Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: STEELE on February 03, 2011, 02:58:56 AM
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I may have to reload AH, because my K4 climbs about 4300-4500, and the spit 16 is climbing at 4600-4800 or better, is this correct?
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Better reload AH as the Spit is climbing to slowly. ;)
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Take a look on this:
http://bbs.hitechcreations.com/scores/planeperf.php?gtype=2&pw=1&p1=86&p2=1&submitButtonName=Generate+Chart
Their fuel duration is the same, 25mins at full power. The k-4 is 7500lbs heavy when its tank is full, its DB-605 D produces 1800hp and it can do 4450ft/min on the deck. The spit16 is 7250lbs heavy, its Packard-merlin can produce 1700hp and it can do 4650ft/min on the deck (well at 1k, it takes a while to reach the maximum climb rate).
Their performance is almost matched then, but a spit16 gains a little bit of advantage. I noticed 4 things:
First, that chart shows the k-4 a bit better than it is in the game. Maybe its from the difference between how i and the chart-drawer tested theese planes.
Second, the spit handles way better at low speeds, and easily catches the numerically almost equal 109.
Third, the 109 has better power to weight ratio, 1 horsepower carries 4,167 pounds, while in the spit16 each horsepower carries 4,264 pounds. Not as much difference, but the spit gains advantage even though it should perform a bit worse. This is from the spits larger wings and more lift.
Fourth, they have the same amount of power, and the spit16 is much slower. That means the spit-airframe is way more draggy than the 109 airframe.
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I am not a spit16 pilot or a 109-K4 guy for that matter. However to me it seems the Spit16s nose starts to fall in the vertical clime some what faster than the 109-K4. I can turn the 109 around at the top of the stall faster also. The 109 takes damage way better than any Spitfire. If I get hit by a BB the spits come apart.
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Brody,
I believe our K-4's DB 605D produces 2000hp at WEP with C3 fuel.
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I believe our K-4's DB 605D produces 2000hp at WEP with C3 fuel.
I dont think so. Then our 109 could do 5000+ft/min easily, due to its extremely good power to weight ratio, and sweep every spit from the floor. It currently isnt able to do it. Also the germans were pretty much outta quality fuel at the end of the war.
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Concensus from past discussions is that we're no even close to the 2000 hp that didn't see much production/use. Although we do have some skins with red legs (meaning C3 fuel if I recall) but this doesn't tie in to the engine model.
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Well, I'm probably wrong then.
Still, is it a sound method to argue backwards from in-game performance?
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No I'm just saying that from in-game performance we don't have 2000 hp modeled in our 109K4s, this per several long debates and various 109 threads, countless requests to add the C3, etc, etc.
Not making any real judgements, just saying how we have it modeled.
Now for a real judgement: Steele, the spit16 is uber in every way. Out turns almost everything in the game, outclimbs everything in the game (it's still doing over 4000 fpm on WEP up to almost 20K), outrolls all but the fastest rollers (which it matches), can insta-ping anything with the hispanos, can accelerate like nobody's business, can chase down even P-51s on the run and catch them (its top speed is enough to catch most planes, but the ludicrous acceleration lets it catch faster planes before they can get to their top speed).
You should know this: Spit16 is super easy mode in every aspect. The only thing it does NOT do is carry 3,000lbs to a target 500mi and back.
Don't be surprised if one chases you down, catches you in a climb, out turns you, out rolls you, or generally is impossible to shake -- that's just how HTC modeled it.
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Indeed. For main arena purposes the XVI is better than the XIV.
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Brody,
I believe our K-4's DB 605D produces 2000hp at WEP with C3 fuel.
Only if the boost was 1.98ata. C3 power was approx that of B4 + MW50 power > 1800hp. 1.98ata wasn't cleared for use till late March 1945.
The Germans had quite a lot of C3 fuel with production being ~ 2/3 of all avgas production. The problem was they couldn't get it to where it was needed.
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And we still do not have a late model spit.
