Dynamic Thrust Limit Schedule for Engine-Out Control
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Solution Overview
Problem
Multi-engine aircraft face limitations in landing speeds due to engine-out minimum control speed restrictions, which are not effectively addressed by existing solutions that increase weight and drag or reduce engine thrust across all flight phases.
Innovation Solution
A flight control and engine control system that automatically limits the maximum thrust of the operating engine to a value lower than the nominal thrust limit schedule during engine failure, using a reduced thrust limit schedule that is a function of airspeed, detected thrust asymmetry, flight phase, and airplane conditions, allowing for tailored thrust reduction only when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If engine thrust is reduced for all landing and go-around conditions, then landing speed limitation is reduced, but climb performance is degraded
Solution Approach 1:
The patent implements dynamic thrust limitation by calculating different thrust limits based on current flight conditions (airspeed, thrust asymmetry, flight phase, airplane weight). The system continuously adjusts the thrust limit schedule in real-time rather than using a fixed reduced thrust setting, allowing optimal performance across varying conditions.
Solution Approach 2:
The patent applies thrust limitation selectively based on specific flight conditions. The system determines when thrust asymmetry control is actually needed (during engine failure at specific airspeeds and flight phases) and applies limitation only in those cases, while allowing full thrust in conditions where it is safe and beneficial.
2Reliability
If larger vertical tail and rudder are used, then engine-out control capability is improved, but weight and drag increase
Solution Approach 1:
The patent changes the operational parameters (thrust limit) rather than the physical structure (vertical tail size). By adjusting the thrust limit schedule based on flight conditions, the system achieves engine-out control capability without modifying the airplane's aerodynamic surfaces or adding weight.
3Speed
If scaled down thrust is applied over whole operating speed range, then engine-out control speeds are reduced, but thrust available for heavy-weight conditions is reduced
Solution Approach 1:
The system dynamically calculates thrust limits as a function of airspeed and flight conditions. At light weights and lower airspeeds, the calculated thrust limit is reduced to enable lower engine-out minimum control speeds. At heavy weights and higher airspeeds, the full thrust capability is available to meet climb performance requirements.
Data Source
Figure 1
Figure 2A~2C
Figure 2D~2E
AI summary
A flight control and engine control function for a multi-engine aircraft which automatically controls maximum thrust on the operating engine to a value lower than the nominal thrust limit schedule in the event of loss of thrust on another engine. The maximum engine thrust of the operating engine is controlled (limited) such that the resulting thrust asymmetry can be controlled at airspeeds lower than would otherwise be the case. The decrease in engine-out minimum control speed can reduce the limitation on landing speeds that would otherwise be caused by engine-out minimum control speed.