New general aviation aircraft are as iconic as Cessnas 310. Whether because of its aggressive ramp presence, its supporting role in a television adventure series or its suitability for a wide range of missions, the 310 is what many non-pilots recall when piston twins come up in conversation. Its arguably the first “modern” light twin and certainly a classic. While the 310 is all of those things, its also a complicated machine, production of which ended almost 30 years ago. The tall landing gear might be thought of as delicate and its systems demanding, both to maintain and operate. But it still offers substantial transportation value, and the many different variants that were built as the model evolved means it shouldnt be hard to find the right one for your mission.
New general aviation aircraft are as iconic as Cessnas 310. Whether because of its aggressive ramp presence, its supporting role in a television adventure series or its suitability for a wide range of missions, the 310 is what many non-pilots recall when piston twins come up in conversation. Its arguably the first “modern” light twin and certainly a classic.
While the 310 is all of those things, its also a complicated
machine, production of which ended almost 30 years ago. The tall landing gear might be thought of as delicate and its systems demanding, both to maintain and operate. But it still offers substantial transportation value, and the many different variants that were built as the model evolved means it shouldnt be hard to find the right one for your mission.
Cessna introduced the 310 in 1954, finding a niche between Pipers original, relatively underpowered PA-23 Apache, introduced a year earlier, and Beechs Twin Bonanza, which went out of production a few years later. It competed most directly against the Aero Commander 520, but that model was discontinued the same year. The 310 was Cessnas first all-metal, modern twin-replacing the pre-war T-50/AT-17 “Bamboo Bomber”-and was clearly focused on business transportation. It foreshadowed the companys subsequent products and helped usher in its future growth.
And its featured presence in the 1950/60s television drama, “Sky King,” didnt hurt anything. Its namesake hero, played by Kirby Grant, upgraded to a 310B shortly after that model became available. Named “Songbird,” the airplane (several were actually used during the shows production) was as much a star of the series as its actors, perhaps becoming the main reason for the shows popularity on Saturday mornings throughout the 1960s, and even today on DVD.
Cessnas aggressive pursuit of the business market manifested itself in not only the 310s looks, but also its refinement: Many production years saw a new model designation. Cessna brought out the 310B in 1958, the 310C in 1959 and the 130D in 1960, eventually getting to the 310R in 1975 (with a few gaps) before ending production in 1981.
The first 310s came with 240 HP Continental O-470-B engines. From the beginning, a sleek, powerful appearance was a design goal, with tight cowlings and streamlining at the nose and tip tanks (at least by the standards of the day). Split wing flaps eliminating the need for external brackets or tracks and their drag. Distinguishing features of the early models are multiple aft side windows, a straight tail and non-canted “tuna tanks,” named for their shape.
When the 310B came out in 1958, it brought with it a 100-pound boost in gross weight. For the next years 310C, an engine change and gross weight bump occurred with the fuel-injected, 260-HP Continental IO-470D. The TBO was 1500 hours, same as with the earlier powerplants. For the 1960 310D, Cessna swept the tail, as it was doing across its fleet.
The next significant change was in 1962, with the 310G. Cessna introduced canted “Stabila-Tip” tanks, said to be more aerodynamically efficient than the old design. The original non-canted and bladder-equipped tip tanks also had a fuel-pickup problem; an airworthiness directive mandated a hefty increase in unusable fuel. This 310, with bladderless all-metal canted tanks, swept fin and short nose, is one of the most attractive light twins ever built.
Cessna didnt stop there. Cabin size was increased, along with gross weight. What started as a five-place twin became a six-placer with 1963s 310H. By next years 310I, wing lockers and auxiliary tanks became options, as did three-bladed props. One significant difference was the switch from the corrosion-prone overwing exhaust design to an improved underwing arrangement on the 310I. An engine change accompanied the modifications, to the IO-470-U, still of 260 HP and still with a 1500-hour TBO. Another engine change, to the IO-470-V, occurred in 1966 (310K), along with extended, one-piece aft windows on each fuselage side.
In 1969, Cessna consolidated its model line, offering a turbocharged variant of the 310 alongside the normally aspirated 310P and droppng the 320. The T310P came with 285 HP Continental TSIO-520-B engines (1400-hour TBO), three-blade props and a 5400-pound gross weight, compared to the normally aspirated 310Ps 260-HP IO-470V Continentals, optional three-blade props and 5200-pound gross.
From 1970-74, Cessna stuck with the 310Q and T310Q, despite bumping gross weight on the 1972 T310Q to 5500 pounds (5300 for the non-turbo version) and changing to wrap-around “Omnivision” windows by adding a pair of small panes at the top of the aft cabin.
