Movable Headrest for Aircraft Ejection Seat Windblast Control
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Solution Overview
Problem
Aircraft ejection seats fail to adequately protect the pilot's head and neck from acceleration and aerodynamic forces during high-speed ejection, leading to potential injury from helmet tilting forward, aerodynamic lift, and flailing in the windblast.
Innovation Solution
An ejection seat with a movable headrest that deploys to support the pilot's head in a tilted-forward position, using pivotable struts and a flexible strap to maintain the head in a stable orientation and control windblast forces, thereby reducing impact loads and flailing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed headrest is used in the ejection seat, then the structure is simple, but the crewmember's head cannot be supported in the tilted-forward position during acceleration, causing the head to tilt forward and be subjected to harmful aerodynamic forces
Solution Approach 1:
The headrest is designed with movable struts that can pivot between a retracted position and a deployed position. During ejection acceleration, the struts automatically pivot forward to support the crewmember's head in the tilted-forward position, adapting to the dynamic forces experienced during ejection rather than relying on a fixed structure
Solution Approach 2:
The headrest struts are pre-positioned in a retracted state during normal flight, and automatically deploy to the forward support position when acceleration forces are detected during ejection, preparing the support structure in advance before the crewmember's head is subjected to harmful aerodynamic forces
2Ease of operation
If the headrest is positioned to support the head in an upright position, then the structure is simple, but the crewmember's head cannot follow the natural tilt-forward motion during acceleration, causing impact and injury
Solution Approach 1:
The headrest struts are designed to pivot forward dynamically during ejection acceleration, allowing the headrest to follow and support the crewmember's head in the natural tilted-forward position rather than forcing an upright position, thereby reducing impact and harmful forces on the head and neck
3Reliability
If a movable headrest system is implemented to support the head in tilted-forward position, then head protection is improved, but the device complexity and number of moving parts increases
Solution Approach 1:
The headrest struts are pre-configured with pivot joints and positioning mechanisms that automatically engage to support the crewmember's head in the tilted-forward position during ejection, counteracting the harmful acceleration and aerodynamic forces before they can cause head and neck injury
Solution Approach 2:
The headrest system uses movable struts with pivot joints that dynamically adjust to support the crewmember's head during ejection acceleration, providing adaptive protection that moves with the head rather than requiring complex active control systems
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
The solution effectively prevents the pilot's head from being jerked upward or flailed by acceleration and windblast forces, minimizing the risk of injury and ensuring safe separation from the seat during parachute deployment.
Implementation Method 1
one or more flexible strap or lanyard members extend between the struts and the headrest panel to pull the headrest panel into the deployed position
Implementation Method 2
the crewmember's head and neck. During the initial acceleration of the ejection seat, acceleration forces acting on the crewmember's head and helmet tend to pitch the crewmember's head forward and down
Implementation Method 3
aerodynamic flow over the top of the helmet causes a large pressure drop to occur so that the normal pressure inside the helmet acts to pull the helmet upward
Implementation Method 4
the headrest then locks in position to support the crewmember's head from above and behind in the acceleration-induced tilted-forward position
Data Source
AI summary
An ejection seat includes a headrest that, upon initiation of the ejection seat, moves forward to support the pilot's head in a tilted-forward position. By holding the crewmember's head in a tilted-forward position, windblast forces are controlled to prevent the helmet from pulling upward and backward on the crewmember's head. The headrest may include a pair of struts that extend forward around the sides of the crewmember's helmet to support the crewmember's head against flailing from the windblast. A flexible panel extending between the struts and the headrest panel may also be included to further support the crewmember's head against windblast flailing.