Implications of Integrated Life Support Systems in 5 th Gen Fighters

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Suzanna Parker
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1 Implications of Integrated Life Support Systems in 5 th Gen Fighters Prepared by Col Bill Mueller, USAF, MC, SFS Presented by Lt Col Rob Monberg, USAF, MC, SFS

2 Disclosure Information I have no financial relationships to disclose. I will not discuss off-label use and/or investigational use in my presentation This presentation contains the opinion of the author and does not the reflect the view of the U.S. Air Force or Department of Defense.

3 Overview Thesis Problem / Gap Legacy LSS design/understanding 5 th -gen approach to LSS Proposed Solutions Human Systems Integration early Human Systems Integration late

4 Thesis 5 th gen fighters integrate technology and the human to optimize man-machine lethality Similarly, but for different reasons, Life Support Systems (LSS) and Aircrew Flight Equipment (AFE) have been integrated into aircraft Environmental Control Systems (ECS)

5 Thesis The shift from legacy LSS isolated from aircraft systems to 5 th -Gen LSS that are integrated with aircraft systems has created unexpected Human System Integration gaps Effective use of Human Systems Integration (HSI) could have prevented these gaps and provide a means for fixing them

6 Pilots assume high reliability of LSS Historically, LSS was isolated from other aircraft systems and simple in design This combination provided: High reliability Easy checks Straight-forward trouble-shooting Problem

7 Problem Today LSS are different, but same assumptions of reliability and design are made Change in design did not include assessments of HSI domains

8 Legacy Oxygen Systems Simple design with few failures Pure O2 (LOX/GOX) isolated from aircraft systems O2 routed through regulator to pilot Simple PRICE check pre-flight & in-flight On, normal, normal, good blinker, pressure/quantity Hypoxia often the result of bad connection Common remedy, check connections, gang-load If problem, impound LOX and check for contamination

9 Legacy Oxygen Regulator Blinker shows system is working Quantity shows supply Normal/Emergency settings for pressure and concentration

10 Liquid Oxygen (LOX) Systems Main Features Container Pressure Closing Valve Fill Valve Pressure Relief Valves Gauging Build-Up Coil 13 January

11 5 th -gen Oxygen Systems On-Board Oxygen Generation Systems (OBOGS) basis for all 5 th gen LSS Supply is normally from engine bleed air via ECS Product gas mixed at OBOGS (F-35, F-22) Delivered to pilot via Breathing Regulator and G (BRAG) valve Pressure Swing Adsorption (PSA) Basic technology for eliminating nitrogen from normal air Product gas is purified mix of O2, N2, and Argon

12 How OBOGS works Pre-combustion bleed-air from engine compressor routed into aircraft ECS ECS routes air throughout aircraft Cooling equipment Cockpit pressurization Oxygen generation for pilot (OBOGS) OBOGS N2 removed from engine bleed-air by Zeolite through adsorbtion (sticking), then dumping Product gas is purified mix of O2, N2, and Argon

13 How OBOGS works Molecular Sieve Canister - Purge O 2 18% N 2 81% Ar 1% Exhaust Gas Molecular Sieve Canister - Production Purge Orifice O 2 21% N 2 78% Ar 1% Engine Bleed Air O 2 93% N 2 1% Ar 6% Breathing Gas 13 January

14 On-Board Oxygen Generation Systems (OBOGS) 2 molecular sieve canisters Pressure Swing Adsorption As one canister separates O 2 from air, the other purges the nitrogen enriched exhaust This allows continuous breathing operation 13 January

15 How OBOGS works OBOGS product gas breathed by pilot Maximum O2 concentration: 95% Argon is not separated and is therefore concentrated to between 1% and 5% Product gas can be stored in reservoir Standard Regulator adjusts O2 concentration to pilot Product gas can be supplied directly to pilot OBOGS cycling rate adjusts O2 concentration to pilot

16 Changes from legacy to 5 th Gen Preflight and in-flight checks gone Integrated Caution and Warning (ICAW) when system fault detected No information available to pilot to show OBOGS status or O2 concentration Different remedy to problems No regulator to gang-load No blinker to easily detect system leaks Need for Back-up Oxygen System (BOS) in case of OBOGS/Engine/ECS problem or contamination

17 Changes from legacy to 5 th Gen OBOGS depends on: Clean bleed air Clean ECS Proper operation of OBOGS Triggering BOS depends on: Detectable, known fault Adequate volume in BOS Consideration for auto vs. manual selection

18 Changes from legacy to 5 th Gen Difficulty diagnosing hypoxia sx w/obogs Hypoxic hypoxia: Bad connection Unknown problem with OBOGS or supply air If hypoxic hypoxia suspected, no way to verify O2 concentration of product gas Histotoxic hypoxia: Almost impossible to identify contaminant problem Impounding OBOGS doesn t provide source air

19 HSI Solution HSI domain assessment 1. Manpower: # of positions to support system 2. Personnel: Qualities of people put into positions 3. Training: Required to support/use system 4. Environment: Impact on environment 5. Safety: Risk operating in normal/ep situations 6. Occupational Health: Long term exposure issues 7. Human Factors Engineering: Control interface 8. Survivability: Operation in degraded situation 9. Habitability: Living space for pilot

20 Early HSI Solution Early HSI domain assessment HFE: Analysis of pilot-machine interface Active/Background record of O2 concentration/flow Safety: Analysis of pilot in normal/ep situations Determine aircraft system failures that impact life support systems and mitigate risk Survivability: Analysis of failure modes Determine & substantiate appropriate BOS design KEY POINT: HSI requires integration of appropriate domain analysis

21 Late HSI Solution Late HSI assessment Training: Analysis of legacy vs. 5 th -gen training Ensure crews understand/train to LSS EP actions No longer just gang-load your regulator Survivability: Analysis of actions required in degraded situations Ensure crews understand dependencies of LSS Particular emphasis on emergencies with secondary LSS failures/degradations KEY POINT: HSI requires integration of appropriate domain analysis

22 Summary 5th gen fighters incorporate fundamental changes in design of Life Support Systems These changes have created unexpected vulnerabilities in normal/emergency operations Early HSI analysis could have prevented these gaps Late HSI analysis can mitigate or eliminate these gaps

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