Aircraft Thrust Reverser Actuation System Torque Management
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Solution Overview
Problem
Conventional electrically powered thrust reverser actuation systems (eTRAS) face limitations in transmitting sufficient power due to the design constraints of flexible shafts, leading to increased size and weight, and are inadequate for more powerful thrust reverser actuation systems in larger aircraft engines.
Innovation Solution
The system employs a one-to-one correspondence of flexible shafts and actuators, with torque limiting brakes at the power drive unit to manage torque loads and prevent damage, and an energy-absorbing slip-clutch to handle kinetic energy, ensuring structural integrity and positional symmetry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional series arrangement of flex shafts is used to power multiple actuators, then device complexity is reduced, but power transmission capability deteriorates due to cumulative torque loads exceeding flex shaft design limits
Solution Approach 1:
The system segments the power transmission path by providing a dedicated flex shaft for each actuator instead of using a series arrangement. Each flex shaft is independently connected to the PDU and powers only one actuator, eliminating cumulative torque loads and allowing each shaft to be sized appropriately for its specific load requirements.
2Power
If flex shaft core diameter is increased to handle higher torque loads, then power transmission capability is improved, but ease of installation deteriorates due to larger minimum bend radius requirements
Solution Approach 1:
By segmenting the power transmission into separate flex shafts for each actuator, each shaft only needs to handle the torque required by its specific actuator rather than cumulative loads. This allows the use of smaller core diameter shafts with tighter bend radii that can be easily installed in the curved nacelle envelope.
3Reliability
If torque limiting brakes are added at the PDU for each flex shaft, then reliability is improved by preventing torque overload damage, but device complexity increases
Solution Approach 1:
Torque limiting brakes are installed at the PDU for each flex shaft to prevent torque overload damage before it occurs. These brakes are set to lock at predetermined torque thresholds, protecting the flex shafts, actuators, and engine structure from damage during jam conditions or abnormal operations.
4Ease of operation
If conventional series flex shaft arrangement is used, then ease of operation is maintained, but manufacturing precision deteriorates due to difficulty in maintaining output position symmetry
Solution Approach 1:
By providing independent flex shafts for each actuator, the system eliminates the complexity of maintaining positional symmetry in series arrangements. Each shaft-actuator pair can be independently adjusted and calibrated, ensuring precise and symmetric actuator outputs without the cumulative errors that would occur in a series configuration.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively addresses the power transmission limitations of conventional systems, enhancing the reliability and efficiency of thrust reverser actuation systems by ensuring each actuator receives the necessary power and protecting the system from torque overloads, while maintaining symmetry and reducing the risk of damage.
Implementation Method 1
a torque limiting brake or torque brake is positioned between the PDU and the flex shaft
Implementation Method 2
an energy absorbing slip-clutch between the motor and the gear train to absorb the motor's kinetic energy in the event of a sudden jam
Data Source
AI summary
An actuation system includes a power drive unit that drives a plurality of drive shafts that each has a first end individually connected to the power drive unit. The power drive unit includes a geartrain including a plurality of individual gears that are offset relative to each other along the gearbox, and a motor-driven rotation of one of the plurality of individual gears drives rotation of the other individual gears, and each of the plurality of individual gears rotates to drive rotation of a respective one of the plurality of drive shafts. A plurality of torque brakes is mounted to the gearbox, the torque brakes being mechanically coupled to respective individual gears and drive shafts. When the torque being passed through is above a predetermined threshold value, a locking of one of the torque brakes stops rotation of all gears simultaneously to maintain positional symmetry in the actuation system.