gravitational potential energy — in this case, the product of weight in newtons and height gained in metres
* chemical potential energy in the form of fuel in the tanks
* air resistance that dissipates some kinetic energy as heat or atmospheric turbulence.
To simplify the text from here on, we will refer to 'gravitational potential energy' as just potential energy and 'chemical potential energy' as just chemical energy.
We can calculate the energy available to the plane cruising:
• at a height of 6500 feet (2000 m)
• and (air distance flown over time)= 97 knots (50 m/s)
• with mass = 400 kg, thus weight = 4000 N
• fuel = 50 litres.
Then:
• potential energy = weight × height = 4000 × 2000 = 8 million N·m
• kinetic energy = ½mv² = ½ × 400 × 50 × 50 = 500 000 N·m
• momentum = mass × v = 400 × 50 = 20 000 kg·m/s
• chemical energy = 50 litres @ 7.5 million joules = 375 million joules.
Because it is the accumulation of the work done to raise the aircraft 6500 feet, the potential energy is 16 times the kinetic energy, and is obviously an asset that you don't want to dissipate. It is equivalent to 2% of your fuel.
It is always wise to balance a shortage of potential energy with an excess of kinetic energy, and vice versa. For example, if you don't have much height then have some extra speed up your sleeve for manoeuvring or to provide extra time for action in case of engine or wind shear problems. Or if kinetic energy is low (because of flying at lower speeds than normal) make sure you have ample height or, if approaching to land, hold height for as long as possible. The only time to be 'low and slow' is when you are about to touch down.
However, during take-off it is not possible to have an excess of either potential or kinetic energy; thus, take-off is the most critical phase of flight, closely followed by the go-around following an aborted landing approach. Ensure that a safe climb speed is achieved as quickly as possible after becoming airborne — or commencing a go-around — and before the climb-out is actually commenced; see take-off procedure.
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To actually answer Slade's question....
The A-20, F4U, F6F, P-51, P-47, P-38, 190D-9 and 109K-4 all have excellent E-retention.
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My personal picks would be:
F4U, P47, TA152, 109K, 190D, 38.
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One factor not discussed is the illusion of E retention, where it is actually E replenishment. In short, a fighter like the Spit16 sometimes appears to have remarkable E retention. It really doesn't. Just pull off power to idle and you will see that the Spit16 bleeds E like mad. What the Spit16 does have is tremendous acceleration. Its ability to replace or maintain E is spectacular, but it is more of a factor of power loading.
I tested every fighter in the game for level flight linear deceleration. This measures the bleed of speed from 400 mph down to 150 mph by simply chopping the throttle to idle. Spitfires do poorly, as does the Tempest, by the way. F4Us, P-47s and 190s do vastly better. This test does not include E bleed due to the induced drag of maneuvering. That is very difficult to quantify in game.
My regards,
Widewing
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Okay, I've asked it before, and I still don't understand...what is the precise purpose of comparing what amounts to the ballistic coefficient of airplanes with their throttles idled, as opposed to with their engine running, as they tend to be in combat? We aren't shooting the things out of cannons. I've tested zoom climbs, and at the end of the day the Spit16 hangs pretty well with most in the game. If that Spit16 can follow your Jug or Hog into the vertical and shoot, it little matters that the reason is advantageous power loading instead of advantageous mass/drag ratio.
One factor not discussed is the illusion of E retention, where it is actually E replenishment. In short, a fighter like the Spit16 sometimes appears to have remarkable E retention. It really doesn't. Just pull off power to idle and you will see that the Spit16 bleeds E like mad. What the Spit16 does have is tremendous acceleration. Its ability to replace or maintain E is spectacular, but it is more of a factor of power loading.
I tested every fighter in the game for level flight linear deceleration. This measures the bleed of speed from 400 mph down to 150 mph by simply chopping the throttle to idle. Spitfires do poorly, as does the Tempest, by the way. F4Us, P-47s and 190s do vastly better. This test does not include E bleed due to the induced drag of maneuvering. That is very difficult to quantify in game.
