Boots – shoes – and leggings
Patent
1984-01-27
1987-02-24
Gruber, Felix D.
Boots, shoes, and leggings
364428, 303 93, 244111, B60T 804, G06F 1548
Patent
active
046462422
DESCRIPTION:
BRIEF SUMMARY
This invention relates to aircraft automatic braking systems and, more particularly, to aircraft automatic braking control during the time period between main-gear touchdown and nose-gear touchdown.
BACKGROUND OF THE INVENTION
Pitch command signals have been formulated heretofore as shown in U.S. Pat. No. 3,822,047 issued July 2, 1974. In contrast, a preferred embodiment of the present invention provides utilization of aircraft pitch angle data in an automatic braking system.
Heretofore, utilization of the autobrake system on aircraft has tended to derotate the aircraft following touchdown at a faster rate than would occur in a landing in which the pilot utilized manual brakes. This characteristic has been considered undesirable by some pilots since they feel that excessive elevator control is required to prevent a hard nose-gear touchdown. This problem has two roots: main-gear brakes will always impose a pitch-down moment on the aircraft. Present autobrake systems will apply brake pressure immediately after main-gear touchdown whereas a pilot will generally not apply manual brakes until after the nose gear is on the ground. Application of even low-to-moderate levels of braking will cause a rapid derotation of the aircraft if the nose gear is not yet on the ground and is unable to react the resultant pitch-down moment on the aircraft. The pitch-down moment prior to nose-gear touchdown can be reacted only by nose-up elevator control. further aggravated by use of an accelerometer for feedback control of deceleration by the autobrake system. The accelerometer mounted parallel to the aircraft's longitudinal axis is sensitive to pitch attitude such that the indicated deceleration includes not only the deceleration due to change in aircraft velocity but also includes the component of the gravity vector which is resolved onto the aircraft's longitudinal axis. For small nose-up pitch angles, this gravity component is proportional to pitch angle and is opposite to the direction of travel such that the indicated deceleration is less than the actual deceleration. The deceleration error due to pitch attitude may be equal in magnitude to the commanded deceleration but opposite in sign and will cause the autobrake system to substantially increase the brake pressure in order to meet the commanded deceleration. This worsens the derotation characteristics of the autobrake system.
Prior attempts to solve the aforementioned problem resulted in: have provided a solution to this problem by commanding a fixed low value of deceleration prior to nose-gear touchdown, then commanding the pilot-selected deceleration after nose-gear touchdown.
These systems have utilized nose-gear squat switches to detect nose-gear touchdown. While the general approach of commanding a low deceleration level prior to nose-gear touchdown is satisfactory, use of a nose-gear squat switch to detect nose-gear touchdown is not possible on all present aircraft in that a nose-gear squat switch signal is not available to all the present autobrake systems. Additionally, nose-gear squat switches, when present, are installed in an exposed position and are prone to mechanical damage. The relatively high failure rate of the nose-gear squat switches, coupled with the difficulty of detecting the switch failure on a routine basis make it desirable to find an alternative to the nose-gear squat switch to determine nose-gear touchdown.
An attempt to simply delay braking until it could be assumed that the nose-gear touchdown had occurred has proven unsatisfactory in cases where the pilot brought the nose down rapidly in order to make a short landing roll due to the built-in delay in significant braking. This was also unsatisfactory in cases where the pilot held the nose up longer than the assumed touchdown time delay in that application of brakes at that time still caused a rapid derotation of the aircraft. systems utilized wheel speed rather than accelerometers to determine deceleration. As a result, these systems were not subject to a pitch attitude error. Reverting
REFERENCES:
patent: 2942864 (1960-06-01), Sikora
patent: 3598453 (1971-08-01), Riordan
patent: 3926479 (1975-12-01), Bissell et al.
patent: 4007970 (1977-02-01), Romero
patent: 4076331 (1978-02-01), De Vlieg
patent: 4105258 (1978-08-01), Bornfleth
patent: 4410153 (1983-10-01), Romero
Black Thomas G.
Donahue B. A.
Gardner Conrad O.
Gruber Felix D.
The Boeing Company
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