Ask any Harvard owner – there is nothing as cool as owning a radial taildragger – other than owning a twin radial taildragger.
The Birth of a Classic
In the early 1930s the Bureau of Air Commerce (the progenitor to the FAA) challenged plane makers to build a twin-engine small transport plane for general commercial use. There was also a need for a fast, company executive plane.
Walter Beech rose to the challenge and his Beech 18 design neatly filled the gap between the 3- to 5-passenger single engine high performance singles such as the Beech 17 Staggerwing and Spartan Executive, and larger twins such as the Douglas DC-2/3’s, which carried up to 21 passengers.
The prototype Beech 18 made its first flight on January 15, 1937. It followed the then dominant design philosophy of having twin vertical tails – one behind each engine. This had been popularised by the Lockheed Model 12 Electra Junior, which is a scaled-down version of the Lockheed Model 10 Electra, the plane in which Amelia Earhart disappeared in 1937.
The first Beech 18s sold for $30,000, which was just more than twice the price of the Beech 17 Staggerwing. The first Beech 18s were powered by either two 330 hp Jacobs L-6s or 350 hp Wright R-760Es. The 450 hp Pratt & Whitney R-985 became the definitive engine from the pre-war Beech C18S onwards.
The Beech 18 (which is also often just called the ‘Twin Beech’) turned out to be a huge success, with over 9,000 produced between 1937 and 1969. The 32-year production run was a world record at the time, making it one of the most widely used light aircraft. In comparison, Beech only built 745 Staggerwings.
The Beech 18 soon proved its versatility as a civilian passenger and cargo aircraft, on tailwheels, nosewheels, skis or floats. During World War II, the Beech 18 was modified with glass noses into the military AT–7 Navigator and the AT–11 Kansas. These were trainers in which most American navigators and bombardiers learned their skills. Some AT–11s even got a top gun turret with a .30-calibre machine gun for training gunners.
An unusual variation was the AT–10 Wichita, which was a two-place, plywood-skin version of the Beech 18 in which more than half of the Army’s multiengine pilots received transitional training. Also, as the C–45 Expeditor, the aircraft was used to transport high-ranking officers and other personnel.
After the war, civilian production resumed in late 1945 with the highly evolved Model D18S, the first aircraft to be certified post-war.
A significant and easily seen improvement was the result of a complaint from Walter Beech. During an in-flight visit to the toilet of a D18S, Walter didn’t have the headroom needed to pee standing up. So, the cabin height on subsequent models was increased by six inches, creating the larger E18S. This and subsequent models were called Super 18s. The final version was the G18S with a MTOW of 9,700 lb, although later individual examples such as ZS-OIJ, which is an E18S, were approved for a take-off weight of 10,100 lbs, which made it an even more versatile aircraft. A total of 155 of this model were built until construction ended in 1970 with a last Model H18 going to Japan Airlines.
What is noteworthy is that the Beech 18 continued in production for five years after the King Air 90 had been on the market. So even though the small King Air pressurised turboprop had been designed as a replacement, the venerable pre-war Beech 18 soldiered on.
On the Ground
For pilots transitioning from singles, the Beech 18 appears big – with its reach-for the sky tailwheel stance and big round engines. Our test flight example is one of the later Super 18s, ZS-OIJ, which is owned by Flippie Vermeulen of Springbok Classic Air at Rand Airport. With a maximum all-up weight of four and half tons, a wingspan of 14.5m and its two round engines, the Beech 18 is a mini airliner.
Like most Beech-18s, ZS-OIJ’s engines are the very reliable Pratt & Whitney R-985-AN14B supercharged nine-cylinder air-cooled Wasp Juniors. They each produce 450hp at 36 Hg manifold pressure and 2,300 rpm. They drive two-bladed Hamilton-Standard Hydromatic metal constant-speed props.
