Description

Technical Field This invention pertains to a thrust reverser actuation system for multi-engine aircraft and, more particularly, to such a system utilizing a single power source.

Commercial aircraft having jet engines require fan thrust reversers which are lightweight, reliable, and maintainable and which provide safe, dependable operation. It is important that there not be asymmetric reverse thrust with respect to jet engines positioned on opposite wings of the aircraft. The thrust reverser actuation system with a single power source provides for simultaneous operation'.of thrust reverser actuators associated with plural jet engines of a multi-engine aircraft by mechanical connections to the thrust reverser • actuators whereby all of the thrust reversers will be uniformly positioned. If a thrust reverser is jammed against movement the thrust reversers of the other jet engines will stop at the same position to avoid the possibility of asymmetric reverse thrust.

Background Art Jet engines for commercial aircraft utilize fan thrust reversers which are moved between stow and deploy positions and, in the latter position, exert a reverse thrust to reduce .the*forward speed of the aircraft. •

Known actuation systems for the thrust reversers of a jet engine utilize a drive source mounted at the jet engine and which can be operated by a direct power take-off from a jet engine accessory gearbox or by some

other hydro-mechanical, hydraulic linear cylinder, pneu¬ matic or electric power source.

A typical thrust reverser actuator includes a reversely rotatable ball screw associated with a ball nut whereby the rotation of the ball screw can cause movement of the ball nut and a thrust reverser toward or away from the stow position. An example of this type of actuator is shown in the Stearns Patent No. 3,829,020 wherein a plurality of ball screw actuators associated with a jet engine are driven by a suitable rotary prime mover, such as a pneumatic, hydraulic or electric motor and with the alternate of being driven by a direct power take-off from an engine accessory gearbox and synchro¬ nized through angle gearboxes and flexible shafts. When the thrust reversers at a jet engine are positioned independently of those at another jet engine by a drive source at the jet engine, there is a possi¬ bility of asymmetric reverse thrust. There can be a jam-preventing movement of the thrust reversers of one jet engine while the thrust reversers of a jet engine on an opposite aircraft wing continue to move. When asymmetric reverse thrust occurs, considerable pilot skill is required to maintain a safe landing of the aircraft, especially on wet or snow-covered runways. The use of a hydraulic power drive unit as¬ sociated with a jet engine for operation of the thrust reverser actuators is known in the art, with examples of such power drive units being shown in the Flippo Pat¬ ent No. 4,191,094 and the Aldrich Patent No. 4,210,066, both owned by the assignee of this application. These patents show a variable displacement hydraulic motor driving a shaft connectable to thrust reverser actuators and hydraulic circuitry associated with the motor for providing controlled operation in stow and deploy cycles.

With such a power drive unit and control circuitry being associated with an individual aircraft jet engine, there is a sizeable package of components which must be located within the jet engine nacelle. The location of the power drive unit within the jet engine nacelle taken with the requirement for a minimum size of the jet engine nacelle for aerodynamic efficiency requires component design which may adversely affect the cost and weight of the power drive unit. The prior art does not disclose a thrust reverser actuation system for multi-engine aircraft utilizing a single power source for reducing the likelihood of asymmetric reverse thrust.

Disclosure of the Invention

A primary feature of the invention is to provide a thrust reverser actuation system for multi-engine aircraft wherein the actuators for the thrust reversers of the jet engines are driven from a single power source. If the thrust reversers at one jet engine jam, the thrust reversers of the other jet engines will be stopped at the same position to thus avoid asymmetric reverse thrust. The single power source can be located on the fuselage of the aircraft and mechanical shafting extends from the single power source to the thrust reverser actuators at the jet engines. This inventive feature is contrary to the accepted practice of those skilled in the art wherein readily available power at the engine has been used for operating thrust reverser actuators associated with that engine.

Asymmetric reverse thrust resulting from inoperability of thrust reversers of a jet engine mounted on one wing of an aircraft requires a considerable

pilot skill to overcome the difficulty when landing the aircraft, particularly when the airport runway is wet, icy, or covered with snow. The problem is particularly acute with a twin-engine aircraft having high thrust engines. There is still a problem, but it is less acute, with an aircraft having more than two engines since, with a four-engine aircraft, for example, the failure of the thrust reversers in one engine will only affect one-fourth of the total thrust. The inven- tion disclosed herein reduces the likelihood of asymmetric reverse thrust by driving all the thrust reversers from a common power source.