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C3 is just 100 octane fuel, or is there a difference in the chemical make up of it compaired to regular 100oct?
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According to AH's charts, the climb rates are very similar, with the k4 having the advantage at low alts.
(http://bbs.hitechcreations.com/scores/genchart.php?p1=1&p2=86&pw=1>ype=2)
Late in the war though, not only did they have C3 fuel for many of the k4s, they had added a new prop which increased the speed. The prop was sweept backwards in some weird way, which increased the top speed by 18 mph.
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C3 is just 100 octane fuel, or is there a difference in the chemical make up of it compaired to regular 100oct?
German fuel was not gasoline.. It was synthetic, often processed from charcoal and other things.
This is why it belched big black clouds of smoke when pilots attacking bombers would firewall their throttles. Bomber gunners mistakenly reported hits/kills because they thought they had shot the engine up, but it wasn't the case.
The C3 was comparable to 100 octane, at the high end... For using it at lower throttles there were different characteristics. I don't recall if it was the German gas or post-war testing US gas in German planes, but at lower power settings you had greater chances of clogging valves and the like, and one ran lean where the other ran rich, or something confusing.
You can generalize it and say top-end was similar to 100 octane. It's much more complicated, though.
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German fuel was not gasoline.. It was synthetic, often processed from charcoal and other things.
This is why it belched big black clouds of smoke when pilots attacking bombers would firewall their throttles. Bomber gunners mistakenly reported hits/kills because they thought they had shot the engine up, but it wasn't the case.
The C3 was comparable to 100 octane, at the high end... For using it at lower throttles there were different characteristics. I don't recall if it was the German gas or post-war testing US gas in German planes, but at lower power settings you had greater chances of clogging valves and the like, and one ran lean where the other ran rich, or something confusing.
You can generalize it and say top-end was similar to 100 octane. It's much more complicated, though.
I believe their fuel was made from coal not charcoal. It was made using the Fischer–Tropsch process.
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Thank you, you're right... Didn't think about it, but they are different things.
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And we still do not have a late model spit.
What do you mean? Im not a spit expert, but im almost sure the spit8 wasnt in front service until early '44. Which one would be a late-war spit? I cant even think about what a spit8 could do with 150 octane fuel...
Anyway i still LOVE spit16s coming with 5k alt then run from my g-6... lol
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Wow, they made aviation fuel from coal? I just assumed it was some sort of ethanol based synthetics. The climb chart comparison does look very even, hmm. :headscratch:
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Interesting, anyone have any more info on this synthetic fuel? That's pretty crazy.
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Interesting, anyone have any more info on this synthetic fuel? That's pretty crazy.
Good start: http://en.wikipedia.org/wiki/Synthetic_fuel#History
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I can settle this once and for all....The 109K4 is better than the Spitfire..... :rock
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I can settle this once and for all....The 109K4 is better than the Spitfire..... :rock
No
The only thing it can do better is run :old:
(no offence to any of the 109 folks)
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No
The only thing it can do better is run :old:
(no offence to any of the 109 folks)
This is true, the k4 in AH is out classed as a dog fighter by the spit 16....
but,
People in WW2 didn't fight like we do, and the K4 is much faster than the spit 16, so in a situation without icons and people Bnzing out of the sun, as I believe 109s were used (according to what Eric Hartmann wrote, etc..), then the 109 is at an advantage, as the spit can't get to it. They have roughly the same climb rate and the 109 k4 is much faster. Also, being a small aircraft, it is very hard to see in RL.
(http://bbs.hitechcreations.com/scores/genchart.php?p1=86&p2=1&pw=1>ype=0)
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I can settle this once and for all....The 109K4 is better than the Spitfire..... :rock
this
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That chart looks like the K-4 1.98ata of which were only penny pocket in number.
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That chart looks like the K-4 1.98ata of which were only penny pocket in number.
