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Biodynamic Acceleration and Angular Response During Fixed Wing Aircraft Ejection

Description:

TECHNOLOGY AREA(S): Bio Medical 

OBJECTIVE: Develop a new class of small sensors and packaging for routine wear by aircrews capable of recording and storing the magnitude & duration of exposure to impact during an aircraft ejection event. The particular focus should be on sensing the dynamic human body response by recording the linear and rotational (angular) acceleration levels during an aircraft ejection event. The solution may either be standalone or be integrated with some form of aircrew garment (preferably in the head/neck region for example on the helmet, mask, visor, ear cups or some other equipment near the head) that will be worn by fixed wing pilots and should be able to withstand impact/acceleration levels observed between the egress event through the parachute opening shock phase of the ejection process. It is important to consider that any added weight or CG shifts added to the helmet should be minimized or implemented in a way to minimize forward CG additions. Additionally with focus on minimizing decoupling/transfer function from sensor to the head. 

DESCRIPTION: An increasingly important issue in personnel force protection is the ability to quantify injury causation resulting from aircraft ejection events. With the harsh environmental factors associated with an ejection event, it is neither feasible nor possible to test human subjects at these limits. Using rocket sled tests with instrumented manikins and lower G level laboratory human studies we can estimate what the occupant would experience during certain phases of ejection; however, collection of data during actual ejection events would make it possible to acquire unique information that would be very useful in verifying and improving the accuracy of models currently used to evaluate safety equipment in the ejection environments, in addition to providing a useful tool during mishap investigation for understanding potential causes for specific injuries. Data collected during these dangerous events could be useful in increasing the TR level of existing ejection seat technology. Additionally, another potentially useful application of such a data set could be for injury mishap investigation teams to acquire better understanding of the events that transpired prior to a dynamic event. Over time the acquisition of datasets during ejections would allow for revisions in current injury probability models using the acquired data from these events. The aircraft cockpit environment has restrictions which may influence the final system design including: sensor package weight, size, and mounting location in the cockpit or on the occupant. Therefore, the final sensor package must be a self-contained solution (i.e. integrated data collection, sensors, and power) with no reliance on the aircraft for power or activation and ideally not containing batteries that would need periodic replacement. The preferred powering solution would involve use of energy harvesting technologies capable of charging from the native environment. 

PHASE I: Conduct research leading to the development of very small, inexpensive, sensor package that physically captures the magnitude and total energy of acceleration events during an ejection sequence. Results must demonstrate that practical components are feasible, and that such components would have wide application (hence low price). The resulting design should provide linear (X, Y, Z) and angular measurements (rate, and/or acceleration) of biodynamic motion during the egress event covering the time from ejection system initiation through the parachute opening shock phase of the ejection procedure ideally with a sample rate greater than 200 Hz minimum (ideally >1kHz). 

PHASE II: Consists of developing, testing and validation of a prototype system of sensors acquiring biodynamic response data as described in Phase I, and demonstration of its use in both a laboratory and a rocket sled ejection environment (provided by the government). 

PHASE III: Consists of final system validation and undergoing the air-worthiness approval process. This will involve interfacing sensors with actual aircrew on-board and environmental testing as specified by Mil-Std. This phase may also consist of additional rocket-sled testing for final validation and performance testing. 

REFERENCES: 

1: Knox, Ted, Validation of Earplug Accelerometers as a Means of Measuring Head Motion. SAE Paper 2004-01-3538, Proceedings of the SAE Motorsports Conference and Exhibition (P-392). Nov. 30 – Dec2, 2004, Dearborn, MI

2:  Lewis "Survivability and injuries from use of rocket assisted ejection seats: analysis of 232 cases." Aviat Space Environ Med. 2006 Sep

3: 77(9):936-43.

KEYWORDS: Force Protection, Warfighter, Battlefield Stressors, Whole Body Or Component Injury Criteria, Epidemiology Of Injury, Ejection Criteria, And Acceleration Sensors 

CONTACT(S): 

Dr. Casey Pirnstill 

(937) 255-9331 

casey.pirnstill@us.af.mil 

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