The Cessna 310 is one of the classics of general aviation, enjoying a 27-year production run during which it served as Cessnas answer to the Beech Baron, Piper Aztec, Commander 500, and Aerostar. More than 5,400 were built, and there are several major variations.
With so much to choose from, any serious buyer should be able to find an airplane that fits the bill.
But there are things to be careful of when considering a 310. First and foremost is the gear, which is relatively delicate and sensitive to proper rigging and maintenance. The airplane can also be a handful to fly, though pilots note that with proper training and due diligence, it can make a good IFR platform. Finally, theres the 310s somewhat unusual fuel system, though pilots report that its no big deal.
For those readers who are old enough to want to avoid thinking about it, the 310 should look familiar: it was the costar of televisions Sky King adventure series. In fact, the current owner of the third and final 310 used in the show (a 1967 D model), Songbird III, wrote to tell us that its being fully restored. Anyone interested in the airplane or the show is invited to call Ed Lachendro at (414) 475-2544.
The 310 was introduced in 1954, a year after Pipers PA-23 Apache. Though the PA-23 would later be a direct competitor to the 310, the original Apache was far down the scale on power. The 310 competed more directly against the Twin Commander 520 (discontinued that same year) and Beech Twin Bonanza, which was dropped a few years later in favor of the Travel Air and 55 Baron.
The 310 was Cessnas first modern business twin, reflecting the companys strong growth in the 1950s. It was a time when many of the now-familiar Cessnas were first introduced: the earlier 140s and 170s were giving way to 172s and 182s. Cessna was moving aggressively into the business market, and the 310 was a key part, and first element, of that plan. In 1954, Cessnas entire model line consisted of the 170, 180 and 195; so, the 310 represented a giant leap forward for the company.
The 310 was the companys only twin for several years. The nearly identical 320 came out in 1962, followed by the pushme-pullyou Skymaster in 1964. The popular 400 series followed in 1965 with the ill-fated 411.
Unlike many airplanes with long production runs, the 310 went through steady refinement over the years, with a slew of designation letters following the model number. Cessna got up to the 310R (with a few gaps) before ending production in 1981.
The first 310s, built in 1954, were sold as 1955 models. They had 240 HP Continental O-470 engines housed in very tight and aerodynamic (for the time) cowlings. Flaps were of the split type for aerodynamic efficiency (no external flap brackets), and the gear was of electromechanical design. Distinguishing marks of these early models are multiple rear windows, a straight tail, and tuna tanks, so-called for their shape. The 310 was built through the 1957 model year. The 310B in 1958 brought a 100-pound boost in gross weight.
1959 saw the first big change in the 310, with the switch to fuel-injected 260 HP Continental IO-470D engines and another rise in gross weight This airplane was dubbed the 310C. In 1960, Cessna put a swept tail on the airplane, calling it the 310D.
The next significant change was in 1962, with the 310G. Cessna introduced their canted Stabila-Tip tanks, said to be more aerodynamically efficient than the old tanks. (The tuna tanks also had a fuel-pickup problem and an AD mandated a hefty increase in unusable fuel.) This 310, with canted tanks, swept fin and short nose, is one of the most attractive light twins ever built.
More refinements followed: increases in cabin size, further increases in gross weight, various increases in auxiliary tank size and the availability of three-bladed props. One significant difference was the switch from overwing from underwing exhaust on the 310I, and the accompanying introduction of wing lockers.
In 1969, Cessna consolidated its model line, offering a turbocharged variant of the 310 alongside the normally aspirated 310P instead of the 320. The T-310P had 285 HP Continental TSIO-520-B engines, standard three-bladed props and a 5400-pound gross weight, compared to the 310Ps 260-HP IO-470V Continentals, optional three-bladed props and 5200-pound gross.
Breaking with its practice of tacking on a different letter each year, Cessna stuck with the 310Q and T-310Q for five years. In 1975 a big change occurred with the 310R II and T-310R II.
Aside from another bump in gross weight and the move to 285 HP Continental IO-520M engines on the normally aspirated model, the 310R got a whacking great nose job. The proboscis grew 32 inches, and housed a sizable baggage compartment. The 310R also boasted an improved landing gear, though it was still not as rugged as many would like.
The 310R was the final development of the airplane, and stayed in production until the line was closed down in 1981.