I believe that is only true for k4s that achieved 1.98 not using wep and c-3 fuel, I could be wrong though. There were different engines used in the k4, the DB605D, DB605L and DB605DC and different fuels, B-4 or C-3. I think the max non-wep level for B-4 was 1.8 ata and 1.98 for c-3.
On mill power the k4 is faster too, and the k4 has wep that lasts much longer.
(http://bbs.hitechcreations.com/scores/genchart.php?p1=86&p2=1&pw=0>ype=0)
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update, it looks like that 1.98 was banned in Jan 20 1945, then reinstated in March '45 :headscratch:
banning the use of 1.98 ata
http://www.kurfurst.org/Engine/Boostclearances/DB_Niederschrift6730_DB605DBDC_20-1-45.pdf (http://www.kurfurst.org/Engine/Boostclearances/DB_Niederschrift6730_DB605DBDC_20-1-45.pdf)
re-permitting the use of 1.98 ata
http://www.kurfurst.org/Engine/Boostclearances/605D_clearance198.html (http://www.kurfurst.org/Engine/Boostclearances/605D_clearance198.html)
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If you look at AH's speed charts for the 109K it doesn't match the specs for a 1.98ata C3. Instead, it matches 1.8ata B4+MW50 power curves and specs.
This has been argued and debated and discussed ad nauseum. I fail to understand why a few diehards keep claiming we have 1.98ata, especially after all these years.
AH's speeds:
(http://bbs.hitechcreations.com/wiki/images/thumb/0/02/109k4spd.jpg/300px-109k4spd.jpg)
Copied from:
http://bbs.hitechcreations.com/smf/index.php/topic,109853.msg1140560.html#msg1140560
"Speed, again w/o C-3, in the worst condition -
K-4s 593 km/h at SL, 712 km/h at 7500m."
That's 370mph
Copied from:
http://bbs.hitechcreations.com/smf/index.php/topic,157067.msg1770371.html#msg1770371
"Just to see what`s the fuss all about... 1.8ata K-4 vs. 1.98ata K-4.
SL speeds :
595 kph vs. 607 kph
SL climb :
22 m/sec vs 24.5 m/sec..."
That's about 371 mph.
Copied from:
http://bbs.hitechcreations.com/smf/index.php/topic,157067.msg1766393.html#msg1766393
"The Projektbüro estimate from 19.1.45 assumes 9-12159 propeller, and a weight of 7,496 lbs. Documentation listed below demonstrates that the most prevalant configuration for the ME 109 K beginning in around January 1945 would be DB 605 DB engine with 1.80 ata/2800 rpm engine limitations. GL/C-E2 from 1.11.44 gives 360 mph at SL, 441 mph at 24,606 ft. with production 9-12159 propeller. Various engine and propeller configurations were experimented with. The 9-12159 propeller was the standard production propeller but various German curves are extant showing estimated performance of the 109 K4 with 9-12199.10 and 9-17018.10 thin blade (Dünnblatt) props and Projektschraube with 4 light-metal blades. The 452 mph figure often cited as the top speed of the Me 109 K-4 derives from an estimate assumming an experimental 9-12199 Dünnblatt propeller."
That matches closely what we have in-game, depending on the prop used. Note depending on the prop even 1.8ata can have 10mph less sea level speed. Doesn't mean as compared to 1.98ata, it means compared to other 1.8ata setups with different props.
Quoted from (let's say):
http://bbs.hitechcreations.com/smf/index.php/topic,108817.msg1131294.html#msg1131294
"The best figure available for the K4 at sea level is 377 mph"
This compares to the 1.98 ata quoted above, as 607kph.
We clearly have 1.8ata modeled in-game, and every reference including the cockpit instruments from day 1 when the plane was added as a G-10 have shown this.
There, I spelled it out.... here's hoping that never pops up again.
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Krusty, Thank you for the clarification.
