SPIT MK I/II and over boost

[ACE-OF-ACES]

Originally Posted by TomcatViP

Hummm may I remind you that Il2 compare does not take into account E ?

No need!

In that it is something I am well aware of, and none of the standard WWII performance charts like TAS vs Altitude and ROC vs Altitude are depended on the E state. As a mater of fact the test methods are preformed such that E does not factor into the test.

For example, TAS vs. Altitude is a 'level' speed test, as in no change in altitude before or after the TAS value. That is to say you can not dive down from 12kft to 10kft and use that TAS value as the max value at 10kft. The TAS value for 10kft has to be obtained in level flight. That is to say you can not convert altitude into speed (convert energy)

Originally Posted by TomcatViP

The prob with the Spit in old Il2 was not so much with the numbers but with its relaxed "E-liability".

Somehow the very same happen here for now.

This is a perfect example of a 'theory' that has no real world data to support it..

That is to say, I challenge you to find any real world data on this so called "E-liability" of a Spitfire..

After just a few moments you will realize there is no such data..
Thus no way anyone could compare the in game Spitfire E-Liability numbers to the real Spitfire E-Liability numbers
Thus no way anyone could say how well the in game Spitfire E-Liability is simulated

[fruitbat]

Originally Posted by ACE-OF-ACES

No need!

In that it is something I am well aware of, and none of the standard WWII performance charts like TAS vs Altitude and ROC vs Altitude are depended on the E state. As a mater of fact the test methods are preformed such that E does not factor into the test.

For example, TAS vs. Altitude is a 'level' speed test, as in no change in altitude before or after the TAS value. That is to say you can not dive down from 12kft to 10kft and use that TAS value as the max value at 10kft. The TAS value for 10kft has to be obtained in level flight. That is to say you can not convert altitude into speed (convert energy)


This is a perfect example of a 'theory' that has no real world data to support it..

That is to say, I challenge you to find any real world data on this so called "E-liability" of a Spitfire..

After just a few moments you will realize there is no such data..
Thus no way anyone could compare the in game Spitfire E-Liability numbers to the real Spitfire E-Liability numbers
Thus no way anyone could say how well the in game Spitfire E-Liability is simulated

Which does lead to the interesting question, how do 1C and other company's making flight sims actually model E-Liability numbers?

How do they derive these?

[CaptainDoggles]

There's no such thing as "E-liability". It is a concept invented by layperson sim pilots, and is not something that is expressly modeled in any serious flight simulator.

When you increase the load factor on an aircraft (i.e. when you pull back on the stick) then you increase the drag coefficient. This is what slows the aircraft down.

But this is the whole point. For me E-Liability is the capacity of a plane to retain energy which is the sum of speed-based energy and altitude-based energy. I do not want to go into detail but basically E-Liability in a turn for instance will depend on the lift a plane can generate by increasing the angle of attack and how much this will cause drag. The more you pull the more lift your plane generates due to higher angle of attack and the tighter you turn. Now basically ALL planes will be able to generate the same amount of lift or let's say the same amount of lift/weight. A plane however that requires more angle of attack to do so will create - by same aerodynamic performance - more drag than one that does not need this. For instance this would happen to a Spit that has a higher weight. In order to achieve same turn radius the heavier Spit would require higher angle of attack and hence more drag would be created slowing down the heavier Spit more.

Again, if the aerodynamic performance is not as well for a plane (at same weight) it would either also have to pull more angle of attack to create the same amount of lift.

Or, even if another not so performing plane can generate same amount of lift with same angle of attack, it still might generate more drag.

Now if we take into account propulsion too, we can basically say that the plane with the better thrust will be more at ease to compensate higher drag, so even if the plane would have to pull stronger for same turn radius (for instance because of higher weight, aerodynamic performance being similar otherwise) it might still be capable to preserve its speed at the same rate as the lighter aircraft if its engine is powerful enough.

So, summa summarum, it is a darn complicated story. My guess is that no flight sim ever gets so deep into detail to really come up with a good set of data. I think all flight sim FMs are based on some parameters and tweeks to fit quantitave and some qualitative criteria for each plane and hoping that for other qualitative criteria the outcome is ok.

