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#1
04-04-2011, 10:01 PM
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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? 
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#2
04-06-2011, 04:18 PM
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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...
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#3
04-07-2011, 02:52 PM
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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.
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#4
04-07-2011, 08:10 PM
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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.
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#5
04-28-2011, 01:24 PM
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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. Last edited by TUCKIE_JG52; 04-28-2011 at 01:26 PM.
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#6
04-28-2011, 06:01 PM
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Quote:
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...
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#7
04-28-2011, 06:27 PM
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definitely a good effort, but let me just say one thing..
we need to know exactly what parametres are needed in order to provide usable data and not waste any time. It would be worth to try and talk to Luthier about this, so maybe we could be directed in the right way.. Viper has a factual approach to things that is quite the right way to go, but before you jump in this head first try and seek for some support from the guys at Maddox Games.
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#8
04-29-2011, 08:23 AM
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Quote:
 Yesterday I did pressure and temperature measurements. And got some conclusions that must be cross-checked. Pressure measuring method: 1. Place a Ju-88 in a beach (Sea Level). 2. Set altimeter to 0. 3. Read pressure in milibars directly from the Kollsman window, in the upper side of the german altimeter. Temperature measuring method: 1. Place a Ju-88 where you want to test the plane. 2. Read outisde temperature indicator Facts found: A) I get different values of pressure and temperature in the same place every time I reload the mission. Sometimes they'll repeat, but they tend to change more when a different plane is loaded in the same place. ---> Temperature and pressure are not always the same, there's some grade of randomisation. (This must be confirmed). B) Ambient temperature is different from water and oil temperature before starting engine. Clues to test: -There's the possibility to switch from the cockpit of one plane to another, at least altimeters can be cross cheched in that way; same mission load, planes placed together on a beach, check if all altimeters have the same pressure reading in Kollsman when altimeter set to 0. --> If same readings oK, reload the mission to test randomisation of parameters.
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#9
05-27-2011, 02:28 PM
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Quote:
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.
__________________
Asus PZ877-V Intel i3770k Nvidia GTX 980 8gb RAM Windows 10 x64
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#10
05-27-2011, 05:13 PM
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Quote:
I've also got a PhD to finish. Quote:
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.
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