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by Karl Hipp

This article is titled "D" Model because I believe that if Bill Piper and his boys were still building Twin Comanches, the airplane may have evolved into something like mine.

I purchased a 1967 PA-30 "B" model in March of 1996. The airplane was already fairly well equipped.  It had most Miller conversions: the IO-360 200 H.P. engines with Rajay turbos, Miller nacelles, extended nose with baggage compartment, twin nose taxi lights, and heated props and deice boots. Also included were the Miller wet wing tanks at 19 gallons each. Total fuel capacity was 158 gallons. This fit nicely into my plan of an Atlantic crossing and eventually equipping the airplane for extra long range flight.

The Miller conversion: Extended Nose

The Miller Conversion: Nacelles

I began with a panel upgrade.  The Apollo Loran was an ancient beast.  I scrapped it and fitted a Garmin GNC-300 GPS/Comm, which had just been certified for GPS approaches, the first GPS so approved. Also an Apollo Flybuddy GPS was installed. The KX-175's went into my 250 Comanche and I installed a KX-165 and Century NSD-360 HSI in the twin.  The King ADF was also ripped out.  This left me with two Comms, two GPS's, and one Nav receiver.  The airplane was also equipped with color weather radar which takes up lots of space. Since I don't fly in the nasty thunderstorm weather that occurs in the east, I had a Strikefinder in the 250. This had provided good guidance around the stuff we get in the mountainous west, so I installed it in the twin and sold the radar.  I also installed Horizon electronic tachs.

That August, Judy and I attended the ICS Convention at Denver. I met several other twin owners and soon began to exchange ideas about turbo operation, long range flying, overgross operations, and general maintenance issues.  I went away with some new ideas after having met several new friends.

One noticeable difference from my 250, was that the twin not only climbed like crazy, but it didn't come down easily. On a flight we often make to Boulder Colorado this became apparent.  Crossing Corona pass in the 250 at 13,000 msl, I would reduce power to 13-15", fly at the top of the yellow arc, and arrive at pattern altitude.  Using the same technique in the twin I was 4,000 feet above the airport on arrival.  Simple solution:  speed brakes.

I also found the Altimatic III did a poor job of "keeping up" in mountain turbulence.  So when I installed the speed brakes, a Century 2000 was also installed.

At the Denver Convention, I learned of the plan for the 1999 ICS Convention to be held at Cambridge England. This provided me with the excuse I was looking for to cross the Atlantic.  Over the next few years the airplane got 40 more gallons of fuel capacity with nacelle tanks, for 198 gallons total fuel. A paint job and leather interior were also a necessity.

Judy and I made the flight to Cambridge (actually Duxford, a WW2 airbase) in 1999. After the Convention we went on to Germany and spent a week with Richard and Elfie Mueller who we had met at the Denver Convention, after Richard had flown his 250 across the Atlantic to attend the Convention.

We returned to England and spent a day with David and Jenny Buttle, Atlantic crossing veterans.  On departure from David's airport, Blackbushe, I got my first lesson on "British VFR".  The ceiling at Blackbushe was 300 feet in rain. The uncontrolled airspace over Blackbushe goes to 2,500 feet where the London Class "A" takes over. That's right!  Class "A". There is no class "B" in Europe. We departed with no flight plan, climbed to 2,400 feet, and got radar service advisories for the next 200 miles till we got into VMC.  If the weather conditions in Britain are really lousy there is often little chance of getting an IFR clearance in controlled airspace, so you simply fly IMC in uncontrolled airspace.

Upon return from Europe I began contemplating a multi-function display (MFD), but it took some time before that became a reality.  Also, the lack of a backup Localizer/VOR/Glideslope receiver began to bother me.  When the weather is down in a place like Reykjavik Iceland, a #2 Nav receiver would be comforting if the #1 went belly up. I installed a Narco 122D Nav unit which is a self contained Nav/Glideslope and receiver.

In 2001, Judy and I flew British Air to London.  Dave and Jen Buttle picked us up and we flew in David's PA-39 to a European fly-in at Guernsey.  I was fascinated with David's yoke mounted Skyforce moving map. Although the display is monochromatic, the information and detail are excellent.  Upon return to the US, I bought a new color model Skyforce to mount on the yoke.

Last November 2001, I began planning for the "ultimate" panel upgrade. My plan was to have lots of redundancy, along with relocating switches, indicators, and circuit breakers to where they made sense. Many of the switches for the added equipment had been "shotgunned" in wherever there was room at the time.

I began designing the new panel with my friend, John Van Bladeren, who owns Ron and John's Comanche Service. Panels are his specialty.  Numerous faxes, e-mails and phone conversations ensued for the next several months.

By then, for the panel upgrade, I had acquired:

    • An additional altimeter with dual display Kollsman windows (handy for European flying where the altimeter setting is in millibars),
    • Another airspeed indicator,
    • A backup attitude indicator,
    • An Electronics International volt/ammeter to replace the Piper ammeter,
    • A second KT-76A transponder,
    • A King KMD-150 MFD
    • An Apollo audio panel to replace the King KMA-20.

