One thing above all else makes an airplane work we’ll as a business transport: High altitude capability. It means that much of the weather can be flown over, which can make all the difference between getting there and staying on the ground. While turbocharging will get the airplane up to altitude, its pressurization that makes the experience attractive to the executives occupying the cabin.
Enter the 340. Its a relatively economical way to go for a company with a need for a pressurized twin. Though not without its shortcomings-most notably certain loading limitations and an overly complex fuel system-the 340 is nevertheless a fine airplane, one that fits its mission well.
History
The 340 was introduced in 1972 as a lower-cost alternative to the 414, which had arrived in 1970. It was intended to fit into the gap between light twins like the Cessna 310, Piper Aztec, and Beech Baron, and more expensive cabin-class airplanes such as the Beech Duke, Piper P-Navajo and Cessna 421 Golden Eagle.
Though it carries a 300-series number, the 340 and 414 are very similar, sharing the same wing, flaps, ailerons, landing gear and engines. The 340 also has an air-stair door, unlike the 310. Because its lighter and has a smaller cabin, the 340 cruises about seven to 12 knots faster than the 414 on the same fuel. But for the speed, the 340 sacrifices payload (more on that later).
If the prospect of flying above most weather and traffic snarls, free of the constraints of nosebags, appeals to you, the price for admission varies from about $170,000 for an early model to over $330,000 for one of the last off the line. It should be noted that the low figure assumes that the early models engines have been upgraded to the higher-horsepower variant found on later models: While we have no definitive information on this, its a safe bet that there are very few 340s flying which have not been upgraded to the more powerful engines.
Engines installed on 340s from 1972 through 1975 were Continental TSIO-520Ks, which produce 285 horsepower at 33 inches manifold pressure from sea level to 16,000 feet. However, as noted above, most of the K engines in early 340s have been converted to Js or Ns. The TSIO-520J engine, used on early 414s, produces 310 HP at 36 inches manifold pressure. The N engine, installed on later 414s and 340s (the N-engine airplanes are called 340As), produces 310 HP at 38 inches. The major difference between the K engine and the J and N variants is that the latter are equipped with intercoolers (which reduce temperature of induction air as it moves from turbocharger compressors into induction manifolds).
The N engines produce their rated 310 HP up to 20,000 feet and provide higher cruise speeds and better climb and single-engine performance. Three-blade McCauley propellers, formerly an option, also became standard equipment in 1976; earlier 340s came with two-blade McCauleys.
Certification for flight into known icing conditions, when properly equipped, came in 1977. The next year, a maximum ramp weight of 6,025 pounds was approved, and max weight for takeoff and landing was set at 5,990 pounds for the 340A (compared with 5,975 pounds for the 340).
The last notable change occurred in 1979, with the switch to TSIO-520NB engines (the B denotes use of a heavier crankshaft). Subsequent modification of cylinders, valve lifters and piston pins by Continental increased TBO of the NB engines from 1,400 to 1,600 hours in 1983. But Cessna didnt build any 340As (or much of anything else) that year; and after putting together a scant 17 of the airplanes in 1984, production was terminated.
Performance
Though service ceiling touches nearly 30,000 feet, most owners operate between 16,000 and 24,000 feet, where they get 190 to 205 knots on about 30 gallons per hour at 65 percent power and 200 to 217 knots on 32 to 34 GPH using 75 percent power.
Rate of climb at sea level is a respectable 1,650 FPM, but climb performance tapers rapidly above 20,000 feet to a dawdling 300 to 400 FPM in the mid-20s. The 340s single-engine ROC is 315 FPM, better than the 414 (290 FPM), Beech P58 Baron (270) and the Piper 601P (240) and 602P (302) Aerostars. In its class, the 340 is outshone only by its much lighter, centerline-thrust stablemate, the pressurized Skymaster, which climbs 375 FPM on one engine. Single-engine minimum control speed is 82 knots. Stall speeds are 79 knots, clean, and 71 knots in landing configuration.
