I know that the one assignment to unlock the MG14/17 in the new DLC is destroying 2 planes with the Madsen MG Trench, and while it is ridiculous, and we all have our complaints about it, I simply have to ask if its even possible to take out a plane with the Trench variant. I played a quick round of Conquest on Fao to see how it fairs against a plane, and honestly, even though I suck at landing damage on planes with a LMG, I don't think I could do more than 10 damage on the planes in one pass/one magazine. The only way I can see taking out a plane with the Trench variant, is if theyre already severely damaged, and in that case, they are probably far away repairing themselves, and far out of the range of the Madsen Trench.
This is how I faired with it against a plane. Not well. Its like shooting BBs at kevlar.