Cessna’s 620 – the stillborn prodigy

Was it too much? Too soon? Too late? Too expensive? Or too quickly scuttled?

Isn’t that a great name for this article? And don’t the subtitles stimulate the mind, too? I wish I had thought of them, but I appropriated them from an article written in Business and Commercial Aviation magazine in 1969, twelve years after the scuttling lamented in the article, which is about Cessna’s incredible Model 620 four-engined executive transport created in the mid-1950s and cancelled just on the verge of certification and start of production.

The airplane was unique because it was a small version of the modern airliner of the day, sized to carry half a dozen or so executives in luxury accommodations, above the weather, in pressurized, air conditioned comfort (and with an APU that made it self sufficient and comfy on the ground, too) with airliner safety, speed and range.

Cessna 620
The Cessna 620 was a unique design, but never made it into production.

But, uniquely, it was designed to operate out of smaller general aviation airports so common around the country. Nothing quite like it had ever been attempted. The author of the article, named Robert Hoffman, became a folk hero to me, because he concluded what I inherently believed: Cessna had made a grievous error in abandoning the concept.

My judgment was subjective, because although I was one of a small cadre of designers that developed the 620 airplane configuration from concept to proof through wind tunnel testing, my career took me far afield and I was no longer following general and business aviation developments. But I just felt for all those twelve years, and actually till now, that the marketing threat that was cited as the primary reason for canceling the 620, that of propeller-driven airliners being replaced by jets in the late 50s and being available to convert to “inexpensive” executive transports, never matured.

But Hoffman’s analysis was still pretty subjective too, and that the 620 project continues to be an item of interest, curiosity and controversy to this day is evidenced by information, or just as likely by  misinformation, presented about it on the internet. So the purpose of this article is to quantify Hoffman’s conclusions with data on the 620’s competitors of the period, real and imaginary. Let me set the stage with a historical review of the developments, from a quite personal perspective.

In 1952 Cessna didn’t have different aircraft divisions, and all the preliminary design (PD) work, including that which later resulted in the T-37 AF jet trainer and the Model 620 itself was done by the “company’s” Flight Test, Aerodynamics and Preliminary Design group, in which I worked and in which we all did the things implicit in the group title.

In that year we carried on our differing assignments, which for Preliminary Design efforts mainly meant answering “What if ?” questions for management. The results of a survey conducted by, I believe, the National Business Aircraft Association (today the National Business Aviation Association) came out at that time and provided what I will call a survey specification for the “ideal” airplane business executives said they wanted for their fleets.

In PD we set about to answer the question “What would an airplane that met that spec be like?” and more specifically for management, “Could it potentially be a Cessna product?” By the end of the year we had completed a “preliminary” design of the answer to the business aircraft user’s stated desires. Our design would meet the performance requirements of the survey specification and the flight characteristics requirements of the FAA (then still the CAA).

Businessman with secretary
Was the 620 exactly what businesses wanted in the late 1950s?

One of the features that we opted for was four-engine safety, and the use of general aviation engines that allowed low drag profiles for the nacelles. With these small engines, our airplane, later to be named the 620, promised to be relatively inexpensive to operate.

In early 1953 we were instructed to continue the activity as a preliminary design project which meant to us that we should prove our design with a wind tunnel test and explore alternatives for future growth such as a turboprop version and a commuter airline version of the airplane. Since the configuration had the potential of being in airline service, we had to evaluate the differing requirements for certificating to CAA Normal or Transport Category regulations and the effects that would have on the configuration.

Even before the wind tunnel tests were conducted, confidence in the design, and its suitability as a Cessna product, apparently were growing with the company management. Thus the decision to proceed as a regular project was made in the fall of 1953 and a well-known engineering manager in the field, Ralph Harmon, was hired away from Beech to head it.

The wind tunnel test was very successful and our original design continued to be the basis for the airplane that was almost finished with certification in 1957. And as progress continued, Ralph’s M620 program formed the Business Transport Division.

For a time from 1955, my work was totally devoted to the development of the T-37 and for those, then like me, not directly involved with the 620 there was only a strong impression that its program was going really well – impressions supported later by statements by Ralph Harmon that it was the most trouble-free airplane he had ever worked on – and he had worked on a bunch – and by the project’s test pilots that it ranked with the best airplanes they had ever flown (and marveled at manageable control forces without the aid of “boost”).