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update, it looks like that 1.98 was banned in Jan 20 1945, then reinstated in March '45 :headscratch:
banning the use of 1.98 ata
http://www.kurfurst.org/Engine/Boostclearances/DB_Niederschrift6730_DB605DBDC_20-1-45.pdf (http://www.kurfurst.org/Engine/Boostclearances/DB_Niederschrift6730_DB605DBDC_20-1-45.pdf)
re-permitting the use of 1.98 ata
http://www.kurfurst.org/Engine/Boostclearances/605D_clearance198.html (http://www.kurfurst.org/Engine/Boostclearances/605D_clearance198.html)
The JG11 unit was only testing 1.98 ata.
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The JG11 unit was only testing 1.98 ata.
It's irrelevant anyway, as Krusty pointed out with data that we have the 1.8 ata + MW50 model.
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Krusty,
along the k4, I believe it was 1850 metric hp, which equates to almost 1824.66 hp(US). Please correct me if I'm wrong.
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(http://www.spitfireperformance.com/okl-181044-pg5.jpg)
670kph = 416mph
710kph = 441mph
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Thought he was referring to the Spitfire, not the Spit16.
That I agree, 109k4 is better than spit16.
I can settle this once and for all....The 109K4 is better than the Spitfire..... :rock
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There was a mention at the Spit being much draggier due to it's lower top speed. Well, it probably is a bit so, but bear in mind that the Spit 16 is optimized for lower altitude than the 109 which means more parasite drag effect.
Also bear in mind, that parasite drag is less at climbing speed then top speed, while induced drag is more at climbing speed than top speed. Which one has the higher wing-loading anyway.
For a matching power and quite similar weight weight on an older pair (Spit I and 109E) I found the spitfire to climb faster, and pull about 10% more Nm. So the wing seems to create more lift in a climbing position.
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Wow, they made aviation fuel from coal? I just assumed it was some sort of ethanol based synthetics. The climb chart comparison does look very even, hmm. :headscratch:
And do you know what they made their charcoal from!? :cry How dare you all! No respect. :cry
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Back to the original question now, I cant get the K4 to climb as well as the chart says it should, but the sp16 does with ease :noid
Try them both, you will see what I mean :headscratch:
Unless I have a fragged K4 file... hmmm
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What speeds are you climbing at in the Spit and in the 109?
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. Which one has the higher wing-loading anyway.
For a matching power and quite similar...
109K4 has a higher wing loading and the second statement is just false. The K4 has a much bigger engine.
Merlin 70 was 1,710 hp
DB 605D 1.8 ata was ~2000hp
The key to a 109 out climbing a spit 16 safely is two fold.
1) to use the fact that a 109 k4 is significantly faster at all alts.
2) to gently pull off the throttle when climbing in a 109 once you are ~100 mph so that you can keep moving upward without blowing all your 'e' countering the torque.
Also, note that the spits hispanos allow for it to take shots from a good distance away, which means the spit doesn't need to match your climb rate, it just needs to be able to get its nose up for the shot.
(http://bbs.hitechcreations.com/scores/genchart.php?p1=86&p2=1&pw=2>ype=0)
(http://bbs.hitechcreations.com/scores/genchart.php?p1=86&p2=1&pw=2>ype=2)
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Spitfire Mk XVI didn't have a Merlin 70, but the DB605D did produce a good bit more power than the Merlin 266 it did have as well as the Merlin 66 our Spitfire LF.Mk IXe has.
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Spitfire Mk XVI didn't have a Merlin 70, but the DB605D did produce a good bit more power than the Merlin 266 it did have as well as the Merlin 66 our Spitfire LF.Mk IXe has.
Yeah, good correction. That's correct, and the Merlin 66 max output was 1,720 hp at 5,750 ft. The Merlin 266 is a licence built Merlin 66 (I believe by Packard)
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Third, the 109 has better power to weight ratio, 1 horsepower carries 4,167 pounds, while in the spit16 each horsepower carries 4,264 pounds. Not as much difference, but the spit gains advantage even though it should perform a bit worse. This is from the spits larger wings and more lift.