In1975, the 310R II and T310R II sported one of the biggest changes since the types tail was swept: an extended nose. The proboscis grew 32 inches, housing a sizable baggage compartment. The normally aspirated version also got 285 HP Continental IO-520-M engines (1700-hour TBO) and another 200 pounds were added to the gross weight-bringing it to 5500 for both the turbo and non-turbo versions-along with improved landing gear.
The 310R marked the airplanes final configuration, which continued until the line was closed down in 1981. All told, some 5700 copies of the 310 were manufactured, not including its various military versions. Unsurprisingly, the 310Rs are the most numerous, followed closely by the 310Q, a result of sticking with one model for several years.
An old saying about piston twins-they have two engines because they need two engines-refers to whats necessary to obtain their performance and their handling when one engine fails. Both are strong points of the 310, especially the turbocharged versions. Early models feature high-speed cruise in the neighborhood of 175 knots while later ones will top out at around 190. The turbod models can present 225 knots at all-out max cruise, but the fuel burn will be breathtaking. Reduced power settings get 175 knots on later, non-turbocharged models.
Engine-out performance is better than average, with normally aspirated 310s achieving a single-engine service ceiling of just under 7000 feet to 7500 feet, depending on model. Turbos see SE service ceilings of 17,000-18,000 feet climb rates from around 330 to 440 FPM, depending on model and
Figure cruise fuel between 20 GPH for an early, non-turbocharged 310 at economy settings up to 35 or more when flogging a big-bore turbo. Join the Church of the Lean-of-Peak and shave that down to around 28 GPH. Airspeed suffers, of course. Double those numbers, at least at the low end, for takeoff and initial climb.
Speaking of climb, the non-turbocharged models do OK in the low teens and turbo models in the high teens, although their service ceilings can be as high as 28,200 feet (T310Q). Theyre happiest in the mid-to-high teens: One owner told us, “At FL250 [the T310R] performs like a very expensive Skylane.”
Book short-field performance is surprisingly good, especially for the airplanes weight: Landing over a 50-foot obstacle in a 310R will consume 1790 feet, compared to a Model 58 Barons 2498. Taking off over that same obstacle will require 1700 feet in the 310, while a Baron needs 2100 feet. Perhaps unsurprisingly, pilots and owners treat the book numbers with a grain of salt, reporting poorer real-world numbers.
Once airborne, however, 310s provide an extremely stable platform. The only fly in the ointment is the types tendency to Dutch roll, especially in turbulence and in an inexperienced pilots hands, caused in part by the high rotational inertia of fuel in the tip tanks. Experienced owners tell us Dutch rolls are easily dampened with proper technique.
As clean and powerful as the 310 appears, it can get draggy on approach. Relatively large props blank out much of the wing and split flaps produce much more drag than lift. This can be a “good thing,” since the clean airframe can be difficult to slow down until the first notch of flaps is deployed.
Early models came with an approach-flap extension speed of 140 knots, with full deployment available at 120. The 310K bumped the approach-flap speed to 155 knots or so. Subsequent models through early 310Rs are placarded for 160 knots approach-flap extension and 140 knots for full flaps. Drop two knots from those numbers for late 310Rs.
For the early models, up through the 310G, interior space is about average for baggage, which means having to stow some items under and between seats, or at passengers knees. Beginning with the stretched cabin of the 1963 310H, more baggage space was opened up. Wing lockers, whether installed at the factory beginning with the 310I or in the field, can help, as does the 310Rs nose baggage compartment. Removing the aft row from the six-seat airplanes-quick-disconnect seats were optional on later models-can help, too.
Weight and balance must be watched closely. The first nose extension-a small one-occurred with the 310K. But by the 310I, cubic feet available began to exceed the airplanes weight-lifting capability. No longer could a pilot “cube-out” a 310 before overgrossing it and it could be loaded out of forward CG. Adding lots of avionics and other options to the typical model only compounds the problem by upping the empty weight. One solution is STCd vortex generators that can boost max gross by 100 pounds or more. That said, you can find late-model 310s with close to 2000 pounds of useful load.
The 310s full-fuel payload varies depending upon the model, equipment and fuel tank arrangement. Total usable fuel capacity can be 100, 132, 142, 183 or 203 gallons-from 600 to 1218 pounds of fuel. Full-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, like maximum landing weight and zero fuel weight, were introduced with later models.
