ZENAIR’S SUPER ZODIAC CH 601 HDS
I’ve always enjoyed the excellent in-flight visibility of a low-wing aircraft as well as the minimal amount of upkeep needed by an all-metal plane. Aircraft manufactured by Zenith Aircraft Company satisfy both these conditions as well as many others.
Chris Heintz, founder and chief designer of all the aircraft in Zenith’s extensive line of homebuilt aircraft, has all the necessary qualifications to design a superb aircraft. An aeronautical engineer by profession, Chris worked at his profession for many years in Switzerland, then moved on to Aerospatiale where he participated in the Concorde’s stress analysis program. He was later signed up as chief engineer for the French Avions Robin Company where he designed and certificated two- and four-place all-metal light aircraft.
While working for Robin, Chris built his first all-metal homebuilt. He named it the “Zenith” (an anagram for “Heintz”). The Heintz family moved to Canada in 1972 and Chris began designing homebuilt aircraft for the sport pilot population. The company’s first offering in 1974 consisted of plans and some components. Before long there was increasing acceptance of the Zenith design and the company continued to grow. At the present time, there are over 800 Zenair aircraft flying and over 1000 additional aircraft in various stages of completion.
Early in the 1980s, Zenair became aware that a low-cost “primary category” aircraft was needed. By 1984, Chris Heintz had responded by designing the Zodiac 600 (powered with a VW conversion), completed in accordance with FAR 23 standards. When, in 1990, the Rotax factory introduced their now famous 912 – a 4-cylinder 4-stroke engine of 80 hp – Heintz obtained a prototype of the engine and Zenair became the first North American company to use this powerplant, called by some “the engine of the future.”
By 1991, after a number of design improvements, the Zodiac CH-601, powered with the new Rotax, became the cornerstone product of the Zenair Ltd. Company. A short time later, the Heintz family moved its operations to the US and licensing was granted for the manufacturing rights to the firm, now called the Zenith Aircraft Company, in Mexico, Missouri.
While working as a member of the aviation division at Challenge Publications, I traveled to Sun ‘n Fun -the EAA’s annual spring festival in Lakeland, Florida every year. While there, I had the opportunity to meet and work with the talented Chris Heintz and several members of his family at their company booth. Over the years, our associate editors and I have also test-flown several examples of the fine Zenith aircraft and reported on their performance in numerous issues of Sport Pilot magazine.
What’s more, Zenith has one of the most fascinating company booths at Sun ‘n Fun. On the first day of the show each year, members of the company begin building a Zenair – from scratch. This takes place in an open-sided structure to allow spectators to follow the building, process as it progresses and to see how easy it is to build a Zenith aircraft. Heintz family members and employees stand by to answer and graciously answer any and all questions posed by visitors. By closing day, the aircraft is complete, and Chris Heintz test-flies the very aircraft they’ve built during the show.
This spring, Sport Pilot was once again at Sun ‘n Fun to evaluate and report about the sport aircraft which had been brought there. This year’s Sport Pilot crew consisted of Robert Goyer, editor of Sport Pilot, who did all the photography, Joe Fitzgerald, an experienced and accomplished close-formation pilot, and your author, flying the camera plane. We test-flew several light aircraft, and Joe and I either flew in formation or piloted the camera plane, whichever was needed at the moment. (Joe had flown the company Maule M7-235 out to Florida for use at Sun ‘n Fun.)
Because the site of Sun ‘n Fun, Lakeland Airport, experiences a great amount of air traffic, and of necessity, imposes many restrictions on flicht operations there, we elected to operate out of less crowded South Lakeland Airpark, a few miles away.
With its long grass runway (and friendly operators, this small private airport has in recent years become the location of choice for many media photographers and flight evaluation pilots. During the remainder of the year, Wendy and Cliff, both expert chutists, operate a successful sport parachute business, as well as their fixed base operation for sport aircraft.
During one of our many trips around the grounds at Sun ‘n Fun, we had stopped at the Zenair booth where this pretty Zodiac 601-HDS was on display. We chatted with Chris, Sebastian and Nick Heintz, asking them if we might do a flight report on their high-performance version of the 601. They accepted our offer. A day and time was agreed upon, and we came away with arms full of literature of the new model in order to be prepared for the slightly different way the Super Zodiac handled in the air, compared to the CH-106 standard wing version.
Studying the literature, we found that there had been a considerable amount of redesign of the wing. The HDS had a new, tapered wing. Wingspan had been reduced from 27 feet to 23 feet, and wing area decreased from 130 square feet to 98 square feet. Airfoil was tapered to a 34-inch chord at the wingtip. In addition, the full-length ailerons of the HDS’ speed wing provide some very responsive roll rates.
