Beechcraft Model 18

Design and development

By the late 1930s, Beechcraft management speculated that a demand would exist for a new design dubbed the Model 18, which would have a military application, and increased the main production facilities. The design was mainly conventional for the time, including twin radial engines, all-metal semimonocoque construction with fabric-covered control surfaces and tailwheel undercarriage. Less conventional was the twin-tailfin configuration. The Model 18 can be mistaken for the larger Lockheed Electra series of airliners which closely resemble it. Early production aircraft were powered either by two 330-hp (250-kW) Jacobs L-6s or 350-hp (260-kW) Wright R-760Es. The 450-hp (336-kW) Pratt & Whitney R-985 became the definitive engine from the prewar C18S onwards. The Beech 18 prototype first flew on January 15, 1937.

Prior to the Pearl Harbor attack, the Beech 18 was outsold by the Lockheed 12 by two-to-one. However, war priorities forced Lockheed to concentrate on its heavier aircraft, and Beechcraft received a major boost through wartime contracts.

The aircraft has used a variety of engines and has had a number of airframe modifications to increase gross weight and speed. At least one aircraft was modified to a 600-hp (447-kW) Pratt & Whitney R-1340 powerplant configuration. With the added weight of about 200 lb (91 kg) per engine, the concept of a Model 18 fitted with R-1340 engines was deemed unsatisfactory due to the weakest structural area of the aircraft being the engine mounts. Nearly every airframe component has been modified.

In 1955, deliveries of the Model E18S commenced; the E18S featured a fuselage that was extended 6 in (150 mm) higher for more headroom in the passenger cabin. All later Beech 18s (sometimes called Super 18s) featured this taller fuselage, and some earlier models (including one AT-11) have been modified to this larger fuselage. The Model H18, introduced in 1963, featured optional tricycle undercarriage. Unusually, the undercarriage was developed for earlier-model aircraft under an STC by Volpar, and installed in H18s at the factory during manufacture. A total of 109 H18s were built with tricycle undercarriage, and another 240 earlier-model aircraft were modified with this.

Construction of the Beechcraft Model 18 ended in 1970 with a final Model H18 going to Japan Airlines. Through the years, 32 variations of the basic design had flown, over 200 improvement modification kits were developed, and almost 8,000 aircraft were built. In one case, the aircraft was modified to a triple tail, trigear, humpbacked configuration and appeared similar to a miniature Lockheed Constellation. Another distinctive conversion was carried out by PacAero as the Tradewind. This featured a lengthened nose to accommodate the tricycle nosewheel, and the Model 18's twin tailfins were replaced by a single fin.

Operational history

Production got an early boost when Nationalist China paid the company US$750,000 for six M18R light bombers, but by the time of the U.S. entry into World War II, only 39 Model 18s had been sold, of which 29 were for civilian customers. Work began in earnest on a variant specifically for training military pilots, bombardiers, and navigators. The effort resulted in the Army AT-7 and Navy SNB. Further development led to the AT-11 and SNB-2 navigation trainers and the C-45 military transport. The United States Air Force (USAF) Strategic Air Command had Model 18 variants (AT-11 Kansans, C-45 Expeditors, F-2 Expeditors (the "F" standing for "Fotorecon", short for "photographic reconnaissance"), and UC-45 Expeditors) from 1946 until 1951. From 1951 to 1955, the USAF had many of its aircraft remanufactured with new fuselages, wing center sections, and undercarriages to take advantage of the improvements to the civil models since the end of World War II. Eventually, 900 aircraft were remanufactured to be similar to the then-current Model D18S and given new designations, constructor's numbers and Air Force serial numbers. The USN had many of its surviving aircraft remanufactured as well, these being redesignated as SNB-5s and SNB-5Ps. The C-45 flew in USAF service until 1963, the USN retired its last SNB in 1972, while the U.S. Army flew its C-45s until 1976. In later years, the military called these aircraft "bug smashers" in reference to their extensive use supplying mandatory flight hours for desk-bound aviators in the Pentagon.