While were talking about payload is a good time to point out the 310s fuel system on airplanes with all the optional tanks is more complicated than most. It also has a number of idiosyncrasies.
The complications start with nomenclature. Ask a line person where the main tanks are on a given airplane, and theyll likely point to the wing. With the 310, theyd be wrong. Early models only came with the 50-gallon-per-side tip tanks. As there were no tanks in the wings at all, those were main tanks. As time went on, horsepower increased and so did demands for fuel. First came 20-gallon wing-mounted bladders, followed by an additional 11.5-gallon bladder, for 31.5 gallons in each wing. Then came 20-gallon tanks in the wing lockers. In a 310R, as much as 203 gallons can be available.
If the pilot to have the mains topped and takes off without checking the fuel actually went into the right spot … you can guess what might come next.
Thats not the only tricky thing about the 310s fuel system. A fully-equipped 310 with wing locker tanks can have up to 10 fuel drain points and eight fuel pumps. Connecting all this is a relatively complex (when compared to other piston twins) 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 in use by toggling a switch. Confused yet?
Fuel feeds to the engines from either the mains or the aux tanks (but not from the wing locker tanks, if installed). Presuming the mains were full at takeoff, at least an hours fuel has to be burned off if the airplane has 20-gallon aux tanks (90 minutes for 30-gallon aux tanks) because excess fuel is pumped back to the mains. If there isnt room for it in the mains, it goes overboard.
The mains also are the receptacle for the contents of the wing locker tanks and there has to be room for transferred fuel. The pilot should wait until theres 180 pounds or less in the mains before pumping from the locker tanks.
The aux tanks feed directly to their respective engine, and the only pump serving them is engine-driven. In the event that pump or engine fails, the aux tank on that side could hold 30 gallons of deadweight; theres no crossfeed from the aux tanks to the opposite engine.
Hopefully youll never discover this factoid the hard way, but those big tip tanks were originally designed as a safety feature, to get fuel as far from the cabin as possible. Early on, a prototype landed gear-up and the tip tanks separated just as they were designed to do, with no post-crash fire.
The good news? The 310 is not unduly prone to fuel mismanagement accidents, so despite the systems apparent complexity, pilots seem to have little trouble dealing with it. All those tanks can carry a great deal of fuel making six- or seven-hour endurance possible in later models. Early models go for four to five.
The other 310 system usually getting lots of attention is the landing gear. Its relatively tall and, as a result, often thought to be more delicate than with other airplanes. Also, all that fuel hanging out on the wingtips tends to create high side loads.
As with so many other general-aviation landing-gear systems, one of the keys is finding a technician familiar with and knowledgeable about it. The 310s gear system includes a number of components requiring proper rigging during regular inspections. Done properly, trouble can be avoided, but failure to treat the gear with respect increases the odds of failure dramatically.
People with keen familiarity with the 310 tell us of three weak points in the gear system. The nosegear idler bellcrank, located under the pilots feet, is probably the worst since its failure-always at retraction, and always loudly-means two prop and two engine teardowns.
The main-gear torque tubes and inner landing-gear door actuator bellcrank are the other two. If the torque tube fails, it does so during the retraction sequence, leaving the associated main gear down and locked. Extend the rest of the gear and land. If the inner landing gear door actuator bellcrank fails, the inner gear door hangs in the breeze.
According to the late Larry Ball, nearly half of all twin Cessna accidents and incidents were directly related to the gear, and a quarter of them to failure of the nose gear idler bellcrank under the pilots feet. Later model 310s have heavier main gear torque tubes and side brace support brackets. Cessna has a kit available to retrofit earlier airplanes.
Another gear issue that deserves mention is the brakes. Early models had problematic Goodyears. Many were retrofitted with the later, and better, Clevelands. Still, the 310 is large and heavy enough that brake performance can be marginal.
A scan of FAA Service Difficulty Reports going back five years dredged up numerous entries, underscoring the 310 fleets age. Items garnering our attention included a cracked rear mount bulkhead in a right main (tip) fuel tank, sheared horizontal stabilizer attach bolts and a brake disc cracked where its manufacturers name was stamped. But the single system receiving the most entries was, by far, the landing gear.
For example, a Canadian operator reported finding cracks in a right main landing gear extension/retraction torque tube at two places, while another airplane maintained by an Australian facility determined the left and right main landing gear downlocks were in an unsafe condition. Meanwhile, a U.S. operator reported a nose gear extension failure and found a broken bellcrank was the culprit.