My regards,
Widewing
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One factor not discussed is the illusion of E retention, where it is actually E replenishment. In short, a fighter like the Spit16 sometimes appears to have remarkable E retention. It really doesn't. Just pull off power to idle and you will see that the Spit16 bleeds E like mad. What the Spit16 does have is tremendous acceleration. Its ability to replace or maintain E is spectacular, but it is more of a factor of power loading.
I tested every fighter in the game for level flight linear deceleration. This measures the bleed of speed from 400 mph down to 150 mph by simply chopping the throttle to idle. Spitfires do poorly, as does the Tempest, by the way. F4Us, P-47s and 190s do vastly better. This test does not include E bleed due to the induced drag of maneuvering. That is very difficult to quantify in game.
My regards,
Widewing
90 % of the rides cant break 375 mph leval i want to see a fm2 or huricane ect ect do this
only way to do it is to dive and then leval at 400 therfor creating a false test platform
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Here's E retention for ya,
I took up the Tempest for some killing, I have not flown it very often, I know its one of the fastest, and a BnZ monster, I am used to flying the Hurri so its quite a bit different then my "ride",
anyways, after a good sortie with 5 killz, my engine gets hit, I look at the map and realize I am over a sector in enemy territory, so I nose down and head towards closest friendly field, climb at about 1k a min., I get a half sector closer to my field, at about 10k, the engine dies I level out and coast, speed drops quickly so I figure im gonna half to bail, being a temp I say "screw it" gonna try to make it, so here I am, coasting, I don't remember how long it took but I coasted around 20 miles without losing much alt.
I was very impressed with the E holding capabilities, no other plane that I have flown can do that.
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Guys,
Great feedback. You guys answered this from many different points of view.
I learned a lot on this one so far.
Thanks,
Slade :salute
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Im not surprised about the Tempest, and would hate to see anyone confuse it with the Typhoon, "which drops like a rock".
The wings of the Tempest were entirely redesigned for better high Alt. and all around aerodynamics. The radiators as well.
Here, http://hem.passagen.se/chla/tempest.htm , no audio but some original Tempest shots to get you pumped up for the next run. At the bottom is an actual clip of a V1 shoot down by a Tempie. Just follow the prompts to the video page. :salute
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anyways, after a good sortie with 5 killz, my engine gets hit, I look at the map and realize I am over a sector in enemy territory, so I nose down and head towards closest friendly field, climb at about 1k a min., I get a half sector closer to my field, at about 10k, the engine dies I level out and coast, speed drops quickly so I figure im gonna half to bail, being a temp I say "screw it" gonna try to make it, so here I am, coasting, I don't remember how long it took but I coasted around 20 miles without losing much alt.
I was very impressed with the E holding capabilities, no other plane that I have flown can do that.
Fly the Ta-152 then. I made it back home to a friendly airfield several times after loosing my radiator (not oil!) to enemy field ack on the deck.
It simply glides like no other prop plane.
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Here's E retention for ya,
I took up the Tempest for some killing, I have not flown it very often, I know its one of the fastest, and a BnZ monster, I am used to flying the Hurri so its quite a bit different then my "ride",
anyways, after a good sortie with 5 killz, my engine gets hit, I look at the map and realize I am over a sector in enemy territory, so I nose down and head towards closest friendly field, climb at about 1k a min., I get a half sector closer to my field, at about 10k, the engine dies I level out and coast, speed drops quickly so I figure im gonna half to bail, being a temp I say "screw it" gonna try to make it, so here I am, coasting, I don't remember how long it took but I coasted around 20 miles without losing much alt.
I was very impressed with the E holding capabilities, no other plane that I have flown can do that.
I'd say that has little to do with E retention, it has more to do with gliding capabilities.
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Sorry, triple post, it looks like I and Lusche have been caught in an Internet whirlpool. :P
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Yup. some serious intardnet mess
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As said, triple post.
