Aircraft automatic braking system

Claim 2

In an aircraft automatic braking system having a preselected commanded deceleration level prior to touchdown of the main gear of the aircraft, a method of controlling the deceleration level of the aircraft automatic braking system comprising the steps of: increasing deceleration level of the aircraft automatic braking system to a constant level for a plurality of seconds after main-gear touchdown to minimize the amount of elevator control required to counter the pitch-down moment due to braking of the aircraft while still providing a minimum level of braking of the aircraft; determining nose-gear touchdown of the aircraft as a function of pitch angle; and then adjusting the deceleration level of said aircraft automatic braking system to said preselected commanded deceleration level upon determining nose-gear touchdown of the aircraft.

Claim 3

The invention according to claim 1 wherein nose-gear touchdown is determined at a pitch angle of the aircraft of less than one degree.

Claim 4

The invention according to claim 1 further including returning control of the deceleration of said automatic braking system to said automatic braking system in the event nose-gear touchdown of the aircraft is not determined to occur within a predetermined time period subsequent to main-gear touchdown.

Claim 5

The invention according to claim 3 wherein said predetermined time period is about eight seconds.

Claim 6

An aircraft automatic braking control system having means including deceleration selection switching means (30) for providing a deceleration command signal (330), means including main landing gear air/ground switching means (60) for providing signals representative of air/ground status of the main landing gear of the aircraft to initiate autobrake control function (90) of said aircraft automatic braking control system, the improvement comprising in combination: an inertial reference unit (140) for providing signals representative of pitch angle (210) and aircraft longitudinal deceleration (220); means including timing means (290) for providing signals representative of time from main-gear touchdown; means (280) responsive to said signals representative of time from main-gear touchdown for providing initial deceleration on-ramp command signals (190); means (240) responsive to said signals representative of pitch angle (210) for providing a pitch correction term signal (230); nose-gear-down logic circuit means (180) responsive to said signals representative of pitch angle (210) and said signals representative of time from main-gear touchdown for controlling and combining said initial deceleration on-ramp command signals (190), said deceleration command signal (330), and said pitch correction term signal (230) with said signals representative of aircraft body longitudinal deceleration (220) to provide a signal representative of deceleration error (260).

Claim 7

An aircraft automatic braking control system having means including deceleration selection switching means (30) for providing a deceleration command signal (330), means including main landing gear air/ground switching means (60) for providing signals representative of air/ground status of the main landing gear of the aircraft to initiate autobrake control function (90) of said aircraft automatic braking control system, the improvement comprising in combination: an inertial reference unit (140) for providing signals representative of pitch angle (210) and aircraft longitudinal deceleration (220); means including timing means (290) for providing signals representative of time from main-gear touchdown; means (280) responsive to said signals representative of time from main-gear touchdown for providing initial deceleration on-ramp command signals (190); means (240) responsive to said signals representative of pitch angle (210) for providing a pitch correction term signal (230); nose-gear-down logic circuit means (180) responsive to said signals representative of pitch angle (210) and said signals representative of time from main-gear touchdown for controlling and combining said initial deceleration on-ramp command signals (190), said deceleration command signal (330), and said pitch correction term signal (230) with said signals representative of aircraft body longitudinal deceleration (220) to provide a signal representative of deceleration error (260).