Beech 18s were used extensively by Air America during the Vietnam War; initially more-or-less standard ex-military C-45 examples were used, but then the airline had 12 aircraft modified by Conrad Conversions in 1963 and 1964 to increase performance and load-carrying capacity. The modified aircraft were known as Conrad Ten-Twos, as the maximum takeoff weight (MTOW) was increased to 10,200 lb (4,600 kg). The increase was achieved by several airframe modifications, including increased horizontal stabilizer angle-of-incidence, redesigned undercarriage doors, and aerodynamically improved wingtips. Air America then had Volpar convert 14 aircraft to turboprop power, fitted with Garrett AiResearch TPE-331 engines; modified aircraft were called Volpar Turbo Beeches, and also had a further increase in MTOW to 10,286 lb (4,666 kg).

Spar problems

The wing spar of the Model 18 was fabricated by welding an assembly of tubular steel. The configuration of the tubes in combination with drilled holes from aftermarket STC modifications on some of these aircraft have allowed the spar to become susceptible to corrosion and cracking while in service. This prompted the FAA to issue an Airworthiness Directive in 1975, mandating the fitting of a spar strap to some Model 18s. This led, in turn, to the retirement of a large number of STC-modified Model 18s when owners determined the aircraft were worth less than the cost of the modifications. The corrosion on unmodified spars was not a problem, and occurred due to the additional exposed surface area created through the STC hole-drilling process. Further requirements have been mandated by the FAA and other national airworthiness authorities, including regular removal of the spar strap to allow the strap to be checked for cracks and corrosion and the spar to be X-rayed. In Australia, the airworthiness authority has placed a life limit on the airframe, beyond which aircraft are not allowed to fly.

Manufacturer models

Unless otherwise noted, the engines fitted are Pratt & Whitney R-985 radials.

Model 18A

First production model with seating for two pilots and seven or eight passengers, fitted with Wright R-760E-2 engines of 350 horsepower (260 kW), MTOW: 6,700 lb (3,000 kg)

Model S18A

Version of Model 18A capable of being fitted with skis or Edo 55-7170 floats; MTOW: 7,200 lb (3,300 kg)

Model 18B

Improved model with increased range and useful load, fitted with 285 hp (213 kW) Jacobs L-5 engines

Model S18B

Version of Model 18B capable of being fitted with skis or floats.

Model 18D

Variant with seating for two pilots and nine passengers, fitted with Jacobs L-6 engines of 330 horsepower (250 kW), MTOW: 7,200 lb (3,300 kg).

Model S18D

Version of Model 18D capable of being fitted with skis or Edo 55-7170 floats, MTOW: 7,170 lb (3,250 kg)

Model A18D

Variant of 18D with MTOW increased by 300 lb (140 kg) to 7,500 lb (3,400 kg), fitted with Pratt and Whitney R-985 engines with 450 hp each

Model SA18D

Seaplane version of Model A18D, but same MTOW as S18D, fitted with Edo 55-7170 floats

Model A18A

Version fitted with Pratt and Whitney R-985 engines of 450 horsepower (340 kW), MTOW: 7,500 lb (3,400 kg)

Model SA18A

Seaplane version of Model A18A, fitted with Edo 55-7170 floats, MTOW: 7,170 lb (3,250 kg)

Model 18R

Model with Pratt and Whitney R-985-A1 engines with dual-stage blower for increased power at higher operating altitudes, 450 horsepower (340 kW), seven built, one to Sweden as an air ambulance, six to Nationalist China as M18R light bombers

Model 18S

Nine-passenger pre-World War II civil variant, served as basis for USAAF C-45C

Model B18S

Nine-passenger pre-World War II civil variant, served as basis for USAAF F-2

Model C18S

Variant of B18S with seating for eight passengers, and equipment and minor structural changes

Model D18S

First post-World War II variant introduced in 1945, with seating for eight passengers and MTOW of 8,750 lb (3,970 kg), 1,035 built

Two hundred and eighty D Models were made for the Royal Canadian Air Force (RCAF), given the service name 'Expeditor' and delivered between 1951 and 1952. Seating for RCAF was for five passengers, or two RCAF Navigator students and one RCAF navigator instructor. MTOW for RCAF was 9300 lbs.