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Okay, I've asked it before, and I still don't understand...what is the precise purpose of comparing what amounts to the ballistic coefficient of airplanes with their throttles idled, as opposed to with their engine running, as they tend to be in combat? We aren't shooting the things out of cannons. I've tested zoom climbs, and at the end of the day the Spit16 hangs pretty well with most in the game. If that Spit16 can follow your Jug or Hog into the vertical and shoot, it little matters that the reason is advantageous power loading instead of advantageous mass/drag ratio.
The Spitfire Mk.XVI also has an insane sustained rate of climb. However I've left Co-E Spixteens wallowing in the Zoom in an F4U.
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E retention is a combo of a few things: Momentum, airframe aerodynamics, and yes... engine power.
Take whatever airplane you want to test, take it to 10k, dive to 450mph and level off with with normal mil power. According to this tinky dink spread sheet I have that Luche provided the Mossie has the best E retention. While the Mossie does in fact have an awesome ability to retain E, this data was made with engines off.
Trying to guage the "E" retention of an aircraft without taking into consideration the engines is like pushing dragsters down a hill with engines off and whichever one gets to the bottom first has more "power". The engines are a very big part of how well an aircraft can maintain the extra E, dont kid yourself.
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Actually I just took a Tempest up in the training arena and it glided about as good as the Typhoon, which is about as good as a rock. Maybe Im doing something wrong, its still a great airplane. Can someone else try it?
Of them all Ive never had anything glide as good as the LA-7. Bomber-wise the KI-67s are great gliders. Ive taken them in with no power from a sector away. The IL-2 is a surprisingly good glider. Which is a good thing cause the oil is always being shot. As long as you turn for base right away and keep about 1k you should be able to glide in.
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The Spitfire Mk.XVI also has an insane sustained rate of climb. However I've left Co-E Spixteens wallowing in the Zoom in an F4U.
Management of relative E states has everything to do with it though.
My tests showed that starting from 400mph at sea-level, the SpitXVI and the F4U-1A regained almost exactly the same amount of alt in a zoom.
But even if the F4U or whatever massively outzoomed the Spit, the relevant relative comparisons would be performance with the engine running, not at idle.
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Actually I just took a Tempest up in the training arena and it glided about as good as the Typhoon, which is about as good as a rock. Maybe Im doing something wrong, its still a great airplane. Can someone else try it?
Reduce your RPM to minimum.
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Reduce your RPM to minimum.
What he said. You can test it by killing your engine and hit alt X. After you are stabilized reduce your RPM and you will see your nose rise relative to the horizon. This means your sink rate is reduced and glide extended because you have reduced the drag of the prop.
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90 % of the rides cant break 375 mph leval i want to see a fm2 or huricane ect ect do this
only way to do it is to dive and then leval at 400 therfor creating a false test platform
Of course you must dive... No prop fighter can attain 400 mph at sea level. My test measures the bleed associated with drag, of the airframe and the prop.
My regards,
Widewing
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Let's take several fighters with similar max speeds at sea level. P-51D, Bf 109K-4, P-47N and Ta 152H. I load 25% fuel in each, take off and climb to 5k. I level off, build speed to 300 mph TAS. I then dive to 500 feet in WEP, level off and let speed bleed down. I begin timing speed bleed at 400 mph TAS and measure how long it takes to bleed down to 375 mph TAS while in WEP.
P-51D: 65.6 seconds
Bf 109K-4: 52.3 seconds
P-47N: 50.4 seconds
Ta 152H: 47.3 seconds
Which fighter displays the best E retention in level flight?
My regards,
Widewing
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I imagine the Mosquito would do fairly well in that test.
If not, then I've been using a poor tactic with it to deal with La-7s. :P
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Let's take several fighters with similar max speeds at sea level. P-51D, Bf 109K-4, P-47N and Ta 152H. I load 25% fuel in each, take off and climb to 5k. I level off, build speed to 300 mph TAS. I then dive to 500 feet in WEP, level off and let speed bleed down. I begin timing speed bleed at 400 mph TAS and measure how long it takes to bleed down to 375 mph TAS while in WEP.
