Choosing a VFR Panel

One pilot's plan for a minimum, low-budget panel

December 1, 1997

Blue sky above faded into a dull white haze on the horizon. Twelve miles ahead, McMinn County Airport, southeast of Athens, Tennessee, lurked ahead in the haze. At least that's what the line I drew on the Atlanta sectional and my trusty Trimble Flightmate handheld GPS told me. With eight to 10 miles of visibility, I was relying on the handheld and basic pilotage to find McMinn County, my planned fuel stop. A quick scan of the Spartan panel provided no clues; this was a minimalist's approach to aviating.

Tempted late in 1994 by an ad in Trade-A-Plane promising a brand-new Maule MX-7-160 Sportplane (see " Low-Ball Maule," December 1994 Pilot) for the bargain-basement price of just $44,995, I had taken a deep breath and placed an order. Lottery fantasies aside, the chances of purchasing a factory-new airplane are well beyond the means of many pilots. But at 45 grand, how could I go wrong? This was a brand-new airplane — new Lycoming O-320, new Sensenich prop, new airframe, and a fresh four-seat interior filled with new-airplane aroma.

The MX-7-160 will do basically everything a Cessna Skyhawk will do, with better short- and soft-field performance and the allure of a classic taildragger thrown in for good measure. To keep the price to a minimum, however, the Maule Sportplane's panel was bare — as in Piper-Cub basic. Nothing but airspeed, tachometer, altimeter, fuel pressure gauge, fuel gauges, and basic engine cluster surrounded by several square feet of vacant flat black instrument panel. Not a gyro or radio in sight. Though vacuum/gyro and radio packages were offered, the only factory options that I ordered were a com antenna, electric turn coordinator (you need your feet in a Maule), auxiliary power point, and a second wing-mounted landing light.

Operating the Maule would require a refresher on basic pilotage skills, a challenge that I rather looked forward to. The game plan was to fly the airplane with my trusty Icom handheld transceiver providing two-way communications, a portable intercom, and a Trimble Flightmate GPS suction-cupped to the windshield for cross-country work. A hundred hours or so of back-to-basics flight, I reasoned, would allow time to think about my ultimate affordable panel. The panel upgrades could be added as funds allowed.

After a thorough checkout with Ray Maule, the new MX-7-160 was flown solo from Spence Field in Moultrie, Georgia, to my home base in Ohio, using basic pilotage and the handhelds. The trip was as thrilling as it was uneventful — and proof that, with reasonable weather, you don't need a panel stuffed full of two of everything for safe VFR flight. Atlanta's Class B airspace presented a major deviation to the route, and I vowed that a Mode C transponder would be a must if the Maule was to be used for any sort of business travel. Additionally, with the Pittsburgh, Cleveland, Detroit, and Chicago Class Bs all within a 250-mile radius of home base, the transponder became a priority.

As a side note, I can't say enough about the way I was treated at Maule Flight, Inc. while I was getting acquainted with the Sportplane. Ray and Rautgunde Maule run a family operation with complete Maule sales (new and used), service, refurbishment, and pilot training. Ray has logged more than 20,000 hours in Maules and flies one as if the airplane is an extension of his soul. Maule Flight's tailwheel transition course is topnotch. In fact, during my visit Maule Flight was training U.S. military aviators to fly STOL tailwheel aircraft.

The MX-7-160 was flown sans radios for more than a year. Although the system of using portables worked well, the routine of charging and replacing batteries and packing and unpacking the handhelds was growing old. Perhaps the biggest incentive to update the panel was the constant tangle of cables and power cords that I had to deal with. It's tough to keep the cockpit neat and orderly when there is roughly 30 feet of wiring to manage.

The Maule panel provided the same challenges and opportunities that many kitplane builders face. With few constraints I could essentially design my own. In a fairly traditional layout, the Maule panel had cutouts for primary instruments on the left, a center radio stack, and room for creative use of panel space on the right.

Keeping up-to-date on the latest avionics wonders and checking prices, I zeroed in on a Bendix/King KLX 135A GPS/com, KT 76A transponder, and PS Engineering PMA 6000 audio panel/intercom for the radio package. This arrangement provided a solid combination of both VHF and in-cockpit communication ability, contemporary GPS navigation, and room for expansion. At the time, the KLX 135A was the only VFR GPS/com on the market. Recent introductions from II Morrow and Garmin provide alternatives in this logical avionics niche.

Choosing the right shop is just as important as the components you select. I decided to use the shop that has been doing my annuals and general maintenance for the past several years. When you find a shop you can trust, you stick with them. Aero Mechanics handled the entire panel upgrade from vacuum pump to GPS antenna.

