Wind, airspeed...

[Kameni]

First of all: Please try to script somehow that wind does not affect a plane that is in hangar.

I got a situation tonight where my plane turned and hit the wall before I have had a chance to start engines and get hydraulic pressure - thus leaving me no option to counter the wind.

 

Second: Is it realistic that plane reads out speed of 60kmph when it is standing still on runway just because the wind is very very strong (airspeed and stuff)?

Then, again, if you make a strong wind - it helps you take off more easily because SIM reads out speed that is enough to takeoff, while it is visually clear that I am moving at half speed - even thou' it's a side wind.

You have a problem with speed script. It would be nice to fix it so it works properly.

 

If needed, I will provide a video during weekend (it's 1.30 AM now and I am too tired to record/convert/upload).

[71st_Mastiff]

So its a feature, been that way since day one. it even rains inside the hangers.

[IvanK]

"Second: Is it realistic that plane reads out speed of 60kmph when it is standing still on runway just because the wind is very very strong (airspeed and stuff)?"

 

Yes since the Air Speed Indicator is reading AIRSPEED so wind is part of that.

[Weta43]

& if you take off into a headwind (or a crosswind with a headwind component) then it doesn't matter what your groundspeed is - it's ONLY your airspeed that matters.

 

Fly at 130mph into a 130mph headwind, and you'll have no groundspeed - or 260mph if you turn 180 degrees.

[Kameni]

"Second: Is it realistic that plane reads out speed of 60kmph when it is standing still on runway just because the wind is very very strong (airspeed and stuff)?"

 

Yes since the Air Speed Indicator is reading AIRSPEED so wind is part of that.

 

I realise that already, but IDK if it is countered in real life systems.

Would it happen in real life - is my question :) Because I realise that wind would "lie" to the airspeed indicators.

 

& if you take off into a headwind (or a crosswind with a headwind component) then it doesn't matter what your groundspeed is - it's ONLY your airspeed that matters.

 

Fly at 130mph into a 130mph headwind, and you'll have no groundspeed - or 260mph if you turn 180 degrees.

 

I know that, but it is a bit foolish to go on runway and have side wind HELP you take off faster. Somethin' isn't right. It is not 6 o clock wind.

Set your dynamic weather pressure difference to 10000 and try to take off in different headings. Set it to 10000 to have a full feeling of what I'm talking about.

[Kameni]

After all, the main part is Q1: Rescript hangars so it does not rain or blow inside of them. Please :)

[Ich666]

I know that, but it is a bit foolish to go on runway and have side wind HELP you take off faster. Somethin' isn't right. It is not 6 o clock wind.

Set your dynamic weather pressure difference to 10000 and try to take off in different headings. Set it to 10000 to have a full feeling of what I'm talking about.

 

6 o clock wind wouldnt help you take off faster, youd need more runway to gain enough airspeed to take off. Compared to that a sidewind would "help" you, in that you need less runway. However at 60 km/h crosswind you would probably be blown off the runway.

[Hardliner]

I just tested it again, it must be a bug. This is particularly obvious with strong wind and a fast moving carrier. Pretty lame for a "flight simulator" IMHO. This is obviously not just the result of an inaccurate approximation, it's a design mistake.

 

The problem disappears as soon I'm in the air. DCS's strange idea to use two completely different physical models for both air and ground is probably the main reason behind this mess.

[Kameni]

So, we might say it is officially badly designed...?

Anyone else to confirm?

[Kameni]

6 o clock wind wouldnt help you take off faster, youd need more runway to gain enough airspeed to take off. Compared to that a sidewind would "help" you, in that you need less runway.

 

Are you saying this as a real life fact, or a simulator fact, I missed that?

[71st_Mastiff]

Are you saying this as a real life fact, or a simulator fact, I missed that?

 

excuse me, tail wind does help your speed...

[GGTharos]

Not at takeoff.

[159th_Falcon]

Kameni, i'd recommend you study a bit on subjects like aerodynamics and relative speeds.

Cause from what i can read here you have no clue what your talking about.

Not trying to be rude, just trying to be honest. Anyway, let me try and explain about the how and why.

 

So, an airplane fly's because there is Air moving over its lift providing surfaces.

(usually wings)

Though, it DOES NOT matter if the plane is moving trough the air, or if the plane is standing still and the air moving over the wing.

 

The effect is the same, there is air flowing over the wings.

 

If the speed of said air flows fast enough over the wing, a pilot can climb.

(or take off if he is still on the ground).

 

Now, about the airspeed indicator.

This is a device that basically measures airpressure, this pressure gets then converted to a gauge that displays the pressure as speed.

Or to be more precise, it displays AIR speed.

 

So an airspeed indicator indicating an 10 knot headwind whit a plane standing still on the ground is completely realistic, and this happens in all planes in real life.

 

As for Side wind helping in take-off, it depends a bit on the airplane and the exact angle of the wind. 90 Degrees isn't going to help, but doesn't have to make it worse either. Depending on wind speed.

 

An 30 Degrees side wind will most definitely help in take off though.

 

Or better said, you can use a shorter runway because the ground speed upon take-off will be lower then without wind.

 

Finally, do NEVER look at your speed over the ground for anything related to flying the airplane.

It WILL get you in trouble.

(ground speed is important for navigation though).

 

In case you would like to know how i know all this.

I maintain helicopters for a living, have studied aircraft mechanics and systems, as well as aircraft aerodynamics.

At the moment i have about 5 years experience of helicopter maintenance.

