Fly-By-Wire Surface Contact Override for Emergency Landing
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Solution Overview
Problem
Full authority fly-by-wire flight control systems for rotary-wing aircraft face challenges in transitioning to a ground contact state during emergency landings when weight-on-wheel switches are unavailable, such as due to landing gear malfunctions or water landings.
Innovation Solution
A surface contact override transition function is enabled by pilot action, allowing the flight control system to transition through fully augmented, augmentation deactivation, and surface contact states, using a lagged collective stick position to determine when to disable augmentation and transition to a neutral rotor control state, emulating the functionality of weight-on-wheel switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If weight-on-wheel switches are used to initiate surface contact mode, then the transition to ground state is reliable under normal conditions, but the system becomes unusable when landing gear cannot be extended or during water landings
Solution Approach 1:
The patent introduces an intermediary system (accelerometer-based surface contact detection) that mediates between the pilot's control inputs and the flight control system's mode transitions. This intermediary detection method allows the system to determine surface contact without relying on weight-on-wheel switches, enabling emergency landing scenarios to be handled when traditional methods fail.
Solution Approach 2:
The flight control system is enhanced with multi-functionality by implementing a universal surface contact detection mechanism that works across all landing scenarios - normal ground landings, emergency landings with retracted gear, and water landings. This universal approach allows the same control system to handle diverse landing conditions that previously required different or unavailable detection methods.
2Reliability
If full authority FBW flight control system operates in augmented flight mode during landing, then flight control quality is maintained, but unwanted feedback into the control system occurs when the aircraft contacts the ground
Solution Approach 1:
The system dynamically transitions control laws based on detected surface contact. When the accelerometer indicates surface contact, the system automatically switches from augmented flight control mode (with stability augmentation and flight envelope protection) to ground contact mode (with direct pilot control and no augmentation). This dynamic adaptation prevents unwanted feedback by matching the control system's behavior to the aircraft's operational state.
Solution Approach 2:
The system uses feedback from accelerometer data to detect surface contact and trigger mode transitions. This feedback mechanism allows the control system to sense the aircraft's state (in-flight vs. ground contact) and adjust control law augmentation accordingly, preventing harmful feedback loops that would occur if augmented control remained active during ground contact.
3Ease of operation
If augmented control laws are disabled during surface contact, then ground operation control is simplified and feedback is prevented, but the transition process requires complex control law changes
Solution Approach 1:
The system performs preliminary actions by pre-programming multiple control law states (fully augmented, partial augmentation, ground contact) and automatically transitioning between them based on accelerometer data. This preliminary structuring of control modes simplifies the transition process, as the system has already prepared the appropriate control laws for each phase of landing and surface contact.
Solution Approach 2:
The control law transition is segmented into distinct phases: fully augmented flight mode, transition mode with partial augmentation, and ground contact mode with no augmentation. This segmentation allows the complex transition process to be managed through discrete, well-defined control law changes rather than continuous complex adjustments, making the system more manageable despite the complexity involved.
Data Source
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Figure 2
AI summary
A method of transitioning from a complex response flight state to a ground operation control state. Pilot intent is determined through collective position information to control the transition. An independent cockpit switch activates an emergency surface contact transition function for use with a fly-by-wire (FBW) flight control system. Once the surface contact transition function is active, FBW control laws transition from a fully augmented flight state, through an augmentation deactivation state and into the surface contact state.