Cessna’s 340 – Image Justin de Reuck

For the pilot with the means to step up from piston singles to true cabin-class personal transport, the Cessna C340 is a great proposition. It is also the aircraft that many airline pilots chose to move down to – which says a lot about its capabilities.

The subject of our flight review is ZS-JOH, which is a 1976 model 340A. It has been kept in original but excellent all-round condition in the Seaview hangar outside Gqeberha (Port Elizabeth!), which houses the Davidson’s collection of fabulous planes, which includes a P-51 Mustang, a Hawker Seafury, a Harvard, and Patrick Davidson’s unlimited aerobatic mounts, being either a Game Bird or Extra 330, plus an RV-7 which is used as a general run-about.

The flying Davidson family have owned ZS-JOH for 25 years – and they have loved it. Current patriarch Stu Davidson acquired the plane back in 1998 to use as a great way for the family to get around the country – either for work, or pleasure.

Stu Davidson acquired ZS-JOH as fast cross-country transport and it performs that function with excellence – providing a comfortable 200 knot cruise in the teen flight levels – typically around FL130 – FL180.

These are proper personal planes. Any pilot owner, with a need to go places comfortably and efficiently, recognises that a serious plane needs a decent cabin, credible speed and the ability to deal with all but the worst of crappy weather. And since passengers don’t want to spend several hours with a plastic hose in their nostrils, pressurization is almost a necessity.

An American pilot owner reports, ‘My typical trip is business traveling; usually 200 to 250 miles at 10,000 to 15,000 feet, which is the sweet spot for the airplane. I can fly these trips at 20,000 feet or higher when weather is a factor, but for the most part I only get into the flight levels when flying longer legs. It also has the flexibility to fly high or low to take advantage of the winds aloft without a fuel burn penalty. Speed varies with conditions, but I plan on 190 knots true at 12,000 feet and 215 knots true at FL200, burning 34 to 36 GPH of fuel.’

Stu’s son, Red Bull Air Race pilot Pat Davidson, shares what a privilege it is to own one of Cessna’s best cabin class piston twins.

Development

The 340 owes its existence to the boom days of general aviation during the late 1960s and early 1970s when the piston twin market was filled with options. At the entry level, there were the Twin Comanches, Apaches, Aztecs, Barons and Cessna’s 310. At the upper end, the cabin-class Cessna 421, Beech Duke and Piper Navajo were built for bigger budgets and commercial operators.

To appeal to step-up buyers, Cessna’s marketing department claimed that the 340 was a cabin-class development of its already successful Cessna 310. But this is not really true, as most of the 340 is in fact derived from 400 series Cessnas. Thus, the 340 and 414 share the same wing, flaps, ailerons, landing gear and engines.

pressurisation system is the same as that found in Cessna’s 400-series twins, with a maximum differential of 4.2 PSI providing an 8000-foot cabin up to 20,000 feet. Above that, the cabin climbs with the plane.

The 340 may carry slightly less than the 414, but it’s faster on the same fuel burn.

Walk Around

On the ground the 340 is an imposing aircraft. This is not big a piston single, but a cabin class twin with a plus 4000 lb empty weight, which means that empty, it’s still heavier than a Cessna 210’s max all up weight.

Each tuna shaped wing tip tank holds 100 gallons of fuel – again, greater than most singles’ total fuel tanks.

A key differentiator is its airstair door which is more 400 series Cessna than the 310, with its pole dancer stepladder to climb onto the wing and then the slide in through the single right-side door. 

The engines are tightly cowled and complex; with turbochargers and intercoolers. From 1972 to 1975 the engines were Continental TSIO-520Ks, which produce 285 HP at 33 inches MP to 16,000 feet. However, most of the K engines in early 340s have been converted to Js or Ns. The J engine, used on early 414s, produces 310 HP at 36 inches. The N engine, installed on later 414s and 340As, produces 310 HP at 38 inches. This engine became the standard for the 340A and, usefully for South African rough airstrip operations, it also features smaller 75.5-inch diameter props to reduce noise and improve ground clearance.

A key difference between the K engine and the J and N variants is that the latter are equipped with intercoolers. This yields better power and efficiency, with less heat stress on the cylinders.

In 1978 a maximum ramp weight increase to 6025 pounds was approved, and max weight for takeoff and landing was set at 5990 pounds for the 340A, compared with 5975 pounds for the 340. The last significant change in the line came in 1979, with the switch to TSIO-520NB engines (the B denotes a heavier crankshaft and crankcase). Subsequent modification of cylinders, valve lifters and piston pins by Continental increased the time between overhaul of the NB engines from 1400 to 1600 hours in 1983. ZS-JOH has the 310hp intercooled engines and strengthened crankcases.