P-51D: 65.6 seconds
Bf 109K-4: 52.3 seconds
P-47N: 50.4 seconds
Ta 152H: 47.3 seconds
Which fighter displays the best E retention in level flight?
My regards,
Widewing
ok it all looks cute~n~fuzzy
first off, was all 4 planes at same speed at 500 feet when you leveled out ??
if they wher then you have a ligit test. if not you wasted your time.
if the above mentioned planes dive from 5k to 500ft and the dive angle is EXACT SAME
all 4 will reach 500 ft at different speed,therefor even though you start timing at 400 mph the innital leval out speed is where the E retention comes into play
if a plane levals out from a dive at 475 and another at 450 and you time both of them from when they reach 400 to 375 the plane that was going 475 will have more potential E stored.
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seems to me that which ever measure you use re "e retention" you have to have loads of qualifying factors......
Really its the qualifying factors that tell you want to know.............
e.g which is best in the following
High speed level flight (Powered /unpowered?)
Low speed level flight (Powered /unpowered?)
Zoom (inertia & momentum)
Net e retention thru manouvre
Then all the above at various altitudes.
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if the above mentioned planes dive from 5k to 500ft and the dive angle is EXACT SAME
all 4 will reach 500 ft at different speed,therefor even though you start timing at 400 mph the innital leval out speed is where the E retention comes into play
if a plane levals out from a dive at 475 and another at 450 and you time both of them from when they reach 400 to 375 the plane that was going 475 will have more potential E stored.
Huh?
We are talking about kinetic energy or KE = (1/2)mv^
Potential energy is related to altitude. Potential is that energy available should I dive to sea level from 500 feet. Potential energy has nothing to do with my test. PE = mgh, where h = height.
All of the aircraft exceeded 450 mph, but then decayed to 400 mph at a rate associated with total drag. For any given airframe, that rate of deceleration will be unchanged at 400 mph regardless of what level speed was attained prior. Regardless of what speed you begin measuring, the P-51 decelerates slower than the other fighters listed. Why? Lower drag.
My regards,
Widewing
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Before it became a "fad" like the Ta-152, the Ki-61 has very good E retention.
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ok it all looks cute~n~fuzzy
first off, was all 4 planes at same speed at 500 feet when you leveled out ??
if they wher then you have a ligit test. if not you wasted your time.
if the above mentioned planes dive from 5k to 500ft and the dive angle is EXACT SAME
all 4 will reach 500 ft at different speed,therefor even though you start timing at 400 mph the innital leval out speed is where the E retention comes into play
if a plane levals out from a dive at 475 and another at 450 and you time both of them from when they reach 400 to 375 the plane that was going 475 will have more potential E stored.
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I always think it's hilarious when people question WW's testing methods.
:rofl
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I always think it's hilarious when people question WW's testing methods.
:rofl
Yeah, it's amusing. If a guy has published works, is an expert in his field, and if I recall correctly has 300 traps under his belt. He probably doesn't know much about how to test cartoon airplanes for drag. :D
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Before it became a "fad" like the Ta-152, the Ki-61 has very good E retention.
Ki61 has become a fad?? :huh
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Yeah, it's amusing. If a guy has published works, is an expert in his field, and if I recall correctly has 300 traps under his belt. He probably doesn't know much about how to test cartoon airplanes for drag. :D
Yet even WW himself is treated as know-nothing amateur when he questions why the P-51 in AHII doesn't handle more like people who actually tested the things and flew them in combat says it did. Along with everyone else who presumes to challenge the infallibility of AHII in regards to this or any other flight-modeling issues. Curious.
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Yeah, it's amusing. If a guy has published works, is an expert in his field, and if I recall correctly has 300 traps under his belt. He probably doesn't know much about how to test cartoon airplanes for drag. :D
Yea, I think the engineer in this thread would know a bit about devising practical tests.