The smaller speed wing would provide a great boost in performance. Although landing-roll rates remained the same, takeoff roll was increased from 430 feet to 550 feet. As the standard CH-601 climbs at 1200 fpm, and the Super Zodiac CH601 goes up at 1100 fpm, rate-of-climb only decreased by 100 fpm. At 12,000 feet for both versions, service ceiling remains the same.
The big change is the increase in speed. With the same Rotax 912 engine, the 601 has a top speed of 135 mph and a cruise of 120. On the other hand, the HDS pushes the needle to 150 mph top, with a cruise of 140 mph. When wing area is reduced, stall speed often rises. In the case of the HDS vs the 601, the difference is 10 mph. The larger wing permits a docile stall speed of 44 mph, while the speed wing pays off at 55 mph. This flight performance is well within the experience level of the average private pilot.
The great difference in speed permits the HDS to travel 950 miles (equipped with the accessory wing tanks) while the 601 runs dry at 800 with the same fuel load. Without the aux wing tanks, the HDS will cover 550 miles, and the 601 goes 480 miles from takeoff. The published cruise speed of 140 mph with only 80 hp is quite acceptable.
When both versions are rolled onto the scales, both the 601 and the HDS weigh in at 570 empty, and gross weight is the same at 1200 pounds. The useful load for both aircraft is at 630 pounds for fuel and/or passenger and/or baggage weights, depend on which combination is most important for each individual flight.
With a proportional increase in speed, there must also be an increase in the strength of the wing to compensate for the added stress which can be encountered in rough air. In the case of the Zodiac aircraft, and considering Chris Heintz’ extensive background in stress engineering, both aircraft have been designed to bear a “G” loading of plus or minus 9 when flown by only one person, and a still very high plus or minus 6.8 G load factor.
The Zodiac CH-601 HDS, because of all of the above reasons, should make an excellent commuter aircraft for one or two persons. The speeds attained, plus the low fuel bum of only four gallons per hour, not only rivals but also exceeds the excellent qualities of most other aircraft in this size and power category.
By the time we’d finished reading all the particulars about the Super Zodiac, we were rarin’ to go flying. When the scheduled day and time arrived, it was decided that Nick Heintz would accompany me for the evaluation flight. Joe Fitzgerald would fly the camera plane, with Sport Pilot editor, Robert Goyer, doing the photography. As we always do before each air-to-air photo shoot, we held a pilots’ meeting to plan a rendezvous point and possible paths of flight during the shoot.
With everything at the ready, I preflighted the Super Zodiac CH 601 HDS, then taxied it out to the takeoff end of the west runway. As we worked our way into position, waiting our turn to take off, Nick did the engine check, with Joe in the company Maule following suit.
I positioned the Super Zodiac, checking carefully to make sure there weren’t any other aircraft in the pattern at this busy little airport. To the south, the sunny Florida sky was crowded with small aircraft circling, to land.
I opened the Rotax 912 fully and it roared to life. The little Zodiac quickly gathered speed and within seconds, I could feel it getting light. I held it on the ground until it showed 60 mph on the indicator, then started to feed a little “up” into the elevator. It was a hot day, we had a full load of fuel and we were heavy. Under those conditions, the Super Zodiac’s tiny wings needed just a tad more speed to rotate than did those of a stock CH-601.
Once airborne, I leaned back and enjoyed the familiar feel of this good, solid, all-metal aircraft. Controls of the Super Zodiac were very well-balanced as well they should be, since they’d been continuously fine-tuned for almost 20 years in previous Zenith models.
I held the ROC to about 800 feet a minute to allow for better visibility over the nose and to keep the Rotax nice and cool. Ever since its inception many years ago, the liquid-cooled Rotax 912 has proved itself to be one of the best new homebuilt engines on the market. I was glad Zenith had chosen it for the Super Zodiac.
As we reached the agreed-upon altitude, 2500 feet agl, Nick spotted the Maule circling around, so I headed toward it. Within minutes, we were positioning ourselves to the right of the camera plane. A radio call came from its pilot: “Smile….. you’re full frame.” In air-to-air photo talk, that meant the cameraman had a good closeup of us in the cockpit area. (I was having such a good time flying, this pretty little plane, I was already smiling anyway.) However, anyone who’s ever done any amount of air-to-air flying and/or photography knows it requires a great deal of concentration and hard work to fly so closely to another aircraft (without coming into contact with it).
