Aeronautics and astronautics – Aircraft control – Automatic
Reexamination Certificate
2000-07-14
2002-09-10
Poon, Peter M. (Department: 3643)
Aeronautics and astronautics
Aircraft control
Automatic
C244S078200, C318S564000, C091S36300A, C701S004000
Reexamination Certificate
active
06446911
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to vehicle control systems, and more particularly, to a method for electronically controlling controllable devices attached to a surface on an aircraft.
BACKGROUND OF THE INVENTION
In recent years, fly-by-wire flight control systems have replaced many mechanical flight control systems. While older aircraft incorporated complex mechanical assemblies requiring cables and other mechanical components to transmit pilot commands to the control surfaces, fly-by-wire flight control systems were designed to convert a pilot's commands into electrical signals that, when combined with other data, control flight control surfaces. In fly-by-wire flight control systems, a pilot's commands are translated into electrical signals through the use of transducers that sense the pilot's inputs. The electrical signals produced by the transducers are fed to a flight computer, along with other data indicative of flight parameters. Based upon the data it receives, the flight computer generates signals designed to achieve the desired flight path commanded by the pilot. These signals, called flight control surface commands, are transmitted electrically, in typical fly-by-wire control systems, to actuator controller units. There are primarily two commercial fly by wire avionics technologies in the prior art. The first was developed by Boeing while the other was developed by Airbus.
As illustrated in
FIG. 1
, a typical airplane includes fuselage
110
, wings
112
(which provide the lift needed to fly the airplane), vertical stabilizers
114
and horizontal stabilizers
116
(which are used to ensure a stable flight) and engines
118
(which provide the thrust needed to propel the airplane forward).
To guide a vehicle such as an airplane during travel, flight control surfaces are placed on wings
112
, horizontal stabilizers
116
, and vertical stabilizers
114
. The primary flight control surfaces on an airplane include the ailerons
100
, the elevators
102
and the rudder
104
. Ailerons
100
are located on the trailing edges of the wings of the airplane and control the roll of the airplane. An airplane's “roll” is depicted in FIG.
2
A. Elevators
102
are located on the horizontal stabilizer of an airplane and control the pitch of the airplane. Pitching of an airplane is depicted in FIG.
2
B. Rudder
104
is located on the vertical stabilizer and controls the yaw of the airplane. Yawing of an airplane is illustrated in FIG.
2
C.
An aircraft's wings also include spoilers
106
, flaps
120
, and slats
122
, collectively known as secondary flight control surfaces. Spoilers
106
are located on the wings and perform a variety of different functions, including assisting in the control of vertical flight path, acting as air brakes to control the forward speed of the airplane, and acting as ground spoilers to reduce wing lift to help maintain contact between the landing gear and the runway when braking.
Flaps
120
and slats
122
are located on the wings of an airplane to change the lift and drag forces effecting an airplane, with flaps
120
at the trailing edge of wing
112
and slats
122
at the leading edge wing
112
. When flaps
120
and slats
122
are extended the shape of the wing changes to provide more lift. With an increased lift, the airplane is able to fly at lower speeds, thus simplifying both the landing procedure and the take-off procedure.
The primary flight control surfaces described above are operated by a pilot located in the cockpit of the airplane. Rudder
104
is typically controlled by a pair of rudder pedals operated by the pilot's feet. Ailerons
100
are controlled by adjusting a control wheel or control stick to the left or right Moving the control stick to the left typically controls the left aileron to rise and the right aileron to go down, causing the airplane to roll to the left. Elevator
102
is controlled by adjusting a control wheel or control stick to the front or back.
In most smaller airplanes, there is a direct mechanical linkage between the pilot's controls and the moveable surfaces. In most larger airplanes, there may be cables or wires connecting the pilot's controls to the hydraulic actuators used to move the primary control surfaces. In newer planes, a system called “fly-by-wire” has been developed.
When a new airplane is designed and built, and before it can be flown with passengers, it must be certified. In the United States, the Federal Aviation Regulations (“FAR”) govern the certification of planes. The FAR regulates potential problems that may occur in an airplane and divides components into various categories depending on the criticality of the component. For example, a Category A component is a component that, if it fails, results in loss of aircraft. A Category A component is also known as a critical component. A Category B component is a less important component: failure of a Category B component may result in the loss of life, but not the loss of the entire airplane. Components in Categories C, D, and E are even less critical: failure any of those components results in no loss of life.
The actuator controller units control the movement of the aircraft flight control surfaces in response to the flight control surface commands and feedback data obtained by monitoring various output parameters indicative of the operation and position of the flight control surface. Maintaining the normal operation of control channels in flight control systems is vital to proper aircraft control. In the event of control channel failure, the resulting loss of control over a flight control surface could jeopardize aircraft control. Because loss of control is of high concern, the response to control channel failure in flight control systems has been addressed in many ways.
The Boeing fly by wire system is mainly a digital control system with analog backup circuitry while the Airbus fly by wire system is mainly a digital control system. Each fly by wire system controls a computing lane by different technologies. The Boeing fly by wire system, for example, uses three computers, each with three lanes, to achieve a three-way redundancy comparison. A computing lane is an avionics control system having a computing system which communicates electronically with sensors on the aircraft, communicates with sensors which process the pilot's commands or actions, and also communicates with and controls the aircraft's hydraulic actuators. Each computing lane is capable of controlling the aircraft in its entirety. One reason that fly by wire systems use more than one computing lane is to provide redundant systems for safety. Another reason that fly by wire systems use more than one computing lane is to detect a computing lane electronic failure by comparing it to another computing lane, either of identical design or one which is similar in design.
Generally, actuators are controllable devices on an aircraft which are controlled by some other control device, such as a processor, a computer, a central processing unit or like device. Hydraulic actuators are the devices which move certain attached structural portions of the aircraft (such as an aircraft surface). Such structures include the aircraft's airfoils, ailerons, elevators and like structures which move on the aircraft and serve to assist in the operation of the aircraft. These structures are commonly referred to as “flight control surfaces” or “surfaces.” The movement of some aircraft surfaces can be seen, for example, during flight when one views the ailerons moving on the aircraft's wings during aircraft takeoff or aircraft landing. There are also surfaces at the tail end of the aircraft such as, for example, the aircraft's rudder. On some aircraft, there are two elevator surfaces, one on the left side of the aircraft's tail and one on the right side of the aircraft's tail.
In use, most hydraulic actuators receive command signals from a processor or like device. Each command signal corresponds to an ele
Todd John
Yount Larry
Collins Timothy D.
Honeywell International , Inc.
Poon Peter M.
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