I was just doing some research and realized that Mudspike does not have a thread were purely sim pilots can ask real pilots questions about real aviation, in order to make the sim experience more realistic. Make sense?
So let me kick it off:
In DCS, when setting winds manually, it gives you 4 altitude options (currently I’ve got the Imperial units set so I shall no doubt incur the wrath of @schurem); 33ft, 1600 ft, 6600 ft and 26000 ft.
First, are those altitudes special in some way?
Second, In general terms how much greater should one set the 6600 ft and 26000 ft winds? (Obviously if you are modeling a T-Storm it’s different.)
Example: Scattered clouds up at 12,0000 ft. Light winds on the ground - 4 Kts at 33 ft and the automatically set 8 Kts at 1600 ft.
Just keep doubling it? 16 Kts and 32 Kts respectively? Or is there another rule of thumb?
In general, wind speed is affected by the friction layer. The closer the air mass is to the planet, the slower it will be. So, again, in general, wind speed increases with altitude.
As speed increases so will the wind direction turn to the right, in relation to it’s direction, due to the corriolis effect. (To the left in the lower hemisphere).
That’s the theory.
In reality the wind closest to the planet will be mostly affected by terrain.
Wind can increase with altitude only to decrease again when you proceed higher, due to jetstreams and local pressure varitions, humidity and temperature. Just as temperature drops with altitude, you can encounter a temperature inversion where the temp is increasing with altitude, for a while.
Best advice I can give you is to use windy.com and play around with the altitude slider. This will give you some plausible data at least.
Back with FSX and the Jeppesen live (every 15min) weather - you could before flying see data was being loaded in and get an idea for how things go in different situations by using your own location and comparing to the outside.
Can be pretty drastic too - like no wind at surface while a front blows in (and I don’t live around and appreciable terrain blocks).
If we say it with enough authority…it might be true (even if it is not…)
Not really…in fact, for a combat flight sim where the planes can reach up into the 40,000+ flight levels, I’d argue that they would be better off with SL, 10K, 25K, and 40K. The biggest “delta” or change occurs rapidly between ground level winds and about the mid 20s. Above that it is a more gradual change unless you are getting into a jet stream (which can boost you anywhere from 50 to 150 knots!).
In general…in the winter…the most wind we’d see on the east coast of the US is around 120-140 knots at FL350-FL430. Typically out of the southwest because the jetstream tends to dip pretty far south in the winter. In the summer, it moves up and those winds go to higher latitudes. Thus, in the summer, we can sometimes get a little bit farther a little bit faster (shut up @PaulRix) in our planes in the summer (err…but then you have to fly from Nashville to Louisiana to get around the thunderstorms…so there’s that…).
What does all this have to do with DCS World? No idea…because I have no idea what the weather patterns over there are (Caucasus, Persian Gulf, etc…). I honestly never even looked at what the wind levels you can set are in DCS World…it is interesting that they chose 33, 1600, 6600 and 26000…or well, interesting in that I’m not sure exactly why they chose them. They might coincide with millibar altitudes that would be commonly sourced for winds aloft…but I’m not to confident in that.
And the winds can be totally different directions aloft than they are on the ground…so even though you might have a 15 or 20 mph wind coming out of the north on the ground, you can reach a shear level that has that switch around and you are going the other way at 30 or 40mph. Between these levels is usually some fun turbulence…and it wreaks havoc with controllers that are trying to figure out vectors for spacing arrivals (@jross can speak to this)…
Your idea of doubling is not a bad idea depending on your starting value at the ground though. 10 20 40 80 seems reasonable for those altitudes, but 20 40 80 160 might not.
All that typing and no answer. I amaze even myself sometimes.
@boomerang10 - if you are in last place on the Greenie Board do you have to like buy the squadron dinner or something at the next port call? Not because I’m awful at Case I recoveries or anything…I’m asking for…uh…a friend. Yeah.
Thanks all. To sum things up I think you all said, “lt depends…”
Which is often the answer. That said the details you provided are, I think, the key to selecting reasonable wind speeds at various altitudes.
