Hybrid Helicopter Yaw Margin Protection During Acceleration
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Solution Overview
Problem
Hybrid helicopters face a narrow margin for yaw maneuvering during acceleration from hovering to high-speed flight, as the authority of yaw control decreases with increasing mean pitch component, potentially leading to a loss of yaw attitude control margin.
Innovation Solution
A method that inhibits the thrust control when the yaw attitude control margin falls below a threshold, allowing the pilot to maintain a minimum margin for yaw control by temporarily reducing the mean pitch component of the propeller blades, thereby preventing the yaw control from reaching its stop and ensuring sufficient maneuverability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the mean pitch component of the propeller blades is increased to accelerate the hybrid helicopter from hovering to high-speed flight, then the forward speed and thrust are improved, but the yaw attitude control margin decreases and may be lost
Solution Approach 1:
The control computer continuously monitors the yaw attitude control margin by comparing the current yaw control position with the envelope of authorized flight control domain. When the margin falls below a threshold, the system automatically inhibits thrust control orders that would further reduce the margin, and can reduce the mean pitch component to restore the margin. This closed-loop feedback mechanism ensures yaw control reliability is maintained during acceleration.
Solution Approach 2:
The system dynamically adjusts the mean pitch component parameter based on the yaw attitude control margin status. When the margin becomes too narrow, the mean pitch component is reduced to restore the margin, allowing the propellers to maintain adequate antitorque function. This parameter adjustment resolves the contradiction by temporarily sacrificing thrust to preserve yaw control authority.
2Reliability
If the thrust control is inhibited to maintain yaw attitude control margin, then the yaw maneuverability is preserved, but the acceleration performance deteriorates
Solution Approach 1:
The thrust control operates in a periodic manner, being inhibited only when the yaw attitude control margin falls below the threshold and restored when the margin is sufficient. This intermittent inhibition allows the helicopter to accelerate during periods when yaw control margin is adequate, while preserving safety margins when needed, thus balancing acceleration performance with yaw control reliability.
Solution Approach 2:
The system dynamically adjusts the thrust control authority based on real-time yaw control margin conditions. Rather than permanently limiting thrust, the system adapts the thrust response to current operating conditions, allowing full acceleration performance when yaw margin is sufficient and providing protective inhibition only when necessary. This dynamic approach minimizes the impact on overall acceleration performance.
Data Source
AI summary
A method of protecting a margin for controlling the yaw attitude of a hybrid helicopter that includes a lift rotor as well as at least one first propeller and at least one second propeller. A thrust control is configured to generate at least a first order issued to increase a first pitch of first blades of the first propeller and a second pitch of second blades of the second propeller. After a first order has been issued, the method includes an inhibition step for having a control computer inhibit the first order when a yaw attitude control margin, with regard to an envelope delimiting a flight control domain, is and/or will be less than or equal to a threshold.