Offset Propeller Configuration for Hybrid Rotorcraft Ground Clearance
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Solution Overview
Problem
Hybrid rotorcraft face challenges in optimizing ground clearance and frontal area due to the need for a balance between propeller diameter, rotor clearance, and fuselage design, leading to increased weight and potential performance degradation.
Innovation Solution
The design features a fuselage with a longitudinal anteroposterior plane of symmetry, incorporating propulsion units with propellers offset from the central plane, allowing for smaller propeller diameters and increased ground clearance, and includes contrarotating or similarly oriented propellers to maintain performance with reduced power requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If propellers are located far away from the fuselage to reduce rotor clearance, then ground clearance is improved, but the acceptable roll angle on the ground is reduced
Solution Approach 1:
The patent positions propellers at the tips of half-wings extending transversely from the fuselage, utilizing the transverse dimension to achieve both adequate ground clearance and acceptable roll angle. This spatial arrangement in three-dimensional space resolves the contradiction between clearance and stability.
Solution Approach 2:
The propellers are strategically positioned at specific locations (tips of half-wings) where the local geometry provides optimal clearance characteristics. The half-wing structure itself provides the necessary transverse span to maintain roll angle while keeping propellers clear of the ground.
2Power
If propeller diameter is increased to maximize thrust performance, then propulsion capability is improved, but ground clearance and rotor clearance are reduced
Solution Approach 1:
By moving propellers to the transverse tips of half-wings rather than positioning them close to the fuselage, the patent utilizes the transverse dimension to accommodate larger propeller diameters while maintaining adequate ground clearance. The half-wing structure provides the necessary spatial separation.
3Length of stationary object
If fuselage height is increased to maintain roll angle, then ground clearance is improved, but frontal area and drag are increased
Solution Approach 1:
Instead of increasing fuselage height (vertical dimension), the patent utilizes the transverse dimension by extending half-wings laterally from the fuselage. This allows propellers to be positioned at optimal locations for both clearance and roll angle without increasing frontal area.
Solution Approach 2:
The half-wing configuration provides asymmetric positioning of propellers relative to the fuselage, allowing optimized clearance characteristics without requiring symmetric increases in fuselage dimensions. The asymmetric placement at wing tips provides optimal spatial relationships.
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 configuration achieves a significant increase in ground clearance and roll angle while maintaining thrust performance, with minimal power increase during level flight and reduced power consumption during hovering, thus optimizing the hybrid aircraft's design without compromising stability or efficiency.
Implementation Method 1
The propellers then contribute to propelling the aircraft. The use of propellers makes it possible in particular to achieve high forward speeds and to cover considerable distances.
Implementation Method 2
the propellers can generate torque on the fuselage in order to balance the torque from the main rotor and in order to control yaw movement of the aircraft
Implementation Method 3
The rotary wing provides at least some of the lift of the aircraft
Implementation Method 4
The blades of a rotary wing tend to flex while they are in use, in particular during stages of take-off and landing. The amount of flexing increases with increasing distance from the axis of rotation of the rotary wing.
Data Source
AI summary
A hybrid aircraft (1) having a fuselage (2) extending longitudinally along an anteroposterior plane of symmetry (PSYM) from the rear (4) of the aircraft (1) towards the front (3) of the aircraft (1). The aircraft (1) has a rotary wing (6) carried by the fuselage (2) of a lift surface (10) fastened to the fuselage (2) and constituted by a first half-wing (11) and a second half-wing (12). The aircraft (1) has a first propulsion unit (30) carried by the first half-wing (11) and a second propulsion unit (40) carried by the second half-wing (12). Each propulsion unit (30, 40) includes at least one tractor propeller (31, 32, 41, 42), and at least one propulsion unit has two propellers (31-32, 41-42) on the same axis, each of said propellers rotating about an axis of rotation (AX) that is offset transversely from said anteroposterior plane of symmetry (PSYM).