One of the reasons I’ve returned to the simple WX from the more dynamic and seemly realistic system in DCS, is carrier ops. Carriers turn into the wind; specifically turn to get the relative wind down the angle for landings. When setting up a mission, depending on its length, a carrier may move into a crosswind situation by the time the planes come back to land. That would be unrealistic. So the “fixed wind” across the map is better.
Hopefully this will be a good thread to answer these RL pilot questions.
Where you will be met with such a wide range of sometimes conflicting answers you will probably be convinced that none of us really know what we are talking about. And in my case, you’d be correct. My favorite podcast is the Skeptic’s Guide to the Universe (SGU). A few months back they had a segment on what really makes a wing fly. And the answer is: nobody really knows! Bernoulli can only explain part of it. Deflection can only explain part of it. Downwash can only explain part of it. The two air molecules separated by the leading edge and racing each other to the back explains none of it because it’s total BS. Add them all up and you get nothing close to the up vector needed to support the works. So the truth is that despite years of teaching students what makes a wing fly, I never really knew and still don’t.
Neither do you probably. But the wing still flies!
Dude, I spent most of my career working with Naval Aviators. I knew that when I started this thread. My only question I had for the administrators was whether the servers had enough memory to handle the egos involved.
This is why a helicopter pilot is so different a being from an airplane pilot, and why in general, airplane pilots are open, clear-eyed, buoyant extroverts, and helicopter pilots are brooders, introspective anticipators of trouble. They know if anything bad has not happened, it is about to.
One of my instructors was an old H-2 bubba. I’ve always thought the Seasprite was a cool bird, so I asked him what it was like to fly. His face instantly went kinda dark and he said in a low, slow voice,
I used to teach priciples of flight at a flightschool too.
Let’s just say that there’s a big difference between what pilots and engineers are tought.
The easiest explanation of why an aircraft can stay in the air is Newton.
If something has mass, it’s pulled by gravity.
If you want to counteract gravity you must apply an equal force opposite gravity.
That force comes from accelerating mass. Airmass.
So we know that the aircraft must accelerate air downwards, for it to stay above the planet.
The wing does that, but how?
A lot of the things we take for granted is actually theories. Newton had his theory on gravity. Einstein had another. Some theories are more or less proven and can be presented in more or less accurate equations.
As a lot of equations in physics are only valid for certain conditions, there isn’t just a single one that can explain lift. One may be valid for laminar flow but not turbulent. Another is only valid for ideal fluids, which air isn’t. Etc.
Sure, you have the lift formula.
Lift=1/2 air density x speed squared x surface area x coefficient of lift.
Which is like saying that Lift equals the kinetic energy of the airmass times the size of the wing times…something we only can explain so much.
The infamous Coefficient of Lift, CL, bundles the shape of the airfoil, the angle of the relative wind and everything else that we don’t know.
But we can test CL, to a certain degree, in windtunnels and today we have fancy computers that can do the job of the tunnel. But we still can’t calculate Lift with a 100% certainty.
But lift can be approximated, for certain conditions, with great accuracy.
And as computers and coders get better and smarter, new science is added and the approximations get more and more accurate.
So no, nobody has been able to present a 100% accurate equation that will tell you why we can fly. But they are close enough that we can build aircraft.
And we know enough to teach pilots about how their flying affects the aircrafts ability to stay above the planet…
Not sure I agree here… Just because we cannot resolve all single molecules in a flow in a calculation/simulation due to computational limits doesn’t mean that it’s somehow magic… Unless you want to go into fundamental particle physics and explain the origin of matter in the universe of course. But complicated stuff like the energy cascade of turbulence, dissipation, compressibility and so om and so forth is well understood. The whole problem with fluid dynamics is that the equations that describe flow not molecule for molecule but “on average” (Navier-Stokes) do not have a unique analytical solution and so we contend ourselves with assumptions and closure laws to make use of these equations. But in principe that’s the engineers approach w.r.t. the physists approach; we engineers don’t need the exact answer to make stuff that utilizes these principles laid out by mother nature. That doesn’t mean we are not aware of them
Extreme example: some of the pioneers of flight (you might even say all of them) had a poor understanding of what the heck was going on. They still built wings that worked, by looking at birds’ wings or just trying shapes that looked cool.