AN OVERVIEW OF OXYGEN SYSTEM STANDARD FOR MOSAIC AIRCRAFT

Aithre’s Jim Ruttler led ASTM F37 Task Group as the Technical Contact for the development of an oxygen system standard for light sport aircraft.  Also in the Task Group was Mountain High Oxygen, Sling Aircraft, Air Avionics, Surefly, and Dr. James Runnels, MD.  There was no prior oxygen system standard, and Jim formed the Task Group to ensure that oxygen installation standards balanced safety with ease of compliance.  The work led to the development of one baseline standard and two follow on revisions with multiple rounds of member and FAA comments integrated therein.  The standard was unanimously approved by committee members over each of the revisions.  The resulting oxygen system standard F3810-26b is now being reviewed by the FAA along with the other ASTM F37 standards for final adoption and implementation on July 26, 2026.  Once adopted, this F3810-26b standard will provide the specification for manufacturers to follow to install oxygen in MOSAIC light sport aircraft.  

 

Oxygen systems are not always required and will likely depend upon the operating envelope for the aircraft as defined by the aircraft manufacturer.  The FAA final adoption and implementation of the ASTM standards is imminent and will ultimately control, but a portable or installed oxygen system may be required if the aircraft is approved by the manufacturer for flight above 12,500 MSL.  More explanation is below.

The general framework of the MOSAIC implementation is as follows.  The FAA issued new regulations under 14 CFR 22 that set forth the minimum design characteristics of new MOSAIC aircraft, which include systems and equipment under 14 CFR 22.135.  Part 22.135 states that aircraft “must include the systems and equipment required for the specific operations authorized”.  The aircraft manufacturer defines the operating envelope for the aircraft and then must provide the equipment required for that operating envelope.  The FAA then points to industry consensus standards (e.g. ASTM F3810-26b) to specify the minimum requirements for installation of the equipment, such as oxygen systems.  

For oxygen, if the aircraft operating envelope is under 12,500 MSL, there is no requirement for an oxygen system.  If, however, the aircraft operating envelope is defined by the manufacturer to exceed 12,500 MSL and the and the aircraft is designed and intended for flight to higher altitudes, it is likely that the FAA will require either a portable system or installed oxygen system to support that high altitude envelope.  This is because of the FAA regulation 14 CFR 22.135 states that aircraft must include the systems and equipment required for the specific operations authorized, and because oxygen is required by the pilot above 12,500 MSL under Part 91 of the regulations.  

Again, while the FAA will make the final decision during the MOSAIC airworthiness application, if the operating envelope is higher than 12,500 MSL, it is likely that a portable oxygen system that is included with the aircraft will probably satisfy the “required equipment” under 22.135.  Of course, an installed system would also satisfy the required equipment under 22.135 so long as it is installed in compliance with the ASTM 3810-26b oxygen standard.  

 

 

As addressed above, portable systems will probably be allowed so long as they are part of the aircraft required equipment list, and the POH specifies that the portable oxygen equipment is required for flight where oxygen is legally required.  While the F3810-26b standard could be referenced for safety, the F3810-26b standard would not really apply because the standard only relates to installed oxygen systems.  

If the manufacturer chooses to install an oxygen system, then F3810-26b would apply and the manufacturer would need to comply with the standard.   Fortunately, this is easy to do because the wide latitude of technology and installation options that are included in the standard.  For example, the oxygen system can include a bottle system, an oxygen generator system or both.  There must, however, be a means for the pilot to know the amount of oxygen available, the flow of oxygen, and to turn on/off the oxygen during flight.  The oxygen system must be capable of outputting a higher flow rate tied to altitude of around 1 LPM/10k feet, although the actual use rate may be much lower.  And, if bottles or cylinders are used, they must conform to relevant ISO standards and be marked for oxygen service.  The oxygen distribution lines may be polyurethane when the pressure is low and when they are protected by heat sheathing, which eliminates the old Part 23 requirement for aluminum or copper lines.  Lastly, when oxygen generators are used, their temperature should not create a hazard, and they must be placarded to show flow rate and the replacement cycle for the generator element. 

 

 

Under F3810-26b, the POH should include basic use instructions and provide information on functional checks and failure modes.  A maintenance manual should accompany the aircraft to include information on maintenance requirements for the oxygen system.  The aircraft should include warnings, which may be digital, regarding smoking, nasal congestion, grease, maximum ceiling, and hypoxia risks while using the oxygen system.  

 

 

To keep the installations of the oxygen system safe, F3810-26b provides a few obvious recommendations for cleanliness.  Namely, that gloves should be worn and that care should be taken to prevent oil and grease from contaminating the system and lines.  While there is wide latitude given for installation location, there are a few requirements.  For one, there are clearances required for the oxygen lines relative to high current wiring, engine, fuel, hydraulics, and moving parts.  And there should be no surprise that the oxygen system should not be in the firewall forward engine zone or proximate to a high heat source, such as heaters or exhaust.  Otherwise, the manufacturer is generally free to determine the best location for the oxygen system for aesthetics, weight and balance, and safety.  

 

Aithre offers several products that are MOSAIC ready.

The Turbo installed O2i system is a hybrid oxygen generator and bottle system that includes monitoring and control via the Air Avionics partnered HealthView system.  The PU lines, avionics control and monitoring, and backup oxygen with high flow rates all satisfy F3810-26b out of the box.

If portable systems are allowed by the FAA, which they most likely will be, the Aithre Turbo portable oxygen concentrator system would be another fine option for mid range altitudes.  

Any questions should be directed to Jim Ruttler or Zuzana Melherova at Aithre, Inc.