High altitude

A little while back I obtained a Mountain High Oxygen system. This was primarily motivated by having a very bad headache after a long day of flying at 8500 feet. I also like flying at night and while this time of year nightfall comes quite late once we get into the fall there will be more night flying. Your night vision degrades above 5000 feet without supplemental oxygen and I often like to cruise above that point so a portable O2 system makes sense (especially for a flatlander like me).

I haven’t had a chance to try out the system yet since most of my recent trips have been short legs. I had the evening to myself tonight and so I decided I’d take the Cardinal up to a higher altitude and test out the O2 system. Armed with a pulse oximeter to verify my blood oxygen saturation I took off from Nashua and climbed out VFR on a west heading.

Climbing out near Gardner, MA.

I put the oxygen system into “Night mode” which means it will immediately start delivering O2 rather than waiting until a preset altitude. This system is a pulsed-demand controller which means that on each breath in it delivers a meters pulse of gas through a canula (or a mask above 18,000 feet) instead of continuous flow. This is a bit more sophisticated but conserves oxygen so a smaller bottle is needed. As you climb the pulse of gas at the beginning of each inhalation gets longer.

Sipping O2 with the canula.

I stayed on the west heading and kept the climb speed relatively high to keep the engine happy in the thinner air. With a normally aspirated (not turbocharged) engine the amount of power the engine makes is reduced as it climbs. This is offset by reduced drag in the thinner air but eventually a ceiling is hit and you cannot climb any higher. While temps in the climb are more of a concern in a turbocharged engine that can make more power higher up I was still monitoring closely. Soon I was well above altitude of the lower few clouds and you could see the raked evening sunlight hitting the tops of the clouds and making them pink.

Sunlight kissing the clouds above Gardner, MA.

The outside air temperate had dropped considerable and around 11,000 feet it was below freezing outside. The air temperature didn’t drop too much after this point. At this altitude the engine manifold pressure (vacuum) with the throttle wide open was around 16″ – barely above a power setting I would normally use for descending on final approach!

Below freezing outside.

As I got close to 15,500 feet I was struggling to maintain more than a few hundred feet per minute of climb. I decided to head back down. Since I was still maintaining an airspeed somewhat above “best climb” I could have climbed higher but I didn’t want to slow down and be rough on my engine. I leveled off briefly at 15,500 feet, let the engine temperatures stabilize, and turned back.

The big hand is on the 1, the medium hand is on the 5, and the little hand is on the 5…

I had a headwind on me west heading and so as I turned back the headwind turned into a tailwind. This gave me almost 200 knots of ground speed in the descent! Since this was just an out and back I had to make a few turns to avoid overshooting Nashua without an ear bending descent rate. If I was cruising at 15,500 on a real XC trip to take advantage of tailwinds proper descent planning is quite important. A descent starting a hundred miles out would be a more optimum profile.

Almost 200 knots of ground speed in the descent.

As I descended (and did a circle or two to burn off some altitude) the sunset was simply fantastic. Words cannot do the pictures justice so I will just show you them…

Sunset over the Adirondacks.

Sunset over the Adirondacks and Mt. Monadnock.

Sunset over the Adirondacks and Mt. Monadnock.

I managed to avoid being distracted by the sunset in front of me and executed and reasonable nice landing back at Nashua. You can view the full set of photos and larger versions over on my photo site. Enjoy!

4 thoughts on “High altitude

  1. Pete Zaitcev

    Not bad, I was thinking about an oxygen bottle too, but I don’t rent anything that’s a hot performer above the oxigen boundary. In NM we usually cruise 9.5/10.5, as going any lower is impractical. When I cross over into TX, I dive down to 6.5/7.5.

  2. Dan Post author

    I’d want the oxygen at 9.5/10.5 I think. I’d feel safe without it but I’ll feel physically more comfortable with it :) But I live at sea level and that makes a big difference.

  3. Gary

    I have a portable o2 system but need to purchase a new regulator. I sold my 4 place regulator with my big bottle and switched to the small bottle wanting use a two place system by Skyox.

    What pulse ox meter did you get? How did you make out after the test flight? The pictures are absolutely gorgeous…..that sunset is what flying is all about!

  4. Dan Post author

    I have this pulse oximeter: http://www.sportys.com/PilotShop/product/13010

    It seems to work well. I noticed that my pulse rate was increased at altitude as well which is probably a combination of natural physiological response to higher altitude and natural anxiety about making a flight into a regime where I hadn’t been before. When I would take a few photos I’d stop breathing as deeply and the pulse ox would show a decrease… which immediately popped right back to normal as I started with nice deep breaths again.

    I have the sickness of gadget love and so my system is the Mountain High o2d2. It is only two place but conserves oxygen by providing metered pulses based on the static pressure (altitude). The pulse comes right at the beginning of your inhalation.

    I felt pretty good after the flight, no headache. But I felt a bit dehydrated even though I drank a good amount of water during the flight. For a long cruise at altitude I definitely would want to bring at least two liter bottles of water. Probably the pulsed-demand delivery also reduces the nasal drying effect versus continuous flow (but I’ve never used a continuous flow system).

    And as I’m sure you know, the sunset was even more beautiful in person!

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