The C-180 Story
- taken from "Cessna Wings for the World” by William D. Thompson
Continental Motors Corporation had developed a new 225 hp horizontally opposed six cylinder engine, and Hartzell Propeller Company was manufacturing a constant-speed propeller for airplanes of this speed range. It was believed that this powerplant combination would provide cruising speeds that approached those available in the heavier, retractable landing gear airplanes of that era. Evidence of the aerodynamic cleanup was the extensive use of flush rivets on the engine cowling and wing leading edges, cowl flaps, adjustable horizontal stabilizer (to minimize trim drag in cruise), wheel brake fairings (or wheel fairings), a flush carburetor air inlet, and a tubular tailwheel spring.
This 55% increase in horsepower over the C-170 (which had only a 145 hp engine) made us realize that counteracting torque/P-factor effects in the takeoff run and in climb would pose a serious problem to the pilot. Therefore, it was necessary to design a much more powerful rudder system. This, in turn, mandated a larger and higher-aspect-ratio vertical tail. To alleviate some of the excess rudder power in flight, a small dorsal fin was adopted. This prevented the airplane from obtaining excessive angles of yaw with full rudder deflection in flight.
A similar approach was taken in the horizontal tail design because stronger elevator power was needed for 3-point landings with the extra weight of the larger engine. The trimmable horizontal stabilizer required much pilot effort (in number of turns of the trim wheel) to insure a 3-point touchdown at forward center of gravity. Thus a more powerful elevator was a high priority.
In anticipation of the need for more blind flying instruments and radios, a much larger instrument panel was designed to accommodate three horizontal rows of instruments, and a fourth row for switches and controls. This foresight paid off in keeping the panel essentially unchanged until the "basic T" arrangement became an industry standard in 1959. However, this higher panel took away some of the fantastic forward visibility that was featured in the C-170.
To achieve good range and endurance it was necessary to design a much larger (54 gallons) fuel capacity. Following the lead of the large airplane designers, both military and commercial, we adopted rubberized fuel bladders in each wing which were supported by an array of "snap-on" fasteners. To help make these bladders stay in place we had to insure positive pressure in the internal airspace. This requirement led to special attention to the location of the fuel vent tube and attendant problems in the event that the vent tube became clogged with impact ice. It also proved to be a real problem as the bladders aged, where wrinkles sometimes impeded the flow of fuel to the tank outlet. In hindsight, one would have to say that the continuation of aluminum tanks until wet-wing technology was perfected would have been a better choice.
Contrary to the maiden flight date and pilot recorded in "Wings of Cessna" by Edward H. Phillips, the log books of the author and Hank Waring show a maiden flight date of May 26, 1952. The author was assigned as project pilot, and he performed the maiden flight. My memories recall looks of apprehension on bystanders' faces because they feared that this was too much horsepower for such a small airplane! Little did we realize that in later years it would fly with 300 hp in the C-185. Another recollection was difficulty in taxi steering until the reversed rudder cables were reconnected. Fortunately this happened before the airplane taxied 50 feet.
With the prototype, N41697, lightly loaded to a C.G. position at 25% MAC, the takeoff and climb were exhilarating. This was definitely a "hot rod" airplane in the 1950's. Since there was no sound proofing or upholstery installed, the noise level was deafening. However, the vibration level was reasonable, despite the extra power. Of most concern was the question of elevator power, and this was confirmed in a series of simulated 3-point landings at high altitude using different wing flap settings. At this favorable C.G. Position a positive 3-point touchdown was achieved in the landing with half flaps.
In subsequent flight tests at more forward C.G. positions, however, it was difficult to touch down with full flap. One had to trim the airplane completely in the final stage of the approach. Otherwise, the stabilizer would be at too shallow an angle of negative incidence to provide enough elevator power. I learned to handle the chores of adjusting speed, power, flap deflection, and trim wheel motion to get consistent 3-point landing, but I feared that other pilots would not know the combination. The elevator surfaces were already tooled in advance of the maiden flight, and this made me reluctant to call for change.