Unlike its higher-end products, which must be installed by an authorized dealer, Bendix/King offers the Crown Series of radios through traditional retail channels. This allows homebuilders and smaller shops to take advantage of mail-order pricing. If you do take this route, I highly recommend purchasing a prewired harness with the radio. Most larger mail-order operations offer such harnesses as part of the radio package, and they can be a real timesaver. My KLX 135A wasn't delivered with a harness, so Aero Mechanics had to individually wire all the terminals and connections.

The KLX 135A is a neat alternative to traditional navcoms (see " Pilot Products: Bendix/King KLX 135A," October 1995 Pilot). On the communication side, it features a TSO'd 760-channel VHF radio with flip-flop frequency display and seven watts of normal power output, five watts minimum. Controls are logical and easy to operate. The QuickTune function allows you to load any frequency in the GPS database directly into the standby com frequency slot. The navigation side of the KLX 135A can track up to eight satellites simultaneously and has a full complement of VFR GPS functions. The moving-map graphics are rather rudimentary, but the map does provide good situational awareness for special-use airspace.

A Bendix/King KT 76A transponder is mounted below the GPS/com in my center radio stack. Also part of the Crown Series, it features a clean, dark, matte-gray face that blends well with contemporary panel designs and minimizes the cluttered look that many radio stacks have. An AK-350 Ameri-King altitude-reporting encoder was installed behind the panel to provide altitude information to the transponder.

At the top of the center stack is a PS Engineering PMA 6000 audio panel with built-in intercom. In truth, my simple VFR panel can't make use of all the functions that the PMA 6000 offers. Looking toward the future, though, the PMA 6000 is a wise investment. It will easily handle any additional avionics that I might care to cram into the Maule's panel. Should I ever decide to take the step up to IFR certification, the PMA 6000 will be indispensable.

PS Engineering set a new standard by incorporating a high-quality intercom into its audio panel a few years back. The intercom has inputs for the pilot, copilot, and up to four passengers. To take full advantage of the intercom, I wired the Maule with rear-seat headset jacks. PS Engineering designed a great deal of flexibility into the unit. For example, both pilot and copilot have independent volume and squelch controls, and a three-position toggle enables the pilot to be isolated from the passengers or allows the copilot and passengers to listen to the transmissions. The right side of the audio panel features nine illuminated push buttons to activate the full range of avionics, as well as a rotary selector knob that allows the crew to receive and transmit on separate com radios.

The PMA 6000 can be configured with or without a three-light marker beacon receiver. I ordered the unit without the marker receivers for VFR use, but it can easily be upgraded (for about $300) to include the receiver. This versatile selector panel also supports input from two independent music sources (the new PMA 6000-S provides stereo sound) with a pleasant soft mute control to ramp the music up and down between transmissions. Under the right side of the panel Aero Mechanics installed an audio input jack, along with the data port for the KLX 135A, so I can plug in a portable CD player if the notion strikes.

Next, I installed a vacuum system and basic gyro flight instruments. After reviewing the various products available, I decided to purchase all of the primary components from one source — Sigma-Tek — to ensure compatibility. Augusta, Kansas-based Sigma-Tek was recently chosen by Cessna to supply flight instruments for the revamped single-engine line.

Driving the system in the Maule is Sigma-Tek's bidirectional rotation dry air pump. To achieve long service life, the design features an aluminum rotor and composite vanes. Installation on the Lycoming O-320-B2D was as simple as removing the four nuts holding the block-off plate on the back of the engine, mating the supplied gasket, sliding the pump onto the studs, and torquing down the nuts. Plumbing the hoses through the firewall into the cabin is also a fairly simple operation, with a vacuum regulator and air filter mounted behind the panel. Since the bare Maule panel allowed plenty of real estate, a 2.25-inch suction gauge was installed at the far left of the panel, where it could easily be included in the instrument scan.

Top center in my panel is Sigma-Tek's new attitude gyro with warning flag. In the event of an in-flight loss of pneumatic pressure, a red "Gyro" flag drops down from the upper left corner of the horizon. The Sigma Tek directional gyro I selected features a heading bug. The knob on the left of the DG is a standard push-and-turn to set the heading. A knob at the lower right-hand corner of the instrument rotates a bright yellow heading reference bug around to the desired course as a reminder. A standard zero-to-2,000-foot VSI completes the simple instrument cluster. Following Maule's lead, the gauge faces are illuminated by post lights, all controlled by the standard Maule instrument light rheostat.

After the panel upgrade, all that was left to be legal was FAA field approval of the installation, as well as certification of the transponder. Plan ahead if your installation requires a field approval. You are totally at the mercy of the local FAA inspector — and the airplane shouldn't be flown until the sign-off is complete.

As much fun as it was rediscovering virtues of minimalist flight, I am once again spoiled by the security and convenience that the new panel provides. VFR flight is still an eyes-out-of-the-cockpit discipline, but now there's a whole lot more pertinent information at hand inside the cabin.