I’m glad you asked!
The landing pads in Elite dangerous come in three flavours. Small (66m x 55m), Medium (150m x 90m) and Large (213m x 128m) and these are rotating tables that sink into a shaft and rotate 180 degrees before reversing your ship into the hangar below.
See this early render of the Panther LX.
So far so good.
Now a Lakon Type-7 Transporter is (according to my blueprints) 56.1m wide by 81.6m long and 25.4m high. Which means the Type-7 sits well within the maximum size of the pad.
It’s not so big
Compared to the more expensive multi-role Python, the Type-7 is both shorter and narrower despite having similar cargo sizes and yet the Python is Medium ship. So, what’s the problem?
Height. That pesky 3rd dimension is raining on our Medium pad parade!
The highest Medium pad ship is the Federal Assault Ship which is 49.5m wide by 73.8m long and 22.8m high. That means the maximum headroom for a Medium hangar is somewhere between 22.8m and 25.4m, the average of which is a few centimetres short of 24m, so it’s safe to assume that the ceiling is 24m for a ship with gear deployed.
Which, for the Type-7, is a problem because without gear out, it’s already more than 25m high – closer to 27m with feet on the ground.
Like really tall men and women everywhere the poor Type-7 just has to shop elsewhere for hangars big enough, because what fits all those other Medium ships just isn’t tall enough for the Type-7.
And that's why the Type-7 Transporter cannot land on Medium pads. Not because the ship is too big for the pad, but because the ship is too high for the medium hangar.
This is the blueprint for the Lakon Spaceways Type-7 Transporter. The Volvo of the skies, this ship is "boxy but good" and the ideal trader stepping stone before moving on to a Python or Imperial Clipper.
First introduced in version 0.1 Gamma 2.