The unpressurised Cessna 335 was marketed as a simpler, lighter and lower priced version of the 340. It was however not a market success, with only 64 built by the time production ended in 1980. The 340 was far more successful and remained in production until 1984 with 1,287 built.

Climbing into the cabin through the airstair door gives a big-plane feel, but the pilots still have to squeeze through a gap to get to their seats. The cabin is Cessna’s standard wide oval, being 46.5 inches wide and 49 inches high, a very useful 4.5 inches wider than a P-Baron’s. It has lots of space for people and baggage, and of course is pressurised and thus quieter inside.

If owners have any complaints about the 340, they relate to payload range trade-offs. Load enough fuel for a 4.5-hour flight (almost 1000 nm) with reserves and you can take along only two passengers and their bags. Fill the seats with standard 170-pound people and pack away their 30 pounds of baggage each and you can carry enough fuel for two hours of flying. But at 200 knots you can go far in two hours!

A feature Patrick particularly likes about the 340 is its cavernous baggage space. Across the cabin, nose and locker compartments there’s 53 cubic feet of volume, which in theory can take 930 pounds if the fuel and pax load is light.

Most 340s have at least one fuel tank occupying a locker, and typically the nose baggage compartment space is limited by avionics.

A key to using the space is the addition of vortex generators, which brings a 300-pound gross max all-up weight increase.

ZS-JOH has been kept remarkably original and thus simple. The cockpit is still filled with large round ‘steam gauges’ – with nary a glass EFIS panel in sight. This is I suppose natural for a pilot who flies a P-51 Mustang and a Stearman.

Systems

A fully equipped and capable 340 is a complex machine with plenty of sophisticated systems. But Cessna aimed to make it an easy step-up for pilots coming from smaller, simpler planes. Thus the 340 pressurisation system is relatively easy to use. The pilot dials in field elevation plus 500 feet before takeoff and landing and selects desired cruise cabin altitude on initial climb. The rest is simply monitoring the system to make sure it’s keeping the cabin pumped as required. Cessna offered an automatic pressurisation control, which activates and deactivates while climbing or descending through 8,000 feet, but most buyers opted for the variable-control system. This system maintains a sea-level cabin up to 9,000 feet, then delivers the pilot-selected cabin altitude until a 4.2 PSI differential is reached.

Since owners seldom fly their 340s in the 200 flight levels, the pressurisation is more a nice to have than a critical system.

While the pressurisation may be simple, the same can’t be said for the fuel system. Counter intuitively, the 100-USG usable tip tanks are the mains. Then add up to four auxiliary wing tanks, two holding 40 gallons, the other two holding 23 gallons. Add locker tanks, which add another 40 gallons and you have up to 203 gallons in tanks scattered throughout the wings.

The fuel management system consists of fuel selectors for selection of main, auxiliary or crossfeed fuel and other necessary components to get fuel to the engines. The main tanks contain an auxiliary fuel pump and transfer pump.

The optional auxiliary tanks are available in two sizes. These tanks are bladder type cells located between the spars and the outboard wing. Optional wing locker tanks can be installed in the forward portion of each wing locker area. A fuel flow gauge, fuel quantity gauge and a fuel low level warning light are located in the cockpit.

Where things get tricky is knowing which tank to use and when. You use the mains for takeoff and landing. The engines can feed directly from the auxiliary tanks, but fuel in the lockers has to be transferred to the mains, which are the tip tanks. So you have to make room in the mains first, otherwise you’ll vent the pumped fuel over the side.

If you have only one locker fuel tank (which is common on 340s), remember to use crossfeed; dump all 120 pounds from a locker into one tip tank, and the imbalance will be enough to unravel the autopilot.

Cessna never got around to simplifying the fuel systems in its 300-series twins (the Crusader excepted) as it did in most of the 400s. Making the tip tanks the mains has its own issues. Fuel pump attendants have filled the wrong tanks (“Just top up the mains ….”). And newbie pilots have switched to the auxiliary tanks, thinking they were drawing from the tips, and vice versa. Despite this, the 340 hasn’t suffered an inordinate number of fuel-related accidents. (see table).

For operation in colder climates, flight into known ice (FIKI) certification came in 1977 and later, the majority of 340s got what is called full deice. This usually mean boots on the wing and tail (with the exception of the wing stubs), heated props and alcohol spray for both sides of the windshield. None of the systems weight and complexity is really necessary in warmer locations when operated in the teen flight levels. Thus ZS-JOH does not have de-icing equipment installed.

