Fail-Safe Engine Mount with Moment Arm Reduction
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Solution Overview
Problem
Existing aircraft engine mounting apparatuses often fail to adequately address failures under extreme loads, leading to potential engine loss due to insufficient fail-safe mechanisms and stress on normal load-bearing paths.
Innovation Solution
The design incorporates a fail-safe engine support mount with a moment arm reduction feature and oversized apertures that allow for reactive load bearing across multiple axes, reducing stress and providing redundancy in case of failures by establishing alternative load paths during normal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional load-bearing paths are used in engine mounting apparatus, then the structure is simpler, but the fail-safe capability is insufficient and stress concentration occurs during failure
Solution Approach 1:
The mounting apparatus is segmented into multiple independent load-bearing paths including primary attachment assemblies, moment arm reduction features, and alternative load paths. Each path can independently bear loads, and failure of one path does not compromise the entire system. The elongated arm is divided into multiple attachment points that can fail independently while maintaining overall structural integrity.
Solution Approach 2:
The design incorporates fail-safe features that are pre-positioned to engage automatically upon failure of normal load paths. The moment arm reduction feature and oversized apertures are designed in advance to accommodate displacement and establish alternative load paths without requiring active intervention or complex control systems.
2Reliability
If fail-safe mechanisms are added to engine mounting apparatus, then the reliability improves, but the stress on fail-safe engagement becomes excessive
Solution Approach 1:
The fail-safe mechanism utilizes a different geometric configuration with reduced moment arms. By positioning the second lug and fastener closer to the neutral axis of the elongated arm, the lever arm for fail-safe engagement is reduced, thereby decreasing the bending moments and stresses experienced by the fail-safe components during failure conditions.
3Reliability
If oversized apertures are used in the moment arm reduction feature, then alternative load paths are enabled, but the load-bearing capacity during normal operation is reduced
Solution Approach 1:
The aperture size is dynamically optimized to provide adequate clearance for fail-safe engagement while maintaining sufficient load-bearing capacity during normal operation. The oversized aperture allows the fastener to displace and establish alternative load paths upon failure, while the surrounding material geometry and distribution ensure that normal operational loads are adequately supported through the primary attachment assemblies.
4Reliability
If the fastener diameter is reduced to fit the oversized aperture, then the alternative load path engagement is facilitated, but the strength of the connection is compromised
Solution Approach 1:
The fastener and aperture dimensions are carefully selected to provide optimal balance between fail-safe engagement capability and connection strength. The aperture is oversized relative to the fastener diameter to allow displacement and alternative load path formation, while the fastener maintains sufficient cross-sectional area and material properties to bear the required loads when engaged in the alternative load path configuration.
Data Source
AI summary
An engine support mount including an airframe structure having a first anchor surface and a length extending along an x-axis, with a second axis defined perpendicularly to the x-axis. A support member is fixed to the airframe structure and defines a first aperture and a second aperture. A mounting assembly includes an elongated arm and first and second primary attachment assemblies respectively attaching the arm to the support member at the first and second apertures, the arm having a second anchor surface. A moment arm reduction feature includes a lug fixed to one of the anchor surfaces and a corresponding fastener fixed to the other of the anchor surfaces. The first anchor surface is positioned on the airframe structure outside of the first and second apertures, and the second anchor surface is positioned on the arm outside of the first and second attachment assemblies.