Fourth, they have the same amount of power, and the spit16 is much slower. That means the spit-airframe is way more draggy than the 109 airframe.
Both of these assumptions are false.
(1) Power-to-weight ratio means very little. At a glance, it can be an indicator of relative climb performance, but ultimately what drives climb rate is excess power available. If the Spit climbs faster than the 109K-4, then it means that the Spit has greater excess power, regardless of power loading or wing loading.
(2) The Spit and 109 both had almost the same Coefficient of Drag. The difference is that the Spit has almost 70 ft^2 of wing area more than the 109. I'd argue that the Spit probably had a "sleeker" fuselage than the 109K-4, but that extra wing area is what slows the Spitfire down, not a higher Cd. There were some other aspects of the Spit wing that decreased top speed performance (washout), but its not necessarily all about the drag, unless we do the math, and determine that. It could also be a thrust issue. Its possible for one aircraft, making the same amount of power, to create much more thrust than another aircraft with the same power.
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What specs/parameters do you need to know to calculate excess power?
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The key to a 109 out climbing a spit 16 safely is two fold.
1) to use the fact that a 109 k4 is significantly faster at all alts.
Also, note that the spits hispanos allow for it to take shots from a good distance away, which means the spit doesn't need to match your climb rate, it just needs to be able to get its nose up for the shot.
quoted for truth. You can look at all the charts, textbooks as you like but spouting luft paranoia due to lazy piloting skills is pretty weak IMO.
I have never ever caught a 109K4 pro in a vertical climb in any spit. It is only when they try to fight aggressively when they lose to a Spitfire. Putting square pegs in round holes can't fix stupid.
Fuel states, E states, angle of climb WEP no WEP all have a big impact on what you deem to be a "slow" K4.
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What specs/parameters do you need to know to calculate excess power?
Power Available = Thrust X Velocity (TAS)
Power Required = Drag X Velocity
Excess power = Pa - Pr
So, you need the ability to accurately predict thrust from stall speed to maximum speed (a tricky proposition with propellor driven aircraft, especially since thrust changes with altitude, either through changes in engine power or propeller efficiency). You also need to do an accurate model of total drag from stall speed to maximum speed. This is easier to do, but you need to include zero-lift drag, and drag due to lift (and compressibility drag if it rears its ugly head). Drag also changes with altitude due to changes in dynamic pressure, and the parasitic drag and induced drag components change with speed.
So, even if you're merely doing a comparison in level flight, you can imagine how complex this estimation can be. Introduce changing altitudes, and it gets even more complex, since you have to factor in some way to account for changes due to differences in dynamic pressure and engine power and do it repeatedly over some sort of time span.
This is why a lot of people fall victim to over-simplifying by using such metrics as wing-loading and power-loading--because to do the actual analysis required is very time consuming, complex, and sometimes beyond the grasp of most folks aerodynamics knowledge. The best model I've seen on these boards was from DTango, and his response to that epic Brewster thread last year. He mathematically estimated the zoom climb of the Brewster using a Pr/Pa model and posted an Excel graph in the thread. He actually was kind enough to send me the actual spreadsheet used to generate the graph, and it was stunning. Huge spreadsheet involving multiple variables broken down into each second of about a two minute period. Even as detailed as it was, Tango himself will tell you it was a mere estimation--an accurate estimation, but an estimation. I myself have generated a spreadsheet that I can use that will tell me Cdo and Cdi at a given condition for each aircraft in-game, but its dependent on determining an accurate stall speed for each aircraft in that specific configuration (i.e. 25% fuel, 50% fuel, etc.) and does not yet correct for compressibility drag. This was not easy to do, still needs some refinement, and the testing time in-game to determine the stall speed is very time consuming. To do something like this on paper alone (i.e. analyzing an aircraft based purely on its aerodynamic metrics without the ability to test in-game) would take even longer. Just creating thrust curves for each aircraft is very daunting, since propeller efficiency can be such a huge obstacle to model.
