Defining the Cessna 310

The concept for the Cessna 310 was established before I joined the company, and there had been a wind tunnel test completed as well. Having the latter was a little odd as it was the only model of the Cessna airplanes of the period of the early to mid 1950s that was tunnel tested, till those for the four engine 620 and, of course, the T-37 jet trainer.

The Cessna 310
The Cessna 310 was a major departure for the company–all metal, low wing and tricycle gear.

The 310 was also the only one of these 1950s models with two prototypes, and we reverted to just one prototype for the 620, but the Air Force required three of them for the more extensive testing of the higher speed T-37. But the defining experience herein was with the first 310 prototype, which was intended for flight testing leading to certification and was accordingly Spartan–only two very functional seats (they had to accommodate parachutes), with no upholstering and a bare metal floor and exposed main spar in the cabin, and only a couple of stripes for a paint job.

The 310 was to be the company’s first twin engine, retractable-gear design since the UC-78/T-50 Bamboo Bomber of WWII, and the first Cessna ever with a tricycle gear. It was expected to be, and was, the first all metal, high performance twin using the then new fuel-injected horizontally-opposed engines and having all of the fuel contained in wing tip tanks.

Less visible was that it was to be an extension of the company’s single-engine line in that it would fit in a typical T-hangar of the day and be operated out of grass fields. Nothing I will discuss was directly affected by the grass field requirement, but the T-hangar sizing dictated the fuselage length, the wing span, including the tip tanks, and perhaps to a lesser extent the span of the horizontal tail.

That limited the possible solutions to our greatest problem in certification–inadequate longitudinal stability. And that problem was caused by the tip tanks and the flat nacelles which were made possible by the elimination of the carburetor.

I call the following discussion defining, rather than designing, the 310 because only one major change was made before certification, and some of us were convinced that change was necessary and had to come (but I didn’t know it would be on such an expedited basis when it did).

We did however then spend some time evaluating especially one design feature: the wing tip tanks, to understand their contribution to the airplane’s characteristics, and decide whether the tanks should be removed from the configuration for overall improvement of the plane’s performance.

But my first exposure to the 310 was well before its first flight and was to assess alternative ways of determining its drag coefficient to assure ourselves it would be high performance in cruise. The analysis confirmed to my satisfaction that it was going to be fast, showing a cruise speed of over 200 mph, which seemed great to me for the early 1950s. So speed performance wasn’t a big concern any more, though you surely didn’t want to compromise it in any way.

Then I inherited the cleanup of the analysis of the wind tunnel tests. One of the other selections for the configuration was a split flap, to be sure of drag when you needed it on this very clean configuration, such as during power-on approaches. This choice was a departure from flaps selected for other Cessna models of the era.

The tunnel test indicated not only that the split flap gave good incremental lift, but produced so much drag it was almost dangerous. Thus we limited the deflection of the flap from the 75 degrees tested in the tunnel to 60 degrees on the prototype and, based on flight confirmation, limited it further to 45 degrees on the initial production airplanes.

The other thing the tunnel showed was that the configuration didn’t have enough static longitudinal stability, which confirmed an analysis done earlier by some other aerodynamicist. Nevertheless the prototype configuration first flown was entirely that of the less than stable tunnel model.

Now I’m going to disclose something I’ve never mentioned before, even to my Flight Test, Aerodynamics and Preliminary Design colleagues.

In sorting through the accumulated engineering information on the plane, I came across a planform drawing superimposing the 310 on a Beech Bonanza, with the 310 horizontal appearing to be the Bonanza V-tail flattened out to be the 310’s horizontal tail (the vertical tail was of course not depicted in this planform display).

V-tail Bonanza
The V-tail Bonanza–a model for the 310 tail?

I thought to myself that if you were going to emulate a design for speed, that Bonanza was the ideal choice, but not for sizing a horizontal tail on a twin engine model. The drawing did not have a title block, was not signed or dated, and I don’t know who created it or what part it had in defining the early 310. You can tell I’m suspicious of it, though.

The prototype was first flown, solo, in January 1953 by our flight test chief. The second flight was solo, too, but I got to be the first passenger on a 310 on its third flight. I then again got selected to be the project aerodynamicist, flight test engineer, and flight test observer–specifically for certification–and was teamed with the pilot who flew the same mission with me on the 180.