However, just before entering the FAA certification phase, I stopped my soul-searching and demanded a larger elevator. To my relief, Web Moore, Jerry Gerteis, and Tom Salter agreed with that 11th hour decision. It was fortunate because the C-180 performed flawlessly. Our old C-170 oil cooling headaches were lessened because of Continental's integral oil cooler mounted ahead of the right front cylinder which received the full blast of the impact air.
However, Fritz Feutz recalls some nights out in the experimental shop with Tom Salter and Jerry Gerteis debating what oil cooling baffle configurations to fly the next day. Most memorable was Tom's typical statement, "The damn thing won't work - but try it anyway." Early problems were encountered with cracks in the carburetor air box made of aluminum sheet, and these problems persisted for some years. In hindsight, it would have been better to take the weight and cost penalties of a cast or forged aluminum air box assembly like those used with radial engines.
Mort Brown recalled an intake runner manifold in the initial production that was welded up in contours that sometimes caused a very lean mixture distribution. This prevented rapid throttle bursts in flight, and the engine would often falter at the start of a takeoff. In wintertime-temperatures it was sometimes necessary to use carburetor heat for takeoff. To correct this problem, the manifold was soon changed to a casting which gave more uniform internal contours. He also recalled a problem with the carburetor float where a rapid acceleration during takeoff. would produce an interruption in fuel flow. This, of course, was rectified quickly by the carburetor manufacturer (Marvel-Shebler).
A more demanding challenge was reducing noise and vibration. By using a rather sophisticated decibel meter and a vibration meter that recorded vibration amplitudes on a tape, it was possible to pinpoint the most objectionable frequencies. From this data, one could analyze the source of that critical noise or vibration. For example, the propeller (or propeller indexing), engine, muffler, or leaky door seals could be the culprit (or one of the culprits). Typical changes were reducing the propeller diameter or indexing on the crank shaft flange, revising crankshaft dampers, using dynafocal engine mounts, redesigning chamber volumes in the muffler, adding sound deadener material on loose aluminum skins, increasing the thickness of the windows, adding sound proofing fiberglass thickness behind the upholstery, and improving the fit of doors and their seals. At the original gross weight of 2,250 pounds, the C-180 had a top speed of 165 mph and a cruising speed of 150+ mph. The rate of climb at sea level was 1,100 ft/min and the service ceiling was 19,800 feet. With standard equipment, the airplane's price was $12,950.
In accordance with standard practice at the time, the forward-facing fuel vent tube was mounted on the top surface of the wing. In a naive attempt to provide emergency venting with an ice-blocked tube, a small bleed hole was drilled on the aft side of the 900 bend. This hole, of course, was in the low pressure field of the wing, and later we found that, with the vent blocked, fuel would stream out the vent bleed hole and over the wing at a surprising rate. Another problem was the splashing of fuel out of the vent (with a full tank) during heavy braking deceleration in the landing roll. In another misguided effort, we incorporated a simple ball check valve assembly at the extremity of the tube. This only aggravated the accumulation of impact ice and the loss of fuel through the bleed hole.
Fortunately, not many pilots were flying in icing conditions in those days. However, one daring pilot selected the C-180 for a New York-to-Paris flight to commemorate Lindbergh's historic flight. He carried auxiliary fuel tanks in the cabin with a separate (and less vulnerable) fuel venting system. As related later, his standard fuel vent iced up over the Atlantic Ocean, causing a surprisingly high "apparent" fuel consumption when using standard fuel tanks. We had alerted him to this possibility before his flight. However, operation on his auxiliary fuel was normal, and he was able to proceed to Ireland instead of Paris.
That experience prompted us to search for a "protected" location for a fuel vent. After much flight testing, we found a behind-the-wing-strut location that essentially "hid" the vent in all flight attitudes, while, at the same time, providing the required positive pressure in the air space above the fuel. An additional requirement was another increment of pressure to promote sufficient "gravity" fuel flow in steep best-angle-of-climbs at minimum flying weight. As one can appreciate, this meant that the positioning of the fuel vent became very important both in production at the factory and at overhaul facilities In the field.