The HDS’ controls and throttle response were excellent. On our first join up with the Maule, we had to keep slowing down the speedier Super Zodiac, as we kept overtaking the slower camera plane. Once the formation flight was over, though, we were ready to have some fun. After circling over the farmlands for about half an hour, the Maule broke off and headed for home.
I trimmed out the HDS for full-power straight-and-level flight, then pulled out my GPS to check the Super Zodiac’s airspeed indicator. In the calm air of that Florida morning, the trusty hand-held Trimble came up with a solid 149 mph. I lowered the power to a cruise setting, then tried again. This time, the GPS showed 138 mph. I decided not to spend a whole lot of time getting the bird on the step in order to do so, but I’m sure a more experienced Zodiac pilot could easily get the published figures.
I then did a series of high-bank 360-degree turns to the left, then to the right, and the plane followed through without any excessive control inputs. With only minor throttle inputs, it was easy to maintain altitude and speed in the turns. The Super Zodiac’s large ailerons provided just the right amount of control.
Next, I throttled back, then slowed the plane way down to see how it behaved during slow flight at and around published stall speed. The rudder was effective in holding the wings level at low speeds and she paid off with buffeting at about 55 mph. A simple lowering of the nose, and level flight was right there. While the Super Zodiac does not have the stalling characteristics of a Cessna 152, even low-time pilots should have no problem recognizing when it’s time to lower the nose and get the wing flying again.
Because visibility through the HDS’ bubble canopy was excellent, I felt very safe flying so close to the camera plane. The cockpit was very roomy, and I (at 5 feet, 11 inches and 175 pounds) could fly without bumping elbows or shoulders with my fellow pilot, Nick Heintz. With a cabin width of 44 inches, the Super Zodiac should prove to be a very comfortable environment during, a long cross-country flight.
Upon our return to South Lakeland Airport, we found a large number of ultralights, powered parachutes, gliders, trikes and sundry other types of flying machines in the pattern. Because of the heavy traffic, Nick took over at this point and prepared to land the Super Zodiac. As soon as the low-and-slow aircraft were safely on the ground, Nick entered the pattern to land on the east runway, over its wires, poles and other obstacles.
He set his final approach speed at about 80 mph, guaranteeing that the HDS wasn’t going to stall, but when it settled in around effect, it just kept on flying for a bit. Soon the grass was tickling the wheels, then the plane settled in and our flight in the Super Zodiac was over.
Nick taxied the plane back to the hangar and shut down the Rotax, after which we took numerous details shots and beauty shots. Then, with great reluctance, we turned the beautiful little red speedster back over to Chris and Nick Heintz of the Zenith Aircraft Company. It had been a thoroughly enjoyable flight.
“Bridges the gap between high performance and affordability. With the Rotax 912, the SUPER ZODIAC becomes a truly great commuting aircraft. …Cruise at 140 MPH at 80 percent power while still only burning four gallons per hour. Not bad for a plane with a fixed landing gear! …The SUPER ZODIAC will carry two passengers and their gear as far as anyone is likely to want to travel. …SUPER ZODIAC buyers are getting an extremely well-designed kit made up of excellent materials. They are getting a kit they can realistically build by themselves in a reasonable amount of time and without a lot of specialized tools… Strong, durable, cheap to maintain, and fun to fly…”
– SPORT PILOT Magazine
Based on the ZODIAC CH 601 HD, the SUPER ZODIAC features tapered and shortened ‘speed wings’ to achieve a higher cruise speed. The wing span is reduced to 23 feet, and the wing area is lowered to 98 sq. feet, with the airfoil tapering to a 34 inch chord at the wing tips. The speed wings have full-length ailerons for very responsive controls. The SUPER ZODIAC has the same fuselage and tail sections as the CH 601 HD model; the only difference being the outboard wing panels. The outboard wings of the SUPER ZODIAC and the ZODIAC CH 601 HD can actually be interchanged.
Engine Limitations: 65 – 115 hp, up to 265 lbs. max. firewall-forward weight. Alternative engines will affect performance, specifications and flight characteristics of the aircraft. Also, the weight and balance of the aircraft may be adversely affected by alternative engines, and the original fuel system may not be adequate or suitable for some engines. Most alternative engines will require a custom engine mount and engine cowl. Zenith Aircraft Company does not manufacture or directly support engines. The sleek lines of the SUPER ZODIAC give the image of a high performance composite aircraft, while providing the durability and simplicity that only an all-metal aircraft can offer.