E-M Diagram Summary

CHAPTER NINE

BASIC FIGHTER MANEUVERING (BFM) THEORY

An E-M diagram is limited to showing a "snapshot" of parameters due to the simple fact that

aircraft performance varies at different altitudes and gross weights. Figure 9-8 depicts a T-2C

E-M performance at sea level with a gross weight of 11,463 lbs.

An E-M diagram combines three essential parameters on one chart:

Aircraft structural limitations.

Turn performance data (turn rate data and turn radius curves).

Specific power data in the form of Ps curves.

From the above E-M diagram, a few crucial data points can be derived:

Point A: This point at the intersection of the aircraft G limit and lift limit equates to the corner

airspeed. We can see from the diagram that this airspeed is approximately 280 KIAS. Corner

airspeed has been previously defined as the lowest airspeed at which the maximum g is available.

The turn rate at point A is the best instantaneous turn rate. From the diagram, we can see this is

approximately 21 of turn per second. The trade off for maneuvering the aircraft at Point A is

the energy loss. All maneuvering beyond the Ps=0 curve is energy depleting. According to the

legend above the E-M diagram, the energy bleed rate is 63 ft/sec at corner airspeed.

Additionally, the E-M diagram shows the effect each maneuver will have on the aircraft's turn

radius. For example, at Point A (corner airspeed) we can see the turn radius is approximately

1500 feet.

Point B: Point B is the maximum sustained turn rate. Point B is on the Ps = 0 curve. As a

result, we see that a 19 degree per second sustained turn rate can be achieved without losing

energy. The Ps = 0 curve becomes significant when operating on the deck where altitude cannot

be traded for airspeed.

E-M Diagram Summary

From the above T-2C E-M diagram, we can extract data points to make a thumbnail sketch of the

T-2C's maneuvering capabilities:

Corner airspeed

280 KIAS

Max G

6.0* (gross weight dependent)

Max Instantaneous Turn Rate

21 degrees/ second

Max Sustained Turn Rate

19 degrees/ second

Min Turn Radius (at corner speed)

1500 feet

T-2C simulated weapon system

20 MM Guns

(* Max "G" may be lowered by squadron SOP for aircraft life extension).

9-14

BASIC FIGHTER MANEUVERING (BFM) THEORY