Procedures/78th/A2A/BFM

BFM I — Energy and the EM Diagram

This part is based on this video series by The Ops Center by Mike Solyom.

Energy

Every decision in a dogfight is an energy decision. An aircraft's energy state is expressed primarily as airspeed and altitude. The faster and higher you are, the more potential energy you have to maneuver. Energy buys turn rate, separation, and shot opportunities. Waste Energy and you will loose.

The First principle of BFM is simple: build energy and save it until you have a reason to spend it. That reason is either a shot on the bandit or denying a shot on yourself. If neither opportunity exists, maintain or build energy. Do not waste.

The Energy Maneuverability (EM) Diagram

The EM diagram is the definitive tool for understanding how an aircraft performs in a turning fight. It maps turn rate against airspeed for a specific set of parameters: aircraft weight, altitude, throttle setting, and configuration. Every number on the chart is only valid for those exact conditions.

For the F-16C in DCS the reference diagram is: Full AB · Clean · Sea Level · 12300 kg

Key performance figures from this diagram:

Parameter	Value	Condition
Max instantaneous turn rate	24°/s	393 KCAS
Max sustained turn rate	18°/s	523 KCAS
Min sustained turn radius	1,462 ft	246 KCAS
Min turn radius	1,399 ft	169 KCAS

Note: The F-16's G-limiter schedule is not fully reflected in the upper portion of this diagram. Maximum instantaneous performance may be lower than indicated in practice. The DCS implementation of the F-16 Flight Model also severely limits the F16's Sustained turn rate.

Reading the Diagram

The Axes

Horizontal axis: airspeed in Mach (lower) and KCAS (higher)
Vertical axis: turn rate in degrees per second (°/s)

Moving up on the chart means higher turn rate.

The Lines

The Envelope (red)

The outer boundary of what the aircraft can physically do. It is shaped by three limits:

Structural G limit is the maximum G the airframe can sustain; forms the upper-right boundary
Angle of attack limit — the stall boundary; forms the left boundary
Speed limit (Vmax) — the right-side boundary (going supersonic will nearly always kill both your turn rate and radius and is not desirable)

No matter what the pilot does, the aircraft cannot operate outside the red envelope.

Turn Radius Lines (brown)

These straight lines show turn radius in feet at any given point on the chart. Moving up and left gives a smaller radius.

G-Load Lines (gray)

Indicate how many G must be pulled to reach that point on the chart. To achieve a Instantaneous Turn rate of 20° at 400CAS the aircraft needs to pull about 7.5G

Ps Lines (solid black)

Specific excess power lines are the most important lines on the chart. They show whether the aircraft is gaining or losing energy at any given combination of speed and G.

Ps = 0 — the aircraft is exactly maintaining its energy state. This is the sustained turn line. The maximum turn rate achievable while sustaining speed and altitude sits on this line.
Ps > 0 (positive numbers) — the aircraft is gaining energy. It can accelerate or climb while maintaining the current turn.
Ps < 0 (negative numbers) — the aircraft is losing energy. It is spending saved energy for extra turn performance. This is temporary and cannot be maintained indefinitely.

Anything above the Ps = 0 line is an energy expenditure. The higher above it you go, the faster you bleed speed.

Corner Velocity

Corner velocity is the airspeed at which the aircraft achieves its maximum instantaneous turn rate — the peak of the envelope. For the F-16C at sea level this occurs at 401CAS, producing 24°/s.

For the maximum Instantaneous turn the DCS Flight model requires the pilot to pull 9G and decent with over 1200ft/s which is in any way not sustainable unless the a significant amount of Altitude has been built up. DO NOT use this unless you need to safe your life.

Sustained Turn Rate

The sustained turn rate is the maximum turn rate the aircraft can maintain indefinitely without losing speed or altitude. For the F-16C at sea level this is 18°/s @ 523 KCAS.

In practice, sustained operations happen on or near the Ps = 0 line. The pilot's job is to find and hold that point. Sadly in DCS to hold and maintain that line is impossible. To Fly Perfect Sustained Turn Rate you need to pull 9G in full afterburner. You will know that you hit the perfect speed if, at max pull, in a level turn, the Jet neither gains nor looses Max energy.

A sustained 9G turn will black out any pilot. To Compensate the Pilot should fly slighly below the Optimal Speed allowing for higher turn rate while loosing a small amount of energy. Once the Jet reaches around 70-80 KTS below optimal speed the pilot should reduce the pull to about 6G for maximum recovery speed. While only pulling 6G the jet will gain energy fast. Once back at optimal speed continue to pull 9G.

If you overshoot the Optimal Speed you will notice that even at max pull the aircraft is still gaining airspeed. In this case execute a spiral climb to return back to Optimal Speed while utilizing the excess Energy.

If you undershoot the Optimal Speed you will notice that at max pull the aircraft is loosing airspeed fast. Either Reduce pull back to 6G until at better speed or trade altitude for extra Energy.