Thus it was a shock for us to be notified that the 620 Program had been abruptly and completely shut down and its engineers available to be placed elsewhere in the company where there was a need. The explanation given for the termination of the project was that stated above, that it was likely that because of the growing purchase of jet airliners surplus propeller-driven airline transports like the Convair 240 and Martin 202 (and later versions), which could soon be obtained cheaply as surplus and inexpensively converted to executive configurations, would saturate the market for which the M620 was destined.

Convair 240
The Convair 240, a potential challenger to the Cessna 620.

Apparently the decision to cancel was a traumatic one, with hard feelings created among disputing Cessna senior management, and it was further decided not to ever face it again – calling for the destruction of the prototype and all supporting engineering.

In defense, the decision to stop the 620 was also influenced by a number of secondary factors, all negative, that readers most likely have never heard about. For instance, 1957 was a recession year, with all that means in dampened business expectations. There was the additional prospect that further in the future commercial versions of the Sabreliner and Jetstar executive jet transports would come on the market, and since the initial buys would be subsidized by the government for the military, their pricing might be very attractive. (They of course turned out to be in an entirely different category of performance and cost, and were never a major factor in the market segment in question.)

We were just then ramping up production on the T-37 and it was typical in this phase that government payments were not keeping up with expenditures, creating a short term cash flow problem for the company. And, since the T-37 program was being funded by the government, the 620 represented the largest capital investment Cessna had ever undertaken, and failure would have had corporate wide consequences.

Still, with the certification of the airplane almost complete, and the major concern being one of the prospect, not certainty, of the impact of the converted airliners, might not it have been sensible to at least complete the flight tests and then mothball the airplane for potential resurrection were the conditions found to be different than anticipated? Another concern was that the expected cost, and price, of the 620 had grown beyond that originally estimated, but as will be shown that would only have placed it in the price category of later entrees into the market for which it was designed.

A review of historical data shows three things about what would have happened if the 620 had been continued in the late 50s:

  1. The prop airliner conversions to executive configurations would not have been decisive (an often overlooked reason may have been that the DOC for the Convairs and Martins was over twice that for the 620 competitors described below).
  2. Cessna would have had the business for new executive aircraft to itself for five years.
  3. The company would have been positioned to be a major factor in the executive transport field as that business grew substantially in the years after that.  (Of course Cessna redeemed itself with the Citation series of executive jets in the next era of such business aircraft, about a dozen years after the cancellation of the 620.)
Mitsubishi MU-2
The MU-2 was one of many turboprops to enter the market in the early 1960s.

Other authors, pursuing their own interests, have provided the information to determine how important propeller airline conversions to executive configurations turned out to be to the sales in that field. These authors researched the history and disposition of every Convair and Martin liner built, and identified those which either started as or were ever converted to executive use. Their history showed that “conversions” took place on an average of one a month, or a total of about 60 units during a five-year period. (Of course if the 620 had been available, it is likely that some of these conversions would not have been done.) Sixty units seems neither a very large nor a very small quantity, not to be ignored but not enough by itself to discourage entry into the field.

For confirmation let us look at it in terms of the airplanes of the same category as the 620 which actually did enter the market at about the time of the end of what I believe would have been the 620’s five years of exclusive command of the market, around 1963. And these airplane companies put their products on the market not against the prospect of the sales of converted Convairs and Martins, but on the reality of what had actually taken place to that date.

In 1961 Interavia magazine published a feature on the number of contenders being entered into the obviously growing executive aircraft market. Their view of suitable airplanes for it extended from the conventional Aero Commander twin to the aforementioned Sabreliner and Jetstar (with twice the speed of the 620 at well over twice the price).

If we concentrate on just those models in the same operating sphere (all weather, pressurized, etc.) and price regime as the 620 (adjusted for inflation to the later date) the list would contain the following – which, with the exception of the cancelled 620, were still not quite ready to be introduced: the Swearingen Merlin II, Mitsubishi-Mooney MU-2, Beech King Air and, on the margin, the Aero Commander Turbo Commander, all twins.

How would the M620 compare to them on price, performance and accommodations? The 620 would be in a virtual tie in price with the most expensive of these, the King Air, which by the way sold more units than the other three less expensive planes put together (thus high price alone was not a market buster). The 620, with in excess of 50% more cabin cross-sectional area than the others, was by far the most spacious and could accommodate one quarter more passengers in the standard configuration. It would tie for having the greatest range, 1700 miles, but at 260 mph only be within the bracket for cruise speeds for these models, which ranged from 250 mph to 280 mph. Another plus, due its four engines, would be its substantially higher engine out service ceiling, 20,000 feet. It would have a longer field length than the others, but still be well in the category of being able to use smaller general aviation airports.

