How do you properly measure a plane's flight characteristics?

[SpaydCBR]

Hello all.

 

I am new to flight sims and I'm loving BoS so far just practicing taking off, flying around and landing. Maybe a dogfight every now and then. (Taking it slow ).

 

I want to compare the planes' flight characteristics so that I can better understand how to fly them (and how to fight them). Simply flying them I don't feel too much of a difference between any of the planes, so I was wondering if there was some standard way to measure all of a plane's flight characteristics properly, to do a side by side comparison on paper. (Speed, climb rate, dive rate, turn time, roll rate, etc.)

 

Also, if there's any advanced flight behavior that I should know about.

 

I'd appreciate any help.

 

Thanks

[busdriver]

FWIW, when you're flying in the "middle" of the flight envelope (not at the margins/extremes) you probably won't notice any differences. Sitting at a constant 1 G in front of a monitor without any G loads, makes your task that much more difficult. I'm not trying to be dismissive, I've got 40+ years in airplanes and I find it a challenge.

 

Chuck Owl and others have put together some great PDFs to help you with your education. Check them out here http://forum.il2sturmovik.com/forum/82-manuals-tutorials-guides-and-tips/

[ShamrockOneFive]

Well... You can always use a stopwatch and time how quickly you can complete 360 degree turns or how quickly one aircraft rolls over another. You can run an aircraft to its maximum speed in level flight (you can time that too).

 

While there are games where aircraft all fly pretty much the same. IL-2 BoS and its predecessors aren't games like that at all. Despite having similar performance the Bf109F-4 and the Yak-1 fly very differently. Instantaneous turn, roll rate, prolonged turn rate, how they stall, how fast they dive, and so on.

 

To fly at combat levels, it takes time to learn the quirks and how to anticipate them and avoid or use them to your advantage.

[6./ZG26_5tuka]

Most of this is learning by doing. It rarely matter in aerial combat who has a 1m/s higher climb rate or is 15 km/h faster on paper anyway.

 

If you'rd concerned about performamce mainly you can look up some data sheets here on the forum and save you some good amount of time.

 

Characteristics like stall behaviour, critical angles of atttack, max G loads, controll surface pressure forces ect are more important in most combat clashes in BoS.

[-TBC-AeroAce]

Easy answer is that's very hard to actually get accurate numerical data for comparison. U have to be very scientific and thorough. But if u just fly them u will start to get the picture

[GOAT-ACEOFACES]

so I was wondering if there was some standard way to measure all of a plane's flight characteristics properly, to do a side by side comparison on paper. (Speed, climb rate, dive rate, turn time, roll rate, etc.)

Until the game provides a way to log data during flight, as 1C did in IL-2 with DeviceLink, or as 1C did in CoD with C#, no one can say with any certainty how well the planes are matching the real world data. Just too many potential sim pilot errors can be made during testing that can corrupt the results.

 

This statement is based on the hundreds of test logs I have reviewed over the past 10+ from several different flight sim. I found that most of the errors were in the way the user performed the in-game test, and not an actual error in the FM. For example, not taking into account the difference in the in-game atmosphere and the real world data, which is typically corrected/converted to standard atmosphere, but not always! Another example, in WWII some countries the beginning of a rate of climb test started from a dead stop on the runway, where as others the beginning of a rate of climb test started with the plane air born at a low altitude. Not a big impact on the rate of climb data, but it does affect the time to climb results. Little difference like that can have a big effect on the results.

 

So, until we have a way to log the in-game data, any and all in-game testing should be taken with a grain of salt. As a bare minimum a video should be recorded during the test so others can review the methods used during testing.

 

On a related note, Combat Pilot Accounts..

 

Combat Pilot Accounts are great sources of information for the planes flying qualities, like the stick felt like it was in cement, the sounds it makes when you do this, the vibrations you feel when you do that..

 

But..

 

Combat Pilot Accounts are worthless sources of information for the planes performance!

 

Reason being combat pilot accounts are typically one sided stories that says more about the pilot vs pilot skill than plane v.s. plane performance.. That and the combat pilot accounts typically do not contain enough information to recreate the scenario in-game to see if you can obtain the same results, let alone the other planes state.. Than there is the human factor, with regards to pilot accounts years after the fact, the simply truth is memories change and are lost or become inaccurate over a period of time. And like the old fisherman telling us about the 'big one' that got away, they tend to embellish the facts over time, that is to say the fish gets bigger each time the story is told. That is just human nature found in us all... For example, take Brian Williams recent snafu!

 

For example, for every German pilot combat account of his Bf109 being able to out turn a Spitfire, their is a British pilot combat account of his Spitfire being able to out turn a Bf109..

 

Yet to this day people still think some sort of statistical average can be gleamed from pilot accounts.. But that is a pipe dream IMHO, for so many reasons, but probably the most important reason being, you never get a chance to read the after action report from the pilots that were killed in action!

 

Last, but not least, remember that no flight simulation ever was, is, or will be perfect! Hence the title 'simulation of flight' as opposed to just 'flight'.

[SpaydCBR]

Thanks for the feedback guys. I guess this will be harder than I thought.

 

Let's say I just looked up the stat sheet for the BF 109 G2 instead of measuring it myself. I want to make sure I understand what I'm reading.

