We know that lighter vessels like frigates and cruisers can in fact land on planets, for the purpose of discharging their drive cores, because that is specifically allowed for in the codex: "The safest way to discharge a core is to land on a planet and establish a connection to the ground, like a lightning rod. Larger vessels like dreadnoughts cannot land and must discharge into a planetary magnetic field".
So dreadnoughts are too bulky for landings, but not a frigate like either the SR-1 or SR-2.
As I recall, the ME2 codex says simply that "Its shuttle can make landings the Normandy cannot attempt," presumably in heavy gravity or storms. But that doesn't actually rule out landings on other planets. The ME3 codex rather oddly diverts this to the original SR-1: "Its state-of-the-art Kodiak shuttle can make landings the original Normandy could not attempt." SDoradus (talk)
In ME2, the SR-2 easily docked at Nos Astra, so even back then, it was clear that it can land on planets (in this case, Illium). Land Raider
The question is even more problematic, since the direct quotation from the codex clearly stays in opposition to what we see in very Mass Effect 3 opening. One Alliance Dreadnought (the one which gets destroyed by a Reaper) is clearly visible within Earth's atmosphere. -Caru
Caru is resurrecting a post over two years old. Also, ships touching down on planets is covered in the codex (and in earlier posts). The Normandy is not "suddenly" able to land in planets - it's had that ability since ME1 (you see it hovering in Virmire, for example). It's also worth observing that even in ME2 it was made clear that frigates landing on planets was perfectly possible, especially when discharging their drive cores "by touching a planet surface". SDoradus (talk)