Aircraft Low-Speed Safety via Load Factor Limiting
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Solution Overview
Problem
Aircrafts require oversized elevators and actuating means to perform low-speed avoidance maneuvers, and adjustable tailplanes risk stalling during these maneuvers, leading to potential loss of control and over-sizing issues.
Innovation Solution
Implementing a method that limits the diving load factor to 0.3 g to 0.7 g and blocks the pitch-up inclination of the adjustable tailplane at a lower speed threshold, allowing the elevators to assist in trimming and preventing stalling during low-speed flight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the aircraft is designed to perform sudden avoidance maneuvers at low speed with full dive capability, then the elevators and actuating means must be oversized to handle the extreme load factors, but this increases device complexity and weight
Solution Approach 1:
The invention changes the load factor parameter from the conventional full dive capability (0 g) to a limited range (0.3 g to 0.7 g). This parameter modification allows the elevators and actuating means to be sized for the actual required performance rather than the theoretical maximum, reducing device complexity and weight while maintaining adequate avoidance maneuver capability
Solution Approach 2:
The invention applies partial action by implementing a load factor limitation that prevents the aircraft from achieving full dive capability. The limitation to 0.3 g to 0.7 g represents a deliberate reduction from the extreme 0 g condition, providing sufficient avoidance capability without requiring the full structural capacity for extreme maneuvers
2Force
If the adjustable tailplane is deflected to high pitch-up inclination for trimming at low speed, then the pitch-up moment is sufficient to counteract the high diving moment, but the local incidence exceeds the stalling incidence during avoidance maneuvers, causing loss of effectiveness
Solution Approach 1:
The invention applies preliminary anti-action by pre-limiting the diving load factor to 0.3 g to 0.7 g before the avoidance maneuver is executed. This preemptive measure ensures that the adjustable tailplane does not need to be deflected to extreme pitch-up inclinations, maintaining its local incidence below the stalling incidence and preserving its effectiveness throughout the maneuver
Solution Approach 2:
The invention modifies the operating parameters of the adjustable tailplane by limiting the diving load factor range. This parameter change prevents the tailplane from operating at extreme incidences that would cause stalling, ensuring reliable performance during avoidance maneuvers while still providing sufficient pitch-up moment for trimming
3Ease of operation
If the elevators are returned from full dive position to pitch-up position for pull-out after avoidance, then the aircraft can recover, but the sizing must accommodate the full range of motion from 0 g to high pitch-up, increasing device complexity
Solution Approach 1:
The invention changes the load factor parameter range from the full dive capability (0 g) to a limited range (0.3 g to 0.7 g). This modification reduces the required travel range and force capacity of the elevator actuating means, simplifying the hydraulic system sizing while maintaining the ability to perform the complete avoidance and recovery maneuver sequence
Data Source
AI summary
A method for ensuring the safety of an aircraft flying horizontally at low speed includes determining a lower speed threshold for the aircraft, measuring the actual speed of the aircraft and comparing the actual speed with the threshold. When the actual speed reaches the threshold in the decreasing direction, the diving command of the aircraft is limited to a load factor (fg) greater than 0g.According to the invention:a lower speed threshold is determined for the aircraft;the actual speed of the said aircraft is measured; andthe said actual speed is compared with the said threshold and, when the said actual speed reaches the said threshold in the decreasing direction, the diving command of the said aircraft is limited to a load factor (fg) greater than 0 g.