 

Let's say it said the following:

• Speed at 2000m: 550 kph
• Speed at 4000m: 515 kph
• Climb Rate: 1140m/min at 280 kph
• Turn Time: 20s

Questions:

1. So max speed is just measured at level flight at max throttle at a certain altitude till it can't go an faster? Why is max speed slower at higher altitudes?
2. Climb rate seems to be the hardest for me to understand. Wouldn't I climb faster if I was going faster? Why would the optimal climb speed be 280kph and not like as fast as I can go? Does it just mean that the optimal climb angle is wherever my speed gets maxed out at 280 kph, and at that angle I'd be climbing 1140 m/min?
3. Is turn time just the time it takes to make a full 360 degree turn? At what speed is this typically done at? Max? (I assume a plane can turn better at slower speeds).

I apologize if these questions are silly and appreciate any help.

[busdriver]

Thanks for the feedback guys. I guess this will be harder than I thought.

 

Let's say I just looked up the stat sheet for the BF 109 G2 instead of measuring it myself. I want to make sure I understand what I'm reading.

 

Let's say it said the following:

• Speed at 2000m: 550 kph
• Speed at 4000m: 515 kph
• Climb Rate: 1140m/min at 280 kph
• Turn Time: 20s

Questions:

1. So max speed is just measured at level flight at max throttle at a certain altitude till it can't go an faster? Why is max speed slower at higher altitudes?
2. Climb rate seems to be the hardest for me to understand. Wouldn't I climb faster if I was going faster? Why would the optimal climb speed be 280kph and not like as fast as I can go? Does it just mean that the optimal climb angle is wherever my speed gets maxed out at 280 kph, and at that angle I'd be climbing 1140 m/min?
3. Is turn time just the time it takes to make a full 360 degree turn? At what speed is this typically done at? Max? (I assume a plane can turn better at slower speeds).

I apologize if these questions are silly and appreciate any help.

Q1: Those speeds at 2000 meters and 4000 meters are INDICATED airspeeds, meaning what you can read on the airspeed indicator. The TRUE airspeed is actually higher. But generally speaking you are more interested in your INDICATED airspeed because that's how you know approach and landing speeds, corner velocity, stall speed for a given configuration.

 

Q2: Complicated answer for a very serious question. In simple terms, you will find in your own sim experience that you can attain some max speed in level flight, but as soon as you raise the nose to climb, your speed drops off. Climb steeper, speed drops off further. At some point in the test, you would find (in general terms) that X speed provides the greatest altitude gain over a given distance, and at a slower speed Y you would have climbed to that same altitude in a shorter time. Climbing higher in a shorter amount of time gets you up but potentially leaves you much slower than you desire. So climb performance is a constant trade off.

 

Q3: I'm guessing (like you) that the time to turn is for one level 360 degree turn. It would be at the OPTIMUM speed (which is an INDICATED speed) that varies with weight, altitude, and configuration (external tanks, bombs, etc). This optimum speed is called "Corner Velocity." But you will notice that with thrust limited airplanes, the speed will decay in the turn if you don't decrease the back stick pressure (resulting in a more regular circle) or descend as your turn.

 

Through trial and error in this sim, you will find that you can fly faster, or climb faster, or turn inside the turn circle of different airplanes. 

[Fliegenpilz]

First off: No question is ever silly. Don't be afraid to bother us 

 

1.: Yes, max speed is measured at level flight. You can always go faster in a dive (obviously). But max speed is not necessarily achieved with full throttle; the interplay of throttle, prop, mixture etc. is key. Why is max speed slower at higher altitudes? Simple: the higher you go, the thinner the air. Although your aircraft produces less air resistance in a thinner atmosphere, your engine also produces less thrust, because air is needed as an oxidizer in the combustion process. This is also why you have to adjust the mixture setting the higher you go.

 

2.: No, you don't climb faster when going faster. Of course you initially climb fast, but you can't maintain a faster climb over a longer period of time. To understand this, we have to go deeper into the theories of aerodynamics. Every plane (wing) has a "drag polar" (just had to look this up, in german it's "Polare" ), which might help you get the idea. Picture this: If you go faster, your air resistance also rises. On the other hand your lift always stays the same (equals gravity), so your plane stays in the air (You don't need a higher force upwards while climbing, only to initialize the climb). Now the best "setting" for maximising your altitude gain would be to fly slow, as the energy provided by your engine can be converted into altitude - rather than countering the higher air resistance produced at higher speed. Hope you get what I'm trying to explain 

 

Well, just saw that Busdriver also answered. So, I'm going to leave it here

 

Good Hunting 

[SpaydCBR]

Alright, thanks a lot guys! Very helpful

[361fundahl]

How do I upgrade the turbocharger on my bf109? I heard Borg Warner has a nice new unit perfect for my needs.

[Heywooood]

CHARTS

its the only way to discuss flight models and bugger a forum simultaneously

[6./ZG26_5tuka]

Addition to the climb question: The optimal climb speed aims (as mentioned) for sustained climbs and is defined by aerodynamics, engine and weight. If you take off and want to reach a highest possible altitude over a certain distance you climb according to your recommended climb speed (usually 260 - 280 km/h for WW 2 fighters).

 

Reason being the change of lift and drag your wings produce with increasing AoAs (angle of attack). Whenever you initiate a climb, ie raise your AoA, your wing will start to produce more lift but at the same time induce more drag. The more drag you iniduce the more your plane will slow down which in return reduces your ammount of produced lift.

 

Combine those factors and you'll settle at an optimal aerodynamical climb speed at which all factors balance out nicely for best performance.

 

Of course the engine output is also important as it produces upward thrust at positive AoAs and counters drag. It isnt the primary factor though as ythe plane's aerodynamical factors are dominant.

Edited April 22, 2015 by Stab/JG26_5tuka