Wheels and Brake Assemblies
The main landing gear of the aircraft consists of two sets of trucks, each with four wheels with a total of eight wheels for the main gear, this gives a lot of braking capability and helps in making the 757 so versatile. Each of the eight wheels has a brake, which is operated using hydraulic power.
The nose landing gear is simpler: it has a single strut with two wheels and unlike the main gear wheels, these nose wheels don’t have brakes.
Normal Brake System: This is the primary brake system of the Boeing 757, and it is powered by the plane’s right hydraulic system (there are 3 hydraulic systems (Left, Centre and Right). Beyond just stopping the plane during landings, this system is also responsible for the parking brakes and other backup braking mechanisms.
Alternate Brake System: Think of this as the backup to the normal brake system and it’s powered by the plane’s left hydraulic system should the right not be available.
The nose wheels of the Boeing 757 have a straightforward design, the hub itself is made of two halves, held together with tie bolts. Each wheel-tire assembly is relatively lightweight, weighing about 95 pounds. There’s a feature to prevent over pressure, which activates if the tire pressure gets too high. Also, after takeoff, spin brakes are used to halt the spinning of these wheels once the landing gear is retracted into the bay – these brakes are mounted in the nose gear bay and work by friction to the outer surface of the tyre.
Main Gear Wheels
The main gear wheels are a similar design to the nose wheels and much like the nose wheels, these are also made of two halves. They have a safety feature also for over pressure – this valve steps in to reduce the pressure. Additionally, then there is a safeguard against potential tire failure from brake heat, there are fuse plugs that melt at a specific temperature. The main wheel design also incorporates rotor drive keys for the brake rotors and a heat shield to protect the wheel. Each of these wheel-tire combinations weighs approximately 242 pounds.