This is why everyone on the board should be thankful when guys like Badboy or Tango take the time to actually graph this stuff out, or provide us with tools like the Bootstrap Calculator to do some casual analysis with. Its also why I am continuously impressed with HTCs ability to model all of these very complex calculations in-game. And finally, its the only true reality check you can get to combat all the anecdotal crap that gets slung about on these boards, and from other sources.
Ultimately, there's not one simple equation that takes all of these variables into consideration--its a combination of a lot of formulas and will still only give you an estimation. I don't know if that answers your question or not...
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I can see a nice 3D graph (speed, alt, excess power) for comparing any two planes, if I could manage the calcs.
Is Badboy's 'bootstrap' method for calculating stall speed not accurate enough?
I do remember that prop calcs are a major effort though. The last time I'd tried to calculate a plane's performance in this much detail, I gave up when I got to prop efficiency.. I couldn't even find the prop data.
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I can see a nice 3D graph (speed, alt, excess power) for comparing any two planes, if I could manage the calcs.
Is Badboy's 'bootstrap' method for calculating stall speed not accurate enough?
I do remember that prop calcs are a major effort though. The last time I'd tried to calculate a plane's performance in this much detail, I gave up when I got to prop efficiency.. I couldn't even find the prop data.
Badboy's method is very accurate, it just takes time to fly the profile precisely so you can trust the numbers. I generated some of the aircraft stall speeds using it. For example, the F6F numbers I generated looked good, but I don't trust the 190 numbers I got because the resulting Clmax was higher than I thought it should be. The 190 is a tough plane to determine stall speed for, because it gets so unstable at slow speed, high alpha conditions. But, it'll take maybe 10-15 mins per aircraft per configuration to get numbers you can trust, at least in my experience. I got far enough along to get good numbers for the F6F and generate this:
(http://i125.photobucket.com/albums/p61/stonewall74/F6F-5Drag.png)
For thrust calcs, it is tough. However, there are some close approximations that can be made as long as you stay away from the static condition. Theoretically, with drag numbers, you can determine prop efficiency. Badboy has posted some methodology on that. I'll have to climb back into my books and see if I can find something.
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Just a comment on Badboy's fabulous Bootstrap tool. It's doesn't model an aircraft per se i.e., aero coeffs, thrust, drag, prop, eff. etc. It assumes whatever is modeled in the AH virtual world for a given aircraft for these variables and then calculates turn performance basis whatever the virtual AH flight test data you plug in are. There are gigantic reasons for this - one being Badboy want's the output to be representative of what you will find in the AH virtual world. Badboy is not attempting to remodel the aerodynamics with Bootstrap; he's given a tool to calculate turn performance of AH aircraft based on the aerodynamics modeled in AH itself embedded in the flight test data you plug in.
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This is why a lot of people fall victim to over-simplifying by using such metrics as wing-loading and power-loading--
This needs to be stickied :).
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Gotcha. What I'd want to do is compare such an altitude/speed/excess power graph for each of the AH twins, to a crude powerloading/wingloading/level speed/etc table of these twins, to see just how accurate/inaccurate such a table of vulgar specs is. If you make speed/altitude the horizontal axes, and vertical axis the excess power metric, it would make for very intuitive illustration of a plane's performance.
I'm also curious... How different would such a 3D plot for a plane's excess power in level flight be, from one of Pe while maneuvering (some standard like 2 G)? Could you get a good enough (for general MA dogfighting purposes) idea of the plane's performance/character looking at the level flight 3D plot, or would there be for some/all planes such a change in character/performance (whether taken on their own, or compared to other planes - eg a P38's excess power looking great in level flight but looking barely competitive compared to a Spit's maneuvering excess thrust) that you'd have to see this 3D plot in context with all other maneuvering plots (i.e. a range of G if that's a good metric)... e.g. such a 3D plot with G as fourth dimension - time-varying for G.