A final requirement was the prevention of fuel loss through the vent from fuel sloshing in rough air, or when parked on a sloping ramp. A simple flapper valve was placed in the vent line in each fuel cell that closed when fuel moved toward the vent outlet. To permit expanding fuel (heated from the sun after a refueling) to escape, a bleed hole was added to each flapper valve assembly. This hole also served as a siphon-break in the event of a malfunctioning (open) valve. This redesigned fuel vent system proved to be so effective that it has been used in all subsequent Cessna models that use strut-braced wings.
This "overpowered" airplane was destined to become the world's most popular floatplane. With Edo 249-2870 floats installed the maiden flight was conducted by the author on August 11, 1952 from a 3-wheel floatplane dolly at McConnell AFB with a landing at Lake Afton, 20 miles west of Wichita. As in other floatplane models, the water rudder cable system fraction inhibited the free return of the air rudder during directional stability tests in the balked landing climb. Fortunately, we were able to get FAA permission to loosen the water rudder cables and lubricate the pulleys, and to convince the FAA test pilot that a complete return to straight flight upon releasing full rudder travel was unrealistic. All remaining flight characteristics were satisfactory without any changes to the airframe. Most memorable were the steeply nose-down spin attitudes and the very rapid rotational velocity. The inertia effects of the floats made the spin recoveries less prompt than in the landplane, but this was no disadvantage because we had no intention of qualifying the airplane for acrobatic spins in the utility category. Another memory was the almost vertical attitude needed in dives to achieve the required Vd speed with this high-drag floatplane configuration.
In July of 1955, Edo had developed the amphibious 289-2700 (quadricycle gear) floats, and they had installed them on one of our C-180 prototypes at College Point, NY. The author recalls picking the airplane up at nearby La Guardia airport on July 30, 1955 for some local testing before departing for Wichita the next day, a phone call to my good friend and well-known aviation writer, Bill Strohmeier, in Darien, Connecticut brought forth a suggestion to land in the Darien yacht harbor and to look for him in a dinghy at "red buoy No. 5" where we would moor the amphibian. To my shock, it was surrounded by many hundreds of boats in very crowded quarters. Just as I was about to turn back, I spotted Bill holding up an oar in his dinghy, and with great relief I cut the engine and coasted to his mooring. We rowed to a nearby schooner to join a cocktail party in progress. With a cocktail or two forced upon me and the gentle rolling of this sailboat at anchor, I realized that I was in no condition to fly back to New York. Bill and Bea's strategy had worked, and, of course, I became their overnight guest.
Although Bill had authored the bible of water flying in a book called "Flying Floats", he had never picked up a rating. The next morning, as a designated FAA pilot examiner, I had Bill fly the amphibian through the prescribed maneuvers, and then I wrote out his rating. We laughed because I had learned to fly floats many years earlier from reading his book.
Skiplane testing commenced in November of 1952 on the prototype C-180, N41697, at Wichita. Again, I had the impression that this would be a great skiplane for the north country. Steering with the tail ski was effective in all tested snow depths, and the main skis remain stable in high speed dives. In later years we had similarly good results with the Fluidyne wheel/ski combination. Evidence of these successes are the popular commercial flights to glacier landings at Mount McKinley in Alaska and Mount Cook in New Zealand. Snow landings were performed on the glaciers and wheel landings on the FBO's airport.
As the airplanes aged in rough service, we received reports of stabilizer slippage in high-speed letdowns. To our amazement the two "irreversible" jack screws that supported the stabilizer were slipping in an airplane-nose-up direction. In production flight tests at redline speed, this produced an alarming "g" load, pitching the nose up vertically. On one occasion the test pilot blacked out momentarily and the wings received a permanent set of 50 at the strut/wing juncture. We were unsuccessful in reworking the jack screw tolerances, and the decision was made to add a friction device to the longitudinal trim wheel mechanism. This produced a "ratcheting" noise in the cockpit and increased the force required to make trim changes. However, it solved the stabilizer slippage problem, and the device remained on the C-180/185's throughout the production run.