Utilizing a single power source for the thrust reversers of plural jet engines, the number of drive components required per aircraft are less. Using a single power source, such as a hydraulic power drive unit of the types shown in the Flippo and Aldrich patents previously referred to, only requires that the power drive unit be made sufficiently more powerful to drive the -thrust reverser actuators for two or more jet engines; however, only a single hydraulic control circuit is required. This reduces the number of circuit com¬ ponents per aircraft to resultingly improve reliability. Further, the only connections to the thrust reverser actuators within the engine nacelle are mechanical which require minimal maintenance. The power drive unit is mounted at a central location on the aircraft fuselage and may be easily accessed for service.

With a single hydraulic power drive unit, the only power supply connections required are supply and return ports for hydraulic fluid. When an electro¬ mechanical power drive unit is used, there is only a single electrical connection to be made.

A further advantage of the single power source thrust reverser actuation system resides in the location of the power drive unit in the aircraft fuselage whereby the mounting space permits efficient design of the power drive unit for weight and cost, rather than having to design the power drive unit for placement within an engine nacelle requiring a minimum size for aerodynamic efficiency.

An object of the invention is to provide a thrust reverser actuation system for multi-engine aircraft utilizing a single power source whereby the likelihood of asymmetric reverse thrust is reduced. Still another object of the invention is to provide a thrust reverser actuation system, as defined in the preceding paragraph, wherein the single power, source is a power drive unit mounted in the fuselage of the aircraft and mechanical shafting extends between the power drive unit and the thrust reverse actuators at each of the jet engines whereby, if the thrust reverse mechanism of one engine jams, the thrust reverse mecha¬ nisms of the other engines will be stopped at the same position in order to achieve symmetric reverse thrust.

An additional object of the invention is to provide a thrust reverser actuation system, as defined in the preceding paragraphs, having only mechanical connections between the thrust reverser actuators at the engines and the power drive unit mounted on the aircraft fuselage whereby maintainability of the system is improved because of there being only mechanical components within the engine nacelles and the hydraulic components being accessible at the aircraft fuse'lage.

Still a further object of the invention is to provide a thrust reverser actuation structure for

controlling the operation of thrust reverser actuators associated with plural jet engines of an aircraft comprising, a power drive unit having an output shaft, a pair of mechanical drive trains both connected to said output shaft with one mechanical drive train extendable to the thrust reverser actuators of one jet engine and the other mechanical drive train extendable to the thrust reverser actuators of the other jet engine.

An additional object of the invention is to provide a thrust reverser actuation structure in combina¬ tion with a multi-engine aircraft having a fuselage with a pair of wings extending therefrom comprising, at least one jet engine positioned on each wing, each jet engine having a plurality of thrust reverser actuators inter- connected for simultaneous movement, a power source carried by said fuselage and having an output shaft, and mechanical drive means extended from said output shaft to the thrust reverser actuators at each jet engine whereby a jam of the thrust reverser actuators at one jet engine will cause a stopping of the thrust reverser actuators of the other jet engine at the same position.

Brief Description of the Drawings Fig. 1 is a perspective view of a multi-engine aircraft;

Fig. 2 is a schematic view of the .thrust reverser actuation system in association with plural engines; and

Fig. 3 is a transverse partial section of an aircraft with the thrust reverser actuation system.

Best Modes for Carrying

Out the Invention

The thrust reverser actuation system disclosed herein is for use with a multi-engine aircraft with an aircraft of this type being shown in Fig. 1. The air¬ craft has a fuselage 10 from which extend a pair of wings each having a jet engine associated therewith. A jet engine 12 is shown in association with a wing 14 and a jet engine 16 is mounted on an opposite wing 18 extending from the side of the fuselage not visible in Fig. 1.

Each of the jet engines 12 and 16 is of the type well known in the art wherein the engine thrust can be reversed for rapid reduction of aircraft speed upon landing. This thrust reversal is achieved by the deploy¬ ment of thrust reversers within the engine nacelle which are normally stowed in ^" -an inoperative position.

The thrust reverser actuation system is shown particularly in Figs. 2 and 3. Each of the jet engines 12 and 16 has a nacelle shown in broken line at 20 and 22, respectively in order to facilitate visualization of the thrust reverser actuation structure.