Cessna 620 interior
The interior of the Cessna 620 featured spacious seating for 10.

But one thing clouds these comparisons. We’re comparing the reciprocating engined 620 of the 50s to the turboprop-powered competitors of the mid-60s. Undoubtedly the 620 would have been converted to turbines by then, with a bump up in both performance and cost.

Still, collectively over their lives, just these four airplanes directly competitive to the 620 concept accounted for the sale and delivery of over 4,000 units (and obviously prop airliner conversions were a non-starter against these numbers). Given its several important advantages enumerated above, could there be any doubt that the 620 would have sold well beyond the break-even quantity (normally assumed to be 200 to 300 units for Cessna initiatives in those days) in the race for sales with these airplanes? And most importantly for its place in the field, the 620 would have had a five-year jump to establish itself.

Thus the 620 was the Goldilocks of executive aircraft of the time: not too much, not too soon, not too late and not too expensive, but just right. But this Goldilocks was hijacked by its own company’s management on the way to the market.

So, we see that what B/CA’s Hoffman concluded intuitively is substantiated by the facts – Cessna had made a huge mistake. OK, I’m biased because the 620 is one of my all time favorite programs, but in retrospect the airplane did all the original designers, and the industry spec we worked to, asked of it. And it was ready for the very beginning of the developing corporate aircraft market for which it was intended. What a tragedy that it was never allowed to prove itself in the real competitive world.


  • Excellent article! Good back ground information on a really interesting project – too bad it never went into production.

    One aircraft you forgot to mention above as a potential competitor would be the McDonnell 220 – another still born project.

    This is the kind of blogs I like most – informative, fun and of a period we do not remember that wee.

  • Great article, and the sort of thing that doesn’t get taught in business schools and management seminars, and usually for the same reason that the prototype was destroyed. Managers and leaders don’t like their legacies upended by bothersome facts and data. The surviving prototype would have been an impressive little bird to experience. One would hope that current managers would have the grace and humility to learn from episodes like this, but history doesn’t bolster this hope. Thanks to Harry for keeping the story of this airplane alive.

  • Piper tried the same thing about 10 years later with the Pocono and also ended up canceling the project. Many old Piper types still wonder what would have been if they had continued down that path.

    In the end, it was Beech that filled that market with the 1900. I guess their timing was better and they had a shorter path to take from the King Air.

  • Very interesting story. During that time I was growing up in general aviation and my father was chief pilot for Champs Aviation in Lubbock, Texas (a large Cessna dealer of the day). he along with his fellow pilots were looking forward to the 620 and even at one point had traveled to Wichita to see the factory line that would ultimately build them. I remember all of them were extremely disappointed that it was not produced as around the area there were a great many small airports away from large hubs as well as quite a few people with considerable net worth who would have been interested. The article was sort of a step-back in time for me.

  • Great great detailed story of the Cessna 620.
    It would have made a lot of sense to enter that market business/regional.
    Look at the Falcon business jet that Fedex ordered in the beginning instead of the Canadair Challenger business jet. Bill Lear and the design team had built in a stronger floor due to the Fedex interest in the plane.Well the short side of the story is the Regional Jet RJ built later by Bombardier was a giant success story.The Cessna 620 was on track of becoming a prop/turboprop early bird of the Rj’s.
    Thanks Harry and mr. Hoffman for this great story.

  • An interesting story. Presumably Cessna carefully studied the DeHavilland Dove and Heron aircraft in developing their concept at Cessna.

  • I’m late to this game, but Harry does not mention, or take into account converted military planes used for business purposes.

    In the early ’60s, the company I worked for flew two Lockheed -18’s, one with P&Ws and one with Wrights. A converted Lockheed PV-2, a Howard 250 and a Howard 500. They all were inexpensive to buy even with sumptuous interiors and full heads. They all chugged AvGas at prodigious rates (300 gph/per hour/per engine at T.O. power and 100 gph/per hour/per engine for cruise in the Howard 500). AvGas was cheap then and we saved even more by fueling from our own underground tanks.

    We flew them well into the early biz-jet age.