Instantaneous vs Sustained

	Instantaneous	Sustained
Definition	Maximum turn rate achievable at any moment	Maximum turn rate maintainable indefinitely
F-16C value (sea level)	24°/s @ 393 KCAS	18°/s @ 523 KCAS
Energy cost	High: Far above Ps = 0, bleeding speed fast (expect around 50kts/s)	None if optimally flown on Ps = 0 line
When to use	Short bursts for a shot opportunity or to deny a shot	Default gameplan in any sustained turning fight

Instantaneous turn rate is spending saved energy. It is a powerful tool but a temporary one. A pilot who pulls to instantaneous continuously will bleed to low speed, and lose the fight on energy.

How Altitude and Stores Affect the Diagram

The reference diagram is for sea level, clean, full AB. Both altitude and external stores degrade performance:

Altitude: thinner air reduces lift and engine thrust. Turn rate and sustained performance both decrease. The same airspeed produces a larger turn radius at altitude.
Weight: Fuel or Stores will both make you heavy. The heavier you are the worse the performance. As you burn fuel the optimum Sustained turn rate Speed will decrease into manageable Levels.

Practical Application

In the fight itself: treat energy like money. Build it, save it, and spend it only when the return is worth it. A valid shot, or surviving by denying the adversary a shot oportunity. Spending energy for no tactical gain is a losing strategy.

BFM II — Angles and Geometry

Angles and Definitions

Antenna Train Angle (ATA)

The ATA is the position of the bandit left or right of the fighter's nose on the radar display. ATA 0 means the target is dead ahead. ATA 30R means the target is 30° to the right of your nose.

The ATA is a property of your own aircraft's orientation. It changes when you maneuver. It does not change instantaneously when the bandit maneuvers.

On the F-16 FCR, ATA is read on the horizontal axis.

Target Aspect (TA)

Target Aspect, not to confuse with Aspect Angle is how the bandit appears from your perspective. Specifically, the angle from the bearing line of the fighter to the nose of the target. It describes which part of the bandit you are looking at.

TA 0 —you are looking at the bandit's nose (head-on)
TA 90 — you are looking at the bandit's side
TA 180 — you are looking at the bandit's tail (pure stern)

TA is signed left or right depending on which side of the bandit you are observing.

Unlike ATA, Target Aspect is entirely determined by the bandit's heading relative to the bearing line between you. You cannot change it instantaneously. You can only influence it over time by maneuvering to change the geometry.

The F-16 does not display TA directly. It displays the Aspect Angle (AA), which is the supplementary angle of TA (AA = 180° − TA). A tail-aspect shot has AA 0; a head-on shot has AA 180.

Common TA labels used in brevity:

TA	AA	Label
0°–30°	150°–180°	Hot
31°–75°	105°–149°	Flank
76°–110°	70°–104°	Beam
111°–150°	30°–69°	Drag
151°–180°	0°–29°	Cold

Cut

Cut is the angle from the Fighter Heading (FH) to the Bandit Reciprocal (BR). It describes where your nose is pointing relative to the bandit's course.

Cut is an older concept but remains one of the most useful tools for predicting how the geometry will evolve. Three reference cases:

Cut greater than Collision Course — your nose is in front of the bandit. Over time, TA decreases and Lateral Separation decreases. You are closing the geometry aggressively.
Cut equal to Collision Course — the magic case. TA is captured: it does not change. Lateral Separation decreases. If co-altitude, you will eventually collide.
Cut less than Collision Course (Zero-Cut / Parallel) — your nose points at the bandit's reciprocal. TA increases over time. Lateral Separation is captured: it does not change.
Cut-Away — your nose points away from the bandit entirely. Both TA and Lateral Separation increase. Used to build angles or lateral room.

Degrees to Go (DTG) / Heading Crossing Angle (HCA)

DTG is the number of degrees the fighter needs to turn to be parallel to the bandit's flight path. It is the supplementary angle of Cut. A useful memory aid: Degrees to Go — where? Parallel.

Lateral Separation (LS)

Lateral Separation is the perpendicular distance between the two flight paths. It determines how much maneuvering room exists for a conversion. It is approximated as:

 LS (ft) = TA × SR × 100

Where SR is slant range in nautical miles. Lateral Separation matters most when planning a stern conversion or assessing whether a shot is geometrically viable.

Direction of Passage (DOP)

DOP describes the direction the bandit would cross your flight path if neither aircraft maneuvered. Called as left-to-right or right-to-left. Useful shorthand for building SA quickly.

Slant Range (SR)

The straight line-of-sight distance between the two aircraft in three-dimensional space. On the F-16 FCR this is the range displayed on the scope.

Pursuit Types

The type of pursuit describes where your nose is pointing relative to the target.

Pursuit Type	Nose Position	Common Use
Lead Pursuit	In front of the target	Collision Course, gun employment from RQ
Pure Pursuit	Directly at the target	Simple conversions; commonly overused by new pilots
Lag Pursuit	Behind the target	Geometry management, WVR maneuvering