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where u get of saying that...numbers dont translate into a pilots skill...funny i climb with both spit 16's and k4s.. and have no trouble in a vert fight vs either
just my 2 cents
TheDude
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Gotcha. What I'd want to do is compare such an altitude/speed/excess power graph for each of the AH twins, to a crude powerloading/wingloading/level speed/etc table of these twins, to see just how accurate/inaccurate such a table of vulgar specs is. If you make speed/altitude the horizontal axes, and vertical axis the excess power metric, it would make for very intuitive illustration of a plane's performance.
I'm also curious... How different would such a 3D plot for a plane's excess power in level flight be, from one of Pe while maneuvering (some standard like 2 G)? Could you get a good enough (for general MA dogfighting purposes) idea of the plane's performance/character looking at the level flight 3D plot, or would there be for some/all planes such a change in character/performance (whether taken on their own, or compared to other planes - eg a P38's excess power looking great in level flight but looking barely competitive compared to a Spit's maneuvering excess thrust) that you'd have to see this 3D plot in context with all other maneuvering plots (i.e. a range of G if that's a good metric)... e.g. such a 3D plot with G as fourth dimension - time-varying for G.
There are various ways to graph it for comparison. The term "envelope" actually comes from a type of excess power graph where you can see graphically, the speeds needed to keep the aircraft "inside" the envelope. Some of them can get pretty complicated, but some are more simple. Let me get some things cooking this week and I'll see if I can put together a full blown power curve. Basically, my chart is just missing the power available plot and a curve for power required. I'll see if I can't finish it up and post it. I'll use the F6F data I already have, then post it just for an example. Then perhaps we can treat your specific comparison. I'll move it to a new thread to keep from mucking this one up...
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Alright. I'll make a quick & dirty sketch of what I had in mind, you can tell me if it's realistic in that other thread where I'll post it.
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Gotcha. What I'd want to do is compare such an altitude/speed/excess power graph for each of the AH twins, to a crude powerloading/wingloading/level speed/etc table of these twins, to see just how accurate/inaccurate such a table of vulgar specs is. If you make speed/altitude the horizontal axes, and vertical axis the excess power metric, it would make for very intuitive illustration of a plane's performance.
I'm also curious... How different would such a 3D plot for a plane's excess power in level flight be, from one of Pe while maneuvering (some standard like 2 G)? Could you get a good enough (for general MA dogfighting purposes) idea of the plane's performance/character looking at the level flight 3D plot, or would there be for some/all planes such a change in character/performance (whether taken on their own, or compared to other planes - eg a P38's excess power looking great in level flight but looking barely competitive compared to a Spit's maneuvering excess thrust) that you'd have to see this 3D plot in context with all other maneuvering plots (i.e. a range of G if that's a good metric)... e.g. such a 3D plot with G as fourth dimension - time-varying for G.
Several things to comment on:
1) Keep in mind power-loading does not equal excess power (nor specific excess power). Not the same things.
2) As to usefulness of power-loading or wing-loading they are really simplistic figures of merit that need to be used carefully. For issues with power-loading see this post:
Power-to-Weight Ratio Pitfalls (http://bbs.hitechcreations.com/smf/index.php/topic,292493.msg3733952.html#msg3733952)
Let's take a quick look at wing-loading. For Wing-Loading we can arrange the lift equation with wing-loading (defined as variable Ws where Ws = Weight/wing_surface_area) as:
Vstall1g^2 = 2*g*Ws / air_dens * Cl
Notice that the smaller Ws is, the lower the stall speed. The lower the stall speed the lower the turn radius, & also the better the corner performance. That's why wing-loading gets mentioned a lot because it gives us a thumb-in-the-air check of this. Here's the catch & it's a big one. Just looking at wing-loading ignores a huge variable, lift-coefficient which is a function of the shape of the wing airfoil. Looking at the equation for Vstall you'll note that Cl is in the denominator. Ignoring Cl means we would be ignoring any impact the design of the shape of the wing has which is significant.
