Variable Speed Rotorcraft Power Margin Control
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Solution Overview
Problem
In multi-engine rotorcrafts, restoring main rotor drive speed after engine failure is challenging, especially when the rotor is operating at low speeds relative to nominal speed, leading to difficulties in maintaining stable flight.
Innovation Solution
A method that adjusts the displayed mechanical power margin by reducing the safety margin when the rotorcraft is operating at low speeds, providing a power reserve to limit the drop in rotor speed and maintain stability during engine failure, by calculating a limited margin based on current flight conditions and AEO regime limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the main rotor is operated at low speeds to reduce noise and improve performance, then fuel efficiency and noise reduction are improved, but the ability to quickly restore rotor speed after engine failure deteriorates
Solution Approach 1:
The system pre-calculates and stores in a map the relationship between rotor speeds and required mechanical power margins before engine failure occurs. This preliminary action enables the flight control unit to immediately retrieve and apply the appropriate safety margin after engine failure, without requiring complex real-time calculations during the emergency situation.
Solution Approach 2:
The invention introduces a speed-dependent safety margin that acts as a cushion before engine failure. When operating at low speeds, a larger safety margin is maintained in advance, creating a buffer of available power that can be quickly deployed if engine failure occurs, thereby protecting against the worsening of rotor speed drop.
2Ease of operation
If a fixed safety margin is used for mechanical power management, then the system is simple to operate, but the system cannot adapt to varying rotor speeds and cannot provide adequate power reserve at low speeds
Solution Approach 1:
The invention transforms the static, fixed safety margin into a dynamic parameter that automatically adjusts based on rotor speed. The flight control unit continuously monitors rotor speed and retrieves the appropriate safety margin from a pre-calculated map, enabling the system to adapt to varying operational conditions while maintaining automated simplicity for the pilot.
Solution Approach 2:
The safety margin parameter is changed from a fixed value to a variable parameter that depends on rotor speed. By storing multiple safety margin values in a map corresponding to different rotor speeds, the system can automatically select the appropriate parameter value based on current operating conditions, achieving both adaptability and ease of operation.
3Loss of information
If the displayed mechanical power margin shows the full authorized margin, then the pilot has complete information about available power, but the pilot may inadvertently exceed safe power limits during engine failure scenarios
Solution Approach 1:
The invention applies a local quality modification to the displayed power margin information. Instead of uniformly displaying the full authorized margin in all conditions, the system selectively reduces the displayed margin when operating at low speeds, where the risk of excessive rotor speed drop is higher. This localized adjustment provides accurate safety information without sacrificing overall information availability.
Data Source
Figure 1(a)~2
Figure 3~4
AI summary
The invention relates to a method for assisting the navigation of a multi-engine rotorcraft (M1, M2) in the event of an engine failure. A main rotor (1) of the rotorcraft is driven at a variable speed NR controlled by a control unit (8). Calculation means (9) identify an allowable margin (Ma) of mechanical power available to the pilot according to a regime (AEO, OEI) for regulating the operation of the engines (M1, M2) controlled by a control unit (10). Except in the case of an engine failure and when the main rotor (1) is driven at a low speed NR, the margin of mechanical power available to the pilot, displayed on a screen (16), is a limited margin (MI) with a value lower than the allowable margin (Ma). Under these conditions, in the event of an engine failure, a reserve of mechanical power is thus maintained to allow the pilot to quickly counteract the sudden drop in the rotational speed NR of the main rotor (1) induced by the engine failure.