View Full Version : Energy Versus Turn Fighters by Frank "Dart" Giger

06-25-2007, 06:37 AM
some of you probably seen this

found it on simhq

June 11, 2007

IL-2 Series: Fighters

by Frank "Dart" Giger

I've been asked to pick up on the flight simulation series of articles based on the IL-2 series, and figured I'd start off with some general ideas on aircraft to give an idea of the type of articles you'll be seeing.

Let's start out with some of the myths that some very smart folks have debunked for me before we start in on the "How To" articles of Ground Attack, Range Estimation, Carrier Landings, Surviving Online, etc.

Bear in mind I'm not a Real Life Pilot, inadequately read, and have had to get a grasp of things through trial and error as well as a few "light bulb" revelations from corresponding to Real Life Pilots and, when all else fails, Google.

Energy Versus Turn Fighters

It's pretty common to read that some planes are "energy fighters" while others are "turn fighters." This is a false statement that causes most problems with new sim pilots.

ALL fighters are "energy" fighters! The difference between a Fokker DR1 triplane and a Folke-Wulf 190 is the general flight envelope they inhabit. There is a band of energy, which we generally consider to be airspeed or altitude, that both work best in; if either falls outside of that band, they perform poorly.

My favorite IL-2 series planes, the Yak-1b and the Hurricane IIb, for example, aren't widely considered "energy" fighters, as they operate in an energy band that is lower than most of their contemporary enemies. Yet I can put up a good showing against "superior" or "energy" fighters in either of them simply because I've learned how best to conserve the energy the plane has in a fight and put it to advantage.

Lighter, slower aircraft such as the I-16 or Yak-1b tend to be more forgiving of jerking the plane into a turn and bleeding energy than larger, more powerful ones, but the same forces are at work as in heavier, more powerful aircraft.

In a fight I always keep the throttle at 100% and do my best to fly through maneuvers rather than force the aircraft into a turn or a climb, as both steal more energy than either plane can replace in a timely manner. The idea is to keep my energy state at the plane's best operating band and try to get the other guy to come out of his. It's how I have managed to out-turn a Zero in a Hurricane IIb online.

Simple Rule: The first person to run out of energy loses.

Similarly, the only difference in scissors between a MiG-9 and a P-80 and a Yak-1b and a Bf-109/F4 are the distances used (due to the relative airspeeds). The maneuvers are the same; the principles are the same; it's only the band of energy that is higher.

Flying the Bf-109 and the Corsair is no different " the controls work the same way; it's understanding the band of energy each works best in and how to keep them there is the hard part.

There Is No Up Or Down

This was the hardest concept for me to grasp:

There is no maneuver that can be done horizontally
that can't be done vertically, and vice versa.*

The horizontal turn and the loop are really the same maneuver; the only difference is where energy is traded off in each. Vertical scissors and horizontal scissors are the same thing. I used to think the hammerhead was an exception, but it's not. Pull the nose up too much in a turn and one will produce an angle-of-attack stall (regardless of speed), but without the advantage of being able to trade off the potential energy of climbing the plane tends to depart controlled flight and spin.

Let's take one of my favorite maneuvers, the Split-S:


Performing it is easy, as from level flight one just inverts the aircraft, pulls the stick back, and when level to the horizon, stops pulling back on the stick. The advantages are that one does a U-turn in the sky while converting potential energy (altitude) to kinetic energy (airspeed).

One can also do this maneuver two other ways. One could pull the stick up, wait until the plane is parallel to the ground, and roll the plane from the inverted position at the top, trading kinetic energy for potential energy " a half loop.

Or one can do the invert-and-pull-back while the plane isn't parallel to the ground. Half roll and pull back on the stick. This is the basic maneuver of the scissors " but with another half roll on the end in the opposite direction.

Why call the same series of control inputs that result in the same maneuver different things? Because it's handy. Half-loop tells one that the direction was up, Split-S down, and scissor (usually) horizontal. When scissors are done vertically, they're called "Vertical Scissors" simply to let folks understand the aspect of the aircraft to the ground.

There's a neat little movie I made of a great scissor fight between myself and our resident Real Life Pilot, SpotC, that has both horizontal and vertical scissors:


It's a big 43MB or so, .wmv format, zipped. It wasn't made for this article; I make little movies to entertain myself when funny things happen.

For those who have the IL-2: Forgotten Battles series, the .ntrk file that the movie was made from:


It's 731 kb. Save to the "records" folder.

* The exceptions are, of course, take offs and landings.

Combat Responsiveness Is More Important Than Top Speed

This is the stuff of many a Flight Modeling debate, starting off with "How did XX plane catch up to me, when the statistics say my plane is faster?"

Combat responsiveness is how quickly a plane can regain lost energy, and it's the difference between a mediocre aircraft and a stellar one.

My favorite comparison is the LaGG-3 (series 66) and the Yak-1b, which were in the skies at roughly the same time. On paper, they seem to be a tie, with little real advantages over the other:



But the Yak-1b, which weighed more and had a less powerful engine, was the one that put up a fight with the Bf-109/F4, while the LaGG-3 was relegated to back line units as soon as it could be replaced due to lackluster performance.

