Procedures/78th/A2A/BFM: Difference between revisions

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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.

@@ Line 10: / Line 10: @@
 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 · 12,302 kg'''
+For the F-16C in DCS the reference diagram is: '''Full AB · Clean · Sea Level · 12300 kg'''
+[[File:F16 EM Diagram.png|center|frameless|945x945px]]
@@ Line 35: / Line 36: @@
 |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.
+'''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 ===
@@ Line 41: / Line 42: @@
 ==== The Axes ====
-* '''Horizontal axis''' — airspeed in KCAS (knots calibrated airspeed)
+* '''Horizontal axis''': airspeed in Mach (lower) and KCAS (higher)
-* '''Vertical axis''' — turn rate in degrees per second (°/s)
+* '''Vertical axis''': turn rate in degrees per second (°/s)
-Moving up on the chart means higher turn rate and smaller turn radius — both desirable. The goal in BFM is always to find and maintain the point on this chart that gives the best performance for the current situation.
+Moving up on the chart means higher turn rate.
 ==== The Lines ====
@@ Line 51: / Line 52: @@
 The outer boundary of what the aircraft can physically do. It is shaped by three limits:
-* '''Structural G limit''' — the maximum G the airframe can sustain; forms the upper-left boundary
+* '''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 upper portion at low speeds
+* '''Angle of attack limit''' — the stall boundary; forms the left boundary
-* '''Speed limit (Vmax)''' — the right-side 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 (dashed orange/brown)'''
+'''Turn Radius Lines (brown)'''
-These curved lines show turn radius in feet at any given point on the chart. Moving up and left gives a smaller radius. The minimum radius is not at the same point as maximum turn rate — there is a tradeoff between the two.
+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 (dashed blue)'''
+'''G-Load Lines (gray)'''
-Indicate how many G must be pulled to reach that point on the chart. At 393 KCAS, pulling to the top of the envelope requires approximately 9G. At the sustained turn point the aircraft is pulling around 6–7G.
+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/grey)'''
+'''Ps Lines (solid black)'''
-Specific excess power lines — 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.
+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.
@@ Line 74: / Line 75: @@
 Anything above the Ps = 0 line is an energy expenditure. The higher above it you go, the faster you bleed speed.
-'''Observed Sustained Turn Rate (orange line)'''
-The actual measured sustained turn rate in DCS. Use this line as the practical reference for what the aircraft will do, not the theoretical Ps = 0 intersection.
 === 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 '''393 KCAS''', producing '''24°/s'''.
+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'''.
-Unlike most fighters, the F-16 does not have a single sharp corner velocity. Due to its flight control system, it has a '''corner plateau''' — a range of approximately '''300–450 KCAS''' across which turn rate remains close to its peak. This gives the F-16 more flexibility than aircraft with a narrow corner speed, as the pilot does not need to hit an exact airspeed to get near-maximum performance.
-Above 450 KCAS, turn rate drops off and turn radius increases significantly. Below 300 KCAS, the aircraft approaches the AoA limit and begins to lose both rate and radius control.
+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 — fast enough to stay in the corner plateau, pulling enough G to maximize rate, but not so much that speed bleeds away faster than AB can restore it.
+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.
-The F-16 at its sustained turn rate is pulling approximately 6–7G in full afterburner. This can be held as long as fuel lasts.
+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 ===
@@ Line 108: / Line 107: @@
 |-
 |'''Energy cost'''
-|High — above Ps = 0, bleeding speed
+|High: Far above Ps = 0, bleeding speed fast (expect around 50kts/s)
-|None — on Ps = 0 line
+|None if optimally flown on Ps = 0 line
 |-
 |'''When to use'''
@@ Line 115: / Line 114: @@
 |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, end up with a large turn radius, and lose the fight on energy.
+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.
+* '''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.
-* '''External stores''' — missiles, tanks, and pods add weight and drag. Performance degrades 15–20% compared to clean configuration depending on loadout.
+* '''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.
-DCS training primarily occurs at low altitude, so the sea level diagram is the working reference. Be aware that any mission flown with a combat loadout will perform below the charted values.
 === Practical Application ===
-The EM diagram does not go in the cockpit — it goes in the pilot's head before the flight. The key numbers to memorize for the F-16C:
+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.
-* '''Corner plateau: 300–450 KCAS''' — stay in this range during a turning fight
-* '''Sustained turn: ~18°/s''' — the default game plan
-* '''Instantaneous peak: ~24°/s @ 393 KCAS''' — available in short bursts when needed
-* '''Ps = 0 at sustained''' — any turn rate above 18°/s is costing energy
-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 a shot attempt. Spending energy for no tactical gain is a losing strategy.