Air Combat and God’s G

In a previous post I mentioned that I participated in an aggressor program up in Alaska, a program that pitted our Lockheed T-33s against the Alaskan Air Command F-4Es. The goal was to break bad habits that fighter pilots can inadvertently pick up if they always train by dogfighting with identical aircraft.

As part of this Dissimilar Air Combat Tactics (DACT) training program, several of us T-Bird pilots were qualified for the DACT missions and, eventually, developed a training program to qualify other T-Bird pilots for DACT.

One of the first things we covered was the effect of gravity (colloquially referred to as “God’s G”) on aircraft performance when engaged in a vertical fight.

Here’s the graphic we used to help explain the concept (typically call the Egg):

Egg-shaped diagram of two fighters in a vertical circle.

Total G is the number displayed on the G-meter in the pilot’s cockpit. Radial G is the actual turning G available after taking into account the 1G always acting on the aircraft (due to the Earth’s gravitation pull). That 1G is the force you feel when standing or sitting on the ground, or when flying along straight and level in unaccelerated flight. That’s God’s G.

If the two fighters in the diagram are exactly opposite each other, each pulling 4 Gs on the cockpit meter, and without vectored thrust of any kind, they will have the same radius of turn when one is at the 3 o’clock position and the other is at the 9 o’clock position. God’s G is neither adding to nor subtracting from their total 4G.

However, if one is at 12 o’clock (the top of the Egg) and the other at 6 o’clock (the bottom of the Egg), then the pilot of the 12 o’clock position will turn tighter despite both aircraft G-meters reading 4 Gs. God’s G is adding another G to his ability to turn, i.e., pulling down and tightening his turn. The guy at the bottom is still reading 4 Gs in the cockpit, but God’s G is subtracting 1 G from his ability to turn, i.e., pulling down and widening his turn.

If they arrive at those two positions (12 and 6 on the diagram) at the same time, the pilot at 12 was the advantage and can maneuver into a position for a quick, high-deflection shot with his guns (a “snapshot”), because for a brief period he will be able to out-turn the guy at the bottom.

Of course, “vertical” fights are often less than purely vertical since many other factors come into play. Despite that, God’s G will still effect both aircraft in varying degrees depending on how close to vertical they are fighting at any given moment…and how far about on the circle they are at that moment.

So, here’s a more realistic diagram of a “vertical” fight tilted off the vertical.

Fightng Egg overlaid with two diagrams of a less-than-vertical fight.

In a real close-in dogfight, of course, many other factors determine the relative effects of God’s G on the dynamics of the fight. The two aircraft are probably not identical and can sustain different levels of G at different airspeeds. One might have vectored thrust capability and can point his nose irrespective of the G-load available to him. One pilot might be better at coaxing the most out of his aircraft.

In any case, God’s G will still effect both aircraft and an understanding of how to turn it to advantage just might be critical in determining who wins.

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