Pulse Oximeters
I enjoyed the article on pulse oximeters (March 2013). You can also buy them at Walgreens or Walmart for $30 to $40. I have an Oxywatch C20, which I bought a few years ago at Walgreens for around $40. It is within one percent of what is used at my medical clinic.
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You mentioned that the units tested were within “two percentage points” of the medical unit. This can be misleading as one can control the level on the pulse oximeter by altering one’s breathing. Most people breathe shallowly. So with the pulse oximeter on a finger reading say 94 percent, one can take very deep breaths and in a minute or two temporarily raise the blood-oxygen levels up to four or five percent.
So, when Dr. Blue recommends using supplemental oxygen when at five percentage points below home, the way the person is breathing matters. A person who is at 98 percent at home and is breathing deeply in flight and reading 93 percent may actually be at 88 percent, a 10 percent reduction in saturation level.
Bob Worthington, Ph.D.
Via email
Cessna 120-140
You continually overstate cruising speeds on old airplanes. No 85 HP Cessna 120 or 140 will ever cruise at 100 knots. It will do 95 to 100 MPH if it is rigged properly. The fastest of the post-war two-placers was the 85 HP Taylorcraft BC-12, which cruises about 100 to 110 MPH.
The high rate of nose overs is because of geometry and weight distribution in the design, since other side-by-side planes of the time don’t have this problem.
The ballooning you discussed is caused by the overly active spring main landing gear. That gear gives back about twice as much as it gets and is to be respected. It is the reason that wheel landings are not to be encouraged for low-time pilots. It is also extremely noisy on the ground because of the gear, much more so than any other of its era.
Gus Causbie
Via email
Social Networking
I would like to add my whole-hearted support to the March article on social networking. The biggest problem I faced as a recreational pilot was “Nowhere to go, with nothing to do.”
Without flying clubs or social groups such as the local group that calls itself the Sunday Morning Breakfast Club, what does the new pilot do once the checkride is completed? Plop down $200, fly around the city for an hour and come home?
Much as I love flying, even I can think of better ways to spend $200. If you add a flying club to bring in both affordability and camaraderie, you’re getting a morning or afternoon of purpose to flying. To me, it’s like the difference between lifting weights by yourself in your basement versus joining a health club with programs, social events and other cool stuff to get you out of your cave.
Henry Fiorentini
Via email
We agree with the social networking article in the March issue and believe that it is a key element to both enjoying and revitalizing general aviation. We are not alone. The recent proliferation of social media geared towards pilots shows that others think so as well.
Of course, “organized social networking” can move beyond the realm of social media and informal networks, it can involve aircraft access. The recent push by AOPA to increase the number and vitality of flying clubs is one example. The popularity of shared ownership options is another. For example, the Aviation Access Project promotes both the lower cost of shared ownership and the development of a community of aviators at its Flight Center locations.
Market research and common sense showed us that aviators love the sense of community in aviation as much as they love the machines themselves. Communities have the potential to grow. Growing the community of pilots and aviation enthusiasts can only be a good thing for an ailing industry.
Len Assante
Aviation Access Project
Correction: In the GTN Owner Survey article in the March 2013 issue, on page 15, we inserted the wrong pie chart under the question “How many repairs have you had on the system?” The correct data are:
0 repairs – 83 percent
1 or 2 repairs – 13 percent
3 or more repairs – 3 percent
Other – 3 percent
