Autopilot Angle of Attack Control for Rotary Wing Drag Reduction
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Solution Overview
Problem
Rotary wing aircraft experience significant aerodynamic drag at high speeds due to their nose-down longitudinal attitude, increasing pilot workload as they must manage multiple parameters to maintain optimal angle of attack and reduce drag.
Innovation Solution
A method and device for automatically controlling the collective pitch of rotor blades to maintain a reference aerodynamic angle of attack, allowing the pilot to focus on longitudinal attitude and forward speed, using equations like α*=θ−arcsin(VZ/TAS) to adjust vertical air speed and pitch, with an autopilot system engaging an assisted mode to optimize angle of attack for reduced drag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the helicopter flies at high speed, then the forward progress is improved, but the aerodynamic drag increases due to nose-down attitude
Solution Approach 1:
The invention changes the control parameter from collective pitch alone to a coordinated adjustment of collective pitch and cyclic pitch. By modifying both parameters simultaneously, the system can maintain optimal angle of attack while flying at high speeds, thereby reducing aerodynamic drag without sacrificing forward progress.
2Loss of energy
If the pilot manually controls multiple parameters to maintain optimal angle of attack, then the aerodynamic performance is improved, but the pilot workload increases
Solution Approach 1:
The invention merges the control functions by linking collective pitch and cyclic pitch adjustments into a single coordinated action. The control system automatically couples these two parameters, so the pilot needs to manipulate only one control input while the system handles the complex multi-parameter coordination, significantly reducing pilot workload while maintaining optimal aerodynamic performance.
3Force
If the collective pitch is increased to maintain angle of attack at high speed, then the lift is improved, but the rotor power requirement increases
Solution Approach 1:
Instead of increasing only collective pitch to maintain lift at high speeds, the invention changes the approach by simultaneously adjusting cyclic pitch to optimize the angle of attack. This coordinated parameter change allows the system to maintain necessary lift with more efficient power utilization, avoiding the excessive power consumption that would result from collective pitch increase alone.
Data Source
AI summary
An autopilot device and method for automatically piloting a rotary wing aircraft, having at least one propulsion propeller, the rotary wing including at least one rotor with blades, the device including a processor co-operating with at least one collective control system for controlling the collective pitch of the blades. The device includes engagement means connected to the processor for engaging an assisted mode of piloting for maintaining an angle of attack, the processor automatically controlling the collective pitch of the blades when the assisted mode of piloting for maintaining an angle of attack is engaged by controlling the collective control system to maintain an aerodynamic angle of attack (α) of the aircraft at a reference angle of attack (α*).