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Ki61 has become a fad?? :huh
Yep, a lot more in the air, same goes for the 152.
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i think we should call mythbusters...........they are after all the masters :rofl :rofl
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I did some testing to measure deceleration with minimal propeller drag. I did this by taking off from a 10k field, accelerating to 300 mph, reducing rpm and then chopping power to idle. I then nosed over and dived to 3k, leveling off. I began recording the time of deceleration from 400 mph to 150 mph. All loaded with 25% fuel.
Results are interesting. More than interesting, they are very odd.
The Ta 152H required 101 seconds, while the 190D-9 required only 63 seconds.
The Spit16 required just 59 seconds, and the Tempest only 58 seconds. Yet, the FM-2 required 65 seconds.
P-51 came in at 94 seconds. F6F-5 at 86 seconds. P-39Q required 67 seconds. 190A-5 took 78 seconds. P-38L also took 78 seconds, and the Mossy needed 79 seconds. The P-47N used up 93 seconds, with the F4U-1A at 92 seconds. La-7 took 75 seconds, the Niki 58 seconds. The Ki-84 used up 75 seconds, and the Ki-61 74 seconds, with the Yak-9U at 73 seconds.
It seems that propeller drag, at either minimum or maximum pitch, is all over the place. How else can we account for the difference between the Ta 152H and Dora? Or, what can possibly account for the FM-2 decelerating slower than the Tempest?
<edit> P-38L requires 111 seconds if both props are feathered (use E key to auto-feather). Compare that to 78 seconds at minimum rpm.
My regards,
Widewing
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Do you have figures on drag area for these planes?
I did some testing to measure deceleration with minimal propeller drag. I did this by taking off from a 10k field, accelerating to 300 mph, reducing rpm and then chopping power to idle. I then nosed over and dived to 3k, leveling off. I began recording the time of deceleration from 400 mph to 150 mph. All loaded with 25% fuel.
Results are interesting. More than interesting, they are very odd.
The Ta 152H required 101 seconds, while the 190D-9 required only 63 seconds.
The Spit16 required just 59 seconds, and the Tempest only 58 seconds. Yet, the FM-2 required 65 seconds.
P-51 came in at 94 seconds. F6F-5 at 86 seconds. P-39Q required 67 seconds. 190A-5 took 78 seconds. P-38L also took 78 seconds, and the Mossy needed 79 seconds. The P-47N used up 93 seconds, with the F4U-1A at 92 seconds. La-7 took 75 seconds, the Niki 58 seconds. The Ki-84 used up 75 seconds, and the Ki-61 74 seconds, with the Yak-9U at 73 seconds.
It seems that propeller drag, at either minimum or maximum pitch, is all over the place. How else can we account for the difference between the Ta 152H and Dora? Or, what can possibly account for the FM-2 decelerating slower than the Tempest?
My regards,
Widewing
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Do you have figures on drag area for these planes?
Drag coefficients:
P-51D: .0175
P-39N: .0217
P-47D: .0243
FM-2/F4F: .0253
F4U-1D: .0267
P-38L: .0270
F6F-5: .0270
My regards,
Widewing
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A few remarks:
I am not surprised by the results for the twin engines. The windmilling props create a huge amount of drag. The twins have two of them. On the other hand, the twins can feather the props and glide forever. Has anyone tried to land a mossie with both props feathered? Try it with no fuel and your rudder shot off :) a little like landing a helium balloon.
Deceleration depends on the Drag/Mass ratio, not just drag.
The drag created by the prop can have strange behavior at high speeds. Unlike real life, planes do not over-rev in AH and I don't know how the low-rev limit works for planes that cannot feather. I suppose the drag will depend on the individual prop and the high/low rev limits. I also suspect that this has an effect on the speed bleed of the light but high powered planes from high speeds and with full power on.
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It seems that propeller drag, at either minimum or maximum pitch, is all over the place.
Of course it would be. Different sized propellers with different pitch limitations windmilling different sized engines at different rpms.