The almighty dollar
As expected, prices for the 310 vary widely based on age and condition. Average normally aspirated 310s run from $40000 for the earliest models up to $191000 for the newest 310R. The market treats the various 310s pretty evenly: theres no real marked jump with model changes as often happens. The biggest gap is between the 310Q and 310R-the 1974 310Q averages $117000, while the 1975 310Q averages $139000. The gap for the turbo models is similar.
How good an investment is a twin? Twins are popular with some pilots because of the perceived safety advantage of having an extra engine. This, of course, must be balanced against the extra hazard posed by single-engine operations when low and slow. The debate has gone on for many years.
Money talks, though, and the true cost of a twin is doubled engine maintenance and fuel bills. The marketplaces answer to the single-vs.-twin question seems to be go for the single…your wallet will thank you. Hence the following fascinating tidbit: a 1981 Beech A36 Bonanza, average price new $160,000, now goes for about $200,000. A 1981 Cessna 310R II, average price new $234,000, now goes for $220,000.
For comparison purposes, a 1981 Beech Baron 58 (same horsepower) fetches about $270,000. A 1981 Piper Aztec (250 HP engines) about $157,000.
This is a strong point of the 310. The early models can deliver cruise speeds of 175 KTAS, and the later ones better than 190 if needed. Turbocharged 310s can do 225 at max cruise. Lower power settings (60 to 65 percent) result in 170 to 180 KTAS in the normally aspirated models. Engine-out performance is better than average, with normally aspirated single-engine rate of climb pegged at anywhere from 330 to 380 FPM, depending on model. Turbo single-engine performance is even more impressive: from 390 to 440 FPM-thats up in turboprop territory, and very impressive for a piston twin. Fuel burn varies with model, but figure about 31 GPH for the later versions.
The normally aspirated models are happiest in the low teens, while the turbos have service ceilings in the mid-20s. Single-engine service ceiling is about 7000 to 7500 feet, or 17,000-18,000 for the turbo.
Short-field performance is quite good on paper. Landing over a 50-foot obstacle in a 310R will consume 1790 feet, compared to a 58 Barons 2498. Takeoff over that same obstacle will take 1700 feet in the 310, while the Baron will want 2100 feet. Pilots report that real-world operations arent as good as these numbers would have you believe.
310s have a reputation for Dutch roll in the hands of new pilots, caused in part by high rotational inertia due to the extra weight of fuel at the wingtips. Experienced owners report that its easily damped with proper technique, however.
The 310 makes for a good, stable IFR platform, according to owners, with excellent cruise stability.
On approach, some power has to be carried. The 310 doesnt glide well, with big props blanking out much of the wing and flaps that produce a lot more drag than lift. Approach speeds are relatively high. Crosswind landings are simple due to good aileron and rudder authority.
Because the gear makes the airplane sit up high, new pilots are cautioned to be careful of hard landings. Combined with the relative fragility of the gear, these can be a real problem.
Up through the 310G, the series is about average for baggage space (about average means frequently having to carry some in the cabin). With the stretched cabin of the 1963 310H, more baggage space was opened up.
Along with that, weight and balance has to be watched more closely. The nose was extended a little starting with the 310K, which helps spread the load. The nacelle lockers introduced on the 310I makes loading options even better. An optional large baggage door was introduced on the 310P. It greatly eases the task of loading and arranging aft baggage.
By the 310I, cubic feet available certainly began to exceed the lifting and weight-and-balance capacity of the airplane. C-310s with lots of avionics and other options compound the loading exercise. Even without radar, some 310s with full fuel push the forward CG limit with just a pilot in front, so there are times when seating has to be assigned.
The 310 is a hefty airplane, particularly in its later variants. Gross weights eventually reached approximately 5500 pounds. Basic empty weight started at 2840 pounds for the original. It exceeds 3000 pounds by the 310C, nears 3200 in the 310P and exceeds 3600 in the 310R (turbo models are heavier still).
Payload with full fuel varies depending upon the model, equipment and fuel tank arrangement. Usable fuel capacity can be 100, 132, 142, 182 or 203 gallons-from 600 to 1218 pounds of fuel. Payload in a lightly equipped 310C with auxiliary tanks might exceed 700 pounds, while it could be as low as 400 pounds in a 310R.