3N: Fitted as a navigation trainer with astrodome and two trainee stations in the cabin; 88 built

3NM: Fitted primarily as a navigational trainer, and is fitted with floor lugs to accept transport seats on removal of navigation equipment; 59 built

3NMT: Basically a 3NM, converted to a transport aircraft; 67 built

3NMT(Special): Fitted as a navigation trainer personnel transport. First navigation training position retained, slightly modified ie: removal of air position indicator and replaced with radio compass and indicator from removed second navigation position; in addition, three reclining-type chairs fitted; 19 built

3TM: Normally fitted with transport type seats, but has the necessary wiring, plumbing, and fittings for conversion to a navigation trainer, including provisions for fitting an astrodome; 44 built

3TM(Special): Specifically modified RCAF Expeditor under Project WPB6, and refers specifically to overseas Expeditors; three built

Model D18C

Variant with Continental R9-A engines of 525 horsepower (391 kW) and MTOW of 9,000 lb (4,100 kg), introduced in 1947, 31 built.

Model E18S

Variant with redesigned wing and MTOW of 9,300 lb (4,200 kg); 403 built

Model E18S-9700

Variant of E18S with MTOW of 9,700 lb (4,400 kg); 57 built

Model G18S

Superseded E18S, MTOW of 9,700 lb (4,400 kg); 155 built

Model G18S-9150

Lightweight version of G18, MTOW of 9,150 lb (4,150 kg); one built

Model H18

Last production version, fitted with optional tricycle undercarriage developed by Volpar and MTOW of 9,900 lb (4,500 kg); 149 built, of which 109 were manufactured with tricycle undercarriage

Military versions

C-45

Six-seat staff transport based on C18S; 11 built

C-45A

Eight-seat utility transport based on C18S; 20 built

RC-45A

Redesignation of all surviving F-2, F-2A, and F-2B aircraft by the USAF in 1948

C-45B

Based on C18S, but with modified internal layout; 223 ordered, redesignated UC-45B in 1943

Expeditor I: Some C-45Bs were supplied to the RAF under Lend-Lease.

C-45C

Two Model 18S aircraft impressed into the USAAF, redesignated UC-45C in January 1943

C-45D

Designation given to two AT-7 aircraft converted as passenger transports during manufacture, redesignated UC-45D in January 1943

C-45E

Designation given to two AT-7 and four AT-7B aircraft converted as passenger transports during manufacture, redesignated UC-45E in January 1943

C-45F

Standardized seven-seat version based on C18S, with longer nose than preceding models; 1,137 ordered, redesignated UC-45F

Expeditor II: C-45Fs supplied to the RAF and Royal Navy under Lend-Lease

Expeditor III: C-45Fs supplied to the RCAF under Lend-Lease

C-45G

AT-7s and AT-11s remanufactured in the early 1950s for the USAF to similar standard as civil D18S with autopilot and R-985-AN-3 engines; 372 aircraft rebuilt

TC-45G

Multiengine crew trainer variant of C-45G; AT-7s and AT-11s remanufactured in the early 1950s for the USAF to similar standard as civil D18S, 96 aircraft rebuilt

C-45H

AT-7s and AT-11s remanufactured in the early 1950s for the USAF to similar standard as civil D18S, with no autopilot and R-985-AN-14B engines; 432 aircraft rebuilt

TC-45H

RC-45J

In 1962, all surviving U.S. Navy SNB-5Ps were redesignated RC-45J.

TC-45J

In 1962 all surviving U.S. Navy SNB-5s were redesignated TC-45J.

UC-45J

AT-7 Navigator

Navigation trainer based on C18S, with an astrodome and positions for three students, powered by 450-hp Pratt & Whitney R-985-25 engines; 577 built

AT-7A

Floatplane version of AT-7; six built

AT-7B

Winterised AT-7; nine built

AT-7C

Based on C18S with R-985-AN3 engines; 549 built

AT-11 Kansan

Bombing and gunnery trainer for USAAF derived from AT-7, fuselage had small, circular cabin windows, bombardier position in nose, and bomb bay; gunnery trainers were also fitted with two or three .30-caliber machine guns, early models (the first 150 built) had a single .30-cal AN-M2 in a Beechcraft-manufactured top turret, later models used a Crocker Wheeler twin .30-cal top turret, a bottom tunnel gun was used for tail gunner training, 1,582 built for USAAF orders, with 24 ordered by Netherlands repossessed by USAAF and used by the Royal Netherlands Military Flying School at Jackson, Mississippi.

