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Into thin air

Stepping into supplemental oxygen

Regulations are our limits, our solid red line, our no-fly zone. For many, that makes them the de facto set of operating principles as well.
Into thin air
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But in many cases that’s neither wise nor particularly safe. According to Aerox’s Scott Ashton, supplemental oxygen is a prime example.

You know the regulation. In layman’s terms FAR 91.211 says on a nonpressurized aircraft as required flight crew we must use supplemental oxygen after more than 30 minutes above 12,500 feet, and all the time above 14,000 feet. Passengers must be provided with the gas above 15,000 feet, although they aren’t required to use it. Most pilots never fly at these altitudes, and therefore have never used or even considered purchasing a supplemental oxygen system, and that’s a mistake, says Ashton.

“[FAR] 91.211 isn’t designed to keep us safe,” he said. “It was a construct to allow people an additional westbound altitude to cross the country without oxygen.” Europe requires oxygen above 10,000 feet, as do certain Part 135 operations.

Buying the system is the first hurdle to overcome, and it can be intimidating and confusing. There are scores of choices to make, including the size of the tank, masks, or cannulas, the type of regulator, and more.

Thankfully, the companies that sell the gear recognize the confusion and have made it easier. Aerox has an online tool that asks about your general flying habits, including how long and at what altitude your legs are, how many passengers you carry, and so on. Mountain High Oxygen has a few helpful videos that clearly explain the process.

There are four parts to every system:

  1. Cylinder. The tank in which the oxygen is stored can be aluminum, carbon fiber, or Kevlar. Aluminum doesn’t have a life limit, while composite cylinders are good for 15 years. Choosing the right size comes down to balancing how much weight you want to carry, how many people are in the airplane, and how often you want to refill the tank. Ashton recommends getting the largest cylinder you feel comfortable carrying in the airplane because filling the cylinder is probably the biggest downside to using supplemental oxygen.
  2. Regulator. Not every company offers a choice in regulator, and most pilots don’t need or want a choice. Just make sure the type of regulator fits the type of tank, which shouldn’t be an issue if you are purchasing the entire system from the same company.
  3. Flow control. This piece ensures you aren’t wasting oxygen or making yourself hypoxic. Mountain High uses an electronic controller it says saves oxygen, while Aerox uses a mechanical system. The only choice to make here is the company to go with since each offers a distinct product.
  4. Mask or cannula. This is one of the easier decisions, and it is based almost solely on altitude. If you’re planning to fly above FL180, but below FL250, you’ll need a standard re-breather mask. Below FL180 a cannula will work. There are various designs on the market, so do a bit of searching to see what works best for you. Aerox recently introduced a headset-mounted cannula that negates the need to wrap tubing around your ears and work at setting the hose on your lip. Instead it swivels up like the microphone boom and sits in place.

A complete four-place system with a seat-back carrier and other accessories is less than $1,500, and deals are usually available at airshows.

Using the system

For most light GA flying cannulas will suffice because they are used below FL180. Although not difficult to use, it's a good idea practicing with the system on the ground before you need to use it in the air.Ashton recommends using the system anytime you’re flying above 8,000 feet during the day and 5,000 feet at night, a number the FAA concurs with. Ultimately where you use the oxygen has more to do with your personal physiology than it does a hard limit. A pulse oximeter that indicates anywhere around 90-percent saturation or below means it’s time to put the oxygen on.

To pilots who have been flying for decades, 8,000 feet probably seems like a conservative number, but research shows that it’s a good guide for when most people drop to 90-percent oxygen saturation or lower. Why is 90 percent the magic number? Consider that if you weren’t feeling well and you went to the doctor and tested at 90 percent, there’s a chance they’d send you to the hospital, which would put you on—you guessed it—supplemental oxygen.

Other than the confusion of purchasing the system, the biggest challenge with supplemental oxygen is filling the cylinder. “Filling is the single biggest barrier to using oxygen,” said Aston. That’s especially true of a smaller cylinder. Imagine wanting to fly a round trip through the mountains between 12,000 and 13,000 feet. The planning will require oxygen be available at both ends of the trip, assuming you don’t have the capacity to make it round-trip. That availability impacts everything from the route you can take to the altitude you can fly and the places you can land.

To pilots who have been flying for decades, 8,000 feet probably seems like a conservative number, but research shows that it's a good guide for when most people drop to 90-percent saturation or lower.That’s one reason Ashton recommends carrying the largest cylinder you can. But if cost, space, or weight are concerns, it’s time to get creative. Most pilots start their search at the FBO, which seems reasonable, but he recommends a maintenance facility. Most have oxygen on hand to fill their customers’ internal systems, and many will be happy to sell you a top-up. If one isn’t available, you can try a local industrial gas supplier, which is where FBOs and others get their supply. Finally, try a welding shop. Although welding oxygen, medical oxygen, and aviation oxygen are sold as different products, Ashton says they are largely the same at the point of sale, and things such as moisture for medical oxygen are only added at the point of distribution. So, don’t advertise that you’re a pilot and using it for an airplane, but there’s nothing wrong with asking a welding shop for a refill.

Maintaining the system is easy. Aluminum bottles don’t have a life limit, while composites are good for 15 years. All types are required to be hydrostatically tested every five years in order to be filled. Which simply means you can use what’s in the bottle if the five years have passed, but will need to get it tested in order to refill it.

Although it requires a bit more planning, adding supplemental oxygen can greatly increase your airplane’s utility, and provide a welcome safety boost. It can also help you arrive at your destination less fatigued, a fact that could alone make the price of the system worth it.

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Ian J. Twombly
Ian J. Twombly
Ian J. Twombly is senior content producer for AOPA Media.

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