Other loading and operating considerations were introduced in the later models. As maximum operating weight increased, limits such as maximum landing weight and zero fuel weight became factors.
Zero fuel weight is a payload limitation that confuses some pilots. A T310R, for example, has a zero fuel weight of 5015 pounds. Anything between that and maximum ramp weight has to be fuel. In one aircraft, maximum payload is 1059 pounds, which can handle six FAA adults (170 pounds) and 39 pounds of baggage. Figuring a maximum ramp weight of 5534 pounds, 519 pounds of fuel can be put in the main tanks.
Calculating climb to cruise altitude of 12000 feet, this allows just under three hours of flight plus reserve at 65% power. The airplane can cover roughly 500 NM in still air with max payload. With all tanks installed and full, on the other hand, it can haul a couple of people and some baggage more than 1200 NM, again at 65% power.
All of those responding to our request for feedback felt the need to point out that the 310s fuel system has gotten a bad rap, and that its not as tough to deal with as people think. The 310s system on airplanes with all the optional tanks is certainly more complicated than most, and it does have a number of idiosyncrasies not shared by other airplanes. Whether these make it hard to deal with depends on your point of view. Well leave it to the reader to decide.
It is true that 310s are not unduly prone to fuel mismanagement accidents, so despite the complexity of the system, pilots seem to have little trouble dealing with it.
It starts with nomenclature. Ask any line person where the main tanks are on a given airplane, and its likely theyll point to the wing. Not so on the 310. For some reason, Cessna decided to designate the tip tanks as the mains, and the wing tanks as the auxiliaries.
This has caused accidents. In 1987 over Delta, Utah a pilot unfamiliar with the fuel system crashed because he thought the mains were in the wings and the auxes at the tips. He ran the mains dry.
Another scenario goes like this…Pilot: Top off the mains, please. Lineperson: Yes, sir, whereupon the auxiliaries get filled to the brim. The pilot then takes off without checking, and with the fuel selectors on the main (tip) tanks as required in the POH. You can guess the rest.
Thats not the only tricky thing about the 310s fuel system. A fully equipped 310 with wing locker tanks can have up to ten fuel drain points, eight fuel pumps and a rather complex plumbing system. Theres no separate gauge for each tank, though the gauge does switch automatically to read the tank being used (but not the wing locker tanks, which have no fuel level senders). The pilot can read the tanks not being used by toggling a switch.
Fuel feeds to the engines from either the mains or the aux tanks (but not the wing locker tanks). The mains have to be run for 60 minutes if the airplane has 20-gallon aux tanks (or 90 minutes for 30-gallon aux tanks) because excess fuel is pumped back to the mains, and if there isnt room for it, it goes overboard.
The mains also are the receptacle for the contents of the wing locker tanks. The same caveat applies-there has to be room enough for the fuel, so the pilot waits until theres 180 pounds or less in the mains before transferring fuel from the locker tanks. Then the transfer pumps are run until the idiot lights go on. At that point the mains may or may not be full, depending on whether the aux tanks have been used and whether the transfer was done with room to spare in the mains.
But wait, theres more. The fuel pickup from the mains is at the rear of the tank, which means that it wont get picked up properly during descent. So, Cessna provided continuous-duty fuel pumps that move fuel from the front to the back of the tank. These pumps are wired to the landing light circuit breaker, so if the landing light shorts the mains can unport.
Its also possible for the pilot to have as much as 30 gallons of fuel that cant be used. The aux tanks feed directly to the engines, so the only pump that serves these tanks is the engine-driven one. In the event of a fuel pump or engine failure, the aux tank on that side becomes useless…no crossfeed from the aux tanks, and no transfer is possible.
Those big tip tanks were originally designed as a safety feature. The idea is to get as much of the fuel as far from the cabin as possible. In fact, one of the prototypes was landed gear-up, and the tip tanks separated just as they were designed to do, with no post-crash fire.
All those tanks can carry a great deal of fuel, making for six-hour endurance in later models. Early models can go four hours.
The other 310 system that gets a lot of attention is the landing gear. It is fairly long and spindly, and more delicate than that of some other airplanes. The fact that theres a lot of fuel hanging out on the wingtips tends to exacerbate the side loads on the gear, as well.