To its credit, Cessna provided information on accelerate-stop and accelerate-go performance in 340 POHs. The book indicates that, under standard conditions, a 340 that loses an engine at lift-off speed (91 knots) can be brought to a full stop within 3,000 feet of brake release. The book also indicates that should a pilot decide to go after losing one on lift-off, the airplane will clear a 50-foot obstacle after traveling less than 4,000 feet over the ground after brake release.
The performance figures above are for 340s with 310-HP engines. Those that still have 285-HP K engines (if any) are nearly 20 knots slower in cruise, use roughly 200 feet more runway for takeoff and climb 1,500 FPM on both engines, 250 FPM on one.
Handling and comfort
No bad habits is how most owners characterize the handling characteristics of their 340s, and most claim to have had very little difficulty transitioning to the heavier twin from lighter and less complicated aircraft.
The airplane does present a double whammy of sorts, being rather clean and therefore difficult to slow down on one hand, and having relatively low gear and flap operating speeds on the other.
For example, flaps can be extended 15 degrees at 160 knots (the limit is 156 knots in the first 300 airplanes built) to help slow the airplane down to max gear-extension speed, a pitiable 140 knots. But slowing the airplane to 160 knots without shock-cooling the engines can be a problem. Owners say descents and approaches require careful planning.
Once the airplane is slowed down with gear and flaps deployed, however, it tends to sink like a rock, according to owners, and some power must be maintained right into the flare. This is due in part to the flaps, which are of the split variety: great at producing drag, but not so good at increasing lift.
The heavy-iron ambience of the air-stair door wears off quite quickly when occupants must squeeze through a very narrow (seven-inch) aisle to their seats. Once seated, though, the cabin is quite comfortable. The 340s cabin is 46.5 inches wide and 49 inches high, about the same size as an Aerostars and 4.5 inches wider than a P-Barons.
Systems
The pressurization system is the same as those found in Cessnas 400-series twins. Maximum differential is 4.2 psi, providing an 8,000-foot cabin up to 20,000 feet; above that, the cabin climbs with the airplane. Most buyers passed on the standard automatic-control set-up, which activates and deactivates while climbing or descending through 8,000 feet, and equipped their 340s with the optional variable-control system, which allows the pilot to program cabin altitude and rate of climb. The variable system maintains a sea level cabin up to 9,000 feet, then maintains the pilot-selected cabin altitude until a 4.2-psi differential is reached.
Managing the pressurization system actually is a piece of cake, requiring only a few seconds each flight. The pilot merely dials in field elevation plus 500 feet before takeoff and landing, and cruise cabin altitude on initial climb. (Of course, saying that you don’t have to fuss much with the system doesnt mean you don’t have to monitor it carefully during flight.)
Fuel system
Its the fuel system that keeps a 340 pilot on his toes. Start with the tip tanks, the mains, which hold 100 usable gallons. Add up to four auxiliary wing tanks, two holding 40 gallons, the other two holding 23 gallons. Throw in locker tanks, which add another 40 gallons. Thats up to 203 gallons in containers strewn throughout the length of the wings. Remember to use the mains, alone, for takeoff and landing. The engines will feed directly from the auxiliary tanks, but fuel in the lockers has to be transferred to the mains. Of course, you have to make room in the mains, first. And if you have only one locker tank (which many 340s do have), remember to use crossfeed; dump all 120 pounds from a locker into one tip tank, and the imbalance will be enough to upset even your autopilot.
Unfortunately, Cessna never got around to simplifying the fuel systems in its 300-series twins (Crusader excepted) as it did in most of the 400s.
For whatever reason, Cessna chose to designate the tip tanks main, just as they did on the 310. This can, and has, caused some problems. Ramp attendants have filled the wrong tanks (Just top off the mains….), and pilots (particularly transitioning pilots) have switched to the aux tanks thinking they were drawing from the tips, and vice versa.
