No Guessing

Dynon Avionics would like to clear up a few errors in the July 2009 article Freedom to See It Differently. The article states that pitch errors can be caused by acceleration because Dynon EFIS products use airspeed to aid in the attitude algorithm. While it is true that airspeed is used to aid the attitude, the reason that airspeed is used is to specifically prevent false pitch changes when an aircraft changes speed. The other claim was that the airspeed needs to be very accurate for attitude to be accurate. However, the attitude algorithm is actually very tolerant of common pitot/static system inaccuracies.

The use of airspeed gives Dynon products data about what the aircraft is actually doing, rather than requiring an algorithm that guesses at airspeed or other aircraft behavior. Dynon believes this approach allows our products to present one of the most accurate attitude portrayals in the industry. As mentioned in the article, the author specifically tried to get the attitude to misbehave, but was unable to. This is no surprise, since the Dynon attitude algorithm can handle pretty extreme maneuvers before it will begin to show any errors. Over the years, Dynon EFISes have been proven to just work without requiring any heroics on the part of the installer or builder.

Since the article was published, Dynon has released a free software update that allows the attitude algorithm to use GPS data as a backup should a pitot become blocked by ice or anything else. With this update, pilots can continue to use all the functions of the Dynon EFIS products as primary references even in the case of a pitot failure. With this update Dynon EFISes join systems like the G1000 in using GPS and airspeed in a redundant way, while also maintaining their position as the most affordable EFISes sold today.

Ian Jordan
Chief Systems Engineer, Dynon

An Avid Fan

Lets give credit to the correct person! The recent article about The Little Bush Plane That Could by Amy Laboda was very enlightening. Dan Denney had no part in the design of the Avid Flyer. It was solely designed on the back of restaurant placemats by Dean Wilson as he dined at the Caldwell, Idaho, Industrial Airport cafe. Denney entered the picture sometime later and, as I understand the relationship, he was to be the promoter. Later, after a parting of the ways, Denney slightly modified the design and started producing it under the name of Kitfox. Today, many other manufacturers are producing aircraft and/or kits that can trace their heritage to Dean Wilson.

Wilson, a self-taught engineer, held more STCs for light aircraft modifications than almost anyone. At his coaxing, I designed and built a hangar on Caldwells airport to accommodate several Avids (with their wings folded of course) in separate private units.

Mack P. Kreizenbeck

Happy to Help

When I was deciding whether to build an airplane I had two main concerns. The first was if building an airplane would be like having to constantly work on a broken car. I don’t particularly like working on my car, and Id most always rather do something else than spend a weekend at it. The second was finding an airplane that I actually wanted to have when it was finished.

After reading an April 2008 article in KITPLANES, I thought the RANS S-19 looked like it met the latter concern, but its a new design. At the time there was only one in existence, and it wasn’t in my corner of the country. So I decided to go about the decision process a little backward: Id start building an empennage kit first to make sure that I would enjoy the build process; if I did, Id inspect and test-fly the demo model to ensure that it was the airplane I wanted.

Sight unseen and trusting your article, I purchased an empennage kit. Im now halfway through the tail and am having a blast. Everything fits together perfectly, and the design and execution of the kit is very well thought out. To my surprise, I found it has been enjoyable, satisfying work-even after a hard day at the office. So recently I made arrangements to travel to the Hays, Kansas, factory for a tour and demo flight. I was very worried that after months of looking at the pictures and dreaming of the perfect airplane that my expectations would be too high.

I didn’t need to be concerned. The folks at RANS were extremely friendly, the factory was clean, well organized and busy, and the S-19 was everything I had dreamed possible. Just as reported in your article, it feels light and maneuverable, visibility out of the bubble sliding canopy is fantastic, and performance is remarkable. Compared to the trainers I was used to flying…well there is no comparison. I cant wait to throw a couple of breakdown bicycles in the back and take off for a tour across the country.

Keep up the great work reporting on kit build choices. It was invaluable help in selecting the perfect kit. Im happy as a clam in Seattle.

Bruce Fox

Department of Corrections

In our July issue, we mistakenly listed test pilot Chuck Berthes total time as 1660 hours. He checked in to remind us that he had that much time as an ensign instructing in Pensacola. So in the spirit of cooperation, lets add a zero to the end to give him full credit for his 16,000-plus hours.

In our August issue, we incorrectly listed the Kitfoxs baggage capacity as 100 pounds. John McBean called to say that the company was proud of the airplanes carrying capacity of 150 pounds. Missed it by that much!

Write to KITPLANES at [email protected]


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