As mentioned above, the long gear legs make the airplane sit much higher than some pilots are used to. This makes hard landings a real possibility, and the gear just cant take that much abuse.
The gear has a number of critical components that must be attended to and properly rigged during annual inspections. If this is done properly, trouble can be avoided, but failure to treat the gear right increases the odds of failure dramatically.
According to Larry Balls The Twin Cessna Flyer, nearly half of all twin Cessna accidents and incidents are directly related to the gear, and a quarter of all accidents and incidents are related to failure of the nose gear idler bellcrank under the pilots feet.
AOPAs Air Safety Foundation further subdivides accidents and incidents into pilot-caused and machine-caused accidents. According to a report prepared for ASF by Aviation Consumer contributor Mike Busch (a 310 owner), two-thirds of the machine-caused accidents in 310s are gear-related.
Later model 310s have heavier main gear torque tubes and side brace support brackets. Cessna has a kit available to retrofit earlier airplanes.
Another aspect of the gear that deserves mention is the brakes. Early models had Goodyears, which caused some problems. Many were retrofitted with the later, and better, Clevelands. Still, the 310 is large and heavy enough that braking performance can be marginal.
A scan of Service Difficulty Reports shows, not surprisingly, that the majority of squawks arise from the landing gear. Aside from the nose gear idler bellcrank, the gear displays a variety of problems associated with torque tubes, support brackets and trunnions. Most of these problems can be traced to a lack of proper maintenance and/or hard usage.
Also high up on the list was the fuel system; not for any particular design issue, but simply because theres a lot of plumbing involved. Putting the main tanks all the way out on the wing tips means long fuel lines, and the large number of tanks, drains and pumps means a lot of fittings that can leak. Older tuna-tank models had a lot of problems with their fuel bladders, but this was dealt with through an AD.
The engines on many 310s are Continental 520s, which have a well-known propensity for case cracking. The IO-470s used on earlier airplanes are much less likely to develop cracks.
Also worth noting are exhaust-related corrosion problems, particularly on early airplanes with over-the-wing augmentor exhaust systems. Turbo models in particular have failure-prone exhaust systems, and are subject to a 50-hour visual inspection AD, 75-23-8. At the time of our last look at the 310 in 1996, the FAA was considering a stiff update to the AD that thankfully did not come to pass.
The props are subject to a couple of ADs: these include the infamous McCauley prop inspection AD (95-24-05) and 94-17-3, repetitive inspection of the prop hub grease fittings.
Other recent and notable ADs include: 98-1-8, replacement of two-piece carb venturis with one-piece units; 97-26-17, ultrasonic inspection of the crankshafts with possible replacement; 96-12-22, repetitive inspections of the engine oil filter adapters; and 96-20-7, repetitive inspection of the combustion tubes on the Janitrol cabin heater.
The most recent type-specific AD, 90-02-13, covers the main landing gear barrel inner bearings. It applies to the 310, 340 and all piston-powered 400 series Cessnas except those with trailing link main gear. It requires inspections for cracks, including magnetic particle inspection every 1,000 hours or the replacement of the bearings with an improved part.
Other miscellaneous problems: magnesium seat back brackets that fail (this has resulted in some accidents), and periodic inspection requirements on the 100-amp Prestolite alternators on 310s with deice equipment.
As with all twins for which they are available, we highly recommend the installation of vortex generators. Micro Aerodynamics makes a kit, and also offers nacelle strakes that reportedly improve stall behavior. VGs are also available from Robertson.
Theres a STOL kit available from Sierra Industries, but the cost is so high that its value is questionable. Vortex generators will give you a much greater return for one-tenth the cost.
One mod that got good reviews from owners are spoilers, which allow pilots to keep the controllers happy with rapid descents without killing the engines in the process.
Also available are engine and prop upgrades from Colemill Enterprises for the 310F through Q, which carry with them gross weight increases. A choice of IO-520 or Voyager IO-550s is offered. Owners of T310s who want engine upgrades can get them from RAM Aircraft.
Owners of twin Cessnas have their own support organization in the form of The Twin Cessna Flyer, headed by Larry Ball. Membership gets you a newsletter and the right to attend well-worthwhile seminars on operations. Call (219) 749-2520. The general Cessna group of choice is the Cessna Pilots Association (www.cessna.org, (805) 922-2580).
