I remember reading on Soda's aircraft page that the Ju87 flies
slightly faster without its landing gear, and so I decided to see if an aircraft's performance could be improved by deliberately ripping off its wheels.
For this test I climbed into a 190A5 with 2x20mm, 2xMG, full ammunition. I recorded my weight, and turned the fuel burn down. I took off. A 190A5 with this configuration weighs 8584 of the game's weight units, and at 1000 feet it has a top speed of 332mph.
I then climbed to 10,000 feet, slowed down, dropped my gear, and dived. The gear came off with a bang. Left gear, right gear, and tailwheel.
The result was that my weight remained at 8584. And my top speed at 1000 feet was still 332mph. The gear mechanism still made a noise as they opened and closed, and there were holes where the gear doors had been, but these seemed to have no effect on the aircraft's speed. Perhaps the aircraft's balance was altered subtly, but I have no way to tell because I am do not fly enough to tell.
I extrapolate from this information that, in the case of fighter aircraft with retractable landing gear, the gear does not weigh anything, and it does not affect performance positively or negatively if you lose it. Perhaps it is different for heavy bombers.
I tried the Ju87 in a similar test. A fully-fuelled, non-bombed Ju87 with full MG ammo weighs 10681 bananas. At 3K it has a top speed of 236mph.
I climbed to 15,000, dived, and ripped off the gear. On the first test I also ripped off the ailerons and smashed into the sea, although I noticed that the aircraft's weight remained at 10681 units, even without the ailerons.
I ran the test again, and found that a Ju87 with ripped-off left and right wheel spats and tailwheel still weighs 10681 units, and it still has a top speed at 3K of 236mph. Perhaps it accelerates better, perhaps it flies as gracefully as Tinkerbell from Peter Pan, but it's certainly not any faster (than it was before - I'm not sure how fast Tinkerbell flew).
I extrapolate from this that (a) the Ju87 and D3 perform the same whether they have gear spats or not and (b) ailerons, elevators etc weigh nothing, and there is no performance benefit from losing them.
I had mental visions of the ultimate 190A5 modded speed demon, with 2x20mm, no MG ammo, ripped-off gear and one ripped-off aileron, but alas it is not to be.