Turn rate and radius questions

[F4UDOA]

Dtango,

Err I kind of agree with you here.

1. The EM diagram that BadBoy posted is for AH. AH is off on stalls in many A/C both high and low.

2. The situation that I presented was using the best sustained turn performance for both A/C. The F4U's best turn is 20MPH slower than the FW190.

If I were to incease the speed of the F4U to equal the 190 I could pull almost 4G's and outstrip the 190 by a faster turn rate.

If I reduce the speed of the 190 to Co-E with the F4U his DPS would drop to nothing because he could no longer pull G.

The scenario I presented was best case for both. The slower the fight gets it leans more towards the F4U, but at 190MPH the F4U can still pull more G than the 190.

My issue is with the relative stalls in AH as compared to historic data. How one chooses to skin a cat is up to them.

BTW, the differences between the two are far from negligable. Zig also has instantanous data in his spreadsheet that matches pretty close to the chart posted, the AH data does not.

And most importantly, Zig's chart is 12,000lbs and Badboys is at 25% fuel which equals 11,100LBS. That is a big difference.

Zigrat,

I would really appreciate any refinement you could provide.

Is there anything you can do for acceleration? Or to account for prop wash while pulling G?

Thanks

[dtango]

F4UDOA:

You've been around the block many times regarding the stall speeds .  I'm not going to get into that long discussion here.  You state that they are in error in AH for different a/c.  I say there isn't conclusive evidence of that.  As Badboy says:

I doubt that very much! I have no doubt at all that every aircraft in the game represents an honest and honorable attempt to model it with the maximum fidelity possible. I've been flying simulations since 1987, and I've flown every online sim ever produced, and I can say without doubt that HTC have certainly shown more commitment to getting it right, and willingness to tweak, than any other developer I've known. In most cases I think they have done an excellent job. My guess is, that if you really want to influence their effort, this might not be the best place to do it.

Regarding AH lift limit (instantaneous turn) envelope, I've already mentioned how hard it is to flight test for that data infact I'm hardpressed to figure out a procedure to accurately flight test for it with the measures of performance feedback we've got in AH.  (I had thought in the past about trying to talk HTC in opening up some of their testing facilities for access because they have alot more powerful tools and methods to allow them to do some pretty interesting testing. )

Zig's spreadsheet and calcs are based on some generalized figures for thrust.  Calculating thrust accurately is an extremely complex proposition especially when you're talking about a range of airspeeds you have to calculate it for.  In my own EM analysis I initially tried the same method and realized that I was getting thrust calculations higher than could be obtained after doing some validation work.

Even assuming the calcs you are using in Zig's spreadsheet are accurate You could maybe pull 4G's in the F4U for maybe 1-2 seconds at 190MPH as your airspeed decays rapidly?  Then it becomes really hard to figure out what the turn performance would be because we have no idea as to the rate of energy bleed of the a/c as you sustain a turn.

And again using the data that you have of best sustained turn speeds of 160mph & 190mph, ~100ft radius and 1 dps turn rate advantage could hardly be characterized as a decisive advantage in my opinion therefore negligible.  But I'm persuadable on this and concede that you could say the F4U has a slight advantage with these numbers but don't think that it translates into much from an angles perspective.

Tango, XO
412th FS Braunco Mustangs

[F4UDOA]

I think something is being lost in the translation here.

If an A/C is supposed to stall at a certain speed at a certain load and it does not then it is not correct. I am not using subjective data.

I also do not wish to get into a conversation about HTC's efforts or credibility. I'm sure they do the best they can.

Based on that I don't want to get into a pissing match. But if you care to compare the data I have provided to AH data at the same load levels and prove I'm wrong the we can pick it up again.

Thankyou for your assistance.

Next subject.

Does anyone have stall data on the FW190, 109 or other.

[dtango]

F4UDOA:

I don't know how we got here nor do I know where to start .  Your first question was about turn performances of F4U1-D vs the FW-190A5.  I have been trying to help you understand turn performance and why you can't come to the conclusion you have with what you started with.

Then you change course and start going down the path of your flight test numbers not matching the V-n diagram you have or Badboy's chart.  You've done this not realizing the aerodynamic nuances involved of which if you understood you'd realize that trying to test for accelerated stall limits is downright hard to do if not impossible to obtain with what we have available in AH.

I'm off to Disney World for a week .  Best of luck with better understanding this topic.  I'm always encouraged by your passion on the subject of a/c performance.  There's a lot for you to understand still.

Tango, XO
412th FS Braunco Mustangs

[F4UDOA]

DisneyLand,

Good luck! Undoubtably there are children in the equation and that means money, patience and Micky Mouse. None of those three are in my possession.

Anyway I don't wan to argue about this stuff. This is what I do to relax.

Good luck and enjoy!!