Each engine has its own independent fuel system consisting of three tanks in each wing, totalling 318 gallons, effectively giving it an endurance of nearly eight hours or a range of 1,100 nautical mile with one hour reserve.
If the plane has been standing for a while, the first task is to ensure that there’s no hydraulic lock in the engines from oil having run down into the lower cylinders. The recommended procedure is to pull each engine through nine prop blades. A sturdy back and shoulders helps.
Unusually for a radial of that vintage, on most of the early B18 aircraft the carburettor air intakes are mounted inside the cowls, in between the cylinders while the intakes for the oil coolers are in the wing’s leading edge, inboard of the engines. To improve engine performance on the higher gross weight E18S, ZS OIJ’s air intake is underneath the engine cowl. These intakes need to be thoroughly checked for birds’ nests during the pre-flight. A notable absence in the Beech-18 is that it does not have oil and air filters (although it does have an oil screen). This makes it unsuitable for operation of dusty dirt strips, especially ZS OIJ with the carb air intakes close to the ground underneath the engine cowl.
The wings are built in three sections: the centre section is integral with the fuselage and carries the engines and main undercarriage. It features a single steel tube monospar which is joined at mid-span to duralumin girders. After some spar failures, Beechcraft called for an AD mandating a cross section metal strap, which is easily visible underneath and across the wing of ZS-OIJ. This makes the wing immensely strong.
Each wing has large metal flaps which are actuated electrically. In contrast, the cowl flaps use cables. Showing its vintage, with the exception of the flaps, all the flying control surfaces and their associated trim tabs are fabric-covered. In an enhancement, the later Super models and some upgraded Supers, such as ZS-OIJ, have no cowl flaps.
The horizontal tail is large – which helps give a wide C of G range. With a maximum allowable gross weight of 10,100 pounds and a dry operating weight of just 6,604 pounds, ZS-OIJ has a useful load for fuel, passengers and bags of 3,287 pounds, which makes it a really versatile aircraft.
The main wheels are fitted with big hydraulic disc brakes and use an electric motor to retract backwards into the engine nacelles. When retracted, like the DC-3, the lower half of each wheel still protrudes, which helps reduce damage in a wheels-up landing. At the back is a sturdy castoring tailwheel – must be locked for takeoff.
In the Cockpit
Access to the cockpit is through the cabin door behind the left wing. You then walk up the sloping floor between the seat backs. It’s an easy step over the main spar and engine controls console into either of the two front seats.
For a first timer it’s a wonderful experience to just sit in the cockpit and absorb the vintage atmosphere and ergonomics. There’s nothing like the smell of an old twin radial – a heady perfume of leather, oil and that priceless secret ingredient that makes an unforgettable olfactory experience.
All aircraft of this vintage are normally an ergonomic nightmare. There are buttons, knobs, levers, handles and switches everywhere. ZS-OIJ however has had a proper panel makeover with a smart plain white enamel finish, and the layout is now far more standard than most original Beech 18s.
The standard six-pack of flight instruments is duplicated left and right with the avionics stack in the middle, to the right of the engine gauges. Each round gauge has dual pointers to show rpm, manifold pressure, oil and fuel pressure, and oil, carburettor and cylinder head temperatures. The ammeter, voltmeter and fuel gauge are half-hidden behind the pilot’s control wheel. The control wheels are mounted on substantial control columns on either side of the cockpit.
Partially hidden behind the left control column is the only fuel gauge. It has a selector switch so it only indicates the one tank at a time. There is potential for real confusion, as the selected tank quantity remaining in the selected tank only is shown on the gauge in ten percent increments. As the size of the three tanks in each wing are different, it can easily lead to a mistake. This confusing system has led to numerous B18s suffering dual engine failures, despite having fuel remaining in some of the tanks. This was the fate of ZS-OEP which had a forced landing under the Lanseria circuit Lanseria some years ago.
