fw 190a5 flight model

[JtD]

Maximum take off weight has nothing to do with the ability of the plane to 'just stay in the air'.

Additionally, figures on wikipedia are wrong, for instance loaded weight (8488 lbs) is used for the stated Spitfire XIV maximum take off weight (9278 lbs with 90 gal drop tank).

[K_Freddie]

You'll find an airline pilot will not take off if his a/c is too heavy (close or beyond recommended takeoff weight)... there must be a reason for this.

[JtD]

Yes, there is. In fact there are several.

[MaxGunz]

If you don't take into consideration what the takeoff speeds, runway lengths and air density are then you won't get much out of takeoff weights.

It's like when The Joke would say that more weight on a plane makes the plane faster because hang gliders fly faster with ballast. Yes the gliders do, because if they don't fly faster they will stall when the unballasted, slower glider is still not stalled.
But -powered- airplanes don't get their energy from their weight, they can go faster using the spinny thing up front. More weight just makes their wings have more drag, which BTW is not proportional to wing loading.

[Herra Tohtori]

Well, that all gets really complicated really fast.

Let's compare two aircraft of roughly same engine power, mass, and wing chord profile - only difference being that the other one has more wing area; for the sake of exercise let's keep the wing's aspect ratio also same, ie. chord length increase is proportionally same as wing span increase.

An aircraft with smaller wings has less parasitic drag.

But it has higher wing loading, which means at the same speed it has to use higher angle of attack, which increases the drag.

Both aircraft, however, have a certain optimal angle of attack at which the wing produces the least amount of drag.

Then, their optimal cruise speed is when they are flying at exactly this angle of attack, and the lift is exactly enough to counter the aircraft's weight.


For the aircraft with smaller wing, this optimal cruise speed will be higher than the aircraft with larger wing. What this means is, basically, that the smaller wing aircraft is better optimized for high speed flight and will achieve better efficiency when flown at higher speeds... and will reach higher top speed at level flight with the same thrust output from the engine!

That last part is actually pretty elementary physics. The top speed of any object is achieved when the power output equals friction/drag losses.

When the power output remains constant but drag coefficient reduces, then the drag losses are equalized at higher velocity.



However, things change drastically when these aircraft are compared in high angle of attack situation. At same angle of attack, the aircraft with larger wing will produce more lift and therefore turn better. There are also other, secondary effects such as better acceleration and better climb rate, which both very much explain why lower wing loading typically makes "dogfighting" easier compared to planes with high wing loading.

This does not necessarily correlate with combat effectiveness of the aircraft. The benefits gained in "angles maneuvers" are lost on energy maneuvers. The aircraft with smaller wing will accelerate faster in a dive, it will have higher dive speed limits, it will be more stable at high speeds, and it will lose less energy at dives and zoom climbs as long as angle of attack is reasonably small.


Of course, this is idealized comparison. There are not many examples where these conditions apply. One example that comes to mind is Ta-152C vs Ta-152H-1. In this case, the Ta-152C had smaller wing and Ta-152H-1 had larger wing. However these aircraft differed in other ways; Ta-152C used the DB603LA engine, whereas the Ta-152H-1 used Jumo 213E engine. Additionally the H model's long wing had much higher aspect ratio and thus was better optimized for high altitude flight due to lower induced drag, which is a different form of drag than parasitic drag...


However, comparison of these aircraft in IL-2 largely corresponds to what I just said. The Ta-152 H-1 accelerates better, climbs better, turns better, and at high altitudes it performs quite a bit better.

The Ta-152C has pitiable acceleration and climb rate, turns like a hippo in a bath tub, and top speed is puzzlingly low (I have some suspicions regarding the DB-603 engine model), but it definitely has higher dive speed, dive acceleration, and it retains energy quite well once you get it really going. It also offers excellent stability.

Which is a better airplane would depend entirely on what you were doing and how.



Wing loading of aircraft varies with g-loading, but typically it's expressed in level flight (1g acceleration), where it can be expressed in mass/wing area which colloquially is understood much better by people, than the actual implications of "wing loading".

If you REALLY want to get into it, wing loading is actually expressed in units of pressure. It is, quite simply, the aerodynamic lift force produced by the wing, divided by the area of the wing.

What does this means from the aerodynamic perspective?


As an aerofoil passes through air, it basically does work on the airflow to create pressure differential between upside and downside of the wing. These pressure differentials generate the lift that is used to counter the aircraft's weight.

The pressure differential is not constant over the wing; at some places it's higher, at the edges it's lower. However, if we were to average the pressure differential over the wing, it would turn out to be exactly the same as wing loading: Force of aircraft's weight, over the surface of the wing.

Why then is smaller wing loading preferable? Because the smaller wing loading means your wing needs to create less pressure differential.

Less pressure differential means less work done by the wing on the airflow - which, incidentally, is one source of drag in airplanes.


This is, of course, quite a bit simplified and it would be better to draw an image but I see this represented very, very well in IL-2. FW-190 included.