He was a WWII fighter pilot who had to get a multi-engine rating for this new duty. After one of his first familiarization flights in our airplane, and before we had started the flight test program, he came storming into the group area and said to me, “You’re trying to kill me” and related that in trying to bank the airplane the aileron response was so slow that he increased the input and then couldn’t stop it from rolling too far and got into what he considered a dangerous attitude.

I thought, but didn’t say, “Why do you blame me for a basic characteristic of the design of the airplane you’re flying? And besides, if I really wanted to kill you I would have done a more thorough job.”

He had encountered one of the difficulties with large tip tanks, when full of fuel, that caused such resisting inertia to rolling and banking the airplane that you had to make a disproportionate input to get it started and then anticipate and reverse it well before you got to the desired bank angle. He didn’t have that problem on fighter planes, or the 180. This was a characteristic that was easily resolved with instruction and familiarization, and as he soon admitted it really wasn’t all that bad.

So, we started the certification process. I’m going to skip over some of the mundane problems (like gear retraction, prop synchronization and vapor lock), and get to the serious ones in my main area of interest. The flight tests showed we couldn’t pass the longitudinal stability requirement. Once this was understood I was given just three days, including doing some additional flights if I wanted, to determine a new area and configuration for the horizontal tail – or we would miss the planned date (seemingly pretty far in the future, so what was the hurry?) for the ceremonial introduction of the production 310 airplane.

I did have some additional flights done to compare to prior analysis and wind tunnel results, and didn’t want to be so safe in adding area that we would give up much speed. I met the deadline, we flew the new tail, and the longitudinal stability requirement was passed, and still with a cruise speed for the airplane above 200 mph.

Note that my assignment was not to solve the longitudinal stability problem, but to size the horizontal tail to overcome it. That was because the problem was caused by the large aerodynamic tip tanks that acted as a lifting body ahead of the wing, and the clean nacelles associated with the fuel injected engines.

The nacelles were elongated in front of the wing and moved the (destabilizing) propellers forward compared to where they might have been on a more conventional nacelle. Obviously those trim, streamline nacelles and hefty but aerodynamic tip tanks were sacrosanct to the original concept of the airplane and couldn’t be changed.

But with the tip tanks came inherent characteristics, some excellent, some good and some bad (but none too evil). Primarily, if you can get all, or nearly all, of the fuel in them and place it far from the passengers they provide a seemingly undeniable safety advantage.

The other contributions depend on their aerodynamic properties and their concentration of mass. Aerodynamically they are a contributor to drag, but those on the 310 were also oval in cross-section so as to create some endplate effect, which might improve climb rate as well as aileron efficiency. And as described above, tip tanks can detract from longitudinal stability. Their mass and related inertia also affect apparent roll performance, again as described above, but adequate lateral control procedures for them can be learned and used (aided by the improvement they can provide in aileron effectiveness). Less apparent is the contribution of their mass to the roll-yaw oscillation known familiarly as Dutch roll. Also to be noted is that their mass contribution lessens as fuel is consumed.

I thought these offsetting features of tip tanks, some good and some bad, ought to be quantified so we would better understand what we might be giving up for their safety advantage. I did this analytically, but convinced the decision makers that we ought to confirm them with brief and concise flight tests (they took four days). This was after we completed the company certification preparation flights, but before the FAA/CAA had done their official certification confirmation, so I planned the tests and wrote the related engineering report, but was not the observer on the flights.

By my plan we flew the prototype with the tip tanks on, full and empty, along with a tanks-off configuration with substitute conventional wing tips. These last two conditions were flown by putting a temporary fuel drum/tank behind the crew inside the cabin and placing it on the airplane centerline there.

Let me dispose of the characteristic of tip tanks I couldn’t resolve in my own mind, that of the annoying Dutch roll oscillation. It is induced by gusts in real (non- experimental/test) flights, but in tests is started by decisively yawing the airplane with no bank, returning the controls to neutral and holding them there, and reviewing the decreasing oscillations in roll and yaw angles as the airplane recovers to undisturbed (near straight and level) flight.

High inertia along the roll and yaw axes, as full tip tanks provide, by theory would result in a longer time and larger number of oscillations to smooth out, and that was certainly proven true on the 310. For the academic in me that was satisfying. But I must not have done the analysis with tanks off or empty, as I was completely surprised in these conditions by how fast the yawed airplane bounded toward and past neutral, and then an equally quick reversal, lowering the time and number of oscillations to recover, but subjecting passengers to high lateral accelerations in doing so. Maybe not so satisfying for the people on board in real flights.