The jet engine 12 has a series of thrust reverser actuators 26 located in a circular array within the engine nacelle 20 and each has a ball screw 27 connect¬ able to a thrust reverser (not shown) in a conventional manner. Each of the ball screws is caused to move lengthwise of the engine by a ball nut 28 in fixed position relative to. the engine. The ball nuts 28 are rotated to cause linear movement of the ball screws 27 by means of a drive from a power source to be described. With an input from a power source to a Tee gear box 30, there are mechanical drive connections extending therefrom in opposite directions in the form of torque transmitting tubes. These mechanical drive tubes are

shown at 32 and 34 and connect to the drives for the ball nuts 28 for each of the thrust reverser actuators

26. A suitable form of mechanical t.orque transmitting structure is shown in the Embree patent No. 4,256,277, owned by the assignee of this application and the structure thereof is incorporated herein by reference.

The jet engine 16 has a similar construction with the thrust reverser actuators 40 circularly arrayed about the jet engine and with each of the thrust reverser .actuators having a linearly movable ball screw 42 associated with a ball nut 44. The thrust reverser actuators are caused to move from a power source, to be described, which connects into a Tee gear box 46 and which has a pair of mechanical torque transmitting drive shafts 48 and 50 extending oppositely therefrom to connect to the drives for the ball nuts 44.

The thrust reverser actuation structure shown for each of the jet engines 12 and 16 utilizing the ball screws and ball nuts is well known in the art and with the power source being at the engine.

The disclosed embodiment of the invention shows the thrust reverser actuators 26 and 40 at the respective jet engines 12 and 16 being operated from a single power source. A jam of the thrust reversers at one jet engine cannot result in asymmetric reverse thrust since the thrust reversers at the other jet engine will stop at the same position as the thrust reversers which are jammed.

The single pQwer source is shown in Figs. 2 and 3 and is located within the fuselage 10 of the aircraft. The single power source is preferably in the form of a power drive unit of the type disclosed in the Flippo and Aldrich patents previously referred to.

The power drive unit has a variable displacement hydraulic motor 60 connected to an output shaft 62 having a gear 64 which meshes with a gear 66 connected to the

Tee gear boxes 30 and 46 by mechanical shafting. -Mechani- cal shafting 68 extends to the Tee gear box 30 of the jet engine 12 and mechanical shafting 70 extends to the

Tee gear box 46 of the jet engine 16. This mechanical shafting can be of the type disclosed in the E bree patent previously referred to. The motor 60 is controlled by a hydraulic control circuit indicated generally at 74 having connections to inlet and return ports of the motor. The control circuitry has connections to a fluid pressure inlet line 76 and a return line 78 and also a command electrical line 80. The output shaft 62 has a hydraulically released brake 82 operable to permit rotation of the output shaft 62 when the control circuit 74 causes operation of the hydraulic motor 60.

As seen particularly in Fig. 3, the power drive unit providing the single power source can be located at a convenient location in the fuselage 10 of the aircraft to facilitate the servicing of the hydraulic components. The mechanical shafting 68 and 70 extends oppositely from the power drive unit through parts of the fuselage and the wings 14 and 18, respectively, for connection to the Tee gear boxes 30 and 46.

With the thrust reversers in inoperative stowed position a command delivered through the command electri¬ cal line 80 to the control circuitry 74 for the motor 60 causes operation, of the motor in a direction to drive the ball screws 27 and 42 of the jet engines in a direction to deploy the thrust reversers. In the event there should be a jam of the thrust reversers at one jet engine, this will cause a stall of the hydraulic motor 60 with the result that the thrust reverser actuators

of the other engine will be stopped in the same position.

Only mechanical structure is positioned within the nacelle of a jet engine. The motor 60 and control circuitry 74 being in the fuselage assists in minimizing the dimensions of the nacelle for aerodynamic efficiency. This also facilitates servicing of the- hydraulic components because of their location in the fuselage.

A power drive unit of the type shown in the Flippo and Aldrich patents would have to be designed with additional power for operating the thrust reverser actuators of plural jet engines which would result in an increase of weight thereof; however, since there is only one control circuit 74 required for a single hydraulic motor 60, the number of components per aircraft are less with resulting improvement in reliability.