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View Full Version : The BoB Flight model - humidity ahd air temperatures. URGENT!



Cap.Solaro
08-27-2006, 08:53 AM
Dear Oleg!
We know that You and Your team are developing real Weather for Battle of Britain.
We all know that the humidity is high presence of water in to the air. So the fluid (the air) is becoming more dense and heavy - the aircraft should have to suffer more air drag and to have increased lift power. About air temperatures - the effect is similar - the hot and rarefied air in to the Desert (hot as 50 degrees of Celsius), will create less lift power compared with the cold and dense air in Norway in to the Winter season.
So be fear with us and create dependency between the humidity, and air temperatures and lift power of the aircraft - it is very simple for genius like You!

All I mean is:
Hot day: Less air drag and less lift power of the wings;
Rainy and foggy day: More air drag and more lift power of the wings;

Best regards
Cap.Solaro

Good friend since 2000!

Cap.Solaro
08-27-2006, 08:53 AM
Dear Oleg!
We know that You and Your team are developing real Weather for Battle of Britain.
We all know that the humidity is high presence of water in to the air. So the fluid (the air) is becoming more dense and heavy - the aircraft should have to suffer more air drag and to have increased lift power. About air temperatures - the effect is similar - the hot and rarefied air in to the Desert (hot as 50 degrees of Celsius), will create less lift power compared with the cold and dense air in Norway in to the Winter season.
So be fear with us and create dependency between the humidity, and air temperatures and lift power of the aircraft - it is very simple for genius like You!

All I mean is:
Hot day: Less air drag and less lift power of the wings;
Rainy and foggy day: More air drag and more lift power of the wings;

Best regards
Cap.Solaro

Good friend since 2000!

FritzGryphon
08-27-2006, 01:41 PM
I don't know about humidity, but temperature has affected performance since IL-2.

In the original IL-2, it was even more pronounced, with aircraft being significantly more manueverable on winter maps. Since then, the difference has been reduced (probably was unrealistic).

If you compare between a desert map at noon, and a winter map at 7AM, you should be able to see it well.

VW-IceFire
08-27-2006, 04:07 PM
I believe most of this is already modeled...at least to a certain extent. You can bet that the detail on this modeling will go up. Oleg seems to be no stranger to aeronautics...I wouldn't worry about it.

WWMaxGunz
08-29-2006, 03:50 AM
It is modelled. The only map with standard atmosphere conditions is Crimea.
You should see more lift and better thrust from prop in cool to cold air which is denser.

Blackjack174
08-31-2006, 08:02 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Cap.Solaro:
the aircraft should have to suffer more air drag and to have increased lift power. </div></BLOCKQUOTE>
I dont know about the drag , but the lift is there, when flying over the coastline from land or simply crossing a river you can notice that the nose rises when you are flying trimmed and without much pilot input.
I think its greatly simplified so that any body of water creates the same lift, dont know how thats in real life.
The surpluss of lift should result in more drag also in il2, if its close to real , no idea http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif

NonWonderDog
08-31-2006, 08:05 AM
In real life there are noticable differences flying over fields, parking lots,and under cumulus clouds. The air under cumulus clouds also tends to be rather turbulent.

Word is that this kind of thing will be in BoB. No one really knows, though.

carguy_
09-01-2006, 07:40 AM
Yes,they are modelled.We have turbulence in bad weather when clouds are low and in the clouds when flying through.

GH_Klingstroem
09-01-2006, 08:01 AM
Just to clearify! Increased humidity in the air will DECREASE performance! The air is getting less dense with and increase of water in the atmosphere not the other way around as the orig. poster wrote!!! The reason is that there are water molecules in the air instead of air molecules and water molecules will not contribute to lift! Only air will!!

Pls check data before posting Capt. Solaro!!

WWMaxGunz
09-01-2006, 08:10 AM
I'd like to see a reference on that.

EDCF_Rama
09-01-2006, 09:04 AM
Klingstroem is right... but the reason he gives is wrong...
Water molecules DO contribute to lift (of course...) like every other molecule would....
But since their weight is less than the molecules they replace (N2 or O2), the air density decrease and so the lift.

That's of course supposing within same air temperature (and overall same condition of altitude/barométric pressure).

NonWonderDog
09-01-2006, 09:28 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by carguy_:
Yes,they are modelled.We have turbulence in bad weather when clouds are low and in the clouds when flying through. </div></BLOCKQUOTE>

No, they're really not. Underneath a fair-weather cumulus cloud is bumpy in real life. It can be the nicest day imagninable, with big white puffy clouds in the sky, and it will be bumpy under those clouds. The worst is always about noonish.

The current turbulence, while the frequency of the bumps has gotten a bit better, is still an on/off switch. There should be little tugs back and forth, up and down all the time when you're flying under the clouds. Now the plane just kind of shakes whenever you're between 750 and 1500 feet and the weather is bad.