This aspect of the tip tank evaluation was inconclusive to me as I had no information on whether longer exposure to lower accelerations was better than shorter exposure to higher accelerations. Interestingly, the pilot and observer of these test flights said they found the (high acceleration) motion with the tip tanks off less objectionable. But since we sought smooth air to get good data in flight testing, thus never experiencing Dutch roll in practice, I had no personal opinion about the possible difference.

Cessna 310 gear up
Having the fuel far away from the cabin proved to be a major safety benefit in the event of a crash.

Of course the standard 310 with tanks would have been subject to both end conditions tested anyway as (full) fuel was consumed during a real flight. So I concluded that Dutch roll characteristics should not be a determining factor in the tip tank controversy. I feel somewhat justified in that I have since never heard of objections to Dutch roll types of motion from users of the 310. (That doesn’t mean that there haven’t been any.)

We did learn something about the 310’s native lateral control capability in tests by which nominal roll rate was determined by rolling ninety degrees from one bank angle to its opposite. The roll rate with tanks empty or off was about 50% faster than with full tanks, indicating the steady maximum rate was never achieved in a 90 degree roll with tanks full. But that great performance with tanks empty showed how good the ailerons really were and how they could provide the necessary control of roll and bank under conditions with tanks with plenty of fuel in them.

Other criteria were more clear cut. There was a very slight improvement in climb rate with tip tanks on (less than one tenth of 1%). In opposition level high speed increased by seven miles an hour with the tip tanks off. Also with the tip tanks off the longitudinal stability improved by a factor of four, by one measure, meaning that without the tanks the horizontal tail area could have been substantially reduced, possibly increasing the level high speed by another 3 or 4 mph, or for a total of over 10 mph (that is 5%, and likely more, of the nominal cruise speed, felt possible since we had added one-third more horizontal tail area to pass the stability test earlier in the flight program).

The airplane’s range would have gone up by that same percentage as well. So basically we gave up some speed and range, and a little on lateral control, too, for the safety afforded with the tip tanks.

Incidentally, for reasons never specifically investigated, the second prototype was a little faster than the first, and the production models were a little faster than the second prototype–so the consumer’s 310 (available at the originally scheduled roll-out!) really was, and is, a high-performance airplane.

So, with all this activity we had first provided the necessary longitudinal stability, then quantified the somewhat offsetting impact of the tip tanks on 310 performance and flight characteristics. With the safety aspects still dominating, they were, as everyone knows, retained. Maybe that decision was preordained, but I felt we needed to confirm the magnitudes of the trade-offs they presented for our own knowledge and satisfaction.

But then came the report of one of the first serious accidents with a 310, in which the airplane was losing altitude and clipped the top of a mountain it was being flown over. The plane skittered down the other side of the mountain, with trees shearing off the wings, the tip tanks rupturing and the fuselage coming to rest further down the slope. Some fuel from the ruptured tanks flowed down the mountain and some of that went into the fuselage. But nothing ignited (with the fuel always distant from any heat or sparks created) and there were no fatalities. It was concluded that the safety aspects of tip tanks, even in this quirky situation, really were worth the compromises they required.


  • My Dad flew a 1955 model 310 (N3010D)for a construction company in Central Illinois during the 60s. Have many, many hours riding along as he flew all over the Midwest chasing parts for broken construction equipment. Of course, I spent many hours sitting in the cockpit playing Sky King too!
    I never flew the 310 much myself. Only 50 hours or so. Still one of the most beautiful light twin ever made.

    • One acknowledged expert, who had owned half a dozen of them, proclaimed the 310 was the best light twin ever produced. He had of course owned and flown many model changes from the protoype and first production model I describe. I didn’t get a multi-engine license till some time later, and those great model changes over the years – which I had nothing to do with – made it my all time favorite airplane to fly.