[fats]

I find it offensive and plain wrong that badboy used something that resembles a spitfire in the diagram and labeled it as Fw 190A-5.


// fats

[Badboy]

Originally posted by fats
I find it offensive and plain wrong that badboy used something that resembles a spitfire in the diagram and labeled it as Fw 190A-5.

Refresh your browser and take another look... But the 190 is just as dead as it was before

Badboy

[fats]

heh.


// fats

[Zigrat]

ok i made some corrections and improvements. who has webspace.. i can email it to you can you can post it

[F4UDOA]

Zig!!


Mememememememememememe!!!!!

[Zigrat]

whats your email. you can email me at gtg877d@prism.gatech.edu i will reply

[joeblogs]

Is this flight test data or is this coming out of a flight model for a particular game?

-Blogs

Originally posted by Badboy
The diagrams give both sustained and instantaneous performance. I've labled the previous diagram so that you can see which curves represent the sustained turns and which ones are instantaneous. Here it is:




Badboy

[F4UDOA]

JoeBlogs,

BadBoys EM diagram is based on AH with 25% fuel.

The acceleration diagram I posted is for real.

I cannot duplicate those stalls in AH.

The F4U chart I posted is for 12,000LBS, BadBoys EM diagram is for 25%fuel or 10,567LBS and still does not match the chart I posted.

IMHO it is not even close.

[dtango]

Hi guys, I'm back from Florida .

As a side excursion I got to visit the National Naval Aviation Museum at Pensacola N.A.S.  That was a gem of a museum to visit!  I had no idea it was as extensive as it was.  I'll have to post some of my pics from there including one of an actual N1K2-J Shinden in a different thread.

Joeblogs - Badboy writes articles for SimHQ and has posted various EM related articles charts like the above from flight testing different aircraft from their respective simulations.

F4UDOA - what flight test procedure did you use to test the accelerated stall limits of a/c?  There are two types of flight tests that are used to do this, both of which are difficult to do correctly in order to capture the data in AH.  The two types of tests that I know of are either constant speed or constant g tests.  

Constant speed tests are used for high performance fighters today and the technique is to fly a procedure called a "wind-up turn" where throttle is fixed, velocity is fixed, and bank angle is gently and smoothly increased until critical aoa is reached.  The trick with this maneuver is that to maintain constant speed the pilot also has to continue to change nose pitch to maintain a fixed velocity while simultaneously increasing bank angle.  The ideal wind-up turn is a spiral descent that gets tighter as bank angles increase and steeper in order for the aircraft to maintain constant speed.

Constant g tests are easier to do than wind-up turns and are perferred for other types of aircraft but still tricky to get right in AH.  In a constant g turn, the aircraft's bank angle (which results in a specific g-load) and altitude are held constant while the speed is decreased until a stall occurs.  To perform this maneuver you need to know which bank angle you want to test for and then try to maintain that bank angle which is a challenge because you will need to provide elevator input to increase aoa as speed decreases in order to maintain a constant bank angle without gaining or losing altitude.

Tango, XO
412th FS Braunco Mustangs

[gripen]

dtango,
AFAIK F4UDOA's flight envelope chart from the manual is based on pull ups not turning. So if someone wants to test if the AH F4U behave like the real plane, these tests should be made with pull ups from straight flight (straight dive is ok too). There is no need to keep constant speed or constant g load, just make pull ups at various speeds at given altitude (say 100-400 mph) and record the speed and g load when the stall happens. Then just just continue testing until you are satisfied with the amount of data and then plot the curves (spreadsheets like the Excel have quick and easy curve fitting utilies).

Testing turn performance is more complicated because you have to keep altitude constant and "ball in the middle" (ie the plane should not yaw; good rudder controll). For instantaneous turn performance testing there is no need for constant g load or speed; all you need is to make level turns at various speeds at given altitude until the plane stalls and record the speed and g load at the moment of the stall (and repeat this until you are satisfied with the amount of data). For the continous turning performance testing the constant speed or g load tests are the right methods but testing procedure is a bit different. In the constant speed test you adjust g load by changing turn rate keeping speed constant until balance is found then record the g load at this given speed. In the constant g load test you keep the g load constant until balance is found and then record the speed.

Sometime ago I tried some pull up testing (10 runs at about 30k, mach 0,4-0,6) with the P-51D (I recorded data with the filming option) because there is very good real life data available for the P-51D for comaprisons (turns and pull ups, icluding lift coefficient). I won't comment results otherwise than there were no surprises for me. The problem with this kind of testing is that it takes really lot of time and effort. Easiest way to make comparisons would be to know formulas used for the AH flight model but I believe these are business secrets. After all the AH is just a game and it does not bother me much if one plane in the AH does not perform exactly like the real one. Nearly allways I visit here I saw a thread or two started by F4UDOA where he whines about something is wrong with the AH F4U if compared to the real one.

gripen