My 500th post – Walter Beech’s masterpiece….the ‘Twin Beech’


Having astonished the aviation world with the performance of his Model 17 – the ‘Staggerwing’ – Walter Beech might have been forgiven if he had sat back on his laurels and continued to ring the changes with his beautiful, swift ‘executive’ biplane. However, it was the late 1930s, and he knew that his company could not survive with only a single product line. Walter Beech gave the job to a team headed by Ted Wells. Their brief was to come up with a design for a twin-engined metal monocoque monoplane with room for two pilots and a minimum of 6 passengers.

A high-strength chrome steel welded tube fuselage, with a tubular steel wing spar of flattened ovoid cross section, formed the core of the Model 18’s structure (more on that later). Power came from a pair of Jacobs L-6 engines (similar to the one used in the Beech F17D) producing nearly 330hp or the 350hp Wright R-760E, driving two-bladed Hamilton metal propellers. Control surfaces were metal framed, but fabric covered. The new Model 18 (soon referred to as the ‘Twin Beech’) made its first flight on Jan 15th, 1937. This prototype, with its two 320hp Wright R-760-E2 engine, became the first Twin Beech sold; it went to the Ethyl Gasoline Corporation of America for $32,752.80. Sadly, the aircraft’s logical market – the smaller U.S. airlines – did not greet the new ‘plane with enthusiasm, and it wasn’t until the small Canadian airline, Prairie Airlines, based in Moose Jaw, ordered two Model S18D’s capable of carrying 7 passengers and two pilots (powered by Jacobs L-6MB engines of 330 hp) that the production started to ramp up. The ‘S’ indicated that the aircraft COULD be operated on floats, but Prairie’s aircraft were never fitted with them.

Prairie Airlines had some major problems with their Jacobs L-6MB engines; cracked pistons and engine failures in flight gave rise to poor reliability. Walter Beech fumed that the Jacobs engines were ruining his airplane, but there were also problems with the Beech undercarriage design. The company had incorporated a chain drive in its retraction mechanism (as it had with the Model 17), and this proved to be not quite strong enough, leading to jammed sprockets and partially retracted undercarriages (and two belly landings, back at the Prairie Airlines home base). Walter Beech promised stronger chain, but this took a redesign.

Although Jacobs tried hard, it wasn’t until the Model 18S was fitted with the ever-reliable 450hp Pratt & Whitney R-985 Wasp Junior, that the aircraft came into its own. It can be said that WW2 was the real game-changer for the Twin Beech. Pre-war military orders had gone to the Philippines, then China and many other air forces, and the British Purchasing Commission were swift to weigh-in with a request for more. Known as the Expeditor MkI and MkII, RAF machines were mostly to be found in the South East Asia Command area during hostilities, where their 900 mile range proved very useful. Eleven UC-45 six-seat utility models were bought by the USAAC in February, 1940, but the entry of the U.S.A. into World War Two in December, 1941 brought a flood of military orders for everything from navigation trainers to bombardment trainers, from utility machines to turreted gunnery trainers. These bore such designations as C-45 Expeditor, AT-7 Navigator, AT-11 Kansan and UC-45J Navigator; there was even an F-2 photographic reconnaissance machine (USMC) and a drone controller, the PCQ-3/DC-45F. The US Navy also utilized the Beech as the JRB-1 to -6, and the SNB-1 to -5, fulfilling many roles from gunnery training to ambulance aircraft. As you can imagine, once seen, every military command wanted the Model 18; orders for thousands of this handy aircraft, in assorted sub-types, flowed into the Wichita factory.

As with other aircraft manufacturers, the end of WW2 brought an almost instant end to all lucrative large-scale military contracts. That didn’t seem to bother Beech, as within two months they brought out the first post-war civilian Twin Beech with refined aerodynamics and other improvements. They were also generating a useful income by another route. Beech did a wise thing, they got into the business of converted and zero-timing military machines – this programme, which ran to almost 900 aircraft, was a huge financial success. Beech gave the ex-military AT-7, AT-11, C-45B and C-45F machines new fuselages, centre-sections and landing gear; Beech reconditioned the outer wings, engines and tail group and turned them into C-45G and C-45H standard aircraft, which made them close to the civilian standard D18S.

Post war Model 18s were worked hard, some carried light freight, or up to 8 passengers (11, if used by skydivers). Others undertook photo-survey work or were converted as executive transports, with a higher cabin roof to give 6″ more headroom. To increase cruising speed, some owners increased the angle of incidence of the horizontal stabilizer, but this came at a price – a higher stalling speed. Longer, squarer wingtips gave a greater wing area, and allowed higher gross weights, as well as improving the stall characteristics; these wingtips were fitted on many re-manufactured C-45G and H models. There were also after-market ‘mods’ for better brakes and stronger landing gear. A company called Volpar produced one of the most radical modifications – a kit to convert the Model 18 to a tricycle undercarriage configuration. This became so popular that the Beech company bought the rights to it, and the last Model 18s were built as ‘nosewheel’ aircraft from the start. Given the long service life of the surviving C-45s, and the heavy landings that some suffered, many Model 18s had a spar strap kit fitted to strengthen the wing spar. However, the holes drilled to allow the fitting of this kit (there were several types) admitted moisture to the interior of the tubular main spar, which corroded in a number of cases. This caused the FAA to issue an Airworthiness Directive, AD 72-27-09R2, instituting a series of non-destructive tests aimed at preventing failure of the wing spar in flight.

The aircraft you see above was built in 1943 as an AT-11, and was delivered in March, 1943 to the U.S. Army Air Forces Bombardier Training School at Childress in Texas. There it would have been flown intensively, carrying pilots, instructors, student bombardiers and a load of up to 1,000ib in 100lb practice bombs. Post-war, it was one of the aircraft re-manufactured as a C-45H (Ser. No. 52-10894) and it was issued on 13th October, 1954 to the 178th Fighter Interceptor Squadron, North Dakota Air National Guard at Hector Field, Fargo, North Dakota, where it was intended to be used as a squadron ‘hack’ and communications machine; ‘894’ was fitted out for two pilots and four passengers. The 178th was flying the F-51D Mustang (as it was then known), but was within weeks of changing its equipment to a first generation jet fighter, the Lockheed F-94A.

In 1960, it was deemed that the aircraft was no longer needed by the Air National Guard, and the C-45 was handed over to the North Dakota Civil Defense Agency, out of Bismark, North Dakota, where it acquired a civil identity, N7916A. By 1968, it is recorded as being operated by the North Dakota State Highway Department.

Eventually disposed of, N7916A languished until it came into the hands of Morton Lester of Martinsville, Virginia, a Life Member of the Twin Beech Society. His restoration of the aircraft to airworthy condition was masterful, as you can see. It is finished in US Navy colours, as a C-45 based at Naval Air Station Chinocoteague, Virginia. It is shown here at the Beechcraft Heritage Museum, Tullahoma, Tennessee.

When the last three Beech Model H18 were delivered to Japan Air Lines in January, 1970, a record production run for a piston-engined aircraft was set at over 32 years. It is unlikely that Walter Beech could have anticipated such a runaway success story for this ‘little airliner’. The Beech Model 18 can truly be said to be a masterpiece.

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R.

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