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 · 12,302 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.

Reading the Diagram

The Axes

• Horizontal axis — airspeed in KCAS (knots calibrated airspeed)
• 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.

The Lines

The Envelope (red)

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
• Angle of attack limit — the stall boundary; forms the upper portion at low speeds
• Speed limit (Vmax) — the right-side boundary

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

Turn Radius Lines (dashed orange/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.

G-Load Lines (dashed blue)

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.

Ps Lines (solid black/grey)

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.

• 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.

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.

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.

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.

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.

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 — above Ps = 0, bleeding speed	None — 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, end up with a large turn radius, 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.
• External stores — missiles, tanks, and pods add weight and drag. Performance degrades 15–20% compared to clean configuration depending on loadout.

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:

• 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.