AT-11A

Conversion of AT-11 as navigation trainer; 36 converted

CQ-3

Conversion of UC-45F, modified to act as drone control aircraft, redesignated as DC-45F in June 1948

F-2

Photo-reconnaissance version based on B18

F-2A

Improved version

F-2B

JRB-1

Photographic aircraft for the U.S. Navy, based on the C18S, fitted with fairing over cockpit for improved visibility, 11 built

JRB-2

Light transport for the U.S. Navy, based on the C18S; 15 built

JRB-3

Photographic version, similar to C-45B; 23 built

JRB-4

Utility transport version, equivalent to UC-45F'; 328 built.

JRB-6

SNB-1

Variant for the U.S. Navy, similar to AT-11; 110 built

SNB-2

Navigation trainer for the U.S. Navy, similar to AT-7, 299 built

SNB-2C

Variant for the U.S. Navy, similar to AT-7C

SNB-2H

Ambulance conversion for the U.S. Navy

SNB-2P

Photo-reconnaissance trainer for the U.S. Navy

SNB-3

Variant for the U.S. Navy, similar to AT-7C

SNB-3Q

Electronic counter-measures trainer for the U.S. Navy

SNB-5

SNB-2s and SNB-2Cs were remanufactured, and designated SNB-5 by the U.S. Navy.

SNB-5P

Photo-reconnaissance trainer for the U.S. Navy

Conversions

PAC Super 18S Tradewind

Custom conversion of Beech D-18S/C-45 to five- to 11-seat executive transport by Pacific Airmotive

Hamilton HA-1

conversion of a TC-45J aircraft

Hamilton Little Liner

Modification of D18S with aerodynamic improvements and new, retractable tailwheel, capable of carrying 11 seats

Hamilton Westwind

Turboprop conversions with various engines

Hamilton Westwind II STD

Stretched conversion powered by two 840-hp PT6As, and with accommodation for up to 17 passengers.

Hamilton Westwind III

two 579-hp PT6A-20s or 630-hp PT6A-27s or 630-hp Lycoming LTS101s.

Hamilton Westwind IV

two 570-hp Lycoming LTP101s or 680-hp PT6A-28s or 750-hp PT6A-34s or 1020-hp PT6A-45s

Volpar (Beechcraft) Model 18

Conversion of Model 18 with nosewheel undercarriage

Volpar (Beechcraft) Super 18

Volpar (Beechcraft) Turbo 18

Beech Model 18s fitted with the Volpar MkIV tricycle undercarriage and powered by two 705-hp Garrett TPE331-1-101B turboprop engines, flat-rated to 605 hp (451 kW), driving Hartzell HC-B3TN-5 three-bladed, reversible-pitch, constant-speed feathering propellers

Volpar (Beechcraft) Super Turbo 18

2x 705 hp (526 kW) Garrett TPE331

Volpar (Beechcraft) C-45G

C-45G aircraft modified with tricycle undercarriage

Volpar (Beechcraft) Turboliner

15-passenger version of the Turbo 18 with extended fuselage, powered by 2 705-hp Garrett TPE331-1-101Bs

Volpar (Beechcraft) Turboliner II

Turboliners modified to meet SFAR 23

Civil

As of 2012, the Beechcraft Model 18 remains popular with air charter companies and small feeder airlines worldwide.

