Flight Testing in CoD

[JG14_Jagr]

You really need to determine what resources you will have to actually measure the data.. using the GUI is not a good idea. Also, certain maps often create issues.. standardize the testng on a particular map..maybe one of the simple online maps...

[Viper2000]

I think that the first thing we need to do is to try to find standard day conditions.

There are quite a lot of possibilities available.

One option would be to use a relatively modern standard like the ISO standard atmosphere or the 1976 US standard atmosphere. This would facilitate compatibility with modern data. However, the ISO standard atmosphere is not directly available for free.

Alternatively, we could attempt to use older NACA standards; doing so would lend an historical flavour to our work, but might complicate comparison with more modern sources. A few possible standards may be found by following the links below. This list is not exhaustive.

1926 NACA standard
1930 simplification
1952 NACA/ICAO standard
1976 US Standard Atmosphere

I suggest that we use the 1976 standard for comparison purposes because this allows us to avoid some otherwise potentially nasty conversions (eg changes to Temperature scales over time...).

Obviously the next thing that we need to do is to find some way of measuring the atmosphere properties on a variety of available maps so that we can pick the best one for testing.

Does anybody have any suggestions as to how we might best go about this?

[TUCKIE_JG52]

Viper, that's a really nice effort, seriously focused... some time ago I was discussing in other forums about real charts of the planes, that were not corrected to the same atmosfere models...

I fly a Cessna 152 and from my early stages of training, I can see the big influence that ambient contitions have in performances like climb rate.

As ambient conditions I mean specially pressure and temperature. For example, before each takeoff I check the forecast for exact data and I get the exact calculation for the Pressure Altitude. If the pressure altitude of my airfield is below the real altitude of the field, that day the Cessna climbs a lot. It's the most common case in winter, with temperatures below ISA (15º) and sometimes pressures over ISA (1013Mb).

The inverse case is a higher pressure altitude when ambient is very hot and low pressures are registered... to the point that if pressure altitude is a lot higher than real altitude of the airfield, it can be a factor that can lead to an accident.

I see that your initial point of view takes this into account, so I'll follow your results with very interest.

I would collaborate with you if I were not so busy with video editing...

[TheGrunch]

We have ambient temperature gauges in the Ju 88 and He 111 if this helps. Likewise, if we can work out exactly the altitude at an airfield (FMB maybe?) and compare it to the altitude given by the aircraft's gauges we may be able to work out pressures.

[TheGrunch]

The biggest problem really at the moment is the lack of a DeviceLink style interface yet and the inaccuracy of the rollover text on cockpit gauges (seems to be 1 decimal place, not very useful when altitudes are measure in km for example). Although I haven't even looked at the no-cockpit view so that might be better.

[TUCKIE_JG52]

Any data on this subject?

I've been focusing in Bf-109E-3 tests.

By landing beside a beach and setting the altimeter to 0, the indicated pressure in all maps is 993 mbar.

Ambient temperature is about 17ºC, but I must confirm with Ju-88 and He-111 instruments.



I've also looking for which are the german standards, named "Normaltag" ("Normal Day"):
I'm not sure about the data they considerred standard, but it looks like 1018mbar and 16ºC.

In this test there's a correction factor developed, but I can't undestarnd what every value really means:
http://www.kurfurst.org/Performance_...5a.html#blatt5

If that correction factor is correct, it would mean that with the current pressure and temperature settings for all maps in CoD, we'll never be able to reach the german values of the performance charts like climbing. Even more if it's considered that, as commented in this post, Bf-109 has an overloading problem:
http://forum.1cpublishing.eu/showthread.php?t=20160

Overloaded E-3 + not so favorable meteorological contitions = our graphs will look always under the german values.

We need to apply correction factors to really evaluate if CoD E-3's performances are correct or not.

[Viper2000]

Originally Posted by TUCKIE_JG52

Overloaded E-3 + not so favorable meteorological contitions = our graphs will look always under the german values.

We need to apply correction factors to really evaluate if CoD E-3's performances are correct or not.

Exactly.

I think that we should probably correct all of our performance references to ISO standard atmosphere conditions to produce an overall aircraft performance database, and then convert performance data from that database to whatever the conditions on our chosen test map are.