      • Harry, Thanks for the article. I believe the 310 accident you referred to in the last paragraph of your article was my Father, J. Grant Robertson. It happened right before my 3rd birthday in early 1955 as far as I know. He was vice president of Clinton Aviation in Denver and I believe it was the first 310 they received. Lee Renshaw was in the left seat and Dad was in the right seat with a prospective client in the back with his son. They blew a piston rod after departing the Eagle, Colorado airport near Wolcott, Colorado. The engine did not feather and tore up the cowling, disturbing the airflow over the wing. That combined with a full load of fuel brought them down. As you said the tip tanks were torn off by trees. The fuselage landed upside down. My Father and Lee were seriously injured being smashed into the instrument panel. The two in the back seat were able to get out and pull Dad and Lee out. There was a fire though as in the insurance photos there was nothing left but the tail section and both Lee and Dad were burned although not badly. Dad’s leg was compressed and he had to wear a lift and a leg brace the rest of his life. He also fractured his scull to the point of his brains hanging out and they removed part or all of his right frontal lobe. It didn’t seem to affect his memory and was back at work after a very long convalesce. He later taught me to fly in a 182.

        This is the the only reference to the accident that I have ever found. Regrettably the insurance photos got lost over the years. Let me know if you can confirm this.
        Thanks, Gary

        • I think definitely it is the same accident. I knew that a Cessna person was involved, but I didn’t remember who (it was Renshaw). I didn’t know the extent you do about it, but the first, or an early serious accident, on a new model is cause for long faces back at the plant – as if your design wasn’t going to ever cause one. Later ones are just statistics. I still think we were told that there was no fire involved – but it was an early report and maybe not comprehensive.

  • Thanks for another great article.
    Was in Australia in the ’70s and flew a B model into all sorts of places and later a K model.

  • I bought a J model with only 3 hours twin time in my logbook, and got my twin rating in the 310. I explored the entire operating envelope wih my flight instructior who had several thousand hours in the 310 including spins. The airplane was solid and made me feel comfortable in any environment. I flew it several thousand hours before fuel costs made me sell it. Of all the hours in my 310, there was only once a gust caught me just before touch down with almost full tanks and tried to roll. The inertia was surprising but managable. If it were not for the price of fuel, I would still have it today. It would carry anything you could fit inside. A real workhorse that looked like a thoroughbred.

    Great article, great airplane!

  • It is terrific to see such an interesting article on the development of the 310. I own two of them, a 1965 310J and a 1975 310R. I have to agree it is the greatest light twin ever built. Others will feel as strongly about the Baron 55/58, but the full package of load, single engine performance (especially with vortex generators), weight and balance, speed and runway performance are a package that can’t be beat, even by the exceptional Baron. All this and it still looks better, and is more recognizable to aviators and non-aviators alike, than any aircraft except the Piper Cub and perhaps the Lear 24. Thanks for sharing your contributions to this superb airplane.

  • Great article. Most of my piston twin time is in the veritable 310s and 320s – fantastic flying machines. I have flown in lots of weather and flown them single pilot IMC with no a/p and they never failed me. Can’t say the same for it’s bigger brother, the C-421, but that’s another story.
    I learned some things I didn’t know about this iconic machine!

  • Did Piper’s success with the Apache during that time have any influence on the 310 design? It seems the fuselage width was a departure from Cessna’s norm, it was more like the Piper.

    • I don’t remember any influence of the Apache in our efforts, but I wasn’t in on the original design work for the 310 – but I believe that any success the Apache had was well after we entered certification of the 310. We had considered both a four place and five place version of the 310, but that was narrowed down to only the five place during the certification process.

  • Harry, your writing is superb on a topic that I have long yearned to know more about – that is, how did all these incredible, iconic designs come into being? I will continue to look to this peerless blog for excellent writing on great topics, but please tell us if there are any books which explore the topic of aircraft design along the lines of your great articles.

  • Thanks for the compliment. There is only one pair of books that I know of personally that might provide the kind of information you are looking for, both by William D. Thompson and entitled “Cessna Wings for the World”, one with the subtitle “The Single-Engine Development Story” and the other “II, Development of the 300 Series Twins …”, the first published in 1991 and the second in 1995,printed by Maverick Publications,Inc. Bill, as I knew him, was with Cessna in the Flight Test and Aerodynamics group for almost 30 years, headed it for a large part of that period, and was my boss there for just over 2 years.I have the books because Bill sent them to me, and had asked me to contribute to the second book (only), which I did. In honesty I have probably read only 10% of them (they must cover almost 40 models, most before or after my time), but despite what I am going to say next, I refer to them to check up on my memory of some things. Bill and I had great differences in how some things were remembered,and as a less controversial case, he mentions an accident in which one of his friends was killed, an accident that I happened to witness, and he is wrong about the date of it by at least a year and a half.
    Before I recommended these books I checked with both the Public and University libraries in Wichita, and both have at least one of them on the shelves, so they could be obtained by interlibrary loan. Of course Wichita is the home of Cessna Aircraft.
    Bill mentions another book, “Wings of Cessna” by Edward H. Phillips, but I have never seen it, so don’t know its format or content.