Empty seats
Probably the biggest drawback to the 340 is its load-carrying ability. Most are very we’ll equipped and can accommodate only around 1,600 to 1,700 pounds of fuel and payload. (The useful loads shown in the accompanying specifications table are maximums and valid only for unequipped airplanes.) Load enough gas for a 4.5-hour flight with reserves, and you can take along only two passengers and their bags. Fill the seats with 170-pound FAA clones and pack away their regulation 30 pounds of baggage each, and you can carry enough fuel for a 1.5-hour jaunt.
Considering the severe payload limitations, the baggage space in the 340 seems a cruel joke. Among the cabin, nose and locker compartments, there’s a cavernous 53 cubic feet of space in which a maximum of 930 pounds can be crammed. That is, however, the maximum. Most 340s have at least one fuel tank occupying a locker, and nose baggage compartment space typically is compromised by avionics gear.
There’s good news, though. The installation of vortex generators brings with it a 300-lb increase in gross weight, and considering an entire VG kit weighs about as much as the air in your tires, its about as close to a free lunch as you can get. One owner called the installation of VGs a real no-brainer. While there’s no way to prove this, we suspect that the efficacy of the vortex generator kits has served to boost the value of 340s at a surprising rate.
Maintenance
Like any other high-performance airplane, a 340 is not one to tolerate skimpy maintenance. If overhaul prices in the $20,000 range (times two), annual inspections at several thousand dollars and operating expenses above $200 an hour are enough to curl your toes (as they do ours), don’t expect to have a good time owning a 340.
Those with the wherewithal to have a good time, though, should be aware of a few items gleaned from typical service difficulty reports that might conspire to ruin their day. First, there are the TSIO-520 crankcases, which have a history of cracking. In mid-1976, Continental switched to heavier cases, which helped a bit but certainly provided no panacea. A couple of knowledgeable sources estimated that about two-thirds of the engines flying in 340s right now probably are cracked in one place or another.
But not all cracks are critical, and the same sources said theyve been seeing far fewer catastrophic engine failures caused by crankcase cracks. The reports also showed cracked cylinders and cylinder heads to be a rather frequent problem. Cracked and blown-out cockpit windows were the subject of several reports, as were cracked Bendix mag housings and distributor blocks, loose horizontal and vertical stabilizer attach bolts and cracked waste gate couplings.
Of course, any prepurchase inspection will include a check for compliance with all ADs, and there have been quite a few. One requires removal of certain oil filters, which were found prone to leak. Another AD (88-03-07) requires inspection of fuel crossfeed lines for chafing and modification of firewall stiffener flanges and fuel lines. AD 87-23-08 calls for ultrasonic inspection of the crankshafts, as does 97-26-17. 75-23-8 mandates repetitive inspections of the exhaust system. 96-20-7 calls for repetitive inspections of the Janitrol cabin heater. 96-12-22 requires repetitive inspections of the oil filter adapters. 95-24-5 deals with repetitive prop inspections. 90-2-13, a type-specific directive, called for replacement of the main landing gear inner barrel bearings.
One very important directive to check for is 82-26-05, which requires visual checks for cracks in the rudder balance weight rib every 100 hours until a new rib is installed. Such cracks have been the subject of numerous service difficulty reports.
Modifications
Much the 340 fleet has had engine modifications performed by RAM Aircraft Corp. RAM, which enjoys an excellent reputation among owners of 300- and 400-series Cessnas, has offered a variety of mods under different names. There are several different mods, among which are the (now discontinued) Series II new Series IV, and Series VI packages, which feature a variety of improvements including new camshafts manufactured by Crane, brand-new steel cylinders, and Hartzell Q-tip props (Series II only), among other things. The packages include a seventh stud on crankcase cylinder pads, which reduces the stresses in these areas that often cause cracks.