Letters: 01/06

Oxygen Starvation?
The first color issue of Aviation Consumer is fantastic. Although I would have still been a loyal subscriber with black-and-white images, the color provides a significant added value and it is much appreciated.

A comment and question. In the pulse oximeter flyoff, the 2 in SpO2 should be a subscript, not a superscript. Sorry to be picky. As an anesthesiologist, SpO2 is a significant concern to me during my patients operations.

Needless to say, I was shocked to see your test pilots SpO2 in the range of 80 to 84 percent. At what altitude was this photograph taken? Was he experiencing symptoms of hypoxia? In the operating room, an SpO2 of 80 percent is a true emergency requiring immediate elucidation of the cause and immediate rectification.

David Breznick, MD
Iron Mountain, Michigan

Our test pilot had been flying at 10,000 feet for 10 minutes when the photo was taken. And no, he wasnt experiencing hypoxic symptoms, other than the usual sense of false we’ll being, narrowed vision and inability to do mental math problems. (Just kidding…)


EFB Comments
Just read your December 2005 EFB article and thought I might send along some experiences and opinions after going through the EFB process in my Baron. Some of the factors that led to a portable EFB solution were these:

Panel geography: Pre-1984 Barons like mine put the radio stack on right side of the panel, not a great place for seeing and using a panel-mount MFD. The cost of these panel-mount MFDs, plus certified weather datalink boxes and charting, is significantly higher than a portable EFB solution.

In-flight weather: From the Boston area, common destinations for me are the upper midwest and Florida. These trips are long enough that you can often count on encountering one (or more) weather issues. Access to NEXRAD and METAR/TAF information inflight is an incredible advantage.

Approach plates: Paper charts to cover the eastern U.S. are an enormous pain and expense for 95 percent of the charts that are never needed. An EFB using Jeppesens JeppView software was very appealing. I print the charts to be used, but have it all available on the EFB. As an absolute back-up, I keep some bound government plates-not too old-appropriate to the trip.

Finally, I liked the idea of having a small and portable PC on the road for DUATS briefings from my hotel, looking up destinations on www.Airnav.com, email and so on.

As for hardware, I knew from previous experience with Windows CE palmtop-type devices that they were not the answer for me. The larger 10.5- or 12-inch screens are fantastic for information display, but simply too big for my cockpit. Realizing I needed an 8.5-inch screen, I studied ADRs Fujitsu solution, Itronixs rugged tablet and the NavAero T-Pad 800. I ordered a T-Pad 800, but the units were backordered and, on further consideration, the cabling issues looked too difficult. So I cancelled the order and went with Hewlett Packards TR3000 rugged Tablet PC, a licensed version of the Itronix tablet (www.itronix.com), but with a slightly faster processor. I believe HP has since stopped licensing this tablet. One resource for Itronix that seems good is www.GroupMobile.com.

It turns out that having a rugged-ized tablet is a good idea because the flight environment can be less than kind. The Itronix is a solid unit. My only wish is for more memory capacity than its maximum of 640MB and a faster processor. The new Motion 8.5-inch tablet probably offers both of these features.

Next purchase was WxWorx software, an XM weather receiver and Aviator Lite subscription, along with a USB GPS. Because I wanted GPS input for both the WxWorx software and my JeppView Flitedeck software, I purchased Fransons GPSGate online. GPSGate is a wonderful and inexpensive utility that allows multiple programs to access one GPS input. (www.franson.com)

Regarding the Aviator Lite subscription, I just didnt see the need for more than NEXRAD and METAR/TAF. Perhaps if I didnt already have a Stormscope, the lightning data would make the full Aviator subscription worthwhile.

I can also give a very good rating to TrueFlights software. For smaller screens, its very readable-better than the Jepps Flitedeck, which had such unreadably small fonts for the enroute page that I bought the TrueFlight software. Credit to Jeppesen though; Flitedecks most recent revision has really improved readability issues on smaller screens.

TrueFlight comes with approach overlays and the actual NACO plates are one click away. Terrain warnings, a great XM weather interface and good GPS configuring all make TrueFlight a solid software choice if you want to run only one package for approach charts, XM weather, a moving map, even fuel prices.

Although your review was lukewarm about the Flight Cheetah hardware, I can tell you that on a tablet PC, the software responds to stylus input very we’ll on screen. TrueFlight seems to be a well-thought out product and technical support is very accessible. Oh, and you are right on the mark about cable ties. Lots and lots of cable ties.

Art Tarlow
Via e-mai


Lean of Peak Reply
In your article on wasting avgas, your statement under Idea 1: As far as were concerned, the data that indicates that correctly executed lean-of -peak operation both saves fuel and lowers EGT and CHTs is inarguable and people who claim otherwise don’t know what they are talking about, requires a response.

The key temperature relating to exhaust valve and seat life is exhaust valve face temperature, not cylinder head temperature, specifically, valve edge and seat temperature. These are only indirectly related to cylinder head temperature. They are directly related to the heat transfer capability of the gases passing over them. The cooling of the exhaust valve face and seats and their resulting temperature is primarily influenced by the temperature and state of the exhaust stream.

At rich of peak, we have some unburned fuel that will cool the valves by changing state, a latent heat exchange. This powerful cooling mechanism is lost lean of peak and we must rely on the direct temperature (sensible) exchange. This is why no one, not even GAMI, will recommend takeoff and climb lean of peak. Think about it, if lean of peak insures lower cylinder head temperatures, why not take off lean of peak? They know why.

No one accurately knows or can measure valve face temperatures. What is the best way to insure cool exhaust valve faces? With excess fuel. Wright engineers, when they developed lean-of-peak operation on the R3350 turbo-compound, used sodium-cooled exhaust valves.

I will continue to fly rich of peak because with the valve technology I can afford, a gallon or two an hour is much cheaper than the alternative. Engine shops will continue to reap the benefits of lean of peak, not because pilots are ham-fisted with the mixture or ignorant, but because they have given away the major method of valve cooling with out advanced valve technology.

David E. Crankshaft Leue
Vista, California

GAMIs George Braly tells us the technology to measure valve temperatures was we’ll established by the 1940s. This data shows that exhaust stream temperatures between 1300 and 1600 degrees F are common, with valve temperatures at 1150 to 1300 degrees. The reality is that the valve cools the exhaust stream, not the other way around.


SureFire Fan
A fellow pilot bought a new flashlight this past weekend. He got the SureFire brand. Oddly enough, the flashlight was sold at a local gun store. I was very impressed with the quality of the product and the crispness and intensity of the light beam.

I am curious, have you looked at these flashlights? Are you aware of the SureFire brand? For more information see www.surefire.com.

Cameron Ninham
Saint Augustine, Florida

Yes, weve tried the SureFire lights and will be reporting on them in a future issue.


In our November 2006 report on carbon monoxide detectors, we gave an incorrect price for the Safe-Test90. The correct price is $410.

In the Used Aircraft Guide chart on page 25, the payload with full fuel values are actually useful load numbers. In the resale chart, values for the 1974 and 1980 models were reversed. Corrected charts are available on the Aviation Consumer Web site.