  • I had a D model. N-18y. I had probably 1,000 hours in this fabulous airplane. Over half
    instruments. It is the only twin I ever flew, with the exception of 5-6 hours in a MU2 in
    the left seat, but with the owner in the right. I flew 18-Yankee from Wings Field (ING)
    to SanJaun, PR twice. My main route was ING to HPN (White Plains, N. Y.) picking up
    and depositing children every other weekend. I have several Air Facts speed records,
    plus five or six articles published in the old Air Facts. Dick Collins’ father, Leighton, was
    very generous in paying me when, actually, I would have paid him. I had only one
    issue with 18y. I lost the left engine, the critical engine, en route from Wings to Montego
    Bay, Jamaica, IFR over the Cheasepeake Bay 4:30 a.m. It ran in the August 1969 —
    Gad, that was long ago — Air Facts. I was right over the middle of the Bay on a moonless,
    night, about 60 miles from Norfolk and 45 from Richmond. Net, net, I shut it down and headed to Richmond. 18 Yankee got me there. So much for the argument twin verses single. I miss flying
    Every day. My ex-naval carrier pilot cardiologist grounded me, probably a good idea. Thanks Facts

  • I have no idea why the lines appeared that way (above). But the 310 was a fabulous airplane.
    The D model went 180 kts all day long. It did oscilate with full tanks when heavy handed, but
    nothing bothersome. And I always had it full. Even the auxiliaries, 15 gallons each.

  • Owned a real early 310 — 2647C –following my early 182. Great ship, but gave a few bad moments such as when flying from BUF to DET down the middle of Lake Erie I watched the light gauge metal of the right engine nacelle slowly crack down the middle! Did not depart the aircraft, so it got prompt patching when I landed! My second 310F, one of only six built, I understand, for a Navy contract competition, Cessna losing out to the Piper which, while substantially slower, had six seats and carried a bit more fuel in the main tanks. Less speed, therefore less range even with the extra fuel — but the evaluation was likely not done objectively. Years later, while the 310 was undergoing an annual, I rented an Aztec, quickly learning the difference between flying a thoroughbred and, as I privately put it, “riding a cow!” The 310F was followed by almost 20 years owning a C-340, RAM converted, which regularly beat the same route time of a client flying an early King Air! I flew — did not own — the C-401, C-402, C-411 and then the C-421 simulator at Flight Safety. None matched the sheer joy of a neatly completed flight in the 310’s and 340!

    • I got my multi-engine rating in an Aztec, cause that’s what the flight school had. I thought it was OK. But then I flew a late model 310 – I don’t remember the model number – and even curbing my natural enthusiasm for Cessna airplanes (since Cessna was the only General Aviation company I worked for)I really thought the 310 was a better deal to fly.

  • I flew the G,H,P(turbo) and the R models with my own single pilot and 310 on 135 operations over a period of 10 years it is the best twin piston at that time out there with over 5,000 hrs in a 310. Dutch roll ? guess it had it but I got use to it.

    The Baron it’s OK but the 310 is my bird.

  • Harry, thanks for the references, I will track them down. I know you’re of course a Cessna guy but one lineage of aircraft I have a particular interest in alongside that of Cessna is those that Ted Smith had a hand in, from the Douglas A-26 through the Aero Commander line to the Aerostar. Any ideas for resources that tend in that direction?

    Thanks again,


    • Sorry – I knew of Ted Smith, but never met him, and the only books I have read – and not thoroughly – were the two I previously mentioned. I know this apparent lack of interest sounds inconsistent but when I left Cessna I got into such things as the manufacture of airline and military airplane major assemblies, design and manufacture of space launch vehicles, and design and manufacture of high speed surface transportation vehicles. And it seemed wherever I was what was offered to fly were Cessna airplanes I already knew – the 150, 170 172, 182 and 310. I became a sky diving pilot flying- 30 year old 182s!

