Aces High Bulletin Board
General Forums => Aces High General Discussion => Topic started by: Widewing on August 20, 2003, 10:53:14 PM
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One of the denizens of the rec.aviation.military newsgroup is a fellow named Vlado Lenoch. Vlado is a warbird owner and his collection includes a P-51D (Moonbeam McSwine) and a T-33.
We were discussing a post that referred to a Spitfire XII executing a split-S from 1,000 feet. I didn't believe it and tested the AH SpitV SpitIX and SpitXIV. None could come close to pulling a split-S from that height. Vlado mentioned that he needs at least 2,000 feet for that maneuver in his Mustang to ensure adequate margins of safety. So, with Vlado's info that the P-51's corner velocity was 270 mph, back I went to AH (offline) for some testing.
I started testing at 200 mph, and concluded with the 270 mph corner speed.
According to Vlado; "Maximum G limit AND minimum TAS provide minimum radius "loops". The maximum G is the structural
limit and the minimum speed at which the maximum G could be obtained is the target TAS. This target TAS sometimes requires the addition or subtraction of power to obtain and or sustain. In the Mustang it is 270 mph."
I filmed the exercise and reviewed it later. As you will see by the test results, the tightest radius was obtained at the highest speed.
Here's what I tried. I took a P-51D with 25% fuel. I climbed to 2,000 feet and adjusted throttle till airspeed was stable. After rolling inverted I pulled off the power and pulled through the half-loop. Testing was done over water so that I had a consistant and reasonably level surface below.
All airspeeds where verified before pulling through.
At 200 mph TAS, I cleared the water by 8 feet! Visual estimate via film. I was less than a single prop blade length off the water.
At 250 mph TAS, I cleared the water by about 85 feet. Better but still little margin.
At 270 mph TAS, I cleared the water by about 220 feet. Much better.. plenty of room.
Unlike the first two, I was able to pull 6G+ at 270 mph (was blacking out).
Tonight in the MA, some guy was whining endlessly about having his Spitfire Mk.XIV out-turned by a P-51B. In all likelihood, the fight occurred right in the Mustang's sweet spot between 250 and 300 mph, where it can hang with just about anything long enough to get a killing shot in.
So, you Mustang guys who don't already know, keep it near corner velocity and you will find yourself having more opportunities and surviving more fights with the so-called turnfighters.
My regards,
Widewing
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Good stuff.
So how do you figure out the ideal corner velocity in other planes?
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all you spity an lala drivers , pay no attention to widewing :cool:
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You use a chart like this one for each aircraft.
(http://www.simhq.com/_air/images/air_011b_9.jpg)
Unless you can get someone to post them or or tell you.
Or you can also do a LOT of semi-accurate offline testing. ;)
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Let's post one with greater relevancy:
(http://www.simhq.com/_air/images/air_011b_4.jpg)
Notice that between 260 and 320 mph the P-51D can turn with the Spit IX.
My regards,
Widewing
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Wide, Shhhhhhhhhhhhhhhh! I've mentioned the pony's sweet spot in another thread, although relative to other plane's turning abilities at speeds, I'd rate it another 50 MPH higher. It's what allows me to get such great snap shot opportunities at spits and other turners..you know the routine: get 'em fast, watch them break turn, chew off pieces of their plane with the.50's in the snap, look for the next guy. Sweeeeeeeeeeeeeeeeeet!
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Widewing;
Where you get those charts?
Thanks;
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WHOAOooooooo
Excellent POST !!! Thank you :)
I remember in and old sim everything changed when I discovered the CV of F4uD, you could outturn everything!!
In that sim CV for F4u was 190 mph with 1 notch of flaps!!!!
In the chart above......have you consider that 1 notch of flaps could give you even a better turn???
And a request...Plzzzzz CV for 190-D9!!! :) :)
Salute
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So if you were unable to pull off your tests in a game you wouldn't believe it could be possible in real life?
Being good or what ever you may be able to preform in a flight sim means squat really. No matter how good you may think the flight model may be.
...-Gixer
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Right. I'll be the first one to ask: What exactly IS "corner speed"? The only times I've heard it mentioned have been in FlightSimdom. And those charts - eeek - those charts... I never could work anything out using those damn things - preferred an aviation calculator. What are these charts telling us?
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Corner speed is the velocity at where you achieve your maximum turn ratio in degrees per second.
As diagram shows..P-51 will get its best turn at 260 mph. It means that as you are driving faster or slower than that you are turning worse.
As you go faster than that your turn radious gets larger and you spend more time to turn the same degrees. As you get slower...you are losing drag and you cant pull so hard to achieve those dps.
So, if you mantain your P51 at 260 mph and you turn with a spit at 300, you can out turn him and kill him, as you get faster or slower the spit will begin to gain dps on you.
Salute
Kosk
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Ahhh forgot it.....
I am pretty sure that with flaps you could have a chance of getting a better CV.
