SKY KING'S FAVORITE
Is the Cessna 310 Today's Best Twin Engine Used Plane Buy?
By Gene Smith - Air Progress Magazine - June 1987 N13DP The tower cleared N13DP and we rolled easily onto runway 13 as I slid the twin throttles slightly forward. Planting the nose wheel on the white center line, I held the brakes briefly and ran the 260 hp Continental IO-470s up past 20 inches, then got off the binders and let the airplane have her head. She leaped forward, and hardly had the throttles hit the stop than we were passing through 95 mph indicated as I led in a little back pressure, lifting the nose. 
She hopped off at 105, zipped almost instantly through the 111 mph blue line (Vyse), and the electric gear motor whined busily as the rollers began their 15-second journey into the belly. We hurtled skyward at better than 1700 fpm, indicating 140 mph. We weren't pushing things, but from the beginning of the roll to lift-off couldn't have been more than 1000 feet, into a quartering 7-knot wind. It was more than twenty years since I first flew an airplane very similar to this; more than dozen years since I'd even been in a 310. N13DP was busy telling me how much I'd missed. Frankly, I'd forgotten how much fun it was! The very first twin I ever flew, in fact, was a '56 model C-310, N210T. That was 22 September 1962, and the dual session lasted 90 minutes. In a sense, I never got over it. I can close my eyes even today and call up the sense of speed, of harnessed power; recall the introduction to single-engine work, and the struggles to trim the airplane out as Roy Courdin brought the right engine back to zero thrust, the further struggles to retrim when he restored normal power. I can also remember the airplane's odd inclination to skate sideways coming down final with the gear and flaps down, and how the flywheel of the big tip tanks exaggerated any novice over-controlling tendencies. Not to mention the way you kept the last few inches of power on until the mains were only a whisker away from the paving; then chopped the throttles and flared. If not, the 310 didn't land—it arrived, with a tooth-rattling thump of the stiff gear. In a word, the early 310 did not suffer fools gladly. She still doesn't. That's one of the things I like about her. But I like her eagerness, too, her sprightly yet solid feel, her docile stall and superb single-engine control. I like her speed, her cabin. I like nearly everything about her. She's a hell of an airplane! And these days, she's probably the biggest transportation bargain around: An IFR-capable 200 mph-plus airplane, often with autopilot and oxygen, that can be bought licensed and flying for less than the price of a luxury car. Cessna built 5242 of these airplanes between 1954 and 1982, N13DP and 289 of her sisters in 1960. They also produced 575 of the closely-related turbocharged 320 Skyknights between 1961 and 1969. After that, they simply sold 'Turbo 310s" as well as the garden variety model. And, beginning in 1971, the 340 — a 310 with a new pressurized walk-through fuselage. From the first, this sporty-looking "Businessliner," as Cessna dubbed it initially, was intended more as a medium than a light twin. It was aimed at the same market Beech sought with the Baron, rather than at the buyers of Piper's Apache and later Twin Comanche. The first ones had 240 hp. carbureted Continental O-470s, each with twin exhaust stacks exiting over the top of the wing just about even with the rear seat passengers' ears and grossed about 4,500 pounds, as I recall, but this quickly went to 4,600. Only 14 were built in 1954, but the reception was such that 228 were built in 1955, and production was full speed ahead then clear through the 1970s. With 100 gallons of gas and a typical payload of 800 pounds, a 1955 or '56 model 310 will carry four FAA-standard people and 120 pounds of bags at 200 mph three hours plus reserve. Not only that, it will carry them in great style. The airplane's tapered 36-foot, 11-inch wing and 175 square feet of wing area give it a wing loading of only 26.3 pounds per square foot, while he power loading is just 9.58 pounds per horsepower. This translates into an 800-foot takeoff ground run (1405 feet over 50 feet), an initial maximum climb rate of 1,700 fpm and a service ceiling of just over 20,000 feet. While not exactly an Apache in the short field department, the early 310 will land over a 50-foot obstacle in 1720 feet and in 620 feet of ground roll. This is good enough to get in and out of any place you have any business taking five people, presuming both engines stay hitched. If they don't, you could have some problems— but nothing insoluble. The minimum control speed is 80 mph, best single-engine climb speed 105. Best single-engine climb should be around 300 Fpm, and single-engine