I’ve been playing a lot of Ace Combat 5 and 7 lately, so I have fighter jets in the brain. And today I learned something I’d never have thought was possible from looking at the way those games or RPGs like GURPS model them.

Apparently, modern fighter planes are so fast they can shoot themselves down by outrunning their own cannon fire! Implausible, you say? Well, if you read this bit of news you’ll see that it actually happened in January of this year with an F-16, and that there are records of at least one other incident from back in 1956 with a Grumman F-11.

The gist of it is that shells are fired from the aircraft’s cannon at a speed equal to that of the aircraft plus their muzzle velocity, as you’d expect. However, they’re quickly slowed down by drag, so it’s possible for a plane flying at high speeds to accelerate past the bullets it just fired and maneuver itself into a position to be hit by them.

GURPS and most RPGs just tend to treat projectiles as having infinite speed. A character shoots, and the bullet flies out to its maximum range before the end of that character’s turn. This is a pretty decent approximation for the type of combat that usually happens in these games, which is between people on foot and at relatively short ranges. GURPS Tactical Shooting does have some additional rules for projectile flight time, but those are optional and mostly meant for snipers1. None of the existing rule sets contemplates the speed and ranges involved in jet age air combat.

Do we need specific rules for this hazard? I would say not. It’s even more of a niche situation than long-range sniping, and the bookkeeping required to track it would not be all that fun even in a realistic game about air combat. No, what we have here is an excellent result to use if someone rolls a critical failure on a Gunnery or Pilot test. Even if you go on to become the Ace of Aces, your squadron-mates will forever embarass you with stories of that one time you shot yourself down.

  1. Who are famous for not moving at supersonic speeds. ↩