In a traditional Beech Baron idiosyncrasy, the power quadrant is a non-standard floral bouquet of both long and short stemmed coloured knobs. The prop pitch levers are on the left, throttles in the centre, and mixtures on the right. The stubby levers that control the manifold heaters and oil shutters are between the main power levers.
A sub-panel below the console carries the fuel selectors, T-handles for the tailwheel lock and park brake, plungers for oil bypass and oil shut-off. The undercarriage selector is to the left of the sub-panel and the flaps to the right, ahead of two large fuel selectors.
A wheel on the right side of the pilot’s seat operates the elevator trim; there’s a small wheel for aileron trim and, like an early Cherokee, a handle in the roof (which resembles a car’s window winder) but unlike the Cherokee it’s for rudder and not elevator trim. Elevator, rudder and flap position indicators are at the bottom of the righthand instrument panel.
Seemingly added as an afterthought to the top of the left side instrument panel are two large red buttons. These are pushed to electrically feather the Hamilton Standard hydromatic propellers in two seconds. The button then pops out. Pushing it in again unfeathers the blades and causes the prop to windmill.
This is a Beechcraft and so everything is built to last. The yoke is mounted on an arm that looks like it’s been borrowed from a bridge, while the rudder pedals are for pilots who wear boots. Flippie Vermeulen says, “Rightly so as the pilot has to have his feet high up on the rudder pedal, within immediate reach of the brakes at all times during take-off and landing.
Flying the Beech 18
The start requires a ritual with the many buttons, switches, knobs and levers to be pushed, pulled, twisted, turned and set. Items that pilots of modern planes will be unfamiliar with include the oil shut-off plungers, closing the oil shutters and selecting the fire extinguisher to the appropriate nacelle.
Crack the throttle open, shout “clear prop!” out the window and energise the starter. The big two-blade propeller begins to revolve and after six blades scythe past the window you turn on both mags. From within the bowels of the cowl comes a cough and a grunt as a couple of cylinders fire somewhat hesitantly then backfire. Hopefully before it dies a few more cylinders fire and smoke from burned oil and over-primed cylinders streams back from the exhaust. Suddenly the remaining cylinders burst into life, turning the two propeller blades into a shimmering blur. The engine soon settles into a contented chuntering.
Taxiing the 18 is typical taildragger, so S-turns are required, especially so with the long nose on ZS-OIJ.
The pre-takeoff checks are lengthy but conventional. They include cycling the props and testing the feathering system, ensuring that the oil shutters are set and the oil bypass is in, fuel selectors to front mains and cross feed off. All the trimmers are set for takeoff. Flaps are only utilised for short field takeoffs. Last, but by no means least, the tailwheel must be locked once the aircraft is perfectly lined up with the runway.
The before-takeoff pilot briefing includes the procedures to be adopted in the event of an engine failure both before and after ‘red line’ speed (velocity of minimum control, (Vmc) is 82 knots) has been attained. Review the other critical air speeds, such as the limiting speeds for the undercarriage and flaps, and confirm that climb-out speed will be around 100-110kt.
Once lined up, gradually stabilise the power at 20 inches HG boost with the brakes applied to ensure symmetrical power, then increase the power to 36.5 inches and 2,300 rpm for takeoff. Even though the twin rudders are in the propwash, they do not produce significant steering until reaching 30 to 40 knots.
The engines’ rumble swells to a growl, and the needle of the ASI starts to move. With radial engines swinging big props there’s a lot of metal whirling around on each wing, and gyroscopic precession is a force to be reckoned with. If you pick the tail up too quickly to see over the nose, a swing is almost inevitable. Flippie Vermeulen says that it helps to lead with the right rudder and initially tap the right-hand brake pedal now and again to keep the big twin on track until its going fast enough for the rudders to be effective.
With 900 supercharged horsepower the Beech 18 accelerates fast. At 80 knots ease the yoke back. As the wheels leave the ground check forward on the yoke to let the speed build to blue line speed.
