Engine Cowling Latch Interlock for Safe Opening Sequence

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Solution Overview

Problem

Existing aircraft engine cowling designs risk damage to components if opened while the deflection limiter band is engaged, as technicians may inadvertently operate the latches out of sequence.

Innovation Solution

An interlock mechanism with a lock element and indicator paddle, coordinated by a linkage assembly, prevents the cowling latch from disengaging when the deflection limiter latch is engaged, ensuring proper sequential operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the cowling latch is allowed to disengage freely, then the ease of operation is improved, but the risk of component damage increases due to inadvertent out-of-sequence operation

Engineering Contradiction:

Improveease of cowling latch operationVSAvoidcomponent damage risk

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The interlock mechanism requires the deflection limiter latch to be disengaged before the cowling latch can be operated. This preliminary action ensures that the deflection limiter band is properly released prior to cowling opening, preventing component damage while maintaining operational simplicity through automatic interlocking.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The lock element acts as an intermediary between the deflection limiter latch and the cowling latch. It physically blocks the cowling latch handle from moving when engaged, and only allows operation when the deflection limiter latch is disengaged, thereby mediating the sequence of operations and preventing harmful out-of-sequence actions.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If an interlock mechanism is added to prevent out-of-sequence operation, then the reliability is improved, but the device complexity increases

Engineering Contradiction:

Improveoperational sequence reliabilityVSAvoidlatch system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The interlock mechanism is merged with the existing latch system by integrating the lock element into the cowling latch assembly. The lock element, indicator paddle, and linkage are combined with the latch handles to form a unified system that provides interlocking functionality without requiring separate independent mechanisms, thereby minimizing added complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The interlock mechanism is self-regulating through automatic engagement and disengagement of the lock element. When the deflection limiter latch is disengaged, the lock element automatically moves to allow cowling latch operation. When the cowling latch is engaged, the lock element automatically blocks further operation, eliminating the need for additional control systems or manual intervention.

Inventive Principle:

Principle #25Self-service

3Reliability

If the lock element physically blocks the cowling latch handle, then the prevention of out-of-sequence operation is improved, but the ease of operation deteriorates due to additional manual steps

Engineering Contradiction:

Improveprevention of out-of-sequence operationVSAvoidease of latch disengagement

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The indicator paddle provides visual feedback to the operator about the status of the deflection limiter latch. When the deflection limiter latch is engaged, the indicator paddle position clearly shows that the cowling latch cannot be operated. This feedback mechanism guides the operator through the correct sequence without requiring additional manual steps or complex procedures.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The lock element serves as a physical mediator that automatically translates the state of the deflection limiter latch into the operational status of the cowling latch. Instead of requiring the operator to remember or follow complex procedures, the lock element automatically enables or disables cowling latch operation based on the deflection limiter latch state, simplifying the operator's task while ensuring proper sequence.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentEP4458676B1Cowling latch interlock mechanism

Publication Date: 2026.02.11 THE BOEING CO

Figure 1
Figure 2A
Figure 2B

AI summary

An aircraft engine cowling (102) comprises a first cowling portion (104) and a second cowling portion (106) moveable relative to each other. A cowling latch (114) secures the first cowling portion (104) and the second cowling portion (106) in a closed position. The aircraft engine cowling (102) further comprises a deflection limiter band (122) and a deflection limiter latch (124) moveable between an engaged state and a disengaged state for the deflection limiter band (122). An interlock mechanism (240) prevents disengagement of the cowling latch (114) while the deflection limiter latch (124) is in the engaged state. The interlock mechanism (240) includes a lock element (124, 126) moveable between a first position that prevents disengagement of the cowling latch (114) and a second position (222) that enables disengagement of the cowling latch (114). The interlock mechanism (240) also includes an indicator paddle (242) movable to contact the deflection limiter latch (124). A linkage assembly (510) coordinates movement of the lock element (124, 126) with movement of the indicator paddle (242).