    • In assessing and developing the 620 we were responding to a published specification thought to be the best desires of business aircraft owners and operators in the early 1950’s, and those aircraft you mention didn’t seem to be competetive within that spec, for one or another reason, and their market already developed and measurable. And that’s the way we felt about the Dove and Heron, the latter which we used most in comparative analyses. In considering the future competition those surplused prop driven airliners, when converted, appeared to be a factor in the business aircraft market. Their initial cost was expected to be competetive, but their operating expenses relatively high – and therefore selectable if the buyer’s expected passenger load, or space desired, was more than the marketing spec preferences we were designing to. In keeping with changing market desires we grew the 620 in standard passenger load and range, but all accomodated within the original structural envelope.
      I think the fuel consumption and other operating expenses for the planes you mentioned were more in the category of the airliners than the 620, and a factor in the buyer’s considerations.
      Again, the 620 would have had its intended market to itself into the early 60’s.

  • possible factors relating to the CESSNA 620 cancellation:

    Looking across town in Wichita in those days, it appears Mrs. Beech cancelled the Beech 120 (aka “mini Gulfstream”)for possibly some of the same reasons – namely – too big a step up from the installed customer base. Looking at the large number of Twin Beech 18’s and Super 18’s in corporate hands, Beech surely looked hard at the cost delta to trade up from its loyal customer base to what it was proposing. The King Air obviously was a smaller and more affordable step for a larger number of prospective buyers.

    Cessna must have faced a similar question: “what CESSNA model owner population do we have for whom this would be a next logical step. They didn’t have any SUPER 18 equivalent in their customer base. The step up would be a bigger hurdle for the 620.

    Also we should remind ourselves who was postioned as the “corporate airplane” at the time – “Beechcraft are the airfleet of American business” was the factory slogan and also the reality in the marketplace. This branding and positioning advantage by Beech must also have figured into the CESSNA decision.

    Last but not least: the 620 appears to have been pretty much a clean sheet of paper design. By contrast, Beech practiced successfully incremental product development and refinement. Think Models 35, 95 and 50 Twin Bonanza, Queen Air 65, 80, 88 pressurized; military unpressurized NU-8; King Air 90, 100, etc etc. What I remember distinctly from 1964 is the ridicule and criticism heaped on the Beech King Air while Aero Commander and the 4-engine POTEZ 840 were lauded as huge achievements in some corporate FBO pilot lounges.

    Beech Aircraft finally did bring out a clean sheet design which abandoned any hint of incremental design evolution: the Star Ship. RAYTHEON’s strategic response to Beechcraft’s decades long aversion to bold product moves is understandable even if terribly executed. I recall an extended conversation in the 1980’s with a CESSNA design engineer and his list of design choice criticisms which he predicted would doom the announced StarShip program – ultimately coming true in a commercial debacle of a magnitude inconceivable to be asociated with Beech Aircraft.

    But the ongoing aftermath and legacy of the sale of control of Beech Aircraft by Mrs. Beech is a business school story for another time.

  • We never considered Beech a competitor for the M620 market as it – and they – existed at that time, and we never considered the 620 as an extension to our existing line (even if it was a model number twice that of the M310), and especially not to be handled by our existing dealer organization. A separate Division was organized for it at Cessna, which included a different market organization and approach. And interest, and suggestions for improvements, in the model from business aircraft owners and operators was being solicited and received throughout its development.
    We used to conjecture that filling up one 620 would exhaust the entire fuel supply of some of our smaller dealers.
    Later some aviation enthusiasts considered the King Air to be a competitor to what the M620 would have offered about five years earlier.

  • Harry’s comment: – that Cessna did not see the 620 as connecting to its existing customer base or dealer organization is exactly what I would rate as a magnitude greater risk for the compoany at that time.

    In B-school marketing parlance the 620 would be “new product – new market” thus putting that investment in the highest risk category even though also potentially in the highest reward category.

    interesting perspectives from the Cessna group – thank you.

    • Our company’s approach at that time was that whenever we had a departure in our new products that did not fit with our existing customer base, even if that new product sprung from our only preliminary design group of the time (we had no divisions in 1952), a new division was formed to handle all aspects of the venture: production, marketing, engineering, etc. It started with the T-37 and its Military Airplane Division, which caused us to form a Commercial Airplane Division for our old (General Aviation) products, and then the Business Aircraft Division for the 620. My personal, and admittedly biased, opinion is that the Military Airplane Division was successful and the Business Aircraft Division would have been too if allowed to continue. The company attitude was adventuresome and it led to some interesting undertakings.

      • no doubt Cessna was more adventuresome then Beech after Walter Beech passed from the scene – this is especially true in Mrs. Beech’s lter decades at the helm. “preserving what we have” evidently became more important than achieving milestone innovations.

        Interesting to view all these events from a perspective of decades later.

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