I still enjoy IL-2, but don't delude yourself into thinking that the turbulence is realistic. What I've seen of the plan for BoB looks to be much better.

Cap.Solaro
09-02-2006, 04:57 AM
I am right! The air with high presence of water in it will create more lift power!
As much denser and heavy is the fluid, as much is the lift power which he creates - for example look at the boats and ships with underwater wings - the wings have same air wing profile - just like the aircraft, but with less wing area (of the underwater wing), thay lift up more weight (the body of the ship) above the water. That is because the fluid - the water is more dense than the air. It is very simple!

EDCF_Rama
09-02-2006, 05:45 AM
No you're wrong.

Air water (water vapor) is less dense than Air at same temperature and pressure.
When you compare the molecules, it's an evidence (H2O weight is less than N2 or O2)

In order to give you a reference, I did a quick google search with words "Air water density"
First link of the list is
There (http://www.usatoday.com/weather/wdensity.htm)
Go to the chapter "Humidity and air density" and you'll get a much better explanation.

Everybody flying in real know this.

You are confusing water and water vapor

WWMaxGunz
09-02-2006, 06:25 AM
Yes humid air at the same temperature and pressure is less dense.
It's why water vapor rises until the air won't support it and it falls out to form clouds.
Water vapor is funny stuff anywhere near state change which is common in the atmosphere
up to certain heights.

Down low where you have liquid water giving up vapor you also have air that is cooling.
Might be lower density than same temperature dry air but it's denser than hotter air and
that is likely what people experience, I know I have.

When water vapor drops out of air it gives heat back to the air as well. A good deal of
heat for such a 'light' molecule. Enough to power storms including hurricanes. Water
vapor in air really is a funny thing. It's very conditional.

Thanks for the reference, btw.

EDCF_Rama
09-02-2006, 06:57 AM
I totally agree that cool air is denser than hot air and that variation of density due to temperature is(for a given altitude) more important than for other causes... I was just answering for humidity effect.

Cap.Solaro
09-02-2006, 03:33 PM
Hmmmmm...Do You think, that 1 cubic meter of dry air is heavyer than 1 cubic meter of air with high presence of water in it? I do not thing so...but...I am not sure...any other opinions!? I think: more heavy fluid - more lift power. Are You agree?

WWMaxGunz
09-02-2006, 03:48 PM
Solaro, as long as the water is purely vapor and not droplets then, and be sure of this,
at same temperature and same pressure the dry air is heavier. It is just that the wet
air we know mostly is usually cooler.

Water is funny stuff because it is a dipole molecule.

Cap.Solaro
09-03-2006, 01:07 AM
WWMaxGunz, may be becose as You say, the vaporised water mixed with air is lighter than the dry air, thats why the clouds fly and do not fall down. The clouds just float in to the sky becose they are lighter than the surrounding dry air. Defenitely there is difference between water and air mixed with vaporised water (as fluids).

WWMaxGunz
09-03-2006, 11:33 AM
The clouds you can see are droplets and are denser than air but supported by updrafts.
Water vapor is transparent to all light you can see. When vapor is losing energy to become
liquid it is also losing a lot of heat. The final bit of heat is when the bits bond to each
other and the energy state is lower, and that's a very real step in heat. It is the same step
as going from liquid water to water vapor, the heat of fusion of water and the real energy
that makes steam power so strong. What I say, water is funny stuff.

erco415
09-03-2006, 02:45 PM
For sure, an increase in humidity results in a decrease in aircraft performance. However, humidity has less of an effect on performance than temperature or altitude. Thus, every RL aircraft pilot's operating handbook that I've ever seen gives performance charts referencing temperature and altitude and no mention of humidity.
erco

Cap.Solaro
09-03-2006, 03:56 PM
OK! Thanks to all. I am not competent to argue further.It seems that only air temperature realy matters. But what do you thing finaly:
Does the humidity decrease or increase at all the aircraft performance - thus way it should have to afect the aircraft propeler performance too?

Skoshi Tiger
09-04-2006, 03:13 AM
I've had to wait until I've got home and to me reference books before I could post this one.

Aviation/Aerospace Fundimentals(Sanderson 1978)
"In computing density altitude, the small effect of humidity is usually disregarded, therefore, temperature and barometic pressure are the two variables considered in most aircraft performance computations."

Also I went through my instruction book for my Kane Dead Reconing Computer and it didn't have any reference to humidity either.

Also if I remebered the two years I spent in England I couldn't remember any day when it wasn't 100% humidity and either drizzling, raining, snowing sleeting or foggy, then again I was staying in Denley Moor!

