Aft Engine Segmentation for Aircraft Thrust Reliability
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Solution Overview
Problem
Conventional aircraft propulsion systems require all engines to operate properly for takeoff, increasing the likelihood of grounding due to mechanical issues when an additional engine is integrated into the vertical stabilizer for increased thrust.
Innovation Solution
A propulsion system featuring primary engines mounted under the wings and an aft engine at the tail section, where the aft engine can contribute to net thrust without being necessary for normal takeoff, allowing for reduced fan size and weight of primary engines, and can operate at less than full capacity during takeoff while supplementing thrust during climb and cruise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If an additional engine is integrated into the vertical stabilizer to provide additional thrust, then the total thrust of the aircraft is increased, but the likelihood of the aircraft being grounded due to mechanical problems is increased
Solution Approach 1:
The propulsion system is segmented into two independent groups: primary engines mounted under the wings and an aft engine mounted at the tail section. The primary engines are sized to provide sufficient thrust for normal takeoff independently, while the aft engine provides additional thrust for climb and cruise but is not required for takeoff. This segmentation allows the aircraft to maintain reliability by ensuring that failure of the aft engine does not prevent normal takeoff operations.
Solution Approach 2:
Different engines are assigned different functional roles based on their location and capability. The primary underwing engines are designed with larger fan sizes to provide sufficient thrust for takeoff, while the aft engine is optimized for supplementing thrust during climb and cruise phases. This local differentiation of engine roles allows the system to achieve high total thrust while maintaining takeoff reliability.
2Power
If all engines are sized to provide substantially identical amounts of thrust, then each engine can contribute equally to total thrust, but the aircraft cannot takeoff normally if any single engine fails
Solution Approach 1:
The engine fleet is segmented into primary engines (requiring operation for takeoff) and an aft engine (optional for takeoff). This segmentation allows the primary engines to be sized for equal thrust contribution while the aft engine serves as a supplemental asset that does not compromise takeoff capability if its own failure occurs.
3Power
If the aft engine is sized to provide the same thrust as primary engines, then maximum thrust capacity is maximized, but the weight and complexity of the propulsion system increases
Solution Approach 1:
The aft engine is designed to provide partial thrust contribution (at least ten percent greater than or less than the maximum primary engine thrust) rather than equal thrust. This partial action approach allows the aft engine to effectively supplement thrust during climb and cruise while reducing the overall complexity and weight of the propulsion system compared to having all engines sized for maximum equal thrust contribution.
Data Source
AI summary
A propulsion system for an aircraft including a plurality of primary engines is provided. The plurality of primary engines includes at least a first primary engine and a second primary engine, each configured for mounting to a respective one of a pair of wings of the aircraft. The propulsion system additionally includes an aft engine configured for mounting at a tail section of the aircraft. The plurality of primary engines are sized to provide an amount of thrust sufficient for the aircraft to takeoff without use of the aft engine, such that the aft engine may be configured as a non-prime reliable engine.