Light Aircraft Oxygen System
 

I have a requirement to fly at altitudes up to 20Kft, for periods of up to 2 hours in a light twin aircraft that is unpressurised (PA-31-310). The aircraft has an oxygen system, with oxy provided to the cockpit and cabin seat positions. Simple oxy masks (with a microphone for the pilot) are installed under the seats.

The system is serviceable, although we have never used it in anger, and there is no 'instruction manual' for its use so I don't know much about it except that I assume it simply provides 100% oxy until the gas runs out (there is a pressure gauge in the cockpit)!

I have many years experience of flying on oxygen from time in the military, so am quite familiar with the whole concept, but I have absolutely no experience at all of flying on a system such as the one fitted to my current aircraft (which itself is cleared for operation up to 24Kft).

I think my question will span across more than one forum (medical for starters), but I thought I would begin here, to see if anyone can provide some advice for operating the system from a technical viewpoint.

Does anyone know where can I find advice on system operation, how to check it before flight, how to check it in flight, and so on. Very grateful for your advice.

First you'll need to identify the system. Most likely there is an STC for the installation (mx records check) and, almost certainly, a relevant FMS in the POH ?

O2 is also a factory option in the PA31. The one I operate has it. I'll check its manual tomorrow and make some notes for you. May not be much use if its system is different to yours.

Thanks, I'll have another look in the AFM but I'm pretty sure it's a factory fitted system.

Anyone know anything about physiological effects?

Can I fly legally with passengers under an AOC...? If so, does anyone know where the relevant regs are in EU Ops or any other document?

Where to find info?
 

Surely you can get the information regarding operational requirements and limitations on the use of the system from the relevant governing body (CAD). If you are unsure of how the system operates the first requirement is to find out. How much time on oxy do you have? Is it 100% flow or is it able to be diluted? Above what altitude MUST you use oxygen? These seem to be basic questions you need to have answers for before flying to high altitudes.

You might want to take a look at the aircraft manufacturer's website and see if there is an AFM supplement listed for the oxygen system.

Most manufacturers do not make the full supplements available on their website, but they typically will provide a document that gives you the dates of most recent revision to both the AFM and the AFM supplements. If you see that there is a supplement published, try giving the manufacturer a call (call their customer support department) and ask them if they would be so kind as to send you the latest issue of the AFM supplement for the oxygen system. Most manufacturers will do this at no charge if you (i.e. the aircraft operator) have a subscription to the AFM revision service for the aircraft.

Be aware that during the production history of the aircraft, the manufacturer may have fitted more than one type (or size) of oxygen system. So, before you call the manufacturer, get together with your maintenance technician and find out exactly what the specification of the system fitted to your aircraft is.