service ceiling 7500 feet. The trick, of course, is to get the airplane cleaned up and flying before you run out of air speed, altitude and ideas simultaneously. I recall riding in the back seat of a '55 model (along with two other men) while a flying buddy took his multi-engine check ride with an examiner at Joplin, Missouri. This was back in the days when training and check rides) were given under conditions as realistic as everyone could make them, so the examiner cut the mixture on the right engine about 100 feet in the air, just as the gear was coming up. The airplane began to settle, and until the wheels thumped into the wells there seemed some doubt as to whether we would be able to avoid de-roofing a hangar at the far end of the field. Finally the owner/pilot got the situation under control. We began to breathe again. Sweat stood out on his temples. His neck was beet red. He restarted the right engine, climbed to pattern altitude, swung around and landed. He taxied up to the FBO where the examiner worked, opened the door, and said firmly, "Get out!" The examiner got. We got out, too. Then the owner went to Oklahoma, and hired another, more cautious examiner. But the point is, given any kind of chance, the Cessna 310 is a safe airplane that does its best to take care of its pilots. Indeed, Cessna demonstration pilots used to regularly rack 310s into alternating 60-degree left and right banks with one engine caged — and encouraged humble aviation writers to do the same. At speeds comfortably above Vmc, you understand. . .  We weren't doing any of that today. First, my wife was in the back, and she doesn't take kindly to such shenanigans. Second, N13DP isn't a factory demonstrator, but a well-worn 5500 hours TTAF) Part 135 veteran used by Mid-America Aviation, owner Jim Bolden for charter work. Third, J. U. Ricks just wasn't the type. Ricks, the current named insured charter pilot, is mother of those retired USAF types, a veteran C-130 pilot of worldwide experience who guarded the power levers as a leprechaun guards his treasure—as so many of them do. A tall man with a wide smile, Ricks does twin charter flying for several FBOs in the district and retains much of the by-the-numbers aircraft-commander attitude ingrained by decades in uniform. He flies N13DP fairly regularly; 110 hours in the last six months. So we turned right and cruise-climbed at 140 I AS and 800 fpm (half its climb capability) to 4,500 feet for what was clearly going to be more of a familiarization flight, a renewal of old acquaintances, than a full-fledged exploration of performance parameters. By 1,960, the inevitable weight increases had begun to affect the 310. N13DP weighed 3460 pounds empty and grossed 4830, giving it a useful load of 1,370 pounds—of which the 130 gallons of fuel (total, including two 15-gallon auxiliary fee; tanks in the wings) accounted for 780 pounds, leaving a payload allowance of 590 pounds. We were probably 200 pounds under that, this day. On the other hand, the airplane was powered by twin 260-horse I0-470s, giving it the excellent power-to-weight ratio of 9.29 Ibs/hp, It would be a long time before the airplane did any better! By '71, allowable gross had climbed to 5,300 pounds—but power was still a pair of the faithful 260 hp IO-470s. Leveling at a density altitude of 5,000 feet, I set up 24 square, which should've been just about 75 percent power on 26.67 gph and yielding a true airspeed of 214- 215 (I know, everybody's pushing knots these days, but the airplane's calibrated in mph, everybody understands mph, so bear with me). 310 takes a while to stabilize. It took N13DP about three minutes, by which time we were indicating 191 for a computed true of 201 mph on 28 gph — the apparent cumulative result of the years in harness. Or, perhaps, indicator error, since we made no effort to time it across the section lines. Backing off to 23 inches and 2300 rpm, I indicated 181 for a TAS of 196 mph—6/10 under book, on what the flowmeter said was 24 gph, while the book insisted it should be 24.6. Slowing down and banking rapidly left and right to clear the area, I pulled off the power and hauled back easily on the control column. Somewhere back there, that 17-foot-wide elevator went to work, and by the time the airplane quit flying, we were indicating 68 mph. The stall was as gentle as I remembered, and preceded by enough shuddering, buffeting and general complaining to wake even the most bone-headed pilot. Throwing out the gear and full 35° flaps. I got the airplane down to 64 IAS before it quit, again gently and straight ahead, but with less pitch change than before. Trying it again with 17 inches of manifold pressure made little apparent difference, except to dampen the nose dip. I opted to relax back pressure and