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Rotorcraft Crash Sensor for Active Safety Systems and Mishap Dynamics Recording


TECHNOLOGY AREA(S): Bio Medical, Human Systems, Air Platform

OBJECTIVE: Develop a system capable of recording crash dynamics and detecting crash events in real-time, enabling the application of advanced, and life-saving, crash protective technologies.

DESCRIPTION: Current crash protective systems on Naval Aviation platforms rely on primarily "passive" safety systems to protect pilots and aircrew in the event of a crash or other mishap, such as hard landings. Current crash protection technologies, such as aircrew tethers, inertia reels, restraint systems, and energy-absorbing seating systems, minimally respond or adapt to an in-progress or impending mishap. The result is technologies optimized for neither specific crash environments, nor operational use. Crash protective systems are designed to protect aircraft occupants during representative crash pulses, and, in some cases, compromises must be made between crash protection and operational usability. If a crash sensor/recording system were employed, safety systems (such as restraint pretensioners, airbag systems, crashworthy seats, or mobile aircrew restraints) could actively respond to an impending or ongoing crash event.In Naval Aviation, no recordings are made of crash acceleration data from mishap events, outside of infrequent test events. The dynamic environments that crashworthiness and escape system engineers work with are often reconstructed more from subjective assessment than from available data. A number of assumptions create a best-educated guess as to the actual conditions of an event. In many cases, the dynamic environments to which U.S. Navy and Marine Corp aircrew are being exposed during mishaps are not known. Further incremental increases in mishap survivability have been hindered by the void of actual mishap acceleration data in spite of the fact that computerized controllers can sense and respond to a developing acceleration environment related to an aircraft crash or escape event.The Navy is seeking a crash detection/recording capability to measure accelerations (notionally +/- 1000g) and angular rates (notionally +/- 2,500 deg/sec) at locations of interest distributed throughout the airframe at sample rates (notionally 20,000 samples/second) and quality necessary to reconstruct the highly kinematic environment present during mishaps. In addition, a system/sensor design, methodology, and algorithm to detect and discriminate mishaps from other events in real-time, such that active safety systems can be triggered early enough in the mishap event to improve occupant survivability and prevent inadvertent activation. The advantage of distributing sensors, including accelerometers and/or angular rate sensors, in multiple locations of interest is that accelerations and rotation rates associated with mishap detection may occur at different times throughout the airframe. Depending on crash conditions a system capable of sensing/recording at multiple locations has the potential to detect mishaps sooner than a single crash sensor, enabling timely activation of crash protection systems.The proposed system to record and detect crashes should be capable of:(1) recording crash accelerations and angular rates at distributed locations throughout air frame at a quality sufficient for crash reconstruction (including pre- and post-trigger data),(2) discriminating mishaps from operational/landing dynamics in real-time,(3) triggering future active safety systems as early as practical during a dynamic event in order to enable effective safety system performance,(4) non-volatile storage of collected mishap data (one or more events) in a single, hardened unit that is located to be readily-retrievable adjacent to an aircraft egress route after a mishap,(5) integration into the aviation platform withoutairframe modification other than physical attachment of sensors or other hardware,(6) operation without access to aircraft power (if possible),(7) operation in the Naval aviation flight environment [Refs 3, 4], and (8) being produced at a price target of less than $10k per unit.The designed capability does not need to include the activation of active crash protective devices; the system should simply provide a local output indicating detection of a probable mishap event. In addition, the algorithms and thresholds associated with mishap detection should be reprogrammable to accommodate a variety of future active safety systems such as restraint pretensioners or air bag systems.Notionally, the desired capability should not require access to aircraft power or recharging of batteries for 60 flight hours. Additionally, the system may not weigh more than 5 lbs. or have an overall volume of greater than 125 cubic inches.

PHASE I: Design, develop and demonstrate feasibility of a crash recording and detection system as outlined in the Description. Identify and document the trade space associated with the proposed performance requirements, including projected system cost. Develop and determine technical feasibility of approaches that minimize airframe integration challenges (SWaP), and support implementation on legacy platforms. The Phase I effort will include prototype plans to be developed under Phase II.

PHASE II: Further develop, test, and demonstrate a prototype system that is capable of achieving the requirements provided for Phase I. Perform validation and verification through a combination of analysis, laboratory testing, and potential full-scale aircraft crash testing and operational flight test.Minimizing the potential for false crash detection events, which could potentially result in the activation of active safety systems, is a focus.

PHASE III: Complete design iteration and system testing. Mature the unit for transition to Naval Aviation platforms and commercial users. Crash sensing and recording systems capable of retrofit into aircraft have significant general and commercial aviation applications. Current “black box” or Digital Flight Data Recorder requirements only require aircraft accelerations to be measured at relatively low sample rates, which are insufficient for triggering or recording mishap dynamics. The collection of high-sample rate data would vastly improve aviation mishap investigation, and enable future crash protective technologies. This innovative system will enable rapid and more accurate accident reconstruction and facilitate a more targeted initial focus on the actual crash scenario. Over time, the collection of mishaps will begin to form a statistical basis that will allow critique and potential revision of existing regulations regarding crash injury mitigation based on real world experience.In addition, retrofit capable active safety systems (such as inflatable restraints or pretensioning restraint retractors) typically rely on local measurement of system accelerations. The advantage of an integrated, distributed system that measures accelerations at multiple points on the airframe is the potential for earlier crash detection and improved mishap survivability. The technology that would be developed and matured during this effort has the potential to benefit general and commercial aviation.

KEYWORDS: Crash Protection, Data Acquisition, Safety Systems, Mishap, Crash, Event Recorder


1. Hall, B., Willis, R. & Bark, L. “Demonstration of Aviation Mishap Reconstruction with On-Board Crash Recording Technologies.” American Helicopter Society, Forum 73, 2017. 2. “Aircraft Crash Survival Design Guide (Vol. I, Publication No. USAAVSCOM TR-89-D-22A).” Applied Technology Laboratory, AVRADCOM, Simula Inc.: Fort Eustis, VA,1989. 3. MIL-STD-810H, DEPARTMENT OF DEFENSE TEST METHOD STANDARD: ENVIRONMENTAL ENGINEERING CONSIDERATIONS AND LABORATORY TESTS (31-JAN-2019). MIL-STD-461G, DEPARTMENT OF DEFENSE INTERFACE STANDARD: REQUIREMENTS FOR THE CONTROL OF ELECTROMAGNETIC INTERFERENCE CHARACTERISTICS OF SUBSYSTEMS AND EQUIPMENT (11-DEC-2015).

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