The three primary methods of achieving deceleration on the runway during the landing roll or a rejected take off are thrust reversers, brakes and mechanical spoilers. Effective and co-ordinated use of whichever of these are available will result in a stopping distance appropriate to the available runway ahead, or the desired runway exit point if sooner.
1) Thrust Reversers
The most important action to achieve deceleration from a speed at which the engines are still producing forward motion is to select all thrust/power levers to the ground idle position promptly, and if available, continue the action through to the selection of reverse thrust or reverse propeller pitch.
This is the first action to begin deceleration and must especially be achieved without delay when a high speed rejected take off is initiated. Thrust reversers and reverse propeller pitch are most effective at high speeds.
Selection at these relatively high speeds must be symmetrical because otherwise, directional control may be prejudiced.
Once the aircraft groundspeed has reduced sufficiently, thrust/power levers should be returned to the ground idle position to prevent ingestion of any FOD which could be present, with reversers stowed once at taxi speed.
2) Wheel Brakes
When an aircraft lands or needs to decrease speed when it has already reached high speeds on the runway, the wheel brakes are used.
If wheel brakes were used on their own to stop the aircraft, the stress caused to the wheels by the mechanical braking components would be so powerful that they would be ripped apart.
However, when used with the other two components we list here they are very effective indeed. The performance of the wheel brakes largely depends on a number of factors.
These include:
a) The condition of the tire tread
b) Tire inflation pressure
c) The condition of the runway surface
d) The degree of brake wear and tear.
e) The majority of modern commercial aircraft are fitted with carbon wheel brakes, but steel brakes may be encountered on older aircraft types.
3) Mechanical Spoilers
Mechanical spoilers are present on both the upper wing surfaces and within the tail cone. When deployed, these spoilers work to increase aerodynamic drag on a moving airplane. Both upper wing spoilers and the “clamshell” spoilers in the tail can also be used in-flight as air brakes, and their doors can be operated hydraulically and pneumatically.
Mechanical spoilers have three main functions:
a) In-flight braking for reduction of speed
b) Air braking when on the ground
c) In-flight roll control used when turning the aircraft
Aircraft are designed to fly “clean”, that is without any drag. Spoilers get their name because they effectively spoil the clean aerodynamics of the aircraft by causing drag and slowing the aircraft.
**Special brief
In the case of an abnormal landing roll or any rejected take off, the appropriate SOPs is to maximize deceleration rate using whatever methods are available, taking account of the degree to which built-in system protections against inadequate wheel rotation are present.
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