I had a thought today while animating a main gear assembly. My understanding of drawcalls is that they basically add up to:
(number of meshes) x (number of materials in those meshes)
Ergo, if I have a fuselage, and it's one part, but has two materials, and I have a wing, and it's one part and one material, and those two meshes and three materials are it, and nothing is animated, then I ought to have three drawcalls. Fuselage would be 1 x 2, wing would be 1 x 1. If I had another five parts, and those used, say, the wing material, then it would be Fuselage ( 2 x 1 = 2 ), and the wing parts ( 6 x 1 = 6) for a total of 8 drawcalls.
I am incredibly lazy, so I combine parts - especially parts that have to be mirrored - relentlessly. If any two parts share a pivot and move together, I combine them. So someone who has a landing gear composed of several parts, but all linked to the top assembly, would have way more drawcalls than me, since I would simply attach all of those meshes into a single part (and treat every part as a "mini-scene" in and of itself, selecting and hiding certain elements when it came time to map).
Might this, combined with my not wanting to manage more than three or four texture sheets, be why my drawcall counts have historically been so low? The default airplanes seem to follow this methodology (hence the awkward shading on the 737 vertical stabilizer - the ten or so extra vertices would have been worth a separate smooth group, I think).