The engineering department had many refinements in mind for future model improvements such as electric trim systems, electric flaps, interconnected mechanical trim/wing flap systems, improved instrument panels, etc. However, the bush pilots were adamant in keeping the C-180 unchanged. They said "don't screw it up", and we obliged them for the most part. They were most insistent that the mechanical wing flap system be retained because they needed instantaneous and precise flap modulation on some of their heavy weight floatplane takeoffs from glassy water. The author made periodic trips to Canada and Alaska to solicit ideas for improvements, but it soon became clear that the C-180 was a classic. It was most certainly the best compromise between STOL performance and high cruise speed. In later years, we produced an austere 6-place C-180, and we finally received endorsement of a higher powered version of the C-180 to be described later. The heavier Edo amphibious floats also provided an incentive to opt for more power.
As one can imagine, the leg room in the front seat area was sized to accommodate a 6'2" test pilot and the president, Dwane Wallace, who was well over 6 feet tall. Little did we realize that small female pilots would someday be flying these husky airplanes. One day Jerry Mock of Columbus, Ohio flew her C-180 to the factory to ask for some modifications to the control wheel/seat/rudder pedal positions. At about 4'11" tall and with a generous bosom, she was unable to get the control wheel back for a 3-point landing if the seat (and cushion) were far enough forward for her to reach the rudder pedals. With great engineering skill, we designed large extensions for the rudder pedals that pleased her immensely. With that change she was able to set numerous distance records, including one around-the-world record.
The Missouri State Highway Department reported severe buffeting in one of their C-180's when patrolling with the right door removed. I was asked to duplicate that phenomenon in our prototype with the door removed. The test was unsuccessful under a large range of power settings, speeds, and wing flap setting. Finally, Chief Engineer Jerry Gerteis suggested that I try again with the copilot seat in different locations. He assumed that that might tune (or detune) the airflow into the cabin to create a resonant frequency. His theory was correct, because one particular location of the copilot seat created an alarming buffeting of the entire airplane. The wing tips moved about 4 inches in a flapping motion, and it was necessary to reduce power below that required for sustained flight. On the other hand, moving the seat only a few inches either direction eliminated the buffeting. The solution was a 2-3 inch wide spoiler plate affixed to the forward door post to deflect the air blast away from the cabin. This became a kit for operators who removed the door for photographic or skydiving flights with parachutists aboard.
The impressive versatility of the C-180 was demonstrated to the author on one hot, windy, and dusty day in August. The flight to Eagle, CO was planned in a C-190 with the chief engineer as a passenger. However, the weather bureau reported a dense dust cloud just west of Wichita that reached to 20,000 feet. We recognized that to save the engine from abrasive damage, only the C-180 could climb that high in such a short distance. The flight was made at 20,500 feet (over the dust clouds) using oxygen masks, and the landing was made on schedule at Eagle, CO. No doubt, Alaskan bush pilots could relate countless stories of how the C-180 performed on other special missions.
The C-180 benefited from the change to the 230 hp Continental O-470-K engine in 1956. With the gross weight increased to 2,650 pounds, the maximum speed increased to 170 mph and the service ceiling increased to 21,500 feet. In later years the gross weight climbed to 2,850 pounds and climb performance was reduced slightly to a 19,600 service ceiling. Among the more significant changes were a revised instrument panel in the 1959 C-180]B; dual-outlet ports in the fuel tanks (and 84-gallon optional tanks) in the 1962 C-180E; adoption of the C-185 fuselage (with third cabin window), wings, landing gear, and utility seat in the aft cabin for 6-place seating in the 1964 C-180G; optional 300 pound external cargo pod for the 1970 C-180H; camber-lift wing with bonded leaded edges, and cowl-mounted landing/taxi lights in the 1973 C-180J; optional bubble window for the cabin door(s) in the 1974 C-180J; and a 2400 rpm Continental 0-470-U engine and basic-T flight instrument grouping in the 1976 C-180K. Prices increased from $12,950 in 1953 to $41,910 in 1978, and the 28 year production run was completed on September 10, 1981.