Why? Pilots would be able to assess their damage. Maybe not to the degree of 'alt-d'
but surely our virtual counterparts shouldn't be left in complete ignorance by disabling
such. And attempting to program the gauges to reflect the potential extent of damage
may be too much a row to hoe for now.
The gauges already reflect damage and it wouldn't leave pilots in any kind of ignorance. There's already the auditory cue that something is damaged. There's already an indicator for tail wheel, left gear, right gear, engine oil, engine temp. There's oil smoke, coolant steam, fuel vapor, fire, blood.You can visualize all of the control surfaces from the cockpit of most planes, and wing gun damage for that matter. Disabling system damage display would increase immersion by leaving pilots to depend on their guages, eyes and ears and a nearby wingman to assess their damage situation.
Why not just not use Ctrl-d you say. Well remember game immersion is something players general wont want until they have to experience it, and then they dont want to lose it. And by this way it would make the AH experience that much richer. Not to mention every player in the game is just going to tell you to use ctrl-d when you ask them to look your plane over for damage.