Automatic Propeller Ground Stop Mechanism for Drag-Free Flight
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Solution Overview
Problem
Aircraft propellers spin uncontrollably on the ground due to external forces, posing safety hazards and potential damage, especially in electric-motor aircraft lacking natural braking mechanisms.
Innovation Solution
A propeller ground stop mechanism that automatically engages when the propeller is not powered and disengages during operation, using a preload element and brake pad to apply braking torque when the propeller is stationary and disengage when it reaches a predetermined spin threshold, preventing drag during flight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a propeller ground stop mechanism is added to prevent propeller spinning on the ground, then safety of ground personnel is improved, but device complexity increases
Solution Approach 1:
The ground stop mechanism is designed to automatically engage and disengage based on propeller rotation state. The spring-loaded brake pad engages when the propeller is stationary and automatically disengages when the propeller rotates during flight, eliminating the need for manual operation or external control systems.
Solution Approach 2:
The patent replaces complex mechanical ground stop devices (such as pins, belts, or external locking mechanisms) with a simple spring-loaded brake pad system that uses elastic potential energy storage and release to achieve automatic engagement and disengagement.
2Reliability
If a ground stop mechanism is always engaged to prevent propeller spinning, then propeller control is improved, but drag increases during flight
Solution Approach 1:
The ground stop mechanism transitions from a static always-engaged state to a dynamic system that automatically adjusts its engagement state based on propeller rotation. The brake pad engages when the propeller is stationary and disengages when the propeller rotates, optimizing performance for both ground and flight conditions.
Solution Approach 2:
The mechanism changes the friction parameter dynamically - high friction (engaged) when the propeller is stationary on the ground, and zero friction (disengaged) when the propeller is rotating during flight. This parameter change is achieved through the spring-loaded design that responds to rotational movement.
3Reliability
If manual ground stop devices are used to prevent propeller spinning, then safety is improved, but ease of operation deteriorates due to manual checks required
Solution Approach 1:
The system performs the ground stop function automatically based on the propeller's rotational state without requiring manual intervention. The spring-loaded brake pad self-activates when the propeller is stationary and self-deactivates when the propeller rotates, eliminating the need for manual checks or operations.
Solution Approach 2:
The mechanism uses the propeller's rotational state as feedback to control its own engagement. When the propeller rotates during flight, the centrifugal force or rotational movement automatically triggers the brake pad disengagement, creating a closed-loop system that responds to operational conditions.
4Reliability
If external ground stop devices such as pins or belts are used, then propeller grounding is achieved, but risk of damage increases if devices are not removed
Solution Approach 1:
The ground stop mechanism automatically removes itself from the propeller system when flight conditions are detected. The spring-loaded brake pad that engages the braking surface during operation automatically disengages when the propeller rotates, ensuring no foreign objects remain attached to the propeller for flight.
Solution Approach 2:
The design extracts the ground stop function from separate external devices (pins, belts) and integrates it into the propeller system itself, with the brake pad being part of the propeller assembly that automatically detaches during flight, eliminating the risk of forgotten external devices.
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
Provides safety to ground personnel by keeping propellers stationary on the ground and ensuring smooth transitions to flight mode without additional manual checks, while minimizing weight and drag.
Implementation Method 1
a preload element coupled to the first element and the second element. The preload element is configured to apply a first force in a first rotational direction about the coupling means to the first element
Implementation Method 2
a brake pad coupled the arm portion of the first element. When the net force on the first element is in the first rotational direction, the brake pad engages a braking surface
Implementation Method 3
When the motor powers the propeller to provide thrust, the propeller spin rate reaches or exceeds the predetermined threshold and the resulting centrifugal force causes the propeller ground stop mechanism to disengage
Data Source
AI summary
Embodiments provide a propeller ground stop mechanism configured to keep an unpowered propeller of an aircraft (e.g. when the aircraft is on the ground and not operating) static. The propeller is prevented from rotating due to external forces (e.g. an air flow caused by wind, manual rotation of the propeller). When the propeller is powered, and the propeller is providing thrust, the propeller ground stop mechanism automatically disengages and does not provide any drag. Among various benefits, the propeller ground stop mechanism provides added safety to the ground support personnel.