If Humidity has such a little effect to calculating density altituded ( and its effect on aircraft performance) I'ld hope the developers spend their time on modling the jamming Hispano cannons for a MK1B Spitfire instead.

Then I could pretend I'm George "Grumpy" Unwin

Skoshi Tiger
09-04-2006, 03:20 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
Does the humidity decrease or increase at all the aircraft performance - thus way it should have to afect the aircraft propeler performance too? </div></BLOCKQUOTE>

High Humidity = decreased air density
Low Humidity = increased air density

So if your flying in high humidity your aircraft will perform as if it is at a slightly higher altitude.

Of course if it's actually raining all, that water being sucked into you air intake will act as if you've got water injection so you should be able to fly flat out with less detonation in the engine! http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

WWMaxGunz
09-04-2006, 09:47 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Cap.Solaro:
It seems that only air temperature realy matters. </div></BLOCKQUOTE>

Temperature, Density and to a small degree Humidity.

At that link on page one there is a link at the bottom to AOPA (Aircraft Owners and Pilots
Association) site that has a further link to El Paso something-or-other-about-flying Density
Altitude Calculator that does factor in the Dew point for that extra bit.

IMO the times humidity can getcha is very hot low alt places with really high humidity.
A lot of B-26's crashed in Florida for instance. Maybe some of the margin was humidity error
in computing stall speed taking off and esp landing.

Skoshi Tiger
09-04-2006, 06:38 PM
One point of interest is that the Altimeter only measures pressure height anyway (not actual altitude), so as long as a humidity reading was placed in the preflight information, you could work out the density altitude yourself.

I think that the important thing is that all the planes in the game will still be on a level playing field and no one would be getting any real advantage, except at the extreme limits of the aircraft altitude where 500 or so feet difference in altitude would make a difference!

Then we will need our MkVII Spitfires to catch those pesky high altitude recon planes anyway!(After hour long chases!)

The effects of humidity in the atmosphere would effect all planes in roughly the same way (give or take a fraction of a percent in advantage to a particular airplane in speed due to increased drag etc).

It would be bad if a mission builder could engineer the climate to advantage or disadvantage certain aircraft.

"A lot of B-26's crashed in Florida for instance. Maybe some of the margin was humidity error in computing stall speed taking off and esp landing."

Hey they didn't call it the "widowmaker" for nothing! But if take away all the takeoff and landing accidents then it had one of the lowest loss records of any combat aircaft in WWII. (or so I've read!)

Jambock_Dolfo
09-05-2006, 07:44 AM
Air density is what you guys are really after.
Altitude, humidity and temperature are just factors influencing density.
Please do not get things mixed up.

-dolfo

Skoshi Tiger
09-05-2006, 06:39 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Jambock_Dolfo:
Air density is what you guys are really after.
Altitude, humidity and temperature are just factors influencing density.
Please do not get things mixed up.

-dolfo </div></BLOCKQUOTE>

Good point! I think the discussion here is based on the least significant of those factors http://forums.ubi.com/groupee_common/emoticons/icon_rolleyes.gif

....but thats just the kind of guy's we are! http://forums.ubi.com/groupee_common/emoticons/icon_cool.gif

BfHeFwMe
09-05-2006, 08:17 PM
The only aircraft performance chart you'll ever find, that has anything to do with humidity, is the amount of water standing on a runways effects on braking. So slight it's a non-factor on air performance. Now temperatures and thermals are another story.

WWMaxGunz
09-05-2006, 10:43 PM
thermometer .... check
barometer ...... check
dewpoint sling . check

density guage .. ?
density guage .. ?
DENSITY GUAGE! . ?

Okay, who forgot to pack the air density guage?

Jambock_Dolfo
09-05-2006, 10:54 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by WWMaxGunz:
thermometer .... check
barometer ...... check
dewpoint sling . check

density guage .. ?
density guage .. ?
DENSITY GUAGE! . ?

Okay, who forgot to pack the air density guage? </div></BLOCKQUOTE>

Engineers who calculate performance work the density stuff.
Pilots use temperature and altitude information on performance tables. Because those are the variables avaliable that influence density.

An airfoil doesnt care about the temperature of the air flowing over it. It cares about the quantity of air molecules. That means density.
Of course temperature makes a great deal of influence on density. So does altitude. Humidity (water vapour) can only account for 4% of volume on a given air mass. And, as mentioned beore, you will find no data nor table regarding humid air for flight planning criteria. You will find takeoff performance tables for wet or contamminated runways. Also charts for landing on wet or slippery runways.
As I said before, please do not mix things up.

-dolfo

Cap.Solaro
09-06-2006, 12:56 AM
You are right Jambock_Dolfo - all we are talking about is air density - volume of molecules. Diferent weather conditions = Diferent fluid = diferent performance! It must be established some benchmark after the reach of which the performance must be affected in some degree - I think.