With the flaps and undercarriage up, and the speed at blue line, at 300 ft pull the throttles and props back to climb power of 31” and 2,100 RPM.
Both the undercarriage and flaps are electric, a Beech trademark used on all its subsequent complex planes. For a normal takeoff the gear comes up commendably quickly. In case of electrical failure, the wheels and flaps can be hand cranked up and down.
Although the controls forces are delightfully light and super effective for its age, the pitch trim changes constantly with speed changes and so needs continuous attention. The controls are nicely harmonised and the authority good which makes the aircraft really manoeuvrable, as can be seen by the displays at airshows by Flippie Vermeulen. The aircraft has positive stability around all three axes, and it is not difficult to fly on instruments, as long as it is trimmed properly.
You enter a steep turn and make bank and pitch changes with your fingertips—almost as if the controls were boosted – which they are not. While most 18s have electric elevator trim, but many pilots prefer using manual trim. Your right hand falls naturally to the trim wheel, which moves easily and effectively.
The visibility is pretty much what you would expect of a WWII transport with round engines outside the smallish flat-pane cockpit windows. It’s not bad, but not great.
Slow flight is surprisingly benign, and with the flaps down and a bit of power you can see 68 KIAS, while Vne is 220kt, and impressive 3 times ratio.
One-G stall speeds at maximum weight are 81 KIAS (flaps up) and 73 knots KIAS (flaps down). Mild buffeting and mushy controls warn of an impending power-off stall, but there’s little warning of a power-on stall. Instead, a stick-shaker on the left control column lets you know.
In the cruise at less than gross weight, with an engine at zero-thrust to replicate a dead engine with the prop feathered, the performance is acceptable. But losing an engine just after takeoff on a hot day with a full load would be a white-knuckle moment.
On downwind you get busy with the flaps, and undercarriage. Flippie Vermeulen points out that normally the undercarriage is not lowered until the final approach decent is commenced. With its slab sides and small tail, the 18 can be a handful in a crosswind. The demonstrated 90° crosswind component is just 11 knots, but this is the demonstrated figure in the POH. Flippie says that he has had to do landings in up to 20 knot crosswinds.
There’s a slight nose-down change in trim as the wheels lock down. Reduce speed to 100 kt and turn base. On final, lower the rest of the flap and pull the throttles back a bit more while lowering the nose and pushing the props to full fine.
Aim to cross the fence at a Vref of 80 knots. Squeeze the throttles closed, check the sink and then let the grand old dame settle gently on to her main wheels. The bigger tailwheel types need wheel and not 3-pointer landings. The actual touchdown should be gratifyingly soft. Check forward on the yoke to hold the main wheels on the runway.
Although it is delightful to handle in flight, it can be a handful on the ground, especially during the rollout after landing. Come to a full stop, then unlock the tailwheel and taxi clear of the runway. Flaps up and cowl flaps open for the taxi back. Slide the window open to cool down.
Conclusion
The Beech-18 is indeed a true classic. Its inherent qualities have earned the respect of many pilots and operators. It has been successfully operated as a crop sprayer, it has done fish seeding, dry ice cloud seeding, firefighting, delivered air mail and served as an air ambulance. It has starred in numerous movie productions, dropped countless skydivers, and been the plane of choice for weapons and drug-smuggling. It has served as an engine test bed, towed banners and done skywriting.
In South Africa Flippie has used ZS OIJ successfully on luxury flying Safaris for the past 10 years. The reliability of its Pratt and Whitney R985 engines has allowed Springbok Classic Air to operated ZS-OIJ as far afield as Seronera in the Northern Serengeti in Tanzania.
As with the other big piston-powered planes, it’s a lot more than the sum of its parts, which are really simply a disparate collection of metal, rubber, leather and plastic.
Perhaps the best comment comes from long-time owner and fan, Enrico Bottieri, who said, “There are many Beech twins, but only one Twin Beech.”
