Brake systems

Consultation of a specialist
(Skirko Oleg,excerption from article for the magazine " General Aviation")

As to the other landing gear element, the brake system, It is worth noting that utilization of elements specifically designed for certain technical conditions will ensure controllable motion on the ground and ability to stop at the desired point. .

At present a designer has a wide choice of brake systems, but these are mainly manufactured in the Western countries. Either for this reason or due to the too casual attitude to the brake system design on light aircraft one can see either mechanical bike brakes or hydraulic brakes with unreasonably small wheel cylinders and brake discs.

In the table below you can see the pressure on the master cylinder piston necessary to skid the wheel with different diameters of master cylinder pistons. These calculations have been based on the parameters as follows: wheel diameter 420 mm, aircraft weight 450 kg, master cylinder piston diameter 14 mm, brake disc diameter 200 mm.

Variant of one side wheel cilinder:

Wheel cylinder piston diameter, mm
Pressure on the master cylinder piston, kg
Pressure in the brake system, atm


Variant of two side wheel cilinder:

Wheel cylinder piston diameter, mm
Necessary pressure on the master cylinder piston, kg>
Pressure in the brake system, atm.


As we can see from the table above, with smaller diameter of the working cylinder piston and the brake disc it is almost impossible to put as much pressure on the master cylinder as necessary to create the necessary pressure in the brake system, which means that braking will not be efficient enough, wheels will continue to turn. When designing a brake system it is desirable to use: wheel cylinders with the maximum possible piston area; master cylinder ensuring fluid consumption necessary to create working pressure; brake discs of diameter as big as necessary to ensure the required braking moment.

We have designed and organized production of a complete set of elements of a hydraulic brake system for ultralight aircraft which ensure braking of aircraft with up to 750 kg takeoff weight. These are master brake cylinders, wheel brake cylinders, brake discs, fittings for various pipes.

Wheel cylinders can be of various types, as follows: one side single-piston cylinders mounted outside the brake disc, two side double-piston wheel cylinders.

Master cylinder travel ensures consumption of fluid necessary for functioning of double-piston wheel cylinders on two main wheels of an aircraft.

Designing the main cylinder and wheel cylinders we were trying to ensure maximum hydraulic transmission ratio and therefore the maximum braking power. Master cylinder piston has 14 mm diameter, wheel cylinder piston has 38 mm diameter. However, it is necessary to note that braking efficiency depends not only on the parameters of the brake system but also on the mechanical transmission ratio and configuration of the brake lever or footbrake, brake hose rigidity, wheel diameter.

We have also developed and produce additional devices, like parking valve which is used to ensure braking when the aircraft is parked with the engine on. In case of an aircraft with dual control the braking system can include the dual control valve which we also produce. This valve allows every pilot to engage brakes independently.To maximize control efficiency when taxiing the valve that ensures separate braking of each wheel can be included into the braking system. This device allows to block either only one (left-hand or right-hand wheel, depending on the position of the pedals) or both wheels when braking by means of brake lever which is located on the aircraft control stick.

The main component parts of the brake system are made of aluminum alloy D16T(2024), sealings are gasket sleeves and rings made of brake fluid-resistant rubber.


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