 

 

Here's a site that explains (most off) the above WAY better then i ever could.

 

Dynamic Flight

Basic Aerodynamics

Relative Wind

[GGTharos]

Pretty lame for a 'test' or 'bug report' IMHO. What did you test? How did you test it? Where's the track?

 

I just tested it again, it must be a bug. This is particularly obvious with strong wind and a fast moving carrier. Pretty lame for a "flight simulator" IMHO. This is obviously not just the result of an inaccurate approximation, it's a design mistake.

 

The problem disappears as soon I'm in the air. DCS's strange idea to use two completely different physical models for both air and ground is probably the main reason behind this mess.

[Kameni]

 

So an airspeed indicator indicating an 10 knot headwind whit a plane standing still on the ground is completely realistic, and this happens in all planes in real life.

 

 

 

An 30 Degrees side wind will most definitely help in take off though.

 

 

All I asked is does instruments in RL react to air speed like in simulator.

I am not so clueless, even thou I don't know exact words to describe what I know and what I don't.

 

As for "30 deg. side wind" - thanks for being the only person to clarify to me that a non-90 deg. side wind does help for a "shorter" takeoff.

 

And - I did not get offended. Neither myself, neither anyone else can know everything. If I had a problem with my lack of knowledge, I wouldn't make a public question.

"Clueless" is a bit harsh word, and can be interpreted as you trying to mock at me, but it's ok, I realise you didn't have that intention and I am grateful for your help mate :)

 

Second: Is it realistic that plane reads out speed of 60kmph when it is standing still on runway just because the wind is very very strong (airspeed and stuff)?

As you see - I am not so clueless. Just needed confirmation to what I've come to conclude in brackets. And it helps to get clarification on the fact that headwind actually helps you take off in a shorter notice. Basically I was unsure more than clueless...

But I realise it's a bother to read previous posts, after all - we're all here when RealLife allows us to...

Edited April 25, 2013 by Kameni

[Kameni]

Pretty lame for a 'test' or 'bug report' IMHO. What did you test? How did you test it? Where's the track?

 

This is a friendly post, because it saddens me to see you answer like this to anyone, since I have so much hopes for DCS and on top of that I heard a lot of good things about you personally from simmers.

 

No matter who or why says that your product is "Lame" it is very wrong to get down to that level of anger an vocabulary and answer him in this manner. It is not what professionals do. If you were my worker, I would be worried about the public picture you just gave the rest of us. I realise you're making a point that he didn't give any proofs to his conclusion. But that could've been said like this:

"I would like you to upload the specific track for analysis, because we can not really react or check your claims based only on words. You probably understand that anything you see as a bug, whether if it is a bug or not, is just a tip of the iceberg of data that came to manifest in front of your eyes. So, for any serious answer from us, we need your track for detailed analysis. Thank you"

 

I understand the amount of pressure you people have to cope with, I do a "tight schedule job" as well, but this is not a way to talk to your customers who should (and in my case WANT) to give you money for your work.

 

P.S. I never uploaded track because after 159th_Falcon's explanation it was clear that there is no bug where I thought there was.

Edited April 25, 2013 by Kameni

[Weta43]

Not sure if you're re-asking this above, but

Second: Is it realistic that plane reads out speed of 60kmph when it is standing still on runway just because the wind is very very strong (airspeed and stuff)?

 

IAS - yes if you're facing into it, no if it's at 3 or 9 o'clock.

[Kameni]

Not sure if you're re-asking this above, but

Second: Is it realistic that plane reads out speed of 60kmph when it is standing still on runway just because the wind is very very strong (airspeed and stuff)?

 

IAS - yes if you're facing into it, no if it's at 3 or 9 o'clock.

 

Yes yes, but Falcon already explained, and you did in your previous post. :)

It's all clear. Thank you :)

[Yo-Yo]

It's much more interesting that even 90 deg wind can help. Just remember that the sum of two orthogonal vectors is longer than each of these two vectors. Moreover, as the dynamic pressure is proportional to V^2, one can see that for this case

Dynamic_Pressure_Total = Dynamic_Pressure_1 + Dynamic_Pressure_2,

 

where 1 means the pressure of the plane groundspeed and 2 means pressure of the wind.

 

Of course, due to the plane sideslip angle the lift coefficient reduces a little bit but overall lift will increase due to increased dynamic pressure.

 

Ok... and a question: headwind increases the time you fly from A to B. Tailwind decreases it.

What about sidewind? IAS presumed to be the same.

[Kameni]

What about sidewind? IAS presumed to be the same.

 

Depends on the actual angle, I presume - e.g. does it come from 8 or 10 o'clock is not the same. (or 2 and 4)

[Yo-Yo]

Depends on the actual angle, I presume - e.g. does it come from 8 or 10 o'clock is not the same. (or 2 and 4)

Exactly 90 degree.

[msalama]

excuse me, tail wind does help your speed...

 

Tailwind both increases your groundspeed and reduces your airspeed. And we don't want that when taking off, do we ;)

[159th_Falcon]

Exactly 90 degree.

It will actually increase your flight time due to side slip.

 

Simple example whit just random numbers.

 

Lets say your destination is on a HDG of 0 (north)

The wind comes from 09 (East)

 

Now you will have to fly a HDG of about 04 (north east)

to compensate for the side wind.

 

Because of this your effective ground speed towards a HDG of 0

will be less then your speed trough the air at a heading of 04.

 

no idea what the exact ratio's will be though, guess they will differ from plane to plane

[Kameni]

I love this guy :D