  • Harry,

    As a ’68 310N owner for about 14 years, I’d like to thank you for the stability you built into it. There was an inop autopilot installed when I bought it. I decided to fly it for a while and get it fixed when convenient.

    Several attempts were made, unsuccessfully, to fix it, but it was so comfortable to hand-fly, I had no real motivation to spend more money.

    Since 2005, I fly a ’78 340A which is every bit as good.

    Question, both planes have the same characteristic. On landing, I carry a slight bit of forward thrust flowing over the nacelles. This seems to provide some significant lift. When appropriately over the runway, chopping the power seems to ‘dump’ the lift and settle nicely. I’ve flown other twins that do not exhibit this. What say you?

    • I think this relates to what I said about the 310 being my favorite airplane to fly. The other “heavies” like the single engine Navion and multiengine Aztec seemed to just sink when you chopped power – OK if you were close to the ground, but the 310 still had some lift,float and maneuverability and landed more like the single engine Cessna’s. I wish I could take credit for it, but I think it came with the configuration.

      • I enjoyed this article very much. I own a T310Q with the 320hp Ram conversions. I really happen to like the feel and look of those big canted tip tanks (laden with fuel or not)! I find articles like this to be incredibly useful in helping me to better appreciate and understand my machine. I really don’t know how I could ever find a replacement for it that would match its comfort, looks, and performance at a better value. It really is irreplaceable for the money. Reading your article helps me feel even more confident in my choice to own a 310. In my own admittedly limited experience, Flying any other piston AC just feels, well . . . Sort of anticlimactic.

      • I am going to buy a Cessna 310 later in life and the feel and looks are reel nice you should by a Cessna 170 because almost all of them have comefortable leather seats the cruising speed is 137 miles per hour

  • Thanks Harry; first for the 180 story and now the 310. Again, you’ve piqued my interest with your casual mention of “space launch vehicles.” Your writing abilities are truly excellent. Might you want to tell a few more stories on this subject?

    My first plane ride was in my dad’s ’55 C-180. My first (of many) twin flight was in a ’59 C-310C, which replaced the 180.

    Thanks so much for writing these stories!!

    • Thanks very much for the compliment. I don’t think articles on space launch vehicles would fit the Air Facts Journal format and area of interest, and I don’t know of any magazine for which the subject would fit. I did write some very technical articles for rocket science technical journals when the work was being done. As to other articles for Air Facts Journal, my wife says I should write one on a gears up landing we did on the 310 prototype but I think it would be too long if everything was covered. I have thought about some on the T-37 development,but it was not a general aviation undertaking.One subject on that airplane that might fit is one on a random occurence of mild longitudinal instability that had a directly observed cause but no explanation for why it occurred on some units and not others.
      Thus it was not corrected and never caused a complaint during over 50 years of service in its mission. I’ll think some more about that one.

  • Harry,
    I suspect I speak for a lot of the readers if I say that we’d be thrilled to read anything you’re willing to tell us about! GA or otherwise!

    • Thanks for the support. Maybe I’ll write a couple of articles and let the editors decide whether they fir the format or not.

  • I have accummlated over 500 hours in a Q model and fly it regularly for business all over the Rocky Mountain and western states. I have had it in all kinds of weather, always a solid and reliable. When descending through a cloud deck on an instrument approach taking on some rime, the 310 is always stable and predictable. I would recommend anyone looking for a light twin to consider a 310. Great plane! Thanks for all your work Harry! Would like to see more articles like this one about the 310, maybe a book about the history/engineering of a 310??

  • I owned a 310I and later a 310P. A club to which I belonged operated a 310Q. I have about 800 hours in the model. Later I owned two Navajos and flew them over 500 hours, then became a Beech specialist flying all the Baron models, including the pressurized 58P. I also currently provide initial and recurrent training in the Barons and the C340, C414, and C421 airplanes.

    Nothing can touch a 310 for the combination of speed, room, baggage space, comfort and low cost operations. I am a big guy (6’4″) and the 310 is the only aiplane in that group where I have to move the seat forward to comfortably reach the controls. The 310 is still my favorite if I decide to buy another light twin.