For us, these events highlight the need for a 310 expert to conduct any pre-purchase inspection and for a shop with intimate familiarity to do your ongoing maintenance. That said, most retractable-gear airplanes originally designed in the 1950s likely will require similar attention and expertise.
As far as Airworthiness Directives are concerned, the most recent type-specific one is AD 2000-01-16, targeting turbocharged T310P/Q/R models (as well as other turbod twin Cessnas) for detailed, repetitive inspections of the exhaust system. The AD, which replaces AD 75-23-05 R5, is designed to detect and correct cracks and corrosion in the exhaust system, which could lead to an uncontrollable in-flight fire, and was the subject of extensive negotiation among operators and the FAA during the late 1990s. Since it became effective, there have no further exhaust-related accidents in these airplanes, according to those involved with its development.
Another one is AD 90-02-13, which 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 and requires inspections for cracks, including magnetic particle inspection, every 1000 hours or the replacement of the bearings with an improved part.
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 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.
Dollars and Sense
When considering an airplane in production for almost 30 years, and with so many variants, it shouldnt come as a surprise 310 prices vary widely. An early “straight” 310 averages only $30,000 or so in todays market, rising to $155,000 for a turbocharged T310R, per the Aircraft Bluebook Price Digest. Between those extremes, theres no real “spike.” Instead, each successive model sees a modest increment in price. The biggest single gap is between the 310Q and 310R-the 1974 310Q averages around $100,000, while the 1975 310R goes for $115,000. The gap for the turbo models is similar.
With those prices, theres no question the 310 can be a good bargain, although long-time T310R owner Mike Busch tells us, “It is a violation of the FARs to use the words twin and bargain in the same sentence.” It offers twin-engine performance and security, a large cabin and substantial loading flexibility. But those benefits must be balanced against the increased risk of single-engine operations, especially when low and slow. That debates been going on forever, and we wont resolve it here. The same cam be said about the extra expense in engine maintenance, fuel bills, and insurance premiums. Also expect higher fees for annual inspections and even hangaring, and transient parking, when compared to a high-performance single.
The market seems to have an answer for all this: Singles retain more of their value year over year, even during the current downturn. Compare a 1981 Beech A36 Bonanza, which carried an average new price of $160,000. It now goes for around $120,000. A 1981 Cessna 310R II, average price new $234,000, now goes for $145,000. Other twins show similar results.
Mods, Type Clubs
Modifications for the various 310 models run the gamut, from the usual avionics upgrades to improved cabin heaters, auxiliary fuel tanks in the nacelles and cabin, and electrically de-iced props. Other mods include vortex generators (VGs), something we highly recommend for all twins when available. They often come with gross-weight increases, as they can reduce critical speeds. Check Micro Aerodynamics (www.microaero.com, 800-677-2370). PowerPac Spoilers (www.powerpacspoilers.com, 800-544-0169), as their name implies, offers a spoiler kit for the 310R; it requires the Micro Aerodynamics VG kit.
Engine and prop upgrades are available from Colemill Enterprises (www.colemill.com, 615-226-4256) for the 310F through R, and may come with gross-weight increases. A choice of IO-520s or IO-550s is offered; prices and performance gains depend on aircraft model and options selected. Also, RAM Aircraft (www.ramaircraft.com, 254-752-8381) offers engine upgrades for the 310R, but mainly focuses on upgrading powerplants for the turbocharged 310 models.
One of the popular mods, at least for early 310s, was developed by Riley Aircraft Corp., which re-engined 470-powered 310s with a pair of Lycoming IO-540s. The Riley Rocket conversion used normally aspirated engines, with the Riley Turbostream adding a pair of Rajay blowers with manual wastegates. The conversions turned early 310s into rocket ships, but the company has long since gone out of business. Keep that in mind if considering a Riley 310.
All piston-powered twin Cessnas have their own support organization in the form of The Twin Cessna Flyer (www.twincessna.org, 704-910-1790), headed by Bob Thomason. Originally named 310 Owners of America, membership gets you a newsletter and the right to attend worthwhile seminars on operations and maintenance. Overall, however, the Cessna type club of choice would be the Cessna Pilots Association (www.cessna.org, 805-922-2580), which serves all piston-powered Cessna owners with a monthly magazine and detailed, model-specific support.
Ive owned a 1956 Cessna 310 for almost 40 years, first with some great partners and then for 30 years as sole owner. It has 50-gallon, straight, “tuna” tanks and a three-place bench seat in the back. Our family has used it for some wonderful vacations around the country, as well as to Canada, the Bahamas and the Virgin Islands. With grown children, more of our trips are with two passengers and the planes expensive “drinking habit” is challenging to rationalize.