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Of course it would be. Different sized propellers with different pitch limitations windmilling different sized engines at different rpms.
I see, so that explains why there is a huge difference between the Ta 152H and Fw 190D-9 when they both have a Jumo 213 engine and the same propeller?
Guess not, huh?
Remember this equation: KE = (1/2)mv^ M=mass V=velocity. Velocity is the same. The difference in weight (mass) between the two is only about 400 lb, which should be offset for the most part by the Dora's much smaller wing (reduced flat plate area).
My regards,
Widewing
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That is strange, but "It seems that propeller drag, at either minimum or maximum pitch, is all over the place." is not strange in and of itself.
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It's not in and of itself, it's in this specific case.
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It's not in and of itself, it's in this specific case.
Isn't that what I just said?
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It reads like you're trying to argue that there's nothing strange in the test results themselves or in what they imply. I'm officially done trying to string coherent sentences together.
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Perhaps the efficiency of the Ta-152's high-aspect ratio wings reduces induced drag even in level flight enough to account for the effect?
Perhaps the fuselage of the Ta-152 is somewhat more streamlined than the D9, or you tested the Ta-152 with a higher gross weight than the D9 was carrying?
But these are only guesses.
I see, so that explains why there is a huge difference between the Ta 152H and Fw 190D-9 when they both have a Jumo 213 engine and the same propeller?
Guess not, huh?
Remember this equation: KE = (1/2)mv^ M=mass V=velocity. Velocity is the same. The difference in weight (mass) between the two is only about 400 lb, which should be offset for the most part by the Dora's much smaller wing (reduced flat plate area).
My regards,
Widewing
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I always think it's hilarious when people question WW's testing methods.
:rofl
Man, I wish I'd seen this thread sooner. :D
Yeah, I dismissed the guy's argument when he essentially missed the point and simply started regurgitating the things he learned in Physics 101. Chemical energy? What does that have to do with airframe energy retention? E-retention is all about drag, parasitic, and perhaps more importantly the induced drag from performing maneuvers. If during the process of trading potential for kinetic energy (and back again), an aircraft losses less energy, then it has better E-retention.
Perhaps the efficiency of the Ta-152's high-aspect ratio wings reduces induced drag even in level flight enough to account for the effect?
Perhaps the fuselage of the Ta-152 is somewhat more streamlined than the D9, or you tested the Ta-152 with a higher gross weight than the D9 was carrying?
But these are only guesses.
I would expect the Ta-152's longer fuselage to have slightly less drag. I'm thinking you may be right about the Ta's higher aspect ratio wing. The lower induced drag certainly appears to outweigh the increased parasitic drag.
Of course this all assumes that HTC has modelled the Ta accurately. ;)
Widewing,
Have you considered a follow-on test where you recorded velocity loss following a constant g climb? If one were to accelerate to 400 kts @ 5000ft, then measure the final velocity following a (power off) constant g climb (say 3g's) to a higher altitude (say 10,000ft), it might tell us something about E-loss due to induced drag at higher angles of attack (as well as due to elevator deflection). Just a thought. :salute
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Widewing,
Have you considered a follow-on test where you recorded velocity loss following a constant g climb? If one were to accelerate to 400 kts @ 5000ft, then measure the final velocity following a (power off) constant g climb (say 3g's) to a higher altitude (say 10,000ft), it might tell us something about E-loss due to induced drag at higher angles of attack (as well as due to elevator deflection). Just a thought. :salute
I wish there was another viable method. One problem with a 3g climb... You can generate 3g as you maneuver into a climb. However, once you neutralize the controls... 1g. Actually, a vector of 1g. A continuous 3g climb would only be a climb until you pitched over inverted through the horizontal. Of course, the effect of gravity is a factor that will complicate the results.
We have very limited tools for measuring drag.
Nonetheless, thanks for the suggestion.
