The Boeing 737 has a set of two wheels for its nose landing gear and two sets of two wheels for the main landing gear. This is a common layout for single-aisle planes, and it is also shared by the Airbus A320 , for example. What isn't shared with the Airbus, however, is how the gear functions.
This is unusual because almost every other airliner covers its main landing gear doors: the Boeing 757 is a good example of this. Furthermore, there has never been a widebody aircraft with exposed main gear wells.
The low-riding stance of the 737 isn't a factor here. The BAC 1-11, another airliner close to the ground, has doors for its main landing gear, as an example.
But both the ground clearance and the lack of doors have a common reason. That is, simplicity. The 737 in its original form was designed to operate short routes to smaller, less developed airfields.
The idea was to make an aircraft as robust and as simple as possible. Being low to the ground made it easy for ground crews to service the plane.
Additionally, landing gear doors do save some fuel as they're more aerodynamically efficient, but they do add weight.
With all of these factors, Boeing let the gear stick out.
The 737 was a short-haul plane for serving underdeveloped airfields when it was first unveiled, but that's no longer the case.
It's now a huge mainline plane serving major cities that can seat 200 passengers and can even traverse the Atlantic Ocean.
The Boeing 737's design decisions have significant implications for its maintenance, fuel efficiency, and overall performance.
