Air Combat 2 How to Live and Die in the Virtual Sky by Dan "Crash" Crenshaw, www.deltahawks.org
	CHAPTER 2: Fundamentals of BFM (Basic Fighter Maneuvers) While the basic fundamentals and geometry of BFM are not very exciting to read or learn, it is critical to understand these basics. Without knowledge and understanding of these very basic concepts, the remainder of these lessons will seem like so much jibberish. Positional Geometry "Angle Off", "Range", and " Aspect Angle" are the common terms used when describing the relative positions as well as the advantage or disadvantage of one aircraft vs. another. Angle Off: Angle Off is the difference between your heading and that of the bandit. This difference is measured in Degrees. If you and your bandit are heading in the same direction, you would be at an Angle Off of 0° . At 90° angle off, you would be perpendicular to the bandit (see Figure 2-1 for details). Angle Off is also known as HCA (Heading Crossing Angle). This is the basic, root form of other, more specific geometry’s (Angle Off Tail - AOT, and Angle Off Nose - AON). Figure 2-1 Range: "Range" is simply the distance between your aircraft and the Bandit. This can be displayed in feet or miles. Most modern western military aircraft HUD systems (Heads Up Display) read in nautical miles and tenths of miles unless you are less than one mile from the target, then the display will read in feet. Some European/Soviet aircraft use the Metric system in a similar fashion. A nautical mile is 6000 feet. A bandit at a 3000 foot range would display as "3000", a bandit at a 6000 foot range would display as "1" mile, a bandit at a 9000 foot range would display "1.5" miles. Figure 2-2 Aspect Angle: Aspect Angle is the number of degrees, measured from the tail of the bandit, to your aircraft. Aspect Angle indicates your relative position to the bandits 6 o’clock position. Aspect Angle has absolutely NOTHING to do with the heading of your aircraft. Your aspect angle will remain the same regardless of your Angle Off. Aspect angle is determined from the tail of the opposing aircraft. The tail, 6 o’clock position, is 0° . The nose of the Bandit is 180° . If you are on the right side of the bandit, that is right aspect. If you are on the left side, this is left aspect. Figure 2-3 In figure 2-3 the two F-16’s in the lower right corner are both at 45 Right Aspect. The two F-16’s in the upper left are at 135 Left Aspect. Aspect Angle is very important in assisting in determining your position from the bandit. By using Aspect Angle and Range, you can determine the "lateral displacement", or turning room available. ATTACK GEOMETRY Attack Geometry describes your Offensive aircraft’s flight path to its target. Very simply, if you are pointing behind your target aircraft, you are in "Lag Pursuit". If you are "Nose On" the target, you are in "Pure Pursuit". And if your nose is pointing in front of the target, you are in "Lead Pursuit". Lag Pursuit: Lag Pursuit is primarily used for approaching the target. It can also be used when a bandit pulls out of plane; that is, when the bandit pulls out of the same plane of flight, or motion, as the attacking aircraft (See Figure 2-4). To fly Lag Pursuit for any extended length of time, you must be able to out turn the target. In a 1V1 fight with like aircraft, you would not want to maintain a Lag Pursuit for very long. You must be able to out turn the target in order to pull your nose out of lag to shoot guns or a missile. If the target is able to out turn you, or at least match your turn rate, he will be able to keep you in lag and prevent you from getting a shot. Pure Pursuit: Pure Pursuit is exactly what it sounds like. You keep your nose on the target and fly straight at him. A Pure Pursuit path all the way to the bandit will lead to an over shoot. This is reason enough not to fly in Pure Pursuit and put your nose on the target until you are ready to shoot him. Use Pure Pursuit for missile shots. Figure 2-4 F-18 Hornets with missiles Click to continue . . .		Lead Pursuit:   Lead Pursuit is the "short cut" to the target. You fly Lead Pursuit to close on the target and get into weapons parameters. This is also the most commonly used pursuit for Guns shots. You must be careful not too establish Lead Pursuit to early or you will over shoot the bandit when you get in close, unless you have a much higher turn rate than the bandit. When flying against an aircraft with similar abilities (F-16 vs. MIG-29 etc.), you will not be able to maintain a Lead Pursuit for very long, and may be forced into an overshoot situation. It is critical to pick when you go into Lead Pursuit to close the gap to set up in Guns parameters. I have been forced to go Lag to Lead to Lag to Lead, several times over in some dogfights. This is not desirable. You want to pull your nose on the bandit and shoot him, get it