My regards,
Widewing
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I would fully expect the 152 to be better than the 190D9. The 190 wing is one of the less efficient wings in the game, maybe equivalent to the Spitfire. In this kind of test, wing efficiency is probably going to be the largest factor, especially over the full spectrum of speeds as the primary drag component shifts from parasitic to induced as the plane slows down. 190 wings suffer from both, parasitic at high speeds and high induced at low speeds. It may be interesting to see the comparison in drag coefficients for the 190D vs. the 152. I knew the P-51 would be the best since it won't suffer from nearly as much parasitic at high speed, and will have manageable induced at low speeds--especially considering this type of test keeps low AoAs.
Cthulu, during my design process, I've found that generally the shorter the fuselage the lower the drag. The longer fuselage may allow better trim drag characteristics that make it more efficient than the shorter 190D fuselage--we'd have to do the math to make a comparison. Form factor, divergence angles, etc. considered...
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I wish there was another viable method. One problem with a 3g climb... You can generate 3g as you maneuver into a climb. However, once you neutralize the controls... 1g. Actually, a vector of 1g. A continuous 3g climb would only be a climb until you pitched over inverted through the horizontal. Of course, the effect of gravity is a factor that will complicate the results.
We have very limited tools for measuring drag.
Nonetheless, thanks for the suggestion.
My regards,
Widewing
On second thought, 3g's may be a bit extreme. What I'd hoped to describe was an arcing constant g flight path which would terminate at the target higher altitude (but not past the vertical). But in order for any comparison to mean anything, the flight path would have to be duplicated for all aircraft tested, which, as you say, is outside our ability.
Cthulu, during my design process, I've found that generally the shorter the fuselage the lower the drag. The longer fuselage may allow better trim drag characteristics that make it more efficient than the shorter 190D fuselage--we'd have to do the math to make a comparison. Form factor, divergence angles, etc. considered...
The reason I brought that up is that I've seen examples in autoracing (the old Porsche 935 "Moby Dick" comes to mind)
(http://img4.imageshack.us/img4/5513/porsche935mobydickp.jpg) (http://img4.imageshack.us/my.php?image=porsche935mobydickp.jpg)
where lengthening the body reduced base drag more than it increased parasitic drag. Of course, making this comparison, an aircraft fuselage to an auto body, is a stretch at best. ( no pun intended)
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In Hoerner's Fluid Dynamics of Drag he discusses divergence angles and their effect on drag. For example, the taper of the fuselage can't exceed a certain angle or the flow will trip turbulent and create boat-tail drag. I think it was 8 degrees--I'd have to look it up. He also stated his opinions on form factor (roughly stated, the width of an object versus its length) and found, IIRC, that approx 3.5 was optimal for drag reduction. Apparently it was what encouraged the designer to craft the fuselage of the Quest Venture the way it is:
http://airventure.aviation.museum/collection/aircraft/Questair%20Venture%20200.asp
The biggest problem is that you add a lot of surface area as the tail is lengthened and it adds to the overall drag area. As the tail arm gets longer, the size of the empinage control surfaces can become smaller, so there's a bit of optimization that's required to come to the optimal length. Notice the Venture has extremely large control surfaces as a result of its extremely low form factor.
Sorry if I'm repeating something you already know. Either way, you are correct, for any given configuration of height, width, and length, you can arrive at an optimal combination that gives you a lower total drag amount.
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Sorry if I'm repeating something you already know.
Not at all. :salute I usually learn something new whenever you and Widewing post.
I do have a question though: Why does a guy in Reno have a Carolina avatar?
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Why does a guy in Reno have a Carolina avatar?
UNC, Class of '96. Grew up just outside Charlotte. After we win the National Championship next weekend, I'll swap it back to the old avatar of my namesake. ;)
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UNC, Class of '96. Grew up just outside Charlotte. After we win the National Championship next weekend, I'll swap it back to the old avatar of my namesake. ;)
Real sorry to hear that. I'll try to keep it civil, but no guarantees. :D
(http://img25.imageshack.us/img25/7994/ncsulogo.jpg) (http://img25.imageshack.us/my.php?image=ncsulogo.jpg)
Class of '78