bring the throttles up gently in the power-off stalls, losing around 400 feet per maneuver as a result, while in the power stalls, altitude loss was held to approximately 100' or less. I didn't do it this day, but in the past I've stalled 310s down to 60 IAS carrying 28" x 2,350, land full flaps down and 20 degrees nose up. I passed on the single-engine work, too, in deference to possible thermal shock to the engines and my passengers' sensibilities, and headed for airport. However, I know from experience that you scan shut down and feather an engine, use aileron trim to hold it up about 5 degrees and flying with your feet flat on the floor and the ball about half its width. As I recall, speed loss is about 40 mph. Inbound, in N13DP you can drop 15 degrees of flap at 160 IAS, the gear at 140 (up 10 mph from early ones) and the other 20 degrees of flap at 110. In later models, initial flap and gear speeds are raised 20 mph each and full flap was allowed at 160 or below. Standard procedure is to reduce power to about 20 inches well outside the pattern, drop 15 degrees flap and slow to 140 on downwind, throw out the gear just before turning base, fly the base at 120, carry 100 over the fence and touch down somewhere around 70 or 75 mph, adding the rest of the flap as needed—usually on final. My second landing was better than acceptable, and I turned off the active wishing there was some way I could fly this airplane 110 hours in six months. It's that much fun! Not only that, but Bolden says it's fairly cheap to operate. He bought the airplane in May 1981 and has used it for charter since. "Maintenance on a Cessna is one of the lowest of any aircraft," he said. "You don't have much of a problem findin' parts." Bolden figures a total operating cost of $93 an hour, including the airplane's share of his blanket insurance policy and $10 an hour for maintenance. I think this particular craft is one of the most profitable on the market today, because of the up-keep," he added. "They're very competitive in the market. We've seldom had to cancel a charter because of the aircraft." Bolden, it appears, loves the 310 as much as I always have. Later model 310s, of course, have even higher gross weights (to 5,400 pounds), bigger engines (to 300 hp per side with the Colemill and Riley conversions), Airesearch turbochargers that allow service ceilings to 28,600 feet and up to 180 gallons fuel, with all available auxiliary tank options. Beginning in 1962, the straight-up-and-down tuna tanks" were canted to dampen the unwanted flywheel effect (and incidentally provide another 4 square feet of wing area), but the definitive fix came along in '69, with addition of a 3.47 square foot ventral keel that completely cured the yaw stability problem. A new vertical nose gear made for lighter steering and tighter turning circles on the ground. Cabins went to a full six places. Luggage lockers were added in engine nacelles and an extended nose. Also in '69, the new 'Turbo 310" was introduced, with 285 hp TSIO-520s—an airplane capable of 262 mph TAS at 20,000 feet and able to fly over 2,000 miles on 180 gallons. All in all, the 310 is hard to fault—and I've seen old ones offered for sale often recently under $15,000, sometimes under $10,000. I've seen dozens of well-equipped fifteen-year-old airplanes with mid-time engines go begging at prices under $25,000. Those days may soon vanish. .I was talking to Bob Jagitsch, a Little Rock, Arkansas, used airplane dealer, about 310s. He said, "I've probably got 10,000 hours in 310s, and I'll tell you something - they've appreciated legitimately at least 10 percent in the last six months. If people don't buy 'em right now, they're gonna miss out, because the 310 market is roarin"!" He added, "I'm sellin' old 320s right now faster than I ever did! Now, today, a 310R would be goin' at book retail or better. However, these things have sunk for eight years, and they've got a good long way to go." Jagitsch predicted, "If 310s are hot today, they'll pull Barons after them tomorrow and Aztecs the day after that. Eventually, everything that's a good airplane will come back into its own." Twice now in the last couple of years, I've come within a whisker of buying an earlier 310 myself. Both times, when I put a pencil to it, I concluded for the amount of hours I could expect to put on it per year, I just couldn't justify the kind of insurance expense the industry has lumbered everyone with these days. Maybe I should've done it, anyway. . . . I always knew Sky King had the right idea when he and Penny kept buzzing around the West in a tuna-tank 310. That's what I need. My very own "Songbird!" And as it happens, Jagitsch has this old low-time 320 with both engines 233 TT FWF. Cheap. Hmmmm. AIR PROGRESS MAGAZINE JUNE 1987 |
