Letters: 11/01

Pulse Oximeters
I am a long-time subscriber to Aviation Consumer and have been a pilot for more than 26 years.  Your two recent articles on pulse oximeters were excellent. 

However, there’s a critical misunderstanding about pulse oximeters which needs to be explained.  As a practicing anesthesiologist, I use oximeters every day.  The oximeter indirectly measures the oxygen available to the tissues by calculating the percentage of hemoglobin molecules saturated with oxygen. 

However, the relationship between the oxygen available to the tissues and the oxygen saturation percentage recorded by the pulse oximeter is not a linear relationship. 

Pilots should not be fooled into thinking that a reading in the mid- eighties (85 percent) is passing.  The oxygen content available to the tissues drops sharply with a saturation below 90 percent.  Just because a reading of 80 to 85 percent may be passing on an FAA exam, it should not be considered passing for pilots. 

In my profession, we do not allow patients to leave the recovery room after surgery with an oxygen saturation of less than 90 percent oxygen saturation reading of 85 percent is failing. 

Pilots should use oxygen sufficient to keep their oxygen saturation above 90 percent.  I check my saturation readings every 30 minutes and adjust the oxygen flow to keep my oxygen saturation above that value. 

You cannot feel the difference between oxygen saturations until it’s too late.  Most pilots need oxygen anytime they fly above 8000 feet. And remember, it’s the density altitude which dictates the available oxygen in the air, not the pressure altitude. 

Pulse oximeters are cheap insurance against hypoxia.  All pilots who fly unpressurized aircraft regularly above 8000 feet should check their oxygen saturations and use oxygen as indicated by an oximeter.  

-David S. Lennon
Charlotte, North Carolina


I thought the article on pulse oximeters was a good one . As a practical matter, in-flight use of these devices is to use them every 15 to 30 minutes to check your oxygen saturation and adjust the flow accordingly.

I’ve used the Nonin for two years now and find it to be a compact  device which takes up very little cockpit space and doesn’t add any additional wires to the cockpit environment.

-Arthur Willis
Houston, Texas


HSI Child’s Play
In his report on HSIs in the August issue, Larry Anglisano said an HSI makes shooting an ILS so easy that even a 10-year-old could do it.  Indeed, that was one of the reasons why we chose an HSI for our Glasair.  (The other was to save panel space.) 

But I’d never flown an HSI. The problem is that an HSI is still basically a VOR indicator and therefore still requires VOR-type thinking. If you try to fly it as I did—like a 10-year-old playing a video game—you’ll be all over the sky. You just can’t chase the needle, which is the temptation.   It wasn’t until I settled down and started holding headings, waiting to see trends in the HSIs CDI that I finally got the knack.  So, if you do install an HSI to make shooting an ILS easier, get some instruction first.  It’s not quite as simple as it looks.

-Mike Palmer
via e-mail


Cry Integration!
I have been reading Aviation Consumer for about three years now and I really think that you guys are doing a great job.  However, one thing that I have noticed is this: You guys must have an awfully cluttered cockpit from all the stuff you have Velcro’d everywhere, your article on pulse oximeters being the most recent example. 

Is your scan so time consuming with everything that must be Velcro’d to your cockpit that you forget to enjoy the view outside? Many of the things that you review are neat separate devices that scream to be integrated with each other. 

Why do you not suggest this to the manufacturers along with your other observations?  Let me give you some examples:

Why is there only one handheld GPS/COMM?  And why hasn’t it been upgraded? Recently you wrote about CO monitors for the cockpit.  Now you’ve reported on supplemental oxygen systems and   oximeters.  Why not suggest to some brilliant manufacturer that they produce a single unit that monitors cabin air quality for CO, monitors blood oxygen saturation and dispenses oxygen to those being monitored? After all that’s what microcomputers do best; monitor and regulate.

Recently, we have seen MFDs and other such devices integrate weather, collision, GPS, comm, intercom, engine data and so on into one display that reduces pilot workload and increases safety. 

I know that these things come with a price tag but look how integrated units have brought the overall price of high capability down. 

Why not encourage this trend to increase? Or is it disclosure time?  Come on ‘fess up; you guys do own a significant interest in a Velcro factory, don’t you?

-David J. Loring
via e-mail


No Meridian Fan
Even though I think the Piper Meridian has beautiful and stylish lines and a well-equipped cockpit, the aircraft is a joke, in my view.

It is laughable, even ridiculous.  Who in their right mind would buy a “five or six seat” aircraft with a useful load of 310 to 360 pounds with full fuel?  It’s shameful.

A single-engine piston airplane such as the Lancair IV/P gives you similar cruise, more payload, similar range and flight altitudes, for a fraction of the initial and operating cost.  I admit that the two aircraft are in different categories, and the Lancair is a homebuilt/kit airplane, and one cannot compare them fairly.

Still, if I was in the market for a $1.5 million Meridian, I would rather buy a 10-year-old King Air C90 or Cheyenne III/IV.  On the other hand, if I was considering a single-engine turboprop, I’d rather look at the TBM 700 or Pilatus PC-12, admittedly both at a higher price.

-Cameron Ninham
via e-mail


Help Wanted: STS
I read your review of VHF handhelds in the September issue. Nice job. But perhaps you can help me.

I have an old VHF radio, an STS AV 7500 VOR, that looks quite a bit like the JD-200 that you reviewed.

It still works, but the NiCad batteries lose their charge too quickly when not in use. Do you have any idea of how I could get an alkaline adaptor for this radio?

-Brent Bilger
via e-mail