eVTOL Propulsor Layout for Hover Efficiency and Low Cruise Drag
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Solution Overview
Problem
EVTOL aircraft face challenges in balancing low power and low torque levels in hover, low mass in hover, high battery mass fraction, and low drag in cruise, while ensuring reliability and redundancy of systems, particularly in yaw control and thrust allocation.
Innovation Solution
The aircraft design incorporates large, low disc loading propulsors on the wing leading edge and smaller, higher disc loading lift/thrust propulsors on the empennage or tailcone, with ducted fans and fixed pitch propellers, and redundant power systems to achieve efficient hover and cruise flight, while using existing structural elements for lift and thrust.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If large, low disc loading propulsors are used on the wing leading edge, then hover efficiency is improved, but cruise drag increases
Solution Approach 1:
The propulsion system is segmented into multiple propulsors with different functions: large low disc loading propulsors for hover efficiency and smaller high disc loading propulsors for cruise thrust. This segmentation allows each propulsor type to be optimized for its specific operational phase without compromising the other.
Solution Approach 2:
The propulsors are mounted on tilt axes, enabling dynamic reconfiguration of their orientation. During hover, propulsors are positioned vertically for maximum lift; during cruise, they tilt forward to provide thrust while minimizing drag. This dynamic adjustment resolves the contradiction between hover efficiency and cruise drag.
2Power
If smaller, higher disc loading lift/thrust propulsors are used on the empennage, then cruise thrust is improved, but hover lift capability decreases
Solution Approach 1:
The smaller propulsors on the empennage are designed as multi-functional lift/thrust propulsors that can operate in both hover and cruise modes. During hover, they provide additional lift; during cruise, they tilt forward to provide thrust. This universality allows them to contribute to both functions without requiring separate dedicated systems.
Solution Approach 2:
These propulsors are mounted on tilt axes, allowing them to dynamically change orientation between vertical (for lift in hover) and forward-angled (for thrust in cruise). This dynamic capability enables a single propulsor design to excel at both cruise thrust and hover lift.
3Reliability
If redundant power systems are implemented, then reliability is improved, but system mass increases
Solution Approach 1:
The power system is segmented into multiple independent battery systems, each capable of powering the aircraft. This segmentation provides redundancy without requiring a single oversized backup system, optimizing the balance between reliability and mass.
Solution Approach 2:
The aircraft is equipped with more battery systems than the absolute minimum required for flight. This excessive action provides multiple layers of redundancy, ensuring that even if one or more battery systems fail, sufficient power remains for safe operation and landing.
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 design achieves efficient hover and cruise flight with reduced drag, maintains structural integrity, and ensures reliability and redundancy, even in the event of failures, by utilizing redundant power systems and optimized propulsor configurations.
Implementation Method 1
two lift propulsors and two lift/thrust propulsors... Each propulsor is powered by multiple electric motor/controller pairs
Implementation Method 2
Each propulsor is powered by multiple electric motor/controller pairs, which are powered by multiple battery systems
Data Source
AI summary
An electric vertical takeoff and landing (EVTOL) aircraft is disclosed. In some aspects, the aircraft comprises a main wing, an empennage, two lift propulsors, and two lift/thrust propulsors each mounted on a tilt axis.