Facing the nose of a fighter plane the cockpit and engine are the biggest targets, your nose is first in. All the guns are shooting right there. It's when you're passing through you take on other types of strikes,... now you're broadside. The damage model is not a randomizer, it's surface strikes. Hitting a certain part triggers a damage animation and effect for that area.
D9 the radiator is in the nose, in front of the engine like a car, and usually the first thing to go, that or an oil leak, sometimes both. Biggest objects in front view.
In a 38 the engines and cockpit are the largest parts, more likely to be hit first.