[MaxGunz]

Originally Posted by Herra Tohtori

For the aircraft with smaller wing, this optimal cruise speed will be higher than the aircraft with larger wing. What this means is, basically, that the smaller wing aircraft is better optimized for high speed flight and will achieve better efficiency when flown at higher speeds... and will reach higher top speed at level flight with the same thrust output from the engine!

And then they both pull and hold a hard turn. Which one reaches stall first?

The stall speed multiplies by the square root of G's pulled resulting in a greater difference between the planes -- from high speed start it will be the one that runs out of smash first.

However the claim that a 190 should out-turn a Spit at low speed fails right there as you would have to defy physics or have a very poor Spit pilot in the Spit and a very good 190 pilot in the 190 to do so and then we are no longer comparing just the planes.
Take away knowing who is flying which plane (and most other details) and we have a war story to misuse and come up with ignorance-based 'data'.

The real cool stuff happens at higher speeds where turn fighters can't turn so hard without losing speed. The best energy fighting tactics use that whether online or IRL, check with Robert Shaw if you think different. At speed the 190A is booja but then 'at speed' in a 190A is 'high speed' in a Spit V.

[Herra Tohtori]

Originally Posted by MaxGunz

And then they both pull and hold a hard turn. Which one reaches stall first?

They both reach stall at the same angle of attack (assuming, as with earlier premises, that the wing chord profile is the same and only difference is wing area). There is not such thing as "stall speed".

However: If starting airspeed is the same, and both aircraft start turning on the exact same trajectory - same turn rate, same turn radius, then the following applies:

Both aircraft need equal amount of lift to stay on equal trajectory.

As velocity is the same initially, and the only difference on planes is wing area, that means angle of attack must be different between the planes.

That means that the aircraft with smaller wing must hold higher angle of attack to travel on the same path than the larger wing aircraft.

This will, of course, quite fast start making a difference on where on the path the airplanes are. Because the small-winged aircraft needs to pull higher AoA to stay with the other version, it ends up having much more drag, and assuming both planes are having their engines balls to the wall that means the small wing aircraft will start losing energy in the turn much faster than the large winged aircraft.

As the small winged aircraft starts losing speed, it also starts losing lift and thus turning ability, and it needs to start pulling even more angle of attack until critical angle of attack is reached.

In this exercise, it is fairly likely that the aircraft with smaller wing will reach its critical angle of attack first if it tries to stay turning with the other aircraft.

Additionally, if we are to assume that the large wing aircraft starts pulling the turn exactly at the critical angle of attack to begin with, then it is quite impossible for the small wing aircraft to even stay with it on the turn, because it cannot increase its own angle of attack higher than the critical AoA, and stalls immediately at the beginning of the turn - or ends up on a wider turn than the large-wing aircraft.

This, personally, I can confirm with great satisfaction in IL-2.

The stall speed multiplies by the square root of G's pulled resulting in a greater difference between the planes -- from high speed start it will be the one that runs out of smash first.

Did I mention that the concept of "stall speed" is something I personally find rather annoying?

Stall speed is an indicatory value for pilots and only holds at level flight. Aircraft can stall at any speed when thrown around with fists of ham.

Stall speeds are given as the speed at which the aircraft can JUST hold its own weight with its lift, without losing or gaining altitude or airspeed, and holding angle of attack at or very near critical AoA.

It gives some idea of the aircraft's performance since the stall speeds can be compared, however its relation to turning performance is not necessarily 1:1.

However the claim that a 190 should out-turn a Spit at low speed fails right there as you would have to defy physics or have a very poor Spit pilot in the Spit and a very good 190 pilot in the 190 to do so and then we are no longer comparing just the planes.
Take away knowing who is flying which plane (and most other details) and we have a war story to misuse and come up with ignorance-based 'data'.

Amen.

However we can probably both agree that as the FW-190 was introduced it had great successes against the contemporary Spitfires for various reasons, which could be listed but have already been mentioned in the thread.

"Better turning ability" is decidedly not one of them, but the otheres - higher speed, excellent visibility, easy operation of engine to get the most out of it (Kommandogerät love) while Spit pilots had to dick around with engine settings... All of these could easily have made plausible situations where a FW-190 (or entire group of them) "outmaneuvered" Spitfires, using energy tactics, team tactics, and surprise of Spit pilots at finding entirely new aircraft that they've never seen before.

The real cool stuff happens at higher speeds where turn fighters can't turn so hard without losing speed. The best energy fighting tactics use that whether online or IRL, check with Robert Shaw if you think different. At speed the 190A is booja but then 'at speed' in a 190A is 'high speed' in a Spit V.

Yeah, at transient turns (rather than sustained turns) there are some different factors to consider. An aircraft's transient turn rate basically depends on how fast it can dump energy into direction change, whereas sustained turn rate depends on how fast the engine can produce energy to compensate for drag losses, keeping the airspeed constant (and with that, turn rate and turn radius).