Twin-Engine Helicopter Cruise Control With Freewheel Decoupling
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Solution Overview
Problem
Helicopter turbo-shaft engines operate suboptimally in cruise conditions, leading to high specific fuel consumption due to oversizing, and existing methods to reduce fuel consumption are limited by requiring specific operating conditions and potential risks during flight mode transitions.
Innovation Solution
A method for controlling a twin-engine helicopter that allows one engine to operate at reduced power while maintaining engine coupling, using a free wheel mechanism to disengage power transmission and an avionic system to monitor and manage flight parameters, enabling efficient power distribution and transition between nominal and asymmetric cruise regimes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If both turbo-shaft engines operate at cruise speed, then sufficient power is available, but specific fuel consumption increases due to engine oversizing
Solution Approach 1:
The patent divides the power delivery function between two engines, allowing one engine to operate at optimal efficiency while the other is stopped. This segmentation enables the operating engine to deliver required power at higher efficiency points, reducing overall specific fuel consumption during cruise flight.
Solution Approach 2:
The system dynamically transitions between different engine operation modes (both engines running vs. one engine stopped) based on flight conditions. This dynamic adaptation allows the helicopter to optimize fuel consumption by selecting the appropriate configuration for current power requirements.
2Use of energy by moving object
If one turbo-shaft engine is stopped to reduce fuel consumption, then specific fuel consumption decreases, but the helicopter can only operate under determined conditions
Solution Approach 1:
The control system continuously monitors flight parameters and automatically manages engine configurations based on real-time conditions. This feedback mechanism ensures the helicopter operates in the asymmetric cruise regime only when appropriate conditions are met, maintaining adaptability while optimizing fuel consumption.
Solution Approach 2:
The system autonomously determines when to transition between symmetric and asymmetric engine configurations based on pre-defined operational criteria, reducing pilot workload and ensuring optimal fuel efficiency without compromising operational flexibility.
3Use of energy by moving object
If asymmetric cruise regime is implemented, then fuel efficiency improves, but transmission coupling must be modified or redesigned
Solution Approach 1:
The patent introduces a free wheel mechanism as an intermediary element between the engine and transmission. This free wheel allows the engine to be decoupled from the transmission when stopped, preventing reverse rotation and protecting the transmission while enabling asymmetric cruise operation without major transmission redesign.
4Adaptability or versatility
If free wheel mechanism is added to enable asymmetric cruise, then engine coupling is preserved, but device complexity increases
Solution Approach 1:
The free wheel mechanism serves multiple functions: it allows engine decoupling during asymmetric cruise, prevents reverse rotation damage to the transmission, and maintains the ability to operate in both symmetric and asymmetric configurations. This multi-functionality justifies the added complexity by enabling fuel-efficient operation.
Data Source
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AI summary
A method for controlling an aircraft (1) capable of hovering is described, comprising a first engine (10a); a second engine (10b); at least one rotor (3); and a transmission (8) interposed between the first and second engine (10a, 10b) and the rotor (3); the transmission (8) comprises a first and a second inlet (12a, 12b) connected respectively to a first outlet member (11a) of the first engine (10a) and to a second outlet member (11b) of the second engine (10b); the method comprises step i) of placing the aircraft (1) in a first configuration, in which the first and second engine (10a, 10b) make available a first and a second power value (PI, P2); or in a second configuration, in which the first engine (10a) makes available a third power value (P3) greater than the first power value (P1) to the first inlet (12a), and the second engine (10b) delivers a nil power value (P4) to the second inlet (12b); the method also comprises, characterised in that it comprises the steps of ii) detecting a series of parameters associated with the operating conditions of the aircraft (1); and iii) enabling the transition of the aircraft (1) from the first configuration to the second configuration, when the parameters assume respective first values.