over and done with. This sort of maneuvering also bleeds speed at a higher rate, which is just not a good idea. If you find yourself very evenly matched, you may have no choice but to "dance" for a while to line up a good kill shot. Determining the Pursuit Course: There are two positions that the bandit can be in, "In Plane" and "Out of Plane". Figure 2-5 shows both "In Plane" and "Out of Plane" examples. Figure 2-5 "In Plane" is where the attacker and the defender are both in the same plane of motion. If the bandit is "In Plane" with your aircraft, the HUD Velocity Vector will determine the pursuit course you are taking. See figure 2-6 for an example of a Flight Path Marker in a HUD displaying Velocity Vector. Figure 2-6 The Velocity Vector is the direction your aircraft is traveling. For the sake of explanation, this can be determined by the nose of the aircraft. It represents the direction of travel of your aircraft. The Flight Path Marker on your HUD will indicate your Velocity Vector. If the defender and attacker are not in the same plane of motion, then you are "Out of Plane". To determine the pursuit course during "Out of Plane" maneuvers, use your "Lift Vector". Figure 2-7 demonstrates "Lift Vector". Figure 2-7 "Lift Vector" is simply a vector pointing out of the top of the aircraft. This is the direction the aircraft moves at high G’s. You position your Lift Vector by rolling the jet so that the Lift Vector points in the direction you want to go. The nose of the aircraft will track towards the Lift Vector. When an attacker pulls "Out Of Plane", he is technically flying "Lag Pursuit". As he pulls back into the bandit, he may be flying Lead, Pure or Lag pursuit, depending on the maneuver. Remember, when you are attacking, where you position the nose of your aircraft is VERY important. The Weapons Envelope: The Weapons Envelope is often overlooked as a fundamental and listed in other areas of BFM instruction. But if you do not know and understand the Weapons Envelope and how it affects your choice of maneuvers, you will not be able to make good choices for the next move you should make. The Weapons Envelope is the area in which a particular weapon is effective. It takes into account the weapons maximum and minimum range, weapons capabilities, Aspect Angle, Speed, Angle Off, Relative Headings ... what I am I missing? Basically, the Weapons Envelope is determined by every possible variable imaginable. The basic shape of a Weapons Envelope is that of an egg shaped doughnut that you impose over the BANDIT. See Figure 2-8.   Figure 2-8 RMAX is the maximum effective range and RMIN is the minimum effective range of a particular weapon. Figure 2-8 is an example of a weapons envelope of an All Aspect missile. A Rear Aspect missile would not have the front lobe of the "egg". As you can see, the effective operating range to the front of the bandit is much larger than the rear area. Obviously, if you are shooting the bandit in the face, he is moving towards you as your weapon moves towards him ... he is doing half the work for you. While a rear aspect shot forces the weapon to "chase down" the target. If you shoot too soon, the missile will burn out it’s motor before even coming close to the target Remember this when we get to Chapter 4: Defensive BFM.   Figure 2-8 is a "perfect world" example of a Weapons Envelope, the bandit flying straight and level. The shape of the Weapons Envelope will change as the target starts to maneuver and pull G’s. The Weapons Envelope will deform and may grow in one area while almost completely disappearing in another. It should go without saying, the target will attempt to put the less effective portion of the Weapons Envelope towards you. Remember this as well for the Defensive BFM chapter, what works for them will work for you too. Most missiles will have similar Weapons Envelopes, RMIN and RMAX figures being the primary difference. As I said before, Rear Aspect Only missiles would not have the forward portion of this diagram. Guns are the other exception. You are close enough to minimize the effect of the bandits movement for RMAX range, so the "egg" becomes more rounded. There is no minimum range on a bullet. You can have your nose half way up the targets tailpipe and still shoot guns. The problem here is that you may end up killing yourself as pieces of your opponent start coming off and smacking your aircraft. Most recently released sims as well as some on the way have begun to model this aspect of air combat. So beware just how close you get before you take the shot. Go to Chapter 3: Offensive BFM Back to MENU
This material is copyrighted and may not be reprinted in any form without permission of the publisher. Last Updated November 20th, 1998 This article was originally published at the Combat Simulations site

 

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