Also, to provide for more room, the plan was to remove the Strikefinder and install a BF Goodrich WX-500, which would display on the King KMD-150.  The two engine monitors with fuel flow would be replaced with a new JPI-760 EDM, a single unit capable of fuel and temperature measurements for both engines.

I also wanted to install a permanent HF radio. On the prior Atlantic trip I had a Kenwood unit mounted on the side of the passenger seat. Not a good arrangement.  The radio was difficult to operate and the fuel valves were operated not by sight, but feel -- not a good setup. HF is required in parts of the Atlantic. It will also come in handy when Dave Buttle and I fly to Australia for the ICS convention in 2006. Judy and I also have in mind at some future date to fly around the world.   An ICOM 760 HF was installed which  has a removable faceplate. This makes it a good candidate for mounting under the right yoke, since the faceplate can go elsewhere.  It is now mounted on the flip down sun visor on the copilot side.

In June of 2002, I removed the old panel in preparation for the work ahead.

Panel dismanted
Old Panel Removed

The plan was to consolidate switches and breakers as previously mentioned and to move from under the floor some of the more important circuit breakers such as those for the landing gear and fuel pumps. I had the new switch panel made up and installed before John sent the main panels .

1_N8256Y 02-07-03 042
New Switch Panel

The new panel arrived and I installed it in late June 2002. 

On July 3rd, John arrived at my hangar.  After celebrating the 4th with much consumption of typical Colorado refreshments, we began work.  John had brought a bunch of new Klixon circuit breakers with him, and while he was assembling various wiring harnesses, I put together the new breaker panel.

CB Panel
New Circuit Breaker Panel

John and I worked late into each night for the next three days, till he had to return back to his real job.  This is what the panel looked like when John had to leave.

1_avionics 1 001

New Panel

The majority of the wiring was complete, or so I thought.  But it took two more days till I was ready to start installing the goodies. I sure got an education on panel wiring while working with John. What happens is, over the years, as a new radio or instrument is installed and old stuff removed, wiring is added and abandoned.  Wires end up not traveling the most desired route from point A to point B. They end up looping around, back and forth, splices everywhere -- till there is a rat's nest of confusion. So, when a major panel upgrade such as this takes place, it only makes sense to "clean things up".  Here is a shot of the completed panel.

I am working on one further upgrade to the way this aircraft is wired. As mentioned earlier, there is a circuit breaker panel located under the floor.  It is accessed via a small door just aft of the nosewheel housing.  There are still 18 circuit breakers housed in this area and they are the rather large Potter and Brumfield breakers.

I have fabricated a panel to install in the fuselage wall just ahead of the pilot. There is a small panel there now that houses switches for the deice boots, the taxi lights and the wing deice lights, along with the circuit breakers for those systems.

Those breakers and switches will be incorporated into the new panel. I am using the much more compact Klixon circuit breakers in this panel.  Here are photos of the layout and fabrication of the panel and what it looks like. This panel will be installed after the Christmas holidays. 

1_new breaker panel 001

1_new breaker panel 007

1_new breaker panel 015

I think I have accomplished what I set out to do.  Switches have been consolidated.  The fuel pump switches are now where I can actually see them; upper left-top row, rather than under the pilot's yoke.  All of the light switches are in the second row with the landing lights being the first two on the left. The flap actuator is just below the flap indicator where I think it belongs. Only the master, mags, and alternator switches are where the factory put them. I now have a simple check at startup. All the switches in the new panel are DOWN.  All switches below the panel are UP. Simple! 

If Horizon ever gets its single tach unit for the twin approved, that will free up a space on the right. Maybe another T&B will go there?

In addition to the panel upgrades, I made a 100 gallon tank for the cabin. Weight and balance is critical in terms of tank placement.  I have test flown the airplane with it installed and the tank and plumbing all work okay. This will give me a range of over 3,000 miles, and John Van Bladeren and I will be flying N8256Y to Europe in April 2003. The route over will be St Johns, Newfoundland direct to Shannon, Ireland -- about 1,800 nautical miles.  We will meet the girls in Paris and proceed to an European ICS fly-in at Macon, France, and then tour France, Spain, Portugal and Amsterdam.  We plan a return via Iceland.


Karl-pKarl Hipp was born in 1946 in St. Paul, MN, and spent his first 40 years there.  In 1986 he moved toRedstone, Colorado, met Judy, and started a custom furniture and lighting manufacturing business. Karl began to fly in 1988 and two years later bought a 1962 Comanche 250.  After 7 years of ownership, Judy and Karl decided to upgrade to a turbo twin, a more suitable airplane for mountain flying, and now own a Miller converted Twin Comanche, N8256Y.  With 2,000 hours logged, Karl recently earned an A&P certificate to add to his commercial pilot certificate, with SEL, SES, MEL, and Instrument ratings.

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