And, plzzzzzzzz..190-D9 CV now!!!! ;)
Kosk
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Thanks, Load. That makes sense. I remember all that business about tracing a line on the chart until it intersected another line, and then moving across to find the next line etc. :( How I ever pased the PPL writtens - well, I just had to make sure I got all the other questions right! The blue line drops back after corner speed, but then comes down vertical - why is that? And the charts seem to show two corner speeds - is that for WEP and nonWEP? What is the meaning of the altitudes that are shown?
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Well, the line drops vertically because structure cant hold more than 6gs turns over 350 mph....mmmmm I think.
Bottom line is the speed for sustained turns.
And the feet are not height......they are turn radious.
Salute..
PLZ 190-D9 CHART!!!! :( ;)
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Originally posted by Load
Ang you got me..I dont know why there are 2 lines. From the draw I suggest it is turn at 6gs and the other 1 means stall speed...but some1 should confirm.
The 6g lines are the max instantaneous turn rate, the lower lines are max sustained turn rate. At 225 mph the Pony can achieve a 6g turn for a brief moment as speed will drop, however it can sustain a 3g turn as the chart shows without losing speed.
EDIT: Sorry, I was looking at the SPIT IX lines, not the Pony's.
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I think that Corner Vel is also very affected by height of flight...so Widewing....How can you say that CV for P-51 is 260??? Maybe at 10 k it is 300 mph? Am I right?
Salute
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Oh sorry didnt notice charts are for 0 feet ...so I guess they are useful for 10 k??? What do you think?
Salute
Kosk
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yep.. you get a "feel" for the planes best corner speed pretty early. Problem is.. at max g all the planes bleed off speed rapidly. in the case of the 51 and spit9, the spit will reach it's best corner speed half a turn or les in and the 51 will be out of it's envelope. That's why I used to like the Corsairs better, they could turn some and roll some at low speed.
lazs
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The beauty of the airspeed indicator in an airplane is that it is really an air pressure indicator. Because of this, it continues to give you useful information even at high altitude where IAS(indicated airspeed - what you see on the gauge) is no longer even close to TAS(true airspeed - how fast you are really going through the air). Here is how this works.
Suppose that the 1g stall speed is 100mph at sea level and a given weight. Now as your altitude increases the air gets thinner providing less lift. As a result you have to go faster to maintain enough lift to fly, so your stall speed increases. As the air gets thinner you airspeed also reads lower for the same TAS, because airspeed is measured by the air pressure in a pitot tube. Both of these changes are the result of the change in air pressure, and thus they both change at the same rate. What this means is that your stall speed at a given G, and a given weight will be the same in IAS at any altitude! So at 10,000ft if your airpseed indicator is showing 101mph, you might really be going 150mph TAS, but you're about to stall!
Now keep in mind that the sustained turn rates will be different at different altitudes, as the amount of thrust being created can both increase and decrease dramatically because of supercharger gear ratios etc. However the max instantaneous turn performance should remain the same as long as you read the chart as being in IAS.
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Good info Wide, but sadly i hardly ever look at the speed indicator when fighting :) , but if i did look maybe i wouldnt die as much :confused:
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Great topic Widewing; in the jets sims not too long ago like HK, you shot for the player base documented CS speeds or lost in a turn fight. Every time.
Players had figured out the cs speeds the game catered too, and while they were arbitrary to the real fighters, it was still a set simulation constant. Whether they were dead 1 knot on, realistic or not, they were at least close, but you’d better know how the actual sim you were playing made them, and it's stats.
I whined about it away back in AH when I came here, and then just lost interest because no one really thought about that for some odd reason.
I’d like to see real testing numbers. And like Map makers, I have not the competence to provide them, or I would.
If we knew these things like trained pilots of the WWII aircraft variants they flew and faced, there would be better dogfights, or at least performance stats to use in the course of a matchup to try and get an edge. And they don’t have to be historic, just close, and what the simulation creators have dealt us.
I'd like to see a chart for all the AH best corner speeds.
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I think the one reason that corner speeds aren't more of a big deal in WWII sims is that you can only maintain corner speed for a brief moment while turning before your speed bleeds away. Generally you just take all the speed you can get and go vertical with it. In jets you can't do this, as any time the bogey gets his nose on you, you are likely to get shot with a missile. Not to mention that modern fighters like the F-16 can actually make sustained turns at their corner airspeed.
On the other hand, I would venture to say that most of the pilots in the arena don't even think much about using the vertical, and have no concept of one circle vs. two circle fights, or how airspeed affects their turn rate and radius. They just make a hard horizontal turn towards whatever is in front of them and try to get on it's tail.
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I use cornering speed quite a bit in AH, although until this post I didn't know what it was called or that is was actually a quantitative value.. I merely referred to it as the sweet spot. I us it for snap shots in the pony, this thread makes a lot of sense to me.. great info.
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Creamo, Connering speed can be figured out in about 30 sec of flying a plane there realy is no need for charts.
