Fluid-pressure and analogous brake systems – Speed-controlled – Automatic braking including speed governor or hydraulic...
Reexamination Certificate
1999-02-01
2001-02-06
Butler, Douglas C. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Automatic braking including speed governor or hydraulic...
C303S122030, C303S020000, C303S009610, C303S015000
Reexamination Certificate
active
06183051
ABSTRACT:
TECHNICAL FIELD
The invention herein resides in the art of electrical brake control systems for aircraft. Specifically, the invention relates to an electrical brake control system for aircraft which provides for redundancy in the control system such that at least two faults within the brake control system must occur before there can be any inadvertent application of the aircraft brakes.
BACKGROUND ART
In aircraft braking systems it has always been desirable that inadvertent braking be prevented. In the mechanical braking systems of the past, the likelihood of inadvertent braking has been minimal, since brake metering valves simply do not fail in a “pressure applied” or braking mode. However, the advent of electrical or “brake-by-wire” systems has given rise to concerns that a hardware or software failure could result in undesired brake application. A primary concern in such systems is that a software fault might inadvertently apply brakes. In such brake-by-wire systems, the prior art has taught the use of dual software and dissimilar hardware approaches to achieving this redundancy. However, such approaches increase the cost of the braking systems and necessarily decrease their reliability Since the redundancy necessarily requires the implementation of more hardware and/or software, the maintenance problems are aggravated. It is also known to employ a single software system with a hardware monitor to set the hydraulic pressure at the brake and provide appropriate responsive action with respect thereto, but such systems suffer the same shortcomings, and which enables the brake valves with hardware.
There is a need in the art for a simple fail safe brake-by-wire system for aircraft that does not aggravate the reliability factor by significantly increasing the amount of hardware and software employed.
DISCLOSURE OF INVENTION
In light of the foregoing, it is a first aspect of the invention to provide a fail safe electrical brake control system for aircraft in which the shutoff valve of the brake control system is controlled with all hardware circuits, not software.
Another aspect of the invention is to provide a fail safe electrical brake control system for aircraft in which hardware and software operate in parallel to allow for an effective determination if a failure has occurred.
Still a further aspect of the invention is to provide a fail safe electrical brake control system for aircraft in which hardware and software receive and monitor the same avionics inputs, with a hardware branch determining if the system shutoff valve should be on, and the software branch determining if it should be off.
Yet an additional aspect of the invention is to provide a fail safe electrical brake control system for aircraft which is durable and reliable in use, easy to implement with state of the art aircraft brake control brake-by-wire systems, and which provides a fail safe system of significant integrity.
The foregoing and other aspects of the invention which will become apparent as the detailed description proceeds are achieved by an electrical brake control system for aircraft, comprising: a brake coil shutoff valve providing hydraulic pressure to an aircraft brake system; a shutoff valve driver connected to and selectively actuating said brake control shutoff valve; a pair of operator actuated brake pedals allowing the pilot to regulate the hydraulic pressure applied to brakes of the aircraft; a plurality of switches providing data respecting positional status of a landing gear, a landing gear handle, and a weight on wheel switch; a discrete logic circuit interposed between said plurality of switches and said shutoff valve driver for enabling said shutoff valve driver when said switches are in a first predetermined state; and a software controlled microprocessor interposed between said plurality of switches and said shutoff valve driver for inhibiting said shutoff valve driver when said switches are not in said first predetermined state.
REFERENCES:
patent: 3807810 (1974-04-01), Yarber
patent: 3847445 (1974-11-01), Bissell et al.
patent: 3917356 (1975-11-01), DeVlieg
patent: 3926479 (1975-12-01), Bissell et al.
patent: 4252014 (1981-02-01), Ruof
patent: 4293165 (1981-10-01), Hirzel
patent: 4410153 (1983-10-01), Romero
patent: 4572585 (1986-02-01), Guichard
patent: 4760491 (1988-07-01), Hurley
patent: 4834465 (1989-05-01), Guichard et al.
patent: 5044697 (1991-09-01), Longyear et al.
patent: 5397173 (1995-03-01), Bourguet
patent: 5417477 (1995-05-01), Lasbleis
Hill James L.
McFarland Lee E.
Aircraft Braking Systems Corp.
Butler Douglas C.
Renner Kenner Greive Bobak Taylor & Weber
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