Military

 Argentina

Argentine Air Force

Argentine Naval Aviation

 Bolivia

Bolivian Air Force

 Brazil

Brazilian Air Force

 Canada

Royal Canadian Air Force 394 examples from 1941–1972

Royal Canadian Navy 10 examples from 1952–1960

 Chile

Chilean Air Force

Chilean Army

Chilean Navy

 China/ Taiwan

 Colombia

Colombian Air Force

 Costa Rica

 Côte d'Ivoire

 Dominican Republic

Dominican Air Force

 Ecuador

 El Salvador

Air Force of El Salvador

 France

French Air Force

 Guatemala

Guatemalan Air Force

 Haiti

Corps d'Aviation

 Honduras

Honduran Air Force

 Indonesia

Indonesian Army

Indonesian Air Force

 Iran

 Italy

Italian Air Force operated 125 aircraft from 1949 until the 1970s

 Japan

Japan Maritime Self-Defense Force

Japan Coast Guard

 Mexico

Mexican Air Force

 Netherlands

Royal Netherlands Air Force

Dutch Naval Aviation Service

 Nicaragua

Nicaraguan Air Force

 Niger

Niger Air Force

 Nigeria

 Paraguay

Paraguayan Air Force

 Peru

Peruvian Air Force

 Philippines

Philippine Army Air Corps

 Portugal

Forca Aerea Portuguesa

 Somalia

Somali Air Force

 South Africa

South African Air Force

 South Vietnam

Vietnam Air Force

 Spain

 Sri Lanka

Sri Lanka Air Force

 Sweden

Swedish Air Force

  Switzerland

Swiss Air Force

 Thailand

Royal Thai Air Force

 Tonga

Tongan Maritime Force

 Turkey

Turkish Air Force

 United Kingdom

Royal Air Force

Royal Navy – Fleet Air Arm

 United States

United States Army

United States Army Air Corps

United States Army Air Forces

United States Air Force

United States Marine Corps

United States Navy

 Uruguay

 Venezuela

 Zaire

Argentina

AT-11A 3495 - at the Museo Nacional de Aeronáutica de Argentina in Buenos Aires.

C-45H 5621 - at the Museo Nacional de Aeronáutica de Argentina in Buenos Aires.

C-45H AF-555 - at the Museo Nacional de Aeronáutica de Argentina in Buenos Aires.

H18S c/no. BA-752 (former LV-JFH) - at the Museo Nacional de Aeronáutica de Argentina in Buenos Aires.

Australia

E18S c/no. BA-81 (former N3781B) - at the Queensland Air Museum in Caloundra, Queensland.

Belgium

3NM floatplane c/no CA-191 (former C-FGNR) - at Pairi Daiza.

Brazil

AT-11 4615 - at the Museu Aeroespacial in Rio de Janeiro, Brazil.

C-45F 2856 - at the Museu Aeroespacial in Rio de Janeiro, Brazil.

Canada

C-45H 459 - at the Canadian Bushplane Heritage Centre in Sault Ste. Marie, Ontario. Tail code CF-MJY

3TM 8034 - at the Canadian Bushplane Heritage Centre in Sault Ste. Marie, Ontario.

D18S c/no. A-141 (former CF-MPH)- at the RCMP Academy, Depot Division in Regina, Saskatchewan.

D18S c/no. A-142 (former CF-MPI) - at the Bomber Command Museum of Canada in Nanton, Alberta.

D18S c/no. A-156 - at the Canadian Warplane Heritage Museum in Hamilton, Ontario.

3N c/no. A-652 (former RCAF 1477) - at the Royal Aviation Museum of Western Canada in Winnipeg, Manitoba.

3NMT c/no. A-700 - at the Canadian Air Land Sea Museum at Toronto/Markham Airport in Markham, Ontario.

3NM c/no. A-710 - at the North Atlantic Aviation Museum in Gander, Newfoundland and Labrador.

3NMT c/no. A-782 (former CF-CKT) - at the Canadian Museum of Flight in Langley, British Columbia.

3NMT c/no. A-872 - at the TransCanada Highway in Ignace, Ontario.

3NM c/no. A-895 - at the Alberta Aviation Museum in Edmonton, Alberta.

Chile

D-18S c/no. A-1024 (former FACh 465) - at the Museo Aeronautico y del Espacio in Santiago, Chile.

India

D18S identity unknown - at the Hotel Mayfair Lagoon in Bhubaneswar, Orissa.

Italy

C-45F 6668 - suspended inside the Olbia Costa Smeralda Airport passenger terminal in Olbia, Sardinia. This was the first aircraft owned by Alisarda Airlines and was used in the filming of the movie The Last Emperor.

