EVOLUTION OF A HOMEBUILT

As many of you know, I’ve been flying my Christavia MK 1 since July 2004. The plane I fly today is a lot different from the plane that first graced the skies that summer afternoon.

Modifications of my Christavia started even before I began flying. During the taxi tests, I noticed that the toe brake pedals were too upright, and I was riding the brakes during normal rudder inputs. To fix this, I temporarily added hardwood blocks to the bottom of the brake pedals and later installed Cessna rudder pedals that solved the issue.

In the first couple of minutes of flight, the turn coordinator I had installed (salvaged from another aircraft) died and popped the breaker. This was later removed, and a simple ball indicator was mounted below the ASI.

The next series of changes were done to reduce the empty weight of the plane. The heavy Gill G-35 battery was replaced by an Odyssey, the ¾” ply shelf behind the rear seat was replaced by 0.040” aluminum, and the starter was replaced by a Sky-Tec. I did add a little weight in the form of a Grimes dual flasher strobe kit.

By the time winter rolled around that first year, I decided that the tires were too small and the engine needed a pre-heater. So, new 8.00×6 tires were installed along with a Tanis heater.

At this time, the avionics in the Christavia amounted to a handheld Yaesu radio and a Garmin GPS III bolted to the panel. With a trip to Oshkosh being planned for July, I decided that the airplane needed a transponder. To mount the transponder, the radio also needed to be replaced due to space issues.

In went an Icom A-200 COMM radio and a Narco AT-165 transponder and encoder. Things were starting to look quite professional now.

Around the same time, I started considering how I could increase the useful load. I did some careful calculations and determined that the gross weight could easily be bumped by 100 lbs to 1750 lbs. After consulting with the fine folks at Transport Canada, I went through the testing procedure and was issued a new Special Certificate of Airworthiness at the new gross weight.

Before and after shots of the Christavia panel. A lot has changed in 6 years…

I was now ready for Chrissy’s debut trip to Oshkosh 2005. While there, I upgraded to a Bose ANR headset and a new seat cushion, making the return trip far more comfortable. I also did some shopping for a new propeller.

In October, I replaced the metal McCauley prop with an Ivo Magnum 70” prop. Two years later, in July of 2007, I decided to go back to the original McCauley after having it repitched. This seemed to provide the best match of engine, airframe, and prop for Chrissy.

Not much else changed between 2005 and 2008, except for some fine-tuning of the oil cooling system. In May of 2008, I decided to replace the bungee shock absorbers on the landing gear with coil spring units purchased from Wag-Aero. Although they added a little weight, the end result was a plane that’s much easier to land and a lot smoother on grass fields.

The following spring, I replaced the 121.5 MHz ELT with an Artex 406. That, coupled with my SPOT tracker, provides a great combination in the event I ever have an accident.

The last big change took place last winter. I brought the plane to work and upgraded the avionics by adding a new Garmin SL-40 COMM and a new Garmin GMA-240 audio panel. At the same time, I installed the Monroy traffic monitor in the panel and wired it up to the audio panel. This installation allows me to monitor three frequencies at the same time as well as listen to my iPhone simultaneously. This configuration worked well on our trip this summer, and I finally have the avionics stack I wanted.

This spring, I also added a spinner purchased from Great Plains Engines. This allowed me to finally dynamically balance the engine and prop, making it very smooth…

One last modification was done last month when I upgraded the Monroy to provide directional data as well as distance and altitude of nearby traffic.

So, what’s next? Well, I’d love to set up Chrissy for night flying with the installation of an EFIS and engine monitor system, a larger alternator, landing and taxi lights, and position lights. However, with the Wittman Buttercup progressing well, I may leave Chrissy alone and concentrate on putting a high-tech panel in the next plane.

Speaking of the Buttercup, I’ve put my nose to the grindstone and have been getting some things done. I now have all the wing ribs completed, and I’ve been working on the tail. To date, I have the horizontal stabilizers, vertical stabilizer, and rudder completed, along with the fuselage structure. Of course, there are a lot of fittings and pieces to be added, like seats, doors, control systems, landing gear, and other such minor items.

As with the Christavia, I couldn’t leave well enough alone with the original design and have already made a number of changes. First, the leading edge flaps have been replaced with a conventional fixed leading edge. This is both for strength and reduction in complexity.

I’m also putting an O-320 in place of the more conventional O-200. This led to some suggestions from the designer that included adding an additional wing bay by adding a drag wire, anti-drag wire, and compression strut. The wing dimension won’t change; the bays just become smaller.

The latest changes I’ve been making are with the control system. The original system had a single control stick between the sticks. I really prefer the dual control stick with the pivot below each stick. So, borrowing from some other aircraft designs I have kicking around, I’ve come up with a workable system.

The other change in the control system is to use a trim tab. The original trim used a spring that had an adjustable center to provide elevator trimming. Now I can employ an electric trim system, which arrived last week from The Ray Allen Company. I also ordered the trim indicator and stick grips with trim switches.

If you hadn’t noticed, we’ve been a bit dry on material over the past couple of months, so if you’re getting tired of my ramblings, please send in any articles or stories you might have, and you can share the limelight.

I wish everyone a Merry Christmas and a Happy New Year!