The Cessna 172 is the most produced airplane in the history of aviation, whether commercial or military, domestic or foreign, or by any other categorization. Its big brother, the 182, is the second most produced–but so far behind that neither it, nor likely any other airplane, will ever catch up.
And I had been involved with the 172 from the time it was a glimmer in the eye, or a worried thought in the mind, of Cessna management until the finality of the accelerated service test that proved conclusively the durability of its “new” fixed nose gear.
On the 50th anniversary of its first flight, I was feted–along with four others who were there “at the beginning”–as one of the designers of this record sales-setting model, along with the pilots who flew the first flights of the prototype and first production airplane.
The ceremony was held in Wichita by the Aircraft Owners and Pilots Association and I quite happily accepted the accolades that went with it.
But I had a couple of shadowy memories that tempered my feelings about my deserving those honors.
In the early 1950s, the sales of the predecessor Model 170 were perking along nicely, but two competitors made available for sale modifications that introduced a novelty that was getting some attention–a fixed tricycle gear. One was by an actual airplane modification company that even did it on our own airplane, the 170, offering a (I think certificated) version with that different type of gear. Our Chief of Flight Test got to fly it, liked the ease of landing but in general was ambivalent about the mod.
The other was more serious – because it was one of our major rivals, who offered a tricycle gear version of their tailwheel airplane, the Piper Pacer. They called it the Tri-Pacer and it was selling well. (Our other major competitor, Beech, had with its Bonanza a single engine, tricycle gear airplane, but it was of the retractable variety. And we were already comfortable with that idea on our recent high performing twin engine airplane, the Model 310.)
So Cessna management wanted to get an assessment of replacing a tail wheel with a nose gear on a modestly performing, fixed gear airplane like the 170. They acquired a Tri-Pacer and our group leader selected a team, pilot and observer, to conduct a mostly subjective evaluation of it. I was the lucky observer who was picked for the job.
Here are the tradeoffs we considered, before and after conducting the trials:
- Easier to fly, in takeoff and landing. With a tri-gear an airplane would be at an attitude where it would almost take off by itself. But most importantly it conclusively resisted the sometimes difficult to control and dangerous ground-loop usually caused by strong crosswinds in landing.
- Visibility over the nose was much better, an advantage in taxiing.
- The increased drag over a tailwheel configuration, which would decrease cruise speed and, relatedly, reduce range.
- The susceptibility to damage to the nose gear on soft or rough ground–and the 170 was an airplane often used on unprepared fields.
- Difficulty in taxiing in strong winds, with less moment arm available for the nose gear to provide turns compared to the tail wheel type.
I leave out such later concerns as the ground attitude possibly limiting the propeller diameter that could be used, and the need for a centering device for the nose wheel in flight, to keep it from affecting directional characteristics.
Of course our pilot’s opinions on the Tri-Pacer were more important than mine (I had flown the airplane a little during the evaluation), and he was absolutely captivated with how much easier and safer it was to fly, particularly in take off and landing naturally, than a tailwheel airplane.
He even noted that after initial touchdown with a tri-gear the airplane nose lowered, reducing lift and resisting any tendency to rebound into the air. His attitude was even more surprising to me because he was a former fighter pilot who typified the idea that a good landing was any that you walked away from.
My analytical reasoning as an aerodynamicist, and low-time pilot, was that you spent about two minutes each in a flight doing a takeoff and landing, and maybe four hours of cruising where you would sacrifice speed and range. And since I had only flown tailwheel airplanes before this and never had any problem with ground looping, giving up about 5% of cruise performance seemed a large penalty. I was not adamantly opposed to the pilot’s views, and don’t really remember the report we authored, but I’m sure it highly favored the tri-gear approach.
I’ll get ahead of myself here and note that when the sales of the 172 took off (like a tri-gear should) I was embarrassed that I completely missed how important that easy and safe flying was to the host of new pilots it attracted. They were mostly interested in faster transportation (for business or pleasure travel), not just the thrill of flying, and the tri-gear made it possible to conveniently do it for themselves.
That lack of recognition of the importance of easiness to fly to novice airplane owners and users was my first shadowy memory about the 172 development that tempered my satisfaction with my participation.
Still the company was not yet committed and we had proceeded with the next model change to the continuing 170 line, the 170 C. The main change to it was to replace the old elliptical-shaped tail surfaces with modern, more efficient straight ones, like we already had on the 180. And their design was a task I was given, to be done along with the myriad other projects we had going at that time. It was not a technical challenge and sort of slipped my mind, but as a reward it got me the opportunity to fly some of the tests of the 170C prototype, which we went so far as to certificate.
And then the sales of the 170B begin to slip. Quickly, and secretly, work on a tri-gear version began, using the 170C as a foundation, with the main effort being to design the nose gear and its installation in the airframe. About this time I transferred to Cessna’s Military Airplane Division to work on the T-37, and the next thing I knew was that the tri-gear version of the 170 was introduced, and was called the 172. And its sales were so good that the 170 line was essentially discontinued and any concern of the Tri-Pacer as a serious competitor discounted.
But I got a chance to re-enter the 172 development when it was decided to conduct an accelerated service test of the airplane, intended mainly to prove, and improve, the durability of that new nose gear installation. It was to be done on the first production airplane, which became sort of another prototype, and to quickly accumulate one thousand landings (and takeoffs, it was demanded they be equal) of a practical, perhaps rugged, nature.
So all kinds of Cessna employees who were pilots, but not just professionals, were solicited to participate. It was to be conducted continuously (I guess some got time off work), on the East side of the field at the Pawnee Plant, where the airplane was being made, but way East so as not to interfere with traffic at adjacent McConnell Air Force Base, and to use a pattern altitude of 300 feet to stay well below their approach and departure paths.
That prescription resulted in short “circuit” durations, and got a lot of exposure in a short calendar time. The testing was extended to take a period of about two months, during which over 2000 landings were executed, with a total flying time of less than 160 hours. I flew only a couple of evenings, after work at the cross town T-37 plant, and recorded a case where I did 32 landings in less than the scheduled two hours. That’s about three and a half minutes per circuit, just under the average of all flights in the service test, for which the circuit time was closer to four minutes. There was no traffic control to inhibit you, and no other airplanes were scheduled to use that area.
There was a hard surface runway on East Pawnee field, but participants were encouraged to use the adjacent sod as well (I don’t remember it as very rough), and themselves select various takeoff and landing speeds and techniques for a well rounded exposure to real life utilization. Since the test was conducted on the first production airplane, I assume other production airplanes were delivered before the accelerated service evaluation was completed. And although the service test results recommended some modest changes, like some beef up of the supporting firewall, I believe all the airplanes were delivered (though it’s possible some were retrofitted) with a demonstrated and proven durable nose gear installation.
Then many years later I read in a book that I had designed the empennage on the initial 172, the only major change to the 170 other than the nose gear. I thought the author was mistaken, because I had no recollection of doing that. I did concede that I might have forgotten it in the swirl of other activities we undertook at that time. But the author knew more than me, because the 170C airplane was translated wholesale to become the 172, with the exception of the substitution of the nose gear. And I had designed the new empennage for the 170C, so in effect also for the 172.
That I had once, and now again, forgotten about designing the 170C’s new tail was yet another disconcerting thought of mine related to the 172. It served mainly as an admission to myself that the tail design probably wasn’t such a wonderful technical breakthrough. And recognition that, more importantly, the long term record sales of the 172 was a truly unusual business success.