Multi-Engine Aircraft Asymmetric Power Management
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Solution Overview
Problem
Multi-engine aircraft face challenges in rapidly increasing the power output of a standby engine from a low-power to a high-power mode, especially during asymmetric operation, which can lead to thermal stresses and impact engine lifespan.
Innovation Solution
A method and system for operating a multi-engine aircraft that includes a processing unit and storage medium to manage engines in an asymmetric operating regime, allowing for emergency and normal exit modes, where the standby engine's rotational speed and power output are increased at different rates to re-clutch and match the active engine's power, optimizing power transition and reducing thermal gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the standby engine rapidly increases its power output from low-power to high-power mode, then the response time is improved, but thermal stresses increase and engine lifespan is reduced
Solution Approach 1:
The system dynamically adjusts the power output increase rate of the standby engine based on operational context. Two distinct modes are implemented: emergency mode allows maximum permissible speed rate of change for rapid response, while normal mode uses a lower rate of change to minimize thermal stresses. This dynamic adaptation resolves the contradiction by optimizing the power transition rate according to the specific operational situation.
Solution Approach 2:
The system changes the operational parameters of the standby engine based on the type of exit request. The power rate of change parameter is set to different values depending on whether an emergency or normal exit is requested. This parameter adjustment allows the system to achieve rapid power increase when necessary while protecting engine components during routine operations.
2Loss of energy
If the standby engine operates in standby mode with de-clutched gearbox connection, then fuel efficiency is improved, but rapid power response capability is reduced
Solution Approach 1:
The standby engine is maintained in a prepared state with rotational speed control systems ready, allowing it to rapidly increase power output when needed. The engine remains de-clutched during normal operation to save fuel, but the control system pre-configures the engine for rapid activation, resolving the contradiction between fuel efficiency and response capability.
Solution Approach 2:
The system dynamically transitions the standby engine from a low-power de-clutched state to a high-power clutched state based on operational demands. This dynamic state change allows the engine to maintain fuel efficiency during normal operation while being capable of rapid power response when emergencies or additional power requirements occur.
3Loss of time
If the standby engine increases rotational speed at maximum permissible rate, then re-clutching time is reduced, but thermal gradients and mechanical stresses increase
Solution Approach 1:
The rotational speed increase rate is dynamically adjusted based on the operational context. During emergency exits, the maximum permissible speed rate of change is applied to minimize re-clutching time. During normal exits, a lower speed rate of change is used to reduce thermal gradients and mechanical stresses. This dynamic adjustment resolves the contradiction between speed and stress.
Solution Approach 2:
The control system applies preliminary anti-action by limiting the speed increase rate during normal operations to prevent excessive thermal stresses before they occur. This preventive approach allows the system to protect engine components while still maintaining the capability for rapid response when emergencies occur.
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
In an asymmetric operating regime, a first engine (102) is operating in an active mode to provide motive power to an aircraft (100) while a second engine (104) is operating in a standby mode and de-clutched from a gearbox of the aircraft (100). In response to an emergency exit request, the second engine's speed is increased, at a maximum permissible rate, to a re-clutching speed while increasing the first engine's power output at a maximum permissible rate. When the re-clutching speed is reached, the second engine's power output is increased at a maximum permissible rate. In response to a normal exit request, the second engine's speed is increased to the re-clutching speed at a rate lower than the maximum permissible rate. When the re-clutching speed is reached, the second engine's power output is increased at a rate lower than the maximum permissible rate.