Why new designs are as rare as a tailwind
The average customer may not comprehend the reason aircraft designers and manufacturers recycle their basic designs. There are manufacturing considerations, of course: the longer tooling can be used, the less the unit cost, but the principal reason is that basic engineering, testing and use history has proved a structure to be of a predictable strength and performance.
That having been (hopefully) explained may help you understand some of the problems created by the inevitable compromises that surround the introduction of a totally new airplane like the Cardinal.
In reaction to customer demand and a desire for higher performance, Cessna engineers had become intrigued with the NACA series of laminar flow airfoils. Data showed extraordinarily low drag coefficients if precise wing smoothness could be achieved. At the same time, it appeared that higher cruising speeds could be achieved by eliminating the wing struts then in use on all Cessna singles.
The high-performance 210 Centurion was the logical candidate. Design work began on the new wing in 1964. First off, the proposed location of the main spar didn’t match the door posts on the existing 210, so a heavy supporting structure had to be added—but that lessened headroom, which required another compromise.
The next obstacle was that because a cantilever wing is inherently heavier than a strut-braced wing, it normally requires a heavier main spar. Cessna was able to breach the problem (at great expense) by machining a tapered spar. Next, the wing was moved 4½ inches aft for better visibility, but that created a nose-heavy condition and stability problems, the solution of which was a higher-dihedral wing.
Dozens of other compromises had to be made before it was test flown in mid-1965. That was when it was evident that more elevator power was needed, and six sq. ft. was added to the horizontal tail (a fully articulated tail had been considered, but was abandoned after testing). The cantilever laminar flow wing debuted on the 1967 210H/T210H.
Gross weight had, of necessity, grown 100 pounds, and cruise speed increases were a modest two to three mph, although ongoing refinements over the next 15 years would eventually net an additional 20-30 mph.
Even though Cessna had spent millions in development, the 1967 models were priced virtually the same as the year before. It would take a long time to recoup the investment. But one way to get the best value for money spent was to spread the expense across several models, and the venerable 172 seemed to be a good place to start.
The J-bird and its flying tail
Planning for a 1968 introduction, work was started on the 172J in 1965. It was referred to internally as the “J-bird,” and security was tight. The new 172 would have a large, spacious cabin, better pilot visibility, more speed, easy entrance and exit through 47½” wide doors, better flying qualities, tubular steel landing gear and a modern, streamlined appearance. And, by management decree, it had to use a 150 hp engine for cruise efficiency.
All previous flat-engine Cessnas had been powered by Continental, and the 172 had used the 145 hp six-cylinder O-300 model since its 1956 introduction. However, for some reason Continental was abandoning its lower-power engines. Lycoming had a perfect candidate. Cessna was so confident that it ordered 2,000 four-cylinder, 150 hp O-320s before the 172J flight testing was finished, and they took an option on 2,000 more: there was much joy in Williamsport.
To start with, engineers used the new cantilever wing design that was being introduced on the ’67 Centurion, built with scaled-down component thicknesses for the lower target gross weight of 2,350 lb. The wing skins would be thin, but the plan was to machine-rivet the sections that would form the leading edges. However, factory manufacturing engineers rejected the scheme as too expensive, so even thinner aluminum was specified.
The problem was that if the leading edge developed any dimples or waves, it would nullify the low-drag potential of the laminar flow airfoil. The next decision was to place the wing further aft than normal on the fuselage for better visibility. That, of course, produced a nose-heavy condition and aggravated the pitch-down forces caused by wing flaps. In turn, a tremendous amount of elevator power would be needed for tail-low touchdown. At that point, an all-moveable horizontal tail (stabilator) was specified.
The maiden flight was made by test pilot Bill Robinson on July 15, 1966, and it showed that a great deal of development work was needed on the stabilator. Piper had been using the stabilator for quite a few years and knew its idiosyncrasies, but it was new to Cessna. Wind tunnel and flight testing showed that they had over-engineered it, and trim and anti-servo forces were excessive.
In addition, the original 40 degree setting of the wide-span flaps produced a high rate of sink on final, so the maximum deflection was reduced to 30 degrees; the stall penalty was only one mph and landing distance over the 50-foot obstacle increased about 50 feet.
Despite its other good characteristics, the 172J wanted to drop a wing at stall. A high-camber airfoil section at the tip and a 3° twist hadn’t cured the problem, so 12-inch stall strips were installed on the leading edge, placed at a point on the wing that corresponded to the outer end of the horizontal tail. Flaps-retracted stall speed was six knots higher than on the 172H at the same weight. At maximum flap deflection, the increase was only three knots.
The biggest problem showed up in an accelerated 1,000-hour service test, which included 5,000 landings flown by a number of pilots of different experience levels, and engineers found out that many were approaching with excessive speed and over-controlling and porpoising in the landing flare, often resulting in nosewheel landings and wrinkled firewalls. It might prove to be a problem for owners to make the transition from elevator (slow pitch response) to stabilator (quick pitch response).