I have owned three turbocharged Cessna 310s. The latest is a 1976 T-310, purchased new. I strongly recommend the turbocharged models. If you need to get above weather or take advantage of winds at altitude, this plane still climbs well at 18- to 20000 feet, while the normally aspirated 310 runs out of steam at about 10- to 12000. Treated properly, the turbos will go beyond engine TBO. Preheating on cold days, a cool climb speed and slow descent along with 50-hour oil and filter changes will save downtime and money.
The one problem is that Cessna advertises the 310 as a six-place airplane. The R models have a zero-fuel weight limitation, i.e. the amount of weight you can put in the cabin; it has nothing to do with total load. Surprisingly, very few people know what zero-fuel weight is. The 1976 T-310 with most options can only hold four normal-sized passengers. Robertson Performance Systems (800 430-1585) provides a vortex generator kit which not only decreases the Vmc by 10 knots but it also increases the zero-fuel weight by 385 pounds and the gross takeoff weight by 185 pounds. This should be a mandatory investment for all R owners.
I am a professional aircraft broker who specializes in Cessna twins. In the past three years I have focused on 310s and 340s, generally listing six to eight 310s and selling two or three a month. The typical buyer is coming out of a high performance single, and the 310 is to be their first twin. Many callers are desperate for 310 information, with questions about the exhaust, landing gear, engine models and fuel system. To support buyers I offer a 310 information package [Ed. note: Mr. Temple sent us one of these packets. Much of it consists of Cessna Dealer Sales Manual material originally penned by him, with some additional supporting articles. Overall, a good package of background information.]
Mistakes in purchasing a 310 can be huge. This is no Skyhawk. The most common mistakes are failure to conduct a prepurchase inspection or evaluation flight. All too often, the pilots or mechanics doing the prepurchase are simply not qualified, being unfamiliar with the details of the 310s systems and maintenance requirements. The attitude that its just another airplane can cost the buyer dearly. My advice to 310 buyers: Treat the acquisition process seriously. Commit to excellent maintenance and pilot proficiency and youll enjoy one of general aviations great airplanes.
I have owned a 1968 310N for the past four yeas. I am an ATP with about 1200 hours in light twins. Despite its recent appreciation, I believe the 310 remains one of the best values on the used aircraft market. I bought the airplane for $48000 and if I can believe my insurance agent, it would sell today for around $70000.
I fly the aircraft about 100 hours per year and total hourly expenses have been $178. Doubling the flying time would lower the hourly expense to about $140. I can count on one hand the significant expenditures over the past four years: autopilot overhaul ($2500), starter adapter replacement, both engines ($700 each), three-blade prop overhaul including boots ($3500 each). Annuals have averaged $1500-2000, which may seem low-but not unrealistic if you look for an airplane that has been flown and maintained in a consistent manner. Parts availability has never been a problem.
A recurring minor squawk is minor oil leakage from the rocker covers; a problem that has lessened since replacing the cork gaskets with silicone. I have avoided the two big 310 bugaboos: gear problems and exhaust-related corrosion. About every six hours I am on my back under the airplane cleaning the areas in the line of fire aft of the exhaust augmentors. Ive also followed the advice of many to keep the gear properly rigged and lubricated. As for advice, I strongly recommend membership in the Twin Cessna Flyer organization. They are truly dedicated to spreading information vital to the preservation of the fleet.
My airplane is an honest six-seater with a useful load of 1600 pounds. We typically remove the aft two seats (very easy to do), leaving a cavernous baggage area along with the two wing lockers. Each of the latter can accommodate two sets of golf clubs. I flight plan for 175 knots and firmly believe in the highest recommended manifold pressure and lowest recommended RPM settings for the desired percentage of power. Noise level, engine wear, and fuel flow are all reduced. The airplane handles big and is a stable IFR platform. The reputation for Dutch roll and yaw problems is, in my opinion, undeserved. With a little experience you learn to stay light on the ailerons and ride both rudder pedals in turbulence to smooth any untoward tendencies. It is a challenge to grease the landings, but I make every effort to protect that long, spindly gear. I have been taught by 310 drivers with much more experience to set the nose down lightly and avoid high-speed turns that induce side loads on the gear components.