[CaptainDoggles]

Originally Posted by 41Sqn_Stormcrow

So, summa summarum, it is a darn complicated story.

Agree. But I feel that for someone who does not understand the basics of flight performance, it is disingenuous at best to explain something to them in terms of the pseudo-property "e liability".

My guess is that no flight sim ever gets so deep into detail to really come up with a good set of data. I think all flight sim FMs are based on some parameters and tweeks to fit quantitave and some qualitative criteria for each plane and hoping that for other qualitative criteria the outcome is ok.

Also agree. There are a lot of 2nd-order differential equations in aerodynamics that are not efficient to solve in real-time, esp. on consumer-level hardware.

[IvanK]

Specific Excess Power (Ps) is the measure of cough "E-Liabilty", and takes into account the complete picture, i.e aerodynamics power etc. The Fan plot in Il2 Compare provides a single Ps=0 line at 1000m for all types derived from turn times. From this you can determine each types Sustained G capability which is a function Ps. Fan plots were invented for this purpose.

We also know of the calculated Fan plot that the RAE produced for the 109E3 and Spitfire I at 12,000ft. Comparing the values will provide a comparative measure of Sustained turn performance ... or E under G/AOA. The chart gives the 109E 3 a sustained turn capability of 2.4G and the Spitfire MKI a sustained G of 3G.

A 0.6G sustained turn advantage is pretty significant

Neat On line implementation of Il2 Compare whose responsible for that ? V101_Tom or Ace of Aces ? ... be nice to see the fan plots in there as well.

[ACE-OF-ACES]

Originally Posted by IvanK

Neat On line implementation of Il2 Compare whose responsible for that ? V101_Tom or Ace of Aces ? ... be nice to see the fan plots in there as well.

This I..

See the link to the pdf in my previous post.. I have fan plots (aka DogHouse) and Ps charts and more.. I am slowly adding those each weekend that I get some time to work on it.. I actully have the fan plots done, but, I need to add the lables for the constant load factors and constant turn radius lines..

I have done all this before in MATLAB, but never before in a website app in C#, but it is not hard to do, just takes time. My goal is to have everthing that is in that pdf on my webpage.. AND MORE! For example, you can change the fuel loads in my version of IL-2Compare Online, which is something you could not do in the old executable version

[ACE-OF-ACES]

Originally Posted by fruitbat

Which does lead to the interesting question, how do 1C and other company's making flight sims actually model E-Liability numbers?

How do they derive these?

I have to agree with Captain Doggles.. I have never come across that term until today.. So I wouldn't even want to guess at what it means.. I can only assume it is a differnt way of saying specific excess power (Ps).. Which can be calculated from the avaliable IL-2Compare data..

See figure 20 in the following pdf link.

FLIGHT MODEL ANALYSIS OF THE HSFX 5.0b Bf-109G-10 1944

This is the kind of test reports I use to create, until I decided to make a website where people can select the plane they are interested in, at which piont it will calculate all these graphs on the fly (pun intended). I will be adding the Ps chart and others to my website in the following weeks to come

[ACE-OF-ACES]

Originally Posted by ACE-OF-ACES

In that it is something I am well aware of, and none of the standard WWII performance charts like TAS vs Altitude and ROC vs Altitude are depended on the E state. As a mater of fact the test methods are preformed such that E does not factor into the test.

Hmmm before someone jumps me on this.. Allow me to say this better than I said here

Originally Posted by ACE-OF-ACES

In that it is something I am well aware of, and none of the standard WWII performance charts like TAS vs Altitude and ROC vs Altitude are depended on the conversion of E. As a mater of fact the test methods are preformed such that conversion of E (i.e. alt to speed, or speed to alt) is not allowed. That is during a speed test altitude is held constant, thus the change in E is only due to the change in speed. Where as during a ROC test, the speed (climb speed) is held constant, thus the change in E is only due to the change in altitude

There that is more correct

[JtD]

Historical performance data for climb typically comes with a climb speed information. This climb speed hardly ever is constant. Often, TAS increases while IAS decreases. This has an effect on climb performance, and it is measurable. Il-2 compare does not take the planes acceleration into account, and the climb performance in Il-2 compare is a little bit higher than what is achievable in game or would be, even if perfectly modelled, with the real plane.