Rotatable Pitot Tube for Ejection Seat Pressure Measurement
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Solution Overview
Problem
Current ejection seat pitot systems face inaccuracies in dynamic air pressure data collection due to the air inlets not being located in the airstream during the rocket stage of the high energy catapult assembly, affecting ejection mode selection and parachute deployment timing.
Innovation Solution
A rotatable pitot tube system is coupled to the headrest of the ejection seat, with a pitot restraint assembly that translates between a restrained and released state, allowing the pitot tube to rotate from a stowed to a deployed position before rocket ignition, ensuring the air inlet is in the airstream, and an axis of rotation located between the headrest and main parachute assembly to maintain accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pitot tube is mounted in a fixed or flip-up position on the main parachute container, then the device complexity is reduced, but the measurement precision deteriorates because the air inlet is not located in the airstream during rocket stage ignition
Solution Approach 1:
The pitot tube is made rotatable rather than fixed, allowing it to dynamically adjust its position. The tube can rotate between a stowed position (parallel to seatback) and a deployed position (perpendicular to seatback), enabling the air inlet to be positioned in the airstream during ejection while maintaining a simple mounting structure on the headrest.
Solution Approach 2:
The pitot tube rotates to its deployed position before the rocket stage ignites, ensuring the air inlet is already in the airstream when dynamic pressure measurements are critical. This preliminary positioning action prevents contamination of measurements by combustion gases.
2Reliability
If the pitot tube air inlet is positioned close to the catapult assembly, then the device complexity is reduced, but the reliability deteriorates due to exposure to combustion gases affecting measurement accuracy
Solution Approach 1:
The rotatable mounting allows the pitot tube to dynamically position its air inlet in the airstream during ejection, ensuring reliable dynamic pressure measurements for ejection mode selection while maintaining a simple fixed mounting location on the headrest.
3Measurement precision
If the pitot tube is kept in a stowed position during ejection, then the device complexity is reduced, but the measurement precision deteriorates because the air inlet cannot access the airstream
Solution Approach 1:
The pitot tube rotates to a deployed position perpendicular to the seatback during ejection, allowing the air inlet to access the airstream for accurate dynamic pressure measurements, then returns to a stowed position parallel to the seatback when not in use.
Solution Approach 2:
The pitot tube rotation is driven by aerodynamic forces from the airstream itself during ejection, eliminating the need for complex external actuators. The airflow automatically positions the tube correctly for measurement.
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 ensures accurate dynamic pressure data collection, enhancing the reliability of ejection mode selection and parachute deployment timing by keeping the air inlet clear of combustion gases, thereby improving safety and accuracy during ejection.
Implementation Method 1
a pitot tube rotatably coupled to the headrest... collects dynamic air pressure data upon the air inlet of the pitot tube entering the airstream outside the cockpit
Implementation Method 2
The pitot restraint assembly includes a biased member configured to generate an interference with a rail located along a first side of the ejection seat
Implementation Method 3
a high energy catapult configured to expel the ejection seat from an aircraft... a rocket mortar configured to ignite
Data Source
AI summary
An ejection seat may comprise a seatback, a headrest located at an upper end of the seatback, and a pitot tube rotatably coupled to the headrest. A pitot restraint assembly may be operably coupled to the pitot tube. The pitot restraint assembly may be configured to translate between a restrained state and a released state. The pitot tube may rotate from a stowed position to a deployed position in response to the pitot restraint assembly translating to the released state.