The Goose that laid the Golden Egg
As changes and improvements were made, the weight of the prototype began to grow. One cure was reduction in wing skin thickness (which some wags were already referring to as Spearmint gum wrapper) and shaving excess thickness of other parts.
Eventually, empty weight came down to an average of 1,350 pounds, about 75 pounds. higher than the 172. Time was running out. Early in 1967, a date was set for the introduction of the sleek new design in late summer, soon after it was scheduled to receive its Type Certificate.
As the prototypes flew nearly every day, keeping them a secret became an obsession. No pilot was allowed to land at public airports or even fly low enough to be identified. But for all intents and purposes, the company did a good job of keeping it a secret from the public—and especially from the dealers and potential customers, who might postpone a purchase until the sleek newcomer was available.
Manufacturing began early, and plans for a lavish introduction were underway. Then someone asked a very good question. “Let me get this straight,” a brave but anonymous marketer said. “We’re going to drop our best-selling model—the goose that laid the golden egg, so to speak—and replace it with a radically new airplane that’s untried?”
The topic had already been discussed and the motives questioned over lunch pails among the rank and file—who obviously didn’t understand the intricate overview afforded those behind the ivy-covered walls, but nonetheless, a period of extremely uncomfortable silence ensued.
Finally, someone in charge broke the silence with an expletive that communicated the very same lack of foresight. Then with an inspired expression, he presented Plan B. “Okay. How many 172s did we sell last year—sixteen hundred? We have 2,000 engines on order to cover this year’s production and another 2,000 for next year, right? What say we build the new airplane, recertify it as the 172½ or something and keep the old Hawk in the line—powered with those other 2,000 Lycomings?”
That’s not exactly how it happened, but that is what they did.
Everyone got busy. Deadlines were met. Overnight, the 172J became the 177 Cardinal and the 172 continued its charmed life as the 172I.
About 1,100 Cardinals were sold at the gala world introduction in Wichita, where dealers were able to take same-day delivery on their new airplane and fly it home to show to customers. There was just one problem. As nearly every airplane took off from Cessna’s Delivery Center, it popped into the air, then dipped back toward the runway and continued to porpoise over the horizon toward an uncertain fate.
Not surprisingly, it was the same problem that had confronted service test pilots that was now being experienced by the people who were ultimately responsible for selling the airplane. A stabilator replacement program ensued, whereby a unit with leading edge slots was installed to increase landing authority, but the damage had been done.
The Cardinal had the sleek look of a crouching panther, but the speed and strength of a four-week-old kitten, and the typical blanket damnation from pilots was, “It doesn’t fly like a Cessna.”
The net result of the Year of the Cardinal was that, after the deliveries of those first 1,100 aircraft, less than 100 re-orders were booked. Cessna faced the reality that 150 hp was marginal, and immediately set to work on the 177A with a 180 hp Lycoming O-360-E2D engine. It debuted in 1969 and furnished a modest gain in performance—four knots at cruise, 90 fpm more climb and a much higher service ceiling.
Everyone agreed it should have been the engine for the original Cardinal, but the cavalry had arrived too late to save the wagon train. Dealers still trusted the 172I, however. They bought 649 of them in 1968 and more than 2,000 over the next two model years.
While the fixed-gear 177 suffered through another 10 years of mediocre sales, the retractable version (RG) may actually have made the whole program worthwhile. As it became obvious that the 177 was catering to an upscale market, engineers borrowed the technology from the 210.
Using an electro-hydraulic system like the Centurion’s, but with rear-retracting nosegear, the 177RG filled a vacant niche in the Cessna lineup. Gross weight was upped to 2,800 lb. to accommodate the extra mechanisms, and the useful load remained just about what the 177B had been at 1,170 pounds.
The RG was first flown in February 1970 and went to market as a ’71 model. The sleek and modern shape of the basic Cardinal had been seemingly marred only by its “down-and-welded” landing gear, and the RG exercise produced a model that was competitive with the Piper Arrow and Mooney Ranger.
With a 200 hp IO-360 engine, the RG could cruise 80 percent as fast as the 210 for 60 percent of its purchase price, and of all the Cardinal models sold from 1968 through 1978, half were RGs.
The 177 saga provides a short course in not only the engineering, but the psychology of building a new design. While marketing furnishes valuable input on a program, it should be up to the slide rule crowd to determine if it can become a reality.
The Cardinal’s fate was sealed the first time the first dealer struggled off the ground on that 90-degree day in Wichita and porpoised over the horizon. By the time he got home, he had found all of its real or imagined problems and unconsciously conveyed a distrust to his customers. As TV’s Dr. Phil puts it, “There is no such thing as reality; there’s only perception.”
Daryl Murphy and the Super Skymaster both started flying in 1965. As part of the Cessna marketing team that introduced the 177 Cardinal to the world, he offers an insider’s view of the airplane’s short life. Murphy’s work also appears regularly in GA News and Aviation International News.