On the standard factory option, the air conditioning compressor is on the right-hand engine, which requires the engine to be running to get cool air. A popular STC modification is an electric system which can be powered by a ground APU.

Unusually, ZS-JOH does not have air conditioning, and its removal translates into a 90lb improvement in useful load. Patrick Davidson reckons that not having the air conditioning and de-icing saves 150 lbs in empty weight and contributes a significant saving to maintenance costs.

Flying the 340

Cessna’s big twins have a reputation for being comfortable and easy to handle and the 340 fits that mould. Patrick Davidson says, “I like the feel of her on the controls, it feels much more sporty and smaller than she is.”

The 340 was designed with a service ceiling of nearly 30,000 feet. However most owners operate in the high teens, where it can be expected to true between 190 and 205 knots on about 40 gallons per hour.  Patrick reports that, in the low teens, he expects a genuine 200 KTAS cruise with a fuel burn, using a rich of peak mixture, of around 19.5 US gph per engine.

The 340 owes its speed to a relatively slick airframe, but because flap and undercarriage operating speeds are on the low side, it can be a handful to go down and slow down simultaneously.

Rate of climb at max all up weight at sea level is a respectable 1650 FPM, but climb performance tapers above 20,000 feet to 300 to 400 FPM in the mid-20 flight levels. The 340’s claimed single-engine rate of climb is 315 fpm, which is better than the Cessna 414’s (290 fpm), Beech P58 Baron (270) and the Piper Aerostar 601P (240) and 602P (302).

ZS-JOH does not have vortex generators so single-engine minimum control speed Vmc is 82 knots. Stall speeds are 79 knots, clean, and 71 knots in landing configuration. Patrick notes that, “stalls are simple and straightforward. At zero thrust on the left engine, with the right engine at cruising power at 12,000 feet, the 340 stalls at 70 KIAS with flaps and gear up, and it is easily controllable in level flight.”

The Davidsons have operated ZS-JOH off their Seaview grass runway since it was just 1000 m long. Under standard conditions, a 340 that loses an engine at liftoff speed (91 knots) can be brought to a full stop within 1000m of brake release.

The POH also shows that should you decide to fly after losing one on liftoff, the 340 will clear a 50-foot obstacle after traveling less than 4000 feet over the ground after brake release (assuming the pilot cleans it up fast and does everything right).

For the descent, the flaps can be extended to 15 degrees at 160 knots to help slow to max gear-operating speed, which is a low 140 knots. But going down and slowing down without stressing the engines can be a problem. So descents and approaches require planning.

This is an aeroplane that must be flown by the numbers: Key numbers are: Downwind and base: around: 150 Kts. Leave the props at 2300 rpm and mixtures leaned unless you go around. Flaps 15. Gear down at 120 Kts. You can leave the flaps at 15 for the landing, unless trying to get it into a tight space. At mid-weights cross the fence at 105 knots and expect it to touch down at 70 knots.

Once you are on short final with gear and flaps out, it will glide like the proverbial piano, so some power must be maintained right into the flare. This is due in part to the split flaps, which are great for drag, but not so good for lift.

Conclusion

The 340 is a great personal plane for cross country transport for the family and dogs. Pilots agree that it’s fun and easy to fly when flown by the numbers. It’s also comfortable, quiet and best of all, it’s pressurized.

Controls have a solid feel that’s responsive and predictable, yet somewhat heavy, befitting an aircraft with a gross takeoff weight over 6,000 pounds. It’s no effort to fly and is very stable in flight. Hand flying in IMC is no problem. All in all, it doesn’t have any bad habits.

For owner pilots it’s a big complex plane so maintenance will be a big factor. One way of looking at it is that if Cessna were to still be building the 340 it would probably cost U$2m new – so the maintenance bills on an aircraft of that value could be expected to be steep. The fact that you can buy a really nice and clean 340 for U$200,000 which is about a third of the cost of a new Cirrus SR22 or Bonanza G36 means that you have a large lump of change to put aside for maintenance – and you have a far more comfortable and capable aircraft.

ZS-JOH is for sale – for a remarkably good value asking price of R3.5m plus VAT, which is less than the price of a Sling or RV-7. These piston twins represent such good value that there is steady demand from around the world, and especially in the USA.

As a Rand hedge investment, and as a plane to own and fly, ZS-JOH offers a great value proposition. And if the new owner spends a bit on it, for vortex generators and perhaps air conditioning and a new paint job and interior, he will have a truly beautiful aircraft – and a great investment.

54 Comments

  1. Not sure where all of your information came from for the article because the tuna tanks are 50 gallons each, not 100.

  2. Nice!still could happen?

  3. Can’t do 100 gallons, only 50 per tank.

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