A 310 might not be the most expensive (yet) or high-tech airplane you can own, but in my mind flying one is like cruising in one of Detroits vintage big-block V8s: Shes easy to repair, sounds mean, goes fast, and flat-out looks good.
I acquired a 1975 Cessna turbo 310 R model in 1991, and have never regretted it. Shortly after I purchased my 310, I put on vortex generators, which are a must with this airplane. VMC and stall speeds are very close, and the low speed handling characteristics are very benign as a result. Smooth landings are the rule instead of the exception. I do not believe they cost more than a couple of knots, and should be installed on all 310s.
About two years ago I installed Power-Pac Spoilers, and likewise have never regretted it. Center frequently leaves me high and then assumes that I can make a turbo-prop/jet type descent. I knew that I would be replacing the engines, and decided that the spoilers would help assure making it to TBO. The spoilers can be deployed at any speed, and the POH permits using 15 degrees of flaps below 160 knots. This combination permits me to leave the power at 55% (my typical cruise setting) and still descend at 700 to 1000 fpm without exceeding 155 knots. Also using spoilers to produce a drop in airspeed to permit landing gear operation is a nice option to have when too high or hot for normal gradual speed reductions or while descending. I recommend them.
Last year my factory gold medallion remans were about 50 hours past TBO when the latest McCauley prop AD for this model left me with no realistic choice but to replace both props. I elected to have this done at RAM in Waco, Texas, because of their reputation, which is deserved. Although my remans started immediately, ran smoothly, and used very little oil (about 1 qt. per 15 hours), the RAM Series I option got me two new props, two RAM converted TSIO 520 EB engines, new hoses, and a Shadin fuel totalizer at a price comparable to what many good shops quote for two reman engine replacements. The RAM engines have settled in and have about 200 hours on them. I was pleased to observe about 8 to 10 knots increased speed at comparable power settings, a greater rate of climb, and stabilized oil consumption of about 1 quart per 20 hours. I have an Insight Gemini 1200 Graphic Engine Monitor, and the cylinder head temperatures never exceed 350 degrees on the hottest day, leanest mixture, and highest settings used. Of course I dont push the engines to the maximum, and find that I can cruise at 25.5 to 26 inches, 2200 RPM, with a fuel flow at altitudes in the low teens of about 13.5 to 14 GPH and still keep the EGTs below 1520 degrees. The Insight GEM is a valuable addition and permits more accurate leaning by far than a single probe system.
The 310 offers more payload and cabin room than its competitors, and is more stable in turbulence, but at the cost of a heavier control feel than a baron. I believe the 310 is easier to fly IFR, particularly in bumpy conditions, than a Baron even though the Baron may please a pilot on a VFR day with a lighter control feel. The Barons cabin seating and additional door is a plus that I wish the 310 could match, but six passengers can ride in my 310 much more comfortably than in a Baron or a Seneca with club seating. An Aztec is a fine plane, but it is slower and the Aztec, Seneca, and Baron all have smaller, less comfortable interiors for people such as myself-I am 62″, and probably need to read a good diet book instead of the aviation magazines I prefer.
It is important to find a good A&P to help care for your 310. The flap and engine exhaust configuration makes corrosion a problem which must be monitored continuously and treated when necessary. Also the landing gear must be adjusted carefully and properly to insure smooth and dependable operation.The 310s fuel system has been unfairly criticized in the past. It is straightforward: Mains (which are the tip tanks), Auxiliary, Crossfeed, and Off. The pilot must remember to fly about 1 hour of fuel out of the mains before switching to aux. tanks because the engine driven fuel pumps feed more fuel to the engines than they can use except at the highest power settings. The excess is pumped back to the mains and overboard if there isnt room. I find that burning about 20 gal. from the aux. tanks will result in about 8 gal. being added back to the mains.
It is easy to load the airplane, and roughly the same luggage and people which will fit in a full size Chrysler Minivan will fit in the 310, although fuel must be sacrificed to avoid departing over gross. I have never noticed any real difference in flight characteristics regardless of loads, other than the to-be-expected slower rate of climb at gross vs. at light weights.
Occasionally I consider trading up to a 414 or a 421, but the marginal benefits of the air-stair door and pressurization compared with the tremendous cost differential dont make them worth it. In my opinion, the 310 is the ideal light twin, with reasonable single engine performance, safety, looks, comfort, and range.
-Craig A. Van Matre