Aircraft Elevator Nose-Up Command for Braking Traction
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Solution Overview
Problem
Conventional aircraft braking systems face reduced effectiveness in adverse conditions and short runways due to the dynamic loading weight shift from main gear to nose gear during heavy braking, which decreases the normal force on main wheels, leading to reduced traction and braking capacity.
Innovation Solution
Implementing an avionics system that automatically commands a 'nose up' elevator during the braking segment, generating additional downforce on the main wheels and shifting weight from the nose gear to the main wheels, thereby increasing the normal force and traction between the wheels and the runway.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If heavy braking is applied to stop the aircraft, then the braking force increases, but the normal force on the main wheels decreases due to weight shift to the nose gear, reducing traction and braking capacity
Solution Approach 1:
The system applies preliminary counteracting action by commanding the elevator to produce a nose-up pitching moment before and during braking. This preliminary action prevents the harmful weight shift to the nose gear by creating an opposing moment that maintains or increases normal force on the main braking wheels, thereby preserving traction and braking capacity throughout the deceleration process
Solution Approach 2:
The system dynamically adjusts the elevator command based on real-time braking conditions. The flight control system continuously monitors brake application and automatically modulates the elevator deflection to maintain optimal weight distribution on the main wheels during the dynamic braking process, adapting the pitch control to the changing deceleration state
2Reliability
If the normal force on the main wheels is increased to improve traction, then the braking capacity increases, but the weight shifts from the nose gear to the main wheels, potentially affecting aircraft stability
Solution Approach 1:
The system employs feedback control by continuously monitoring aircraft state parameters including weight distribution, pitch attitude, and braking force. The flight control processor uses this feedback to automatically adjust the elevator command in real-time, maintaining optimal weight on the main wheels while preventing excessive nose gear load transfer, thus balancing braking capacity with aircraft stability
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
This solution enhances braking ability and shortens the stopping distance, allowing aircraft to land on shorter runways by increasing the power transfer between the tires and the runway.
Implementation Method 1
The nose up command causes the pitch attitude flight control surface to generate a downforce that increases traction between the main wheels and the ground surface due to a weight shift from the nose wheel to the main wheels
Implementation Method 2
The nose up command causes the pitch attitude flight control surface to generate a downforce that increases traction between the main wheels and the ground surface
Data Source
AI summary
An aircraft includes a processor, an airframe, a pitch attitude flight control surface coupled with the airframe, a nose wheel coupled with the airframe, main wheels coupled with the airframe, and a brake system coupled with the main wheels. The processor is programmed to determine that the aircraft has entered a braking segment of a landing phase of a flight of the aircraft while the aircraft is on a ground surface and to command the pitch attitude flight control surface with a nose up command during the braking segment in response to determining that the aircraft has entered the braking segment. The nose up command causes the pitch attitude flight control surface to generate a downforce that increases traction between the main wheels and the ground surface due to a weight shift from the nose wheel to the main wheels and directly due to the downforce on the main wheels.