3) If you plotted power-loading or wing-loading vs airspeed you wouldn't get anything meaningful. They would each be just a flat straight line (straight with respect to the velocity axis). Most of aerodynamics is quite curvy :) with respect to airspeed, or most any other variable. You can surmise the usefulness of such a crude thing :).
4) Excess power curves would look something like the drag curves Stoney has created above. Multiply drag by velocity and you get power required. Of course you need power available as well. It would look like the following graph labeled as Pxs: (also Pa=power available, Pr=power required)
(http://www.allstar.fiu.edu/aero/images/e5low.gif)
Image Source: FIU (http://www.allstar.fiu.edu/aero/BA-Form&gra.htm)
My recommendation for doing any analysis is to stick with aero conventions (e.g. like the drag curves Stoney has posted). You'll learn a lot in the process too. These things have been thought about by lots of brilliant people for over 100 years. If there were good simplifications for analysis we've already been using them.
If you're interested in some other interesting charts for performance comparisons you can start here:
http://www.vmihosting.com/MWS/Documents/FTM108-chapter6.pdf
Cheers
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If you're interested in some other interesting charts for performance comparisons you can start here:
http://www.vmihosting.com/MWS/Documents/FTM108-chapter6.pdf
Cheers
Moot, this document Tango linked is Chapter 6 of the Navy Fixed Wing Performance Flight Test Manual. I found a site where you can download the entire document in .pdf --can't remember the site, but do a Google Search and you can probably find it. Its a very helpful reference, especially for performance equations. It doesn't give you a "Reader's Digest Version" that's easier to understand, but everything is in there...
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Stoney - if you download the document it automatically converts to .pdf.
As I went through the document I found only two areas where the analysis (in my opinion) would break down as a foundation for a stand-alone dynamic model (vs Comparative). Dtango - thanks for the link.
1.) For sustained Ps=0 turn, constant altitude turn, there is both a Delta drag and a Delta thrust component at low speed which is not fully incorporated when using a level flight Drag Polar.
2.) CLmax for a level flight condition is different from CLmax for sustained turn.
The 'root cause' for the difference (in my opinion) is due to the Elevator as a contribution to "lift"
a. In low speed level flight the elevator deflections and therefore lift contributions due to elevator deflection is relatively low... the 'negative lift' contribution due to incidence required for pitch equilibrium at near stall/level flight is low both because the effective angle of attack and absolute lift force (of the elevator-horizontal stabilizer combination is relatively small to the Wing.
b. In high G sustained turn, the opposite is true. The negative lift contribution due to up elevator on the horizontal stabilizer is of much higher (relative) magnitude to maintain the high AoA of the Wing as it approaches CLmax...thereby increasing the required amount of lift which must be supplied from the wing (beyond that required to offset nW). The 'Net' effect is a slight increase (virtual) to the Weight vector to supply the negative lift effect of the tail.
Having said this, the rudder deflection 'incremental positive' lift offsets somewhat the negative contribution from the elevator.
The net effect is that the resultant contributions of lift vector from the tail and wing are in opposite directions - implying a stall at a higher velocity than predicted using CLmax at level stall for turn modelling? The eternal question is 'how much'
The Delta drag is also increased due to both the trim drag of a higher lift [absolute value] tail (and rudder) but also the miscellaneous viscous drag contributions due to the high AoA.
I need to ponder this a little more.
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The full manual can be found here at the US Naval Flight Test Alumni pages. FTM108 is the fixed-wing performance manual.
US Naval Flight Test Pilot Alumni Library (http://www.usntpsalumni.com/index.cfm?mws=publicdoc.doc)
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Thanks guys I saved these posts.. I'd grabbed ch5 FTM108 already from a previous discussion where it seemed excess power was a better sense of performance than power/wing-loading, but haven't gotten around to figuring out the math yet. I guess ch6 is closer to the heart of how excess power works?
I'll get back to this in about a week once I've got other stuff finished.