Cornering speed in AH is a very small black out circle with the stall horn blowing it loudest.
HiTech
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cool! thanks for the info :cool:
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Originally posted by Mino
Widewing;
Where you get those charts?
Thanks;
Go to Energy management (http://www.simhq.com/_air/air_011a.html) by Leon Smith.
My regards,
Widewing
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Originally posted by Gixer
So if you were unable to pull off your tests in a game you wouldn't believe it could be possible in real life?
Being good or what ever you may be able to preform in a flight sim means squat really. No matter how good you may think the flight model may be.
...-Gixer
That's a valid question Gixer, let's see if I can answer it.
Several years ago a fellow was doing an airshow performance in a Spitfire. He flew a half-loop starting about 30 feet above the runway. Remaining inverted, he let his speed recover and then attempted to pull through in a split-S. It was estimated that he was at 400 meters when he began. The Spitfire pancaked, destroying itself and killing the pilot. Other warbird pilots who saw the wreck or film of it agreed that he began the maneuver too low to ever hope of completing it. Typical of many airshow pilots, this Spitfire pilot probably had he head outside the cockpit and simply misjudged his height.
It's important for sim pilots to remember that when looping an aircraft, you have one G resisting your upward momentum, and after you come over the top, one G assisting or adding to your velocity (I won't go into the concept of constantly changing G vectors, but the statement is generally correct as an example).
Finally, I have tested the AH planes offline using available data for several types. With few exceptions, things like corner velocity and roll rates conform reasonably close to actual flight data. I salute the guys at HTC for their accurate flight models. Maybe not absolutely perfect (as if such a thing were even possible), but better than any other sim (boxed or online) that I have flown.
I know several warbird owners, some with time in Spitfires and none would consider trying a Split-S from 1,000 feet. Vlado Lenoch won't try it at less than 2,000 feet in his P-51D, and the Spitfire can't do it in less than half of that height.
I hope this explains my thoughts on the topic.
My regards,
Widewing
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Originally posted by Sable
I think the one reason that corner speeds aren't more of a big deal in WWII sims is that you can only maintain corner speed for a brief moment while turning before your speed bleeds away. Generally you just take all the speed you can get and go vertical with it. In jets you can't do this, as any time the bogey gets his nose on you, you are likely to get shot with a missile. Not to mention that modern fighters like the F-16 can actually make sustained turns at their corner airspeed.
On the other hand, I would venture to say that most of the pilots in the arena don't even think much about using the vertical, and have no concept of one circle vs. two circle fights, or how airspeed affects their turn rate and radius. They just make a hard horizontal turn towards whatever is in front of them and try to get on it's tail.
Corner speeds are a big deal in WW2 sims. E fighters need to know the CV of their planes to be effective. I get lots of kills in the pony by knowing what speeds I need to maintain in a turn. You also mentioned using the vertical here, that's right on when discussing CV too, it doesn't just refer to horizontal turns. You can use a nose low turn to maintain your speed and pull around inside someone who is using a flat turn and bleeding their E. Going vertical and getting into a "who can loop the quickest" fight is not always the best solution. ;)
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I agree with BlueMako on the importance on knowing what your CV is. Knowing where the 'sweet spot' is can make all the difference in a fight.
BTW- Widewing, looking at those numbers for the P-51D vs. Spitfire Mk IX, it looks like the numbers for the P-51D are very similiar to that of the P-38L in here. The sweet spot for the P-38L is also between the 250-300mph range (think it achieves its best CV at 267mph) and like the P-51D, can out turn a Spitfire Mk IX at similiar speeds.
Do you have by any chance have a EM chart for a P-38 vs. Spitfire?
ack-ack
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Sorry I respect anyones opinion but personally I find any reference between a flight simulator and the comparison of real flight data and what a plane may or not be able to do in real life compared to AH is laughable to say the least.
Agreed HT have done a great job for a PC based simulator. But it's a game. With a slightly more then Arcade flight model given it's basic drag,lift,thrust modeling etc.
So comparing data from real world aircraft performance and applying it to AH to see whether a certain manouver is possible or not is taking things a little far.
I mean at the end of the day anyone can land a B17 on a CV, hardly realistic. Or of any comparison to real world flight physics.
Sorry, I have alot more I can say on the subject but it's late and I have work to get back to.
"Flying flight simulators does not make you a pilot. High G does."
Unknown
...-Gixer
-Hells Angels-
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Originally posted by Steve
I use cornering speed quite a bit in AH, although until this post I didn't know what it was called or that is was actually a quantitative value.. I merely referred to it as the sweet spot. I us it for snap shots in the pony, this thread makes a lot of sense to me.. great info.
..and that, IMHO, is the only use for cornering speed in AH. If you come up behind some1 in a pony and he tries to brake turn you can always lead the dude and get a shot in. I get most kills that way. Apart from that you cant maintain corner speed long enough for it to be of much use.