Aileron augmented directional control and braking
Current landing and braking systems are associated with the approach, flare and rollout.
Automatic and independent brake systems prevent skidding but do not restore the aircraft
to the original trajectory. None use the normal aerodynamic surfaces to augment braking
effectiveness to steer the aircraft during sudden changes in runway surface conditions.
Many aircraft accidents occur during landing. The task of bringing the aircraft to a safe
taxing speed from touchdown in variable weather conditions is the most difficult
manoeuvre that a pilot has to make. There is no opportunity to recover or reattempt the
manoeuvre. It is the only phase of the aircraft operation that has not been effectively
improved through the use of autopilot control systems. Improving this regime of operation
through the use of formally redundant aerodynamic control surfaces is the subject of this
This thesis describes the development and testing of a controller, auto-pilot and ABS
combination that uses ailerons to control the normal loading differential between the main
gear of a B747-100 for the purpose of increasing the directional control so that is it
possible to either minimising the centre line off-set or to maintain heading of a landing
The aileron based differential nonnal loading controller uses the brake line pressure
differential as an input variable to control the ailerons during touchdown. During the
maximum braking case, the brake line pressure is proportional to the difference in runway
friction coefficient, normal loading, and brake disk stack friction coefficient.
Landing aircraft are extremely non-linear in function. To overcome this, a model and
Controller that generates the appropriate non-linear mathematical description of the
aircraft during the landing phase and generates an effective controller that effectively
generates an increase in normal gear force on touch down of 100% and thereby allowing
the aircraft to be controlled in direction during hazardous conditions was developed.
The outcome of the work is that the use of a control scheme and unconventional use of
ailerons can significantly improve aircraft landing characteristics during adverse landing
weather conditions and reduce the number of accidents.
Current advances in future aircraft design are tending towards tailless aircraft such as
Boeing's Blended Wing Body aircraft and a similar study by Airbus. These aircraft do not
have sufficient rudder or engine yaw control at landing speeds. This work provides a
method of steering the aircraft from touchdown to taxi speed through normal force and