Aircraft Wheel Brakes *

In designing brakes for the landing run, account should be taken of aerodynamic forces acting on the aircraft that reduce the ground reaction in addition to helping to retard the aircraft. There are good grounds for designing brakes with a limiting torque, because most British tail-wheel type aircraft will nose over if the brake drag exceeds about 0·2–0·3 times the aircraft weight, and with tricycle landing gear the loads imposed on the nose-wheel structure during severe braking may be critical; furthermore, the danger from bursting a tyre, owing to locking the wheel, cannot be ignored. Calculations made for a hypothetical aircraft indicate that little is gained by designing for a brake drag in excess of about 0·3 times the aircraft weight.

Brakes are used both for steering and limiting the speed of the aircraft when taxi-ing, and in consequence, a very large amount of energy may have to be dissipated by them.

Shoe brakes are standard equipment on German aircraft, and are also widely used in America, but use on British aircraft is confined to the smallest types. British designers have used expander-tube brakes almost exclusively, but disk brakes—popular in America—are now receiving close attention in this country.

The British system of brake control is to use finger operation, with a differential mechanism coupled to the rudder control, but in most other countries foot pedals are employed. The British system necessitates power operation almost always, but direct operation is possible when foot pedals are used. Pneumatic power transmission for brake operation has been widely used on British aircraft, but most other countries have adopted hydraulic operation.