BTW, formation flying is the most obvious way to overcome the 1 d.p. limitations of the cockpit instruments, at least to some degree...

[heloguy]

Originally Posted by Viper2000

I suggest that we use the 1976 standard for comparison purposes because this allows us to avoid some otherwise potentially nasty conversions (eg changes to Temperature scales over time...).

Obviously the next thing that we need to do is to find some way of measuring the atmosphere properties on a variety of available maps so that we can pick the best one for testing.

Does anybody have any suggestions as to how we might best go about this?

I would think that the 1976 standard day wouldn't be the best choice as that's not what testing data from the 30's and 40's was based on. Maybe the earlier two would be the best to use.

As far as ambient conditions, either use the gauges in game and hope they are calibrated correctly, or just e-mail the developers to find out what the stock standard atmospheric conditions are.

If there's a way to adjust atmospheric conditions in the FMB (I would look, but will not have my computer with COD for awhile as I'm in the States), then you could create a mission in the FMB that all testers would be compelled to use that are a part of this project.

Really, the best historical data (if it exists) would be that which has variable test data, such as a curve that represents the difference in performance compared to altitude and temperature on the graph axes in order to adjust for density altitude. If this sim has variable weather as it says, then it will be hard to see if the aircraft performs correctly over a range of temps and pressures if it's only tested on a standard day.

[Viper2000]

Originally Posted by Osprey

I don't know if this ever started or how serious Viper is but I am willing to help with the testing but ONLY if there is some assurance from the development team that it is being taken seriously.

From what I am seeing wider Europe is undertaking a Public Beta test which is adhoc and incredibly disorganised.

So, if we are given genuine co-operation from Luthier & friends, and that we supply genuine reliable information to them to use, then I'm signed up.

I haven't started any work on this yet because, as you point out, we're effectively in a public beta at the moment, and with major code changes taking place so regularly the chances are that a lot of the work we put in would be wasted.

I've also got a PhD to finish.

Originally Posted by heloguy

I would think that the 1976 standard day wouldn't be the best choice as that's not what testing data from the 30's and 40's was based on. Maybe the earlier two would be the best to use.

As far as ambient conditions, either use the gauges in game and hope they are calibrated correctly, or just e-mail the developers to find out what the stock standard atmospheric conditions are.

If there's a way to adjust atmospheric conditions in the FMB (I would look, but will not have my computer with COD for awhile as I'm in the States), then you could create a mission in the FMB that all testers would be compelled to use that are a part of this project.

Really, the best historical data (if it exists) would be that which has variable test data, such as a curve that represents the difference in performance compared to altitude and temperature on the graph axes in order to adjust for density altitude. If this sim has variable weather as it says, then it will be hard to see if the aircraft performs correctly over a range of temps and pressures if it's only tested on a standard day.

Using a 1930s or 1940s atmosphere standard is likely to cause confusion, because all sorts of things were different in those days (eg the definition of the Kelvin).

It's also inherently more likely to produce flame wars because if we pick a NACA atmosphere then people will see American aeroplanes with data which looks like primary source data and potentially German or British aeroplanes with corrected data which disagrees with primary sources. We would then find ourselves having to explain the concept of standard atmospheres and correction factors in the face of vociferous accusations of bias from the large population of trolls that inhabit the forum.

Whatever we do, we're going to end up picking a single standard atmosphere so that we can compare the performance of all the aeroplanes in the sim on the same chart. Apart from anything else, if we don't do this, the chances are the somebody else will do so in a biased way with the intention of forwarding their own agenda, since quite a lot of forum trolls seem more interested in being able to say "my aeroplane is better than yours" than in historical accuracy.

Ideally, I'd use the ISO standard atmosphere, because it's neutral and current. However, I don't think that it's freely available, and that would both interfere with testing and lead to accusations that the process was not transparent.

The 1976 US standard atmosphere is freely available on the internet, and avoids most of the risk of accusations of bias it's post-war*, and it is relatively modern (so we get basically modern SI units, though it uses its own private value of the gas constant, presumably for historical reasons).

*Therefore all of the aeroplanes we test will see correction factors.

[CaptainDoggles]

I've got some of my old university textbooks still, one of them has a standard atmosphere in the appendix; I'll check to see which version it is. The textbook is relatively new so it ought to be a modern ISO atmosphere.