  • Incredible article! Many thanks for the backstory on the Genesis of the 310 series. I’ve spent years at Cessna dealers and working at various airports; and few light twins are as beautiful as the later 310Q and R models.

    I never learned why the 310 was replaced by the short-lived 303. If you have time, perhaps you could shed some light on this decision.

    • That happened long after I left the Commercial Division of Cessna and after I left Cessna, so I have no insight to that decision.

  • great article – well I used to work for the Cessna distributers (Rex Aviation) here in OZ(Australia) for many years & flew most 310 models from the B (which was set up for cloud seeding – later replaced by a 401) to the R model.

    As for the ‘Dutch roll’ I always liked to watch the little nav light on the tip tank at night – if you had the aeroplane all set up & trimmed nicely the lights used to describe an elongated oval.

    As the other bloke said I am also a big bloke & found that I could get very comfy in the cockpit – especially as I did many delivery flights to OZ – some legs went over 16hrs – was just such a fine aeroplane

    • Jon Brunker (I sincerely hope you see this and can reply)

      A beautiful Maserati that took 20 minutes to warm, and Daniel Craig would kill to drive, an XU1 prior to it, a fellow instructor with the first name Judy, and of course there was Mr. Vallance, very skillful driving of the Maz by Johnny Goss at the wheel and Hotel California blasting (I’m still straining to hear those 2 drum beats clearly), a pet stone leached with a string, playing with clouds, fun times with an Aero Commander owned by xyz co, lessons in the cockpit about religion – NOT, chin up’s in the hanger, watching the cumulonimbus grow on a Saturday afternoon while accumulating an hours instruction, a Bentley with a silver body and maroon doors and a nervous father at the wheel – of course he was entrusting me to you :), darling/crazy Pinkfish and ….oh oh it’s so close Pinkfish and Victoria Station??, the ‘nut’ that would take the 340 out in any weather, longhair and a beard to be very proud of – you(the fingernails come to mind as well 🙂 I hope you get this – you changed my life for the better (and I love you). I live in Canada now and have just been watching some great video of Michael Hutchens, and it reminded me of Bon and that led me think of you and the work you did to help ACDC. Peter

      • G’day Peter,

        great to hear from you again – give me a yell –

        as an aside I am now very good friends with the recent past President of the Rolls Royce Owners Club – who also drove a similar Bently to your father’s one.

        see ya

        Jon B.

  • I am looking at a 310 that has some surface corrosion on one of the wings. I am told by the owner that Cessna never sprayed anti-corrosion on the wings of the 310s. Is this an issue?

    • I don’t think it is an issue. The standard method of corrosion protection of aluminum sheet was, and I presume still is, to “clad” the base aluminum alloy with a thin coat of pure aluminum, which is itself corrosion resistant (the alloys are not). The cladding was thin and “non-structural” so as not to affect the functional strength of the sheet, since pure aluminum is not strong like the alloys are. Cladding was done by the metal manufacturer, so no spraying (of anything) was normally done by the airplane manufacturer (unless it was paint, of course). I hope this is not too elemental and I suppose I should consider that the intentionally thin cladding on older airplanes might be worn or locally scratched and show some surface corrosion. I think such corrosion could be “scrubbed” off and a corrosion resistant material – compatible with aluminum – applied. I flew 30 year+ old Cessna’s in fairly demanding skydiving operations and never saw nor was worried about corrosion on the skins.

  • Very enjoyable reading, Harry, about one of my favorite airplanes. I owned and flew a 1956 model 310 for many years. You mentioned the design featured the slim nacelles for the fuel injected engines. My 310 had the carbureted O-470Ms, as did the A and B models. Fuel injection was introduced on the 1959 310C, I believe. Even for carbureted engines. though, the nacelles were slim and very good looking. I’ve read all your blog columns and look forward to many more. Thanks again.

  • Harry,

    Great article. Can you comment on the change from the “tuna” tanks to the “Stabilia-tip” tanks. Were there significant aerodynamic benefits to the change or was it more stylistic?

  • I have operated a 1959 C-310C 2150 hours over a 25 year period. Great machine. Well done! I have often wondered if there was a relationship with the Lockheed C-130 tail (their shape and disposition being very similar to my eye ). I also would love some insight as to the incorporation and purpose of the hefty elevator down spring. Thanks Harry.

