Thrust Reverser Modulation for Aircraft Taxi Speed Control
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Solution Overview
Problem
Aircraft ducted fan propulsion systems produce excessive thrust during taxiing, leading to premature brake wear due to the need for pilots to use brakes to control ground speed, resulting in increased maintenance costs and operational inefficiencies.
Innovation Solution
A thrust reverser assembly with a moveable portion that can modulate air flow through a bleed passage, allowing for autonomous control of thrust levels between fully stowed and fully deployed positions, reducing forward thrust during taxiing by varying the amount of air exhausted from the fan nozzle outlet and bled through the bleed passage, and is activated only when specific preconditions such as weight on wheels and ground speed are met.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the ducted fan propulsion system operates at engine idle during taxi, then the engine runs efficiently, but the system produces more thrust than needed causing excessive ground speed
Solution Approach 1:
The patent modifies the thrust output parameter by diverting a portion of the exhaust airflow through the bleed passage away from the propulsive nozzle. This changes the effective thrust parameter while maintaining engine idle operation, allowing the engine to run efficiently at idle RPM while reducing the actual propulsive force to match taxi speed requirements.
2Speed
If pilots use the aircraft braking system to reduce ground speed, then the aircraft speed is controlled within limits, but the brakes wear prematurely requiring additional maintenance
Solution Approach 1:
The patent applies preliminary anti-action by reducing the excessive thrust before it causes the aircraft to accelerate beyond taxi speed limits. By diverting exhaust airflow through the bleed passage, the system preemptively counteracts the thrust excess, eliminating the need for reactive brake application and thereby preventing brake wear before it occurs.
3Force
If the thrust reverser assembly diverts air flow through the bleed passage, then forward thrust is reduced to appropriate levels, but the system complexity increases
Solution Approach 1:
The patent implements multi-functionality by designing the thrust reverser assembly to serve dual purposes: traditional thrust reversal for braking after landing, and thrust reduction during taxi operations. The same moveable portion, bleed passage, and actuator assembly that provide reverse thrust capability are also used to divert exhaust airflow during taxi, eliminating the need for separate thrust reduction mechanisms.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Reduces brake wear and maintenance costs by maintaining aircraft taxi speed within limits without excessive thrust, allowing for reduced pilot intervention and efficient engine operation during taxiing, while also reducing exhaust gas temperature and blast damage radius.
Implementation Method 1
a moveable portion that is moveable over a continuous range of travel between a fully stowed position and a fully deployed position, wherein movement away from the fully stowed position opens a thrust reverser bleed passage
Data Source
AI summary
A thrust reverser assembly and a method of operating an aircraft during a taxi mode of operation are provided. The thrust reverser assembly includes one or more actuator assemblies configured to modulate a position of a moveable portion over a continuous range of travel between a fully stowed position and a fully deployed position, such that an air flow through said thrust reverser bleed passage is correspondingly varied. The thrust reverser assembly also includes a throttle device that includes a first, ground idle power level position and a second, forward thrust mode position. Movement into the second position may be actuated separately and differently from movement into the first position. An actuator intermediate lock may inhibit actuation of the intermediate forward thrust mode of operation until a plurality of preconditions is met.