De Havilland Canada DHC-4 Caribou

The de Havilland Canada DHC-4 Caribou (designated by the United States military as the CV-2 and later C-7 Caribou) is a Canadian-designed and produced specialized cargo aircraft with short takeoff and landing (STOL) capability. The Caribou was first flown in 1958 and although mainly retired from military operations, is still in use in small numbers as a rugged "bush" aircraft.
The design was further developed as the de Havilland Canada DHC-5 Buffalo, adding turboprop engines and other changes that further improved its short-field performance to the point where it competes with light aircraft even with a full load.
Design and development.
The de Havilland Canada company's third STOL design was a big step up in size compared to its earlier DHC Beaver and DHC Otter, and was the first DHC design powered by two engines. The Caribou, however, was similar in concept in that it was designed as a rugged STOL utility aircraft. The Caribou was primarily a military tactical transport that in commercial service found itself a small niche in cargo hauling. The United States Army ordered 173 in 1959 and took delivery in 1961 under the designation AC-1, which was changed to CV-2 Caribou in 1962.
The majority of Caribou production was destined for military operators, but the type's ruggedness and excellent STOL capabilities requiring runway lengths of only 1200 feet (365 metres) also appealed to some commercial users. U.S. certification was awarded on 23 December 1960. Ansett-MAL, which operated a single example in the New Guinea highlands, and AMOCO Ecuador were early customers, as was Air America (a CIA front in South East Asia during the Vietnam War era for covert operations). Other civil Caribou aircraft entered commercial service after being retired from their military users.
Today only a handful are in civil use.
The Turbo Caribou Program.
PEN Turbo Aviation of Cape May, NJ, has undertaken the re-engineering of the DHC-4A Caribou to a turbine powered variant, designated DHC-4A Turbo Caribou. The conversion utilizes the PT6A-67T engines and Hartzell 5 Bladed HC-B5MA-3M Constant Speed/Reversing propellers. Overall performance has improved and "new" basic weight is reduced while maximum normal take-off weight remained at 28,500 lbs. Maximum payload is 10,000 lbs. Both Transport Canada (11/14/00) and Federal Aviation Administration (2/27/01) have issued Supplemental Type Certificates for the Turbo Caribou. As of Sept 17, 2014, only 3 air frames have gone through the conversion process. PEN Turbo has stockpiled dozens of air frames at their facility in NJ for possible future conversion. . PEN Turbo Aviation named their company after Perry E. Niforos, who died in the 1992 crash of an "earlier" turboprop Caribou converted by a different firm, NewCal Aviation.
Operational history.
In response to a U.S. Army requirement for a tactical airlifter to supply the battlefront with troops and supplies and evacuate casualties on the return journey, de Havilland Canada designed the DHC-4. With assistance from Canada's Department of Defence Production, DHC built a prototype demonstrator that flew for the first time on 30 July 1958.
Impressed with the DHC4's STOL capabilities and potential, the U.S. Army ordered five for evaluation as YAC-1s and went on to become the largest Caribou operator. The AC-1 designation was changed in 1962 to CV-2, and then C-7 when the U.S. Army's CV-2s were transferred to the U.S. Air Force in 1967. U.S. and Australian Caribou saw extensive service during the Vietnam War.
The U.S. Army purchased 159 of the aircraft and they served their purpose well as a tactical transport during the Vietnam War, where larger cargo aircraft such as the Fairchild C-123 Provider and the Lockheed C-130 Hercules could not land on the shorter landing strips. The aircraft could carry 32 troops or two Jeeps or similar light vehicles. The rear loading ramp could also be used for parachute dropping (also, see Air America).
Under the Johnson-McConnell agreement of 1966, the Army relinquished the fixed wing Caribou to the United States Air Force in exchange for an end to restrictions on Army rotary wing operations. On 1 January 1967, the 17th, 57th, 61st, 92nd, 134th, and 135th Aviation Companies of the U.S. Army were inactivated and their aircraft transferred respectively to the newly activated 537th, 535th, 536th, 459th, 457th, and 458th Troop Carrier Squadrons of the USAF (This was Operation "Red Leaf"). On 1 August 1967 the "troop carrier" designations were changed to "tactical airlift".
Some U.S. Caribou were captured by North Vietnamese forces and remained in service with that country through to the late 1970s. Following the war in Vietnam, all USAF Caribou were transferred to Air Force Reserve and Air National Guard airlift units pending their replacement by the C-130 Hercules in the 1980s.
All C-7s have now been phased out of U.S. military service, with the last example serving again under U.S. Army control through 1985 in support of the U.S. Army's Golden Knights parachute demonstration team. Other notable military operators included Australia, Canada, India, Malaysia and Spain.
In September 1975, a group of 44 civilians, including armed supporters of the Timorese Democratic Union (UDT), commandeered a Royal Australian Air Force (RAAF) Caribou, "A4-140", on the ground at Baucau Airport in the then Portuguese Timor, which was in the middle of a civil war. The Caribou had landed at Baucau on a humanitarian mission for the International Committee of the Red Cross. The civilians demanded that the RAAF crew members fly them to Darwin Airport (also RAAF Base Darwin) in Australia, which they did. After the Caribou arrived there, the Australian government detained the civilians for a short period, and then granted refugee visas to all of them. "The Guardian" later described "A4-140" as "the only RAAF plane ever hijacked", and the incident as "one of the more remarkable stories in Australia’s military and immigration history".
The RAAF retired "A4-140", by then its last Caribou, on 27 November 2009. The aircraft, which was manufactured in 1964, was donated to the Australian War Memorial, Canberra.
Civilian operations.
After retirement from military use, several examples of the Caribou have been purchased by civilian operators for deployment in areas with small airfields located in rugged country with few or poor surface transport links.