  • Rereading this material after a couple of years, Harry, I was struck by the difference in rate of roll with the tip tanks removed during test flights. During the tests a temporary fuel tank was installed in the cabin on the fuselage center line.
    If this tip tankless version had gone into production fuel would have been in the wings as in other twins. It seems to me that this would have cut down considerably on the 50% increase in roll rate gained during the test. I flew my 310A several times for a check with the tips almost empty and with full aux tanks(30 gals.). The roll rate was faster but not measurably so, even though the aux tanks were inboard of the engines & thus closer to centerline. Still miss N5209A which was crashed & destroyed by a subsequent owner.

  • You are correct, a version without the tanks but with a logical configuration with fuel in the wings wouldn’t have the results we obtained in the cited test. But this test was a concession to me because I felt we needed test numbers to at least help quantify what the tank configuration “cost” us – so they let me devise a simple series and temporary configuration to do so. It only took four days out of whatever project was being done on the prototype at that time. There was no chance the tip tanks wouldn’t be used – they were a favored concept of our VP of engineering. I transferred to the Military (T-37) division a short time later and didn’t follow commercial models after that. I suppose some later 310 derivatives did have fuel in the wings. The later 620 model did from the start.

  • Great article Harry. I’ve owned a ’55 C-310, N2642C, for the past 16 years. It was the 42nd one made and is the one in the photo featured in your article. It’s been a wonderful airplane. Here is video I produced about it.
    As a few have already pointed out, the first fuel injection model was technically the ’59 C model, but the pressure carbs we have were positioned in the back of the engine to maintain that slim nacelle profile. The way the pressure carbs work, it’s really a primitive form of fuel injection anyway. Great design. Thank you for the article and for helping to bring this great plane to market. N2642C will be 62 in January. Still going strong. I love it. C. Jessen

  • Greetings Harry! I thoroughly enjoyed your articles on the original Cessna310. I was only 5 (five) years of age when I first rode next to my Dad in 1958 out of Columbus, Ohio. My Dad was employed by Foster Lane Aviation at the time and later flew for Mace Jennings Aviation of Worcester, Ma. Of all the hours that he had on 4 engine, and twins through-out WW2 he longed more time in various 310 models over a 10(ten) year period than of all hours of any type rating. He often spoke high praises of the first “Fast Twin” built by Cessna, even a better aircraft than the Stagger Wing Beech. The ability to hold ICE under certain conditions proved invaluable and a major life saver on several situations!!! Yes it was a difficult time to make living in the Private Charter industry in the sixties (60’s) and seventies(70’s)! Under I F R conditions, the 310 was a superior aircraft! In conclusion; in spite of all the heralded accomplishments and praises from numerous qualified aviators out there, I must freely admit that the tip tanks did little or nothing in the overall stability in terms of consistent landings. The same principles for each “payoff” were never same. That fact has proven to be a major flaw in purchasing a used fully over hauled 310 to this day. The single undeniable fact is the Center Wing Spar has been compromised over years of “Hard Landings”. Blame it on the pilots all you want; the real culprit was the “Speed Wing” the very thing that made the 310 unique and successful. The Cessna 310 will always be the epitome of grace, efficiency and elegance! Once again; thank you for your aeronautical expertise! Respectfully, Lance Wing

  • Cessna 310 C and later models.
    Hi all, I flew C310’s, in Ontario, Canada, in the 1960’s and 70’s.
    Total 310 time about 750 hours.
    That pitch ‘sensitivity was quite noticeable although easily adaptable to.
    Read fingertip input flying.
    I did, obviously, discover one thing, NOT a 301 characteristic though.
    The mechanics had checked the O2 bottle up front and in so doing disconnected the nose-wheel gear door actuator rods and LEFT THEN DISCONNECTED.
    The pilot failed to notice this on his ‘walk-around’.
    He took-off, selected GEAR UP and the gear came up but so did the gear doors, jamming the whole mess in a NOT UP, NOT DOWN position.
    Cranking manually did NOT lower the gear.
    Belly up landing at Toronto Int’nl apt.with props feathered and horizontal resulted in remarkably little damage. no one hurt at all. (Shaken but not stirred).
    Mainly antennae and scraped belly metal.
    So guys /Gals check those gear doors for security, please.

    Loved the IN DEPTH coverage in the article. Very informative.
    Would like to read an article like that on a Learjet 23,24,25,30. 5,000 hrs. on those too.

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