Cap.Solaro

WWMaxGunz
09-06-2006, 12:37 PM
I'm not mixing things up or playing at confusing anything.
No simple chart will cover the 3 variables and while the difference is slight it is real.

Engineers figure out air density from the variables to the accuracy they want.
If you don't have a direct guage then that's what you do and I've never heard of one.

It's nice to know that air density is the end point consideration but PILOTS don't get
air density reports.

From the AOPA site; A handy way to find a more precise density altitude is to go to the
weather calculator on the El Paso National Weather Service official Web site.

NOAA Density Altitude Calculator (http://www.srh.noaa.gov/elp/wxcalc/densityaltitude.shtml)

Sorry if this confuses anyone but if it does then they shouldn't be piloting.

Jambock_Dolfo
09-06-2006, 01:26 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Cap.Solaro:
It must be established some benchmark after the reach of which the performance must be affected in some degree - I think.

Cap.Solaro </div></BLOCKQUOTE>

The benchmark already exists, it is the International Standard Atmosphere (ISA)

As for confusing and mixing things, the mention of lack of an air density gauge can be misleading maybe. As if in "oh I dont have a densitometer so density does nothing for me" I believe this is not what you meant though. Agreed, density is not operational information used in the flight deck. Altitude and temperature are. But they are the readily avaliable and translate to density, which is what the wing cares about.
And I do not stay repeating myself to create confusion or fight, just do it because I understood the original posters idea was to have all things factored in on the game engine for performance, NOT for flight planning criteria.
And no, pilots do not get air density reports. But they get alt, temp and pressure and such. That is enough. Simmilarly, most airplanes do not have an angle of attack (AOA) indicator. But they have airspeed indicators. So pilots fly airspeed on basic airplanes (think Piper cub or Cessna Skyhawk, not Learjet or some military ride). Even on big jets we fly airspeed. Some jets have a flight path vector, from which AOA may be derived, but it is not operational to do so.

So, basically, pilots do use altitude, temperature and pressure on their performance planning. But to a physics engine, that translates to density.

Skoshi Tiger
09-06-2006, 06:40 PM
This is the reason why, as a pilot, you calculate density altitude.

This is in fact workingout what altitude you would be at in ISA conditions given the pressure that is recorded around your aircraft.

(Please correct me if i've got muddled up!)

The altimeter is a barometer, it measures the static air pressure around your aircarft.

You set the altimeter to the QNH (which is the Area Sea Level Pressure) where your flying.

This adjusts the altitude to take into account the difference between the QNH and the ISA Seal Level Pressure (approx 1013mb) and gives you your Pressure Altitude.

Because the temperature my vary from ISA standard temperature (approx13C) you need to adjust the pressure altitude to factor in the difference from the ISA temp.

This give you your Density Altitude, which you can use to help you calculate takeoff and landing distances, fuel consumption and other things.

Clear as Mud!

Jambock_Dolfo
09-06-2006, 08:15 PM
Well, sort of...

By definition, pressure altitude is the reading when the altimeter is set to QNE (1013hPa or 29.92inHg).
Density altitude is important, of course, and it can be calculated for the temperature and altitude (by the way ISA is 15‚?C).
What we do in big jets is work a takeof performance chart or table. We have info on field elevation and temperature. This gives us a limit. Then correct for runway slope, wind and QNH. There are different charts to be used when the runway is wet or contaminated. There are also corrections to be made for airplane configurations of course.

On light airplanes (or the ones that do not have a specific performance volume for takeoff - airport planning chart and such) it is useful to determine the density altitude.

There is a story about two young officers on a T-33 on an airbase in my home town, in th e mid70's. The guys planned a ferry flight to some place distant, thus loaded the plane with plenty of fuel. Their takeoff was scheduled for the evening or night but, due to a technical problem it was delayed to the next day. So, they took off at high noon, having their brilliant flying carreer suddenly interrupted by a water tower close to the end of the runway and became a fireball.
In short the temperature was much higher than they had planned for, and the density altitude was much higher than their envelope allowed.

Whew, I believe I write too much nonsense... serves me well for not getting anything better to do on my days off. http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

-dolfo

Cap.Solaro
09-07-2006, 03:21 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">There is a story about two young officers on a T-33 on an airbase in my home town, in th e mid70's. The guys planned a ferry flight to some place distant, thus loaded the plane with plenty of fuel. Their takeoff was scheduled for the evening or night but, due to a technical problem it was delayed to the next day. So, they took off at high noon, having their brilliant flying carreer suddenly interrupted by a water tower close to the end of the runway and became a fireball.
In short the temperature was much higher than they had planned for, and the density altitude was much higher than their envelope allowed. </div></BLOCKQUOTE>

Clear evidence about air density importance...