The early 310s are easier to fly than many high-performance singles. Fuel management is stone simple: a fuel tank for each engine, avoiding the need for switching tanks, unless cross-feeding. There are no cowl flaps and no RPM ranges to avoid. The flaps and gear are electric. The landing gear design is a marvel of simplicity.
The plane has great climb and cruise performance, with a rated gross weight of 4600 pounds. The weight of the fuel in the tip tanks seems to make the plane more stable in turbulence. It also causes some pilots new to the 310 to overshoot bank corrections on landing approaches, but that is soon solved. The plane has three-axis trim and is very stable in pitch. It does not have the same stability in roll. Without an autopilot, copying a clearance in IMC can sometimes result in unusual attitude recovery practice!
The only design complaint I have is with maintenance. Because of limited clearance under the cowling, removal of an exhaust stack (as needed to replace a cylinder) requires lifting the engine off its mounts.
Buyers of early 310s should pay particular attention to the augmenter tube area for corrosion. Also, the nose gear and its actuating mechanism are fairly long and sensitive to excessive landing sideloads or manhandling by tow vehicles-I never let my plane be towed.
An owner should have a copy of the Cessna parts manual, a marvel of beautiful drawings and detailed information. There is considerable variation by serial number within a model and the parts manual has that information. Parts availability is still fairly good, with many parts common to multiple models.
I currently own a 1975 310R with a Colemill conversion. It is undoubtedly one of the best performers in the light twin class. I have owned quite a few twins, but none have the overall performance of the Colemill 310. At gross weight with the OAT at 25 degrees C, initial climb will be around 1200 FPM at 150 knots. In the winter, its much better. Single engine performance is also much better with the conversion.
At cruise, normally between 9000 and 10,000 feet, full throttle produces 21 inches MP. With the props at 2300 RPM, the TAS will be between 190 and 195 knots on an average of 30 GPH total.
My flying does not require [the fifth and sixth] seats which leaves a large area for any cargo. Along with the extended nose baggage and the two wing lockers, there has never been a trip that required me to leave anything behind. The 310R is also a few inches wider than the Barons, making longer trips more relaxing for pilots and passengers.
The 310 is an easy plane to fly and is stable for instrument flying. Some have complained the tip tanks are a little hard to get used to but I have not experienced any problems. It does build up some speed on the descent so a little forward planning is needed to get down without cooling the engines. I have VGs on my plane and would highly recommend them to all. A great safety feature.
Annuals run between $3500 and $6500 depending on what needs to be done. The important thing to have someone familiar with 310s do the annual. Be sure that the gear is maintained in accordance with the manual. If not, I can tell you that you may pay for it later.
For the past nine years I have owned a 1955 Cessna 310, the 42nd to come off the production line. I absolutely love it. I consistently get 22 GPH or better, averaging 175 knots. With full fuel (100 gallons) I still have over 900 pounds of useful load. I do not have aux tanks, but dont feel I need them. After 3.5 hours, Im ready to stop and take a break anyway. And since I only have the tip tanks, I never have to worry about having the selector switched over to the right tanks in fuel-critical situations.
I have repainted her, put in a new leather interior and redone the panel with a GNS 430W, Gemini 1200 engine monitor, ring-lit gauges and other upgrades. I have also reinforced the landing gear structure with the 414 side brace kit.
There are so many misperceptions about these early 310s. For instance, the original over-the-wing augmenter exhaust pipe system was one of the best. The exhaust was blown out these straight pipes cleanly and easily with little chance of the corrosive gases getting hung up anywhere. And, with modern noise-canceling headsets, the roar of these straight pipes (which sounds like bunch of old Harleys) is no longer a problem.
Mill Valley, California
I have been the proud owner of a 1966 Cessna 310K since 1976, and traveled from Oregon to Maine and to the Bahamas and Cayman Islands. There have been numerous times that certain places were not accessible within a time frame had it not been for this plane.
It is right at home both at large airports and 2000-foot grass strips. I am amazed at the overall utility it provides. Time schedules within a 600-mile radius are simple and much more convenient than any commercial airline. The one fact that I think I like best is that my luggage always arrives at the same time I do and at the same place.
Of course, as time passes, parts are a little more difficult to come by and more expensive. My membership in the Twin Cessna Flyer for the past 25 years has been a lifesaver, both for finding parts and getting a decent price on them.
I cant think of any other business or pleasure tool that means more to me. And besides, its fun.
Leonard E. Yokum, Jr.,