The reason was combat responsiveness. The Yak-1b's design made it able to accelerate much faster than the LaGG-3. Though it was heavier than the LaGG, it was also shorter and had a more efficient wing design. In practice, a LaGG was as fast as a Yak-1b (those 12 MPH at top speed can be considered plus or minus on any given aircraft), but it took much longer for the LaGG to get there. Once the LaGG reached a low energy state, it was too long to regain it with the motor it was given.

It simply was underpowered for its design, resulting in slow acceleration and a wide turning radius (which was a byproduct of this).

Once fitted with a beefy radial engine and a few modifications, the LaGG-3 came back as the LA-5, though, and redeemed itself as a premier fighter aircraft.

The ultimate example of poor responsiveness is the Me-262. It had two speeds: Really, Really Fast and Dead Meat. Its acceleration was so poor that it required active escort on takeoffs and landings as there was no way it could simply hammer the throttle and zoom away. The best performance energy band for the 262 was pretty narrow, but since it was so fast it didn't matter in practice. One did not scramble a Me-262 in response to incoming fighters five miles off.

One of the best examples of combat responsiveness is the Bf-109/F4 and /G2; and, naturally, the Spitfires that proved to be the answer to them.

Again, understanding the combat responsiveness of one's aircraft is key to keeping it in the optimum band of energy. In my Hurricane IIb, for example, I don't often hammerhead or perform a great many vertical maneuvers: I perform rolling turns with either a slight climb or descent in the middle of them, as the Hurricane tends to slide in turns and lose energy.

And lastly,

Your Plane Doesn't Want To Fly Straight (and Fast)

Aircraft are wonderful examples of everything working against itself for a common purpose. The engine is pulling the nose downwards and twisting it on its axis, the wings are pulling the aircraft up, while the tail (with the wings) is trying to undo the torque effect (rudder) and the elevators are pulling the tail down to keep the nose up.

It's a balancing act that the designers knew all about, and they had two answers:

Design the plane to be in balance at the cruising speed and altitude so that everything is harmonized.
Enable the pilot to make minor adjustments to the lifting surfaces to compensate for when the plane isn't at cruising speed and altitude.
Welcome to the wonderful world of trim.

If one has ever participated in an air race in a flight sim, the effects of trim become horribly obvious. The same aircraft modeled the same way with the same loads should, because the maths are the same, perform exactly the same. Racing should be a matter of endless ties.

But they're not. Someone will have figured out the right adjustments to fine tune the control surfaces to reach equilibrium while others won't, bleeding speed from their ersatz mounts. The fast guys have recalibrated the plane to where they have a new "center" for the stick.

One of my squad mates is King of Trimming, and it infuriates me at times. He regularly flys faster than I at 80% throttle while I struggle at 100% to keep up. The tiny adjustments I'm making manually each take a toll on efficiency, while he's hands-off and sliding through the air as if greased.

In the IL-2 series, it is why the AI pilots fly faster than we do on take-off, as they have a magical auto-trim built in. They're always in balance!

There are advantages and disadvantages to being in perfect trim. The advantage is obvious: one can fly faster! The disadvantage is that one is flying straight and level, which I think is greatly oversold as a concept in a combat zone. A little slip and climb has been enough to throw off the enemy's aim on a bounce. This is probably why 2GvSAP Chief usually has me in the number two slot behind him!

I'm definitely going to provide definitions for things and gear the articles to the novice or intermediate virtual pilot, taking things step by step without a great deal of technical jargon. As an other-than-natural at flight sims, most of what I've learned has been hands on and based more on practice than theory. Whenever possible, I'll provide a small video to be a companion to the article.

I hope you'll read and learn to enjoy flight simulations as much as I do with the future articles.

06-25-2007, 07:09 AM
i can witness the importance of trim,
ive participated in a few races for fun but as im a pilot that flyes only on my own Premissions i have never gone into trim, (also because i need controls for it)
i have never won a race nor got in as 3rd or 4th
always last or second last.

interesting article.
gives you new hope that its all about preserving energy.
thing is that if you always make Gentle movements and never really turn you are going to be a very easy target as the best way to avoid getting hit is a sharp turn.

06-25-2007, 08:54 AM
Thanks Mac!

06-25-2007, 10:00 AM
One of my squad mates is King of Trimming, and it infuriates me at times. He regularly flys faster than I at 80% throttle while I struggle at 100% to keep up. The tiny adjustments I'm making manually each take a toll on efficiency, while he's hands-off and sliding through the air as if greased.


06-25-2007, 04:20 PM

06-25-2007, 05:24 PM
Dead on the money and very well written.

06-25-2007, 05:57 PM
Dart's stuff is the best. His training videos helped me refine my ground attack skill significantly and I've been playing since 01. They're easy to understand and very straight forward. (They're also fun to watch)

I think the best point from his SimHq article was to "fly through" manuevers. Its an important real world element of flying but it is rarely discussed on these boards. Its especially important for planes like the P-51 and Machi fighters. They turn into completely different aircraft when you allow the airplane to build up the energy it needs to pull through the big manuevers like loops and yo-yo's.

06-25-2007, 06:53 PM
You do realize that the title of this thread will invoke...

06-25-2007, 11:10 PM
Yes I like Darts stuff too.

06-26-2007, 09:58 AM
Just going to bump this because it's a great piece of writing and should be more widely appreciated.

06-27-2007, 10:34 AM