Beech Model 18

With the Model 17 well established, Beech began in 1935 the development of a six/eight-seat commercial transport identified as the Beech Model 18. This was a very different aeroplane from the Model 17, being a low-wing monoplane of all-metal construction, with a semi-monocoque fuselage of light alloy, a cantilever tail unit incorporating twin end-plate fins and rudders, and electrically retractable tailwheel landing gear. Float or ski landing gear was to become optional. Standard accommodation provided for two crew and six passengers, and the initial powerplant installation comprised two 239kW Wright R-760-E2 radial engines mounted in wing leading-edge nacelles.

The initial Model 18A was flown for the first time on 15 January 1937. Even the most interested eyewitness of the event might have been little thrilled by the appearance of yet another twin-engined light commercial and, perhaps, would have expected it to gain only very limited marketing success. He could not have been more wrong, for the type was not only to remain in production for a record 32 years, but has since proved a popular choice for conversion by a number of American companies, with modifications intended to provide improved performance or greater capacity.

However, this glimpse at the future overlooks the early period when perhaps only Walter Beech was convinced that the Model 18 represented a worthwhile project. An improved Model 18B with lower-powered engines also sold in only penny-packet numbers, and the first sign that the company was on the right track came with the Model 18D of 1939. This had 246kW Jacobs L-6 engines, providing improved performance and much the same economy of operation as the Model 18B. Only about 30 of these were sold in 1940, but the wartime demand for these aircraft was to total more than 4,000.

The first US Army Air Corps order, placed during 1940, was for the supply of 11 aircraft under the designation C-45, for use as staff transports, these being generally similar to the civil Model B18S. Subsequent procurement covered 20 C-45As for use in a utility transport role, with interior and equipment changes being made in the 223 C-45Bs that followed. Some of these aircraft were supplied to the UK under Lend-Lease, being designated Expediter I in RAF service. The USAAF designations C-45C, C-45D and C-45E were applied respectively to two impressed B18S civil aircraft, two AT-7s completed for transport duties, and six AT-7Bs similarly modified. Major and final production version for the USAAF was the seven-seat C-45F, with a slightly longer nose and of which no fewer than 1,137 were built. Lend-Lease deliveries from the procurement served with the Royal Navy and RAF as Expediter Us, and with the Royal Canadian Air Force as Expediter Ills. All of the foregoing C-45 designations were changed to a new UC-45 category in January 1943.

In 1941, the Beech AT-7 Navigator was introduced to provide navigation training; this was equipped with three positions for trainee navigators, plus a dorsal astrodome. A total of 577 was built, being followed by six AT-7 As with float landing gear and a large ventral fin. Nine AT-7Bs, basically winterized AT-7s were built to USAAF order: five ¦ were supplied to the UK, one being used by Prince Bernard of the Netherlands during his wartime exile. Final version of the Navigator was the AT-7C with a different powerplant, production totalling 549.

Another version of the Model 18 appeared in the AT (advanced trainer) category during 1941. This was the AT-11 Kansan (originally named Kansas), procured by the USAAF as a bombing and gunnery trainer. It incorporated a small bomb bay, had small circular portholes in place of the standard rectangular cabin windows, a redesigned nose to provide a bomb aiming position, and two 7.62mm machine-guns, one in the nose, the other in a dorsal turret. Production to USAAF orders totalled 1,582; of these 36 were converted for navigation training as AT-11As. Twenty-four AT-11s ordered by the Netherlands for service in the Netherlands East Indies were, instead, taken on charge by the USAAF: they were delivered subsequently to the Royal Netherlands Military Flying School at Jackson, Mississippi, in early 1942.

Last of the US Army Air Force's wartime versions of the Beech Model 18 were photographic reconnaissance F-2s, 14 civil Model B18S being purchased and converted with cabin-mounted mapping cameras and oxygen equipment. They were supplemented later by 13 F-2As with four cameras, converted from C-45As, and by 42 F-2Bs, which were conversions from UC-45Fs: these had additional camera ports in both sides of the fuselage. In June 1948, under a general revision of the USAF designation system, all of the surviving F-2 photo/reconnaissance aircraft were redesignated RC-45A. Similarly, AT-7, AT-7C and AT-11 s dropped their A prefix: at the same time a small number of drone-directors converted from UC-45Fs and given the designation CQ-3 became instead, DC-45Fs.

The US Navy and US Marine Corps also used the Model 18 extensively, to the extent of more than 1,500 examples. Initial procurement related to a version similar to the US Army's F-2, this being designated JRB-1, and followed by a JRB-2 transport, and JRB-3s and JRB-4s equivalent to the C-45B and UC-45F respectively. The designations SNB-1, SIMB-2 and SNB-3 were applied respectively to aircraft that were equivalent to the USAAF's AT-11, AT-7, and AT-7C. US Navy ambulance and photographic versions were the SNB-2H and SNB-2P respectively; the SNB-3Q was an electronic counter-measures trainer.

During 1951-2, in-service USAF UC-45E, T-7 and T-11 aircraft were re-manufactured to zero-time condition and modernised, emerging with the new designations C-45G and C-45H. The former had an autopilot and R-985-AN-3 engines, the latter no autopilot and R-985-AN-14B engines. At the same time, US Navy SNB-2s, SNB-2Cs, and SNB-2Ps were remanufactured under the designations SIMB-5 and SNB-5P. Later, with introduction of the tri-service unified designation scheme in 1962, in-service SNB aircraft were redesignated TC-45J and RC-45J respectively in the training and photographic roles.

With a return to peace, Beech resumed manufacture of the civil Model 18, and in 1953 introduced a new larger and improved version of the D18S. Known as the Super 18 (E18S), the prototype was flown for the first time on 10 December 1953. Structural improvements included external refinements to reduce drag, Geisse safety landing gear for cross-wind operations, the provision of. a separate flight deck, and improved soundproofing. Progressive improvements continued throughout the production of 754 Super 18s, the last examples of the final Model H18 version being built during 1969.

In September 1963 Beech introduced optional retractable tricycle landing gear which had been developed by Volpar Inc. of Los Angeles, California. This company also offered conversions of standard Beech 18s to Volpar Turbo 18 standard, with tricycle landing gear and TPE331 turboprop engines, and also the lengthened turboprop-powered 15-pas-senger Volpar Turboliner. Conversions offered by other manufacturers have included the nine-passenger Dumod I and 15-passenger Dumod Liner, offered by Dumod Corporation; and Pacific Airmotive Corporation's 10-passenger PAC Tradewind and turboprop-powered PAC Turbo Tradewind. Still available from Hamilton Aviation in late 1981 were the Hamilton Westwind II STD and Westwind III turboprop-powered conversion of 17-and eight-passenger capacity respectively.

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A three-view drawing (992 x 682)

lxbfYeaa, e-mail, 14.03.2024 John A Garrison Jr

20

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Peter McHardy, e-mail, 01.10.2020 rickharris392@live.com

Didi the same with SEMO airways and Stage to name a couple.
Cheers,
Peter

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