Challenge
Surging Pilot Physiological Events — A wave of hypoxia-like symptoms in F-18 aviators grounded training operations. Existing monitoring systems failed to identify the cause, requiring a large-scale investigative data collection effort.
When physiological events in F-18 aviators surged in 2017 — manifesting as hypoxia-like symptoms — flight instructors began refusing to train new pilots in their jets. The Navy's Physiological Episodes Action Team (PEAT) launched a multi-year investigation. After ruling out air contamination and oxygen deficiency, NAVAIR equipped F-18 aircrew with enDAQ sensors to record cabin air pressure during every flight, ultimately identifying failing Environmental Control System (ECS) components as the root cause — and building a predictive maintenance system that cut incident rates by 80%.
To further investigate the physiological events, Naval Air Systems Command (NAVAIR) equipped F-18 aircrew with enDAQ sensors to record cabin air pressure during flights. Because of the sensors' compact size and rechargeable battery, aviators could carry them in a flight suit pocket — making data acquisition seamless and scalable across the entire fleet.
After each flight, the air pressure data was downloaded and analyzed, then compared with aircraft maintenance data from the same jets. From this growing database, PEAT determined that while the ECS design itself was adequate, certain ECS components were failing — producing pressure abnormalities capable of causing severe physiological events in aircrew.
Having established the root cause, the team's focus shifted from investigation to prediction. The database of sensor readings, paired with maintenance records, allowed analysts to look backward and identify component degradation patterns before full failures occurred.
Maintenance conducted between 5/8 and 5/18 that corrected identified ECS issues.Through the accurate and reliable data provided by enDAQ's sensors, the Navy developed the Hornet Health and Readiness Tool (HhART) — a cockpit pressure monitoring and warning system capable of identifying underperforming ECS components before they cause incidents. Since HhART's implementation in early 2019, pressure-related physiological events in F-18 aircraft have fallen by 80%.
Beyond HhART, the Navy is installing CPOMS (Cockpit Pressure and Onboard Oxygen Monitoring Systems) across the entire F-18 fleet. These systems record air pressure and oxygen data in real time and send alerts to aircrew about potential aircraft problems — enabling proactive maintenance and furthering the shift away from reactive operations.
| Aspect | Reactive Maintenance (Before enDAQ) | Predictive Monitoring (With enDAQ) |
|---|---|---|
| Detection timing | After a PE or equipment failure | Before failure — based on pressure trend analysis |
| Pilot safety | At risk until fault is identified and repaired | Protected through proactive component replacement |
| Aircraft readiness | Disrupted by emergency and deferred maintenance | Maintained through scheduled, data-driven intervention |
| Data visibility | Limited to post-incident maintenance records | Every flight recorded — fleet-scale pressure database |
| PE incident rate | Surging — instructors refusing to fly | Down 80% since HhART implementation |
A physiological event is an in-flight incident in which a pilot experiences symptoms such as hypoxia (low oxygen), hyperventilation, or other physical impairment that can affect their ability to safely operate the aircraft. In the F-18 context, PEs were manifesting as hypoxia-like symptoms traced to abnormal cockpit pressure caused by failing ECS components.
The Environmental Control System (ECS) manages cockpit air pressure, temperature, and oxygen supply in fighter aircraft. When ECS components degrade or fail, they can produce abnormal pressure profiles that create hypoxia-like conditions for the pilot — even if the overall system design is sound.
The sensors' compact size and rechargeable battery allowed aviators to carry them in a standard flight suit pocket. No aircraft modifications were required, making fleet-wide deployment rapid and scalable.
The Hornet Health and Readiness Tool (HhART) is a cockpit pressure monitoring and warning system developed from analysis of enDAQ sensor data and aircraft maintenance records. It uses data analytics to identify ECS components that are underperforming and likely to fail, enabling proactive replacement before a PE can occur.
Yes. While the Navy's initial application focused on cabin air pressure, enDAQ recorders capture a comprehensive set of environmental parameters including vibration, shock events, and acoustic data. This multi-parameter capability supports broader condition monitoring programs beyond ECS pressure tracking.