Malta

C-45H 8304 - under restoration at the Malta Aviation Museum in Ta' Qali, Malta.

Netherlands

C-45G 51-11665 - at the Aviodrome in Lelystad, Netherlands. This aircraft was used in the filming of the Bond movie Octopussy.

D18S (former PH-UBX) - at entrance of Arnhem War Museum

New Zealand

AT-11 3691 - at the Museum of Transport and Technology in Auckland, New Zealand.

Portugal

AT-11 2504 - at the Museu do Ar in Sintra, Portugal.

AT-11 2508 - at a local park in Leiria, Portugal.

Spain

C-45H AF-752 - at Fundación Infante de Orleans in Madrid, Spain.

Turkey

AT-11 Kansan 6390/9-930 - at Istanbul Aviation Museum.

United Kingdom

E18S c/no. BA-111 (former N575C) - at the National Museum of Flight in East Lothian, Scotland.

United States

AT-11 41‐27561 -at the National Museum of the USAF in Dayton, Ohio. or 42-37493

AT-11B 41-27616 -at the Travis Air Force Base Heritage Center at Travis AFB, California.

AT-11 42-36887 - at the Barksdale Global Power Museum in Bossier City, Louisiana.

AT-11 42-37240 - at the Lone Star Flight Museum in Galveston, Texas.

UC-45 42-37496 - at the Wings Over the Rockies Air and Space Museum in Denver, Colorado. This aircraft was originally an AT-11 before being remanufactured.

UC-45F 44-47342 - at the Alaska Aviation Heritage Museum in Anchorage, Alaska.

TC-45H 51-11529 - at the Tri-State Warbird Museum in Batavia, Ohio.

C-45H 51-11696 - at the Museum of Flight in Seattle, Washington.

C-45G 51-11795 - at the Air Mobility Command Museum in Dover, Delaware.

C-45G 51-11897 - at the Castle Air Museum in Atwater, California.

C-45H 52-10539 - at the 1941 Historical Aircraft Group Museum in Geneseo, New York.

C-45H 52-10865 - at the Travis Air Force Base Heritage Center at Travis AFB, California.

C-45H 52-10893 - at the National Museum of the USAF in Dayton, Ohio.

UC-45J 23774 - at Laughlin AFB in Del Rio, Texas.

RC-45J 51233 - at the Tennessee Museum of Aviation in Sevierville, Tennessee.

UC-45J 51291 - at the Aerospace Museum of California in Sacramento, California.

UC-45J 51338 - at the Minnesota Air National Guard Museum in St. Paul, Minnesota.

S18D c/no. 178 - at the Beechcraft Heritage Museum in Tullahoma, Tennessee.

D18S c/no. A-935 - at the Beechcraft Heritage Museum at Tullahoma Regional Airport in Tullahoma, Tennessee.

C-45H AF-824 - at the Beechcraft Heritage Museum in Tullahoma, Tennessee.

E18S c/no. BA-453 - at the Beechcraft Heritage Museum in Tullahoma, Tennessee.

H18 c/no. BA-670 - at the Lone Star Flight Museum in Galveston, Texas.

Specifications (UC-45 Expeditor)

Data from Jane's Fighting Aircraft of World War II.

General characteristics

Crew: 2 pilots

Capacity: 6 passengers

Length: 34 ft 2 in (10.41 m)

Wingspan: 47 ft 8 in (14.53 m)

Height: 9 ft 8 in (2.95 m)

Wing area: 349 ft² (32.4 m²)

Empty weight: 6,175 lb (2,800 kg)

Loaded weight: 7,500 lb (3,400 kg)

Max. takeoff weight: 8,727 lb (3,959 kg)

Powerplant: 2 × Pratt & Whitney R-985-AN-1 "Wasp Junior" radial engines, 450 hp (336 kW) each

Performance

Maximum speed: 225 mph (195 knots, 360 km/h)

Range: 1,200 mi (1,000 NM, 1,900 km) at 160 mph (260 km/h)

Service ceiling: 26,000 ft (7,930 m)

Rate of climb: 1,850 ft/min (9.4 m/s)