When most think of hypoxia-like physiological events (PEs) some pilots have experienced in the cockpits of aircraft, such as the recent propeller-driven T-6, the common assumption is an issue with the on-board oxygen generating system that supplies oxygen to the pilot. But there are several other variables to consider, one being air quality.
To date, there have been no instances that link air quality to PEs, but that doesn’t remove it from the list of variables to continue to research and consider.
This is where highly advanced sensors come into play, sensors designed and developed by a team of scientists and engineers in both the Air Force Research Laboratory and the Air Force Life Cycle Management Center. Although still in the research and development phase, this team is working together to complete a second-generation sensor package called the Real-Time Air Quality Sensor, or RTAQS, that will sense and assess cockpit air quality in real-time on high performance aircraft during flight.
“Most of the information to determine unexplained PEs is collected post-flight so much of the evidence is likely gone,” said Doug Hopkins, 711th Human Performance Wing chief engineer. “RTAQS is intended to close the gap so that we know what happens during the flight.”
The first version of this sensor package was developed in 2015 and was a collaborative effort between the Airman Systems Directorate and the United States Air Force School of Aerospace Medicine, both within the 711th Human Performance Wing of AFRL. Researchers at the NASA-Glenn Research Center were also part of this collaboration.
“We had a first-generation sensor package that we flight-tested at Edwards Air Force Base in an F-16, we got some results, and then came back to the lab to look for ways we could enhance that sensor with additional capabilities,” said Jennifer Martin, a 711 HPW research chemist.
The team is now testing sensors that could be put on the next version of that original package to improve the performance of its air-quality testing.
“We’re in the early stages – just moving from the first-generation sensor package design to the next,” said Martin. “These sensors could enable us to rule out air quality as a root cause, and they can focus on other variables, such as equipment malfunction, bleed air and environmental control systems to try to figure out the driving force for physiological events.”
This team’s research is part of the military’s on-going effort to find what Air Force Chief of Staff Gen. David Goldfein calls “the smoking gun” regarding PEs.
Part of this research is looking at what other work has been done that could be leveraged with Air Force research.
“RTAQS contains several embedded sensors, some of which were originally developed by NASA for use aboard the International Space Station,” said Martin. “NASA collaborated with us and Makel Engineering, the technical integrator for the electronics and packaging. We’re also leveraging the AFRL Small Business program via a Phase II Small Business Innovation Research award with Makel to help mature this technology.”
Another part of this research is the testing phase, in which these developmental sensors are put in simulated environments that are capable of mimicking what happens during flight.
The Air Force Life Cycle Management Center, also headquartered at Wright-Patterson Air Force Base, provided these environments, namely their accelerometer validation for this testing. David Ryerse, biomedical test technician with AFLCMC, explained that this equipment has the capability to give different vibration profiles of aircraft and vehicles.
“We were contacted by 711 HPW to use our vibration tables,” said Ryerse. “This table is able to do various aircraft profiles such as a jet or a high-vibration vehicle such as an Army Humvee. Whatever profile they wanted to see, we were able to produce the proper vibration profiles. They wanted to be able to see how each of these affected the accelerometer and the data.”
Future versions of RTAQS are planned to sense accelerometry data in addition to air quality, said said Michael Brothers, a research scientist with 711 HPW.
While the team wants to be able to see what chemicals are in the air, another goal is to be able to link those chemicals to a certain event during flight in order to inform the Root Cause Corrective Action teams from AFLCMC, who are responding to the physiological event.
“With this type of real-time sensing capability, we’re trying to correlate maneuvers, aircraft parameters, as well as environmental conditions to possible conditions that could affect air quality,” Brothers said.
These sensors could also contribute to the life cycle maintenance needs of the aircraft, which could possibly improve resource efficiency, explained Grant Slusher, who is also a research scientist with 711 HPW.
“There’s a distribution in how the aircraft’s parts wear out,” said Brothers. “Maybe it’s two months or maybe it’s eight months, but if a maintainer has to go in and check everything after four months, it wouldn’t be known if the part went bad at two months or if it’s still good and might go another four months. So to have a sensor that could automatically indicate that would reduce manpower needs, reduce down time, and maximize resources.”
The team of collaborators has funded studies to test operational aircraft at numerous Air Force bases, said Martin. “We’re also working to design a smaller version of the sensor that’s specific to various cockpit space constraints and that could meet the longer-term vision of fleet-wide integration.”
The team explained they plan to have different versions of this sensor to plug and play with various weapon systems and the program office needs in both the Air Force and U.S. Navy. They also discussed the importance of their collaborations with academics and small businesses to see if down the line, some of their research can be more easily transitioned to other Department of Defense manned airborne platforms.
“The long-term vision of this research is both to develop a sensor package for use in both PE root cause investigations and to integrate air quality sensors into all of our manned airborne platforms,” said Claude Grigsby, technical advisor for 711 HPW’s Human-Centered ISR Division. “These types of sensors could ultimately be utilized for immediate autonomous activation of back-up oxygen systems if an issue with the air supply is detected. When this work was initiated, as follow-up to previous PE investigations supported by the 711th Human Performance Wing, our goal was to create a capability where the pilot no-longer has to function as the sensor in the system.”
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