De Havilland Canada DHC-7 Dash 7

Summary

Description

In the 1960s, de Havilland Canada aimed to expand its line of STOL aircraft into the regional airliner market. The design objective was an aircraft with superior STOL capabilities, able to operate from smaller, city-center airports and unpaved airstrips inaccessible to conventional aircraft. Initial specifications called for a 40-passenger aircraft with a range of 700 nautical miles (1296km) and the ability to operate from 2,000 ft (610 m) runways. Noise restrictions of the 1970s influenced the design, leading to oversized, slow-turning propellers for noise reduction. Development began in 1972, with the prototype DHC-7 first flying on March 27, 1975. The first delivery was made to Rocky Mountain Airways on February 3, 1978. Production continued until 1988. Following de Havilland Canada's acquisition by Boeing in 1986 and subsequent sale to Bombardier, Bombardier sold the type certificate for the design to Victoria-based manufacturer Viking Air in 2006.

The DHC-7 was conceived as a larger, four-engine evolution of the Twin Otter, retaining the high aspect ratio, high-mounted wing, and similar cockpit and nose profile. Cabin pressurization was added, requiring a circular cross-section fuselage. The landing gear folded forward into the inner engine nacelles. A large T-tail was incorporated to keep the elevator clear of the propwash during take-off, a departure from the Twin Otter's cruciform empennage. While the Twin Otter utilized flaperons, the Dash 7 employed reduced-size ailerons to accommodate larger flaps, augmented by two sets of roll spoilers (spoilerons). Inboard roll spoilers operate at all speeds, while outboard roll spoilers function below 130 KIAS. Upon touchdown, both sets extend to disrupt lift, supplemented by ground spoilers. Most of the trailing edge is occupied by a complex, double Fowler flap arrangement, typically set to 45° for STOL landings.

The Dash 7's operational history saw its deployment in various roles. Rocky Mountain Airways, the launch customer, utilized the Dash 7 for scheduled passenger service from Denver into challenging STOLports such as Avon and Steamboat Springs in Colorado. Its STOL capabilities enabled access to airports with short and high-elevation runways, like Telluride Airport. Hawaiian Airlines also employed the Dash 7 for short-field performance at Kapalua Airport on Maui. Military users have included the Canadian Armed Forces, who operated the CC-132 variant (Series 102/103) for personnel and freight transport, and the United States Army, operating several Dash 7 aircraft as surveillance platforms designated EO-5C (formerly RC-7B) under the Airborne Reconnaissance Low program, O-5A ARL-I (converted by California Microwave Incorporated 1991–92), and EO-5B ARL-C (United States military designation for Series 102 converted by California Microwave Incorporated in 1996). The Venezuelan Navy operated one aircraft delivered in 1982. The Dash 7 faced commercial challenges; its four-engine configuration resulted in higher maintenance costs compared to twin-engine turboprops, limiting broader adoption by commuter airlines.

Main Variants:

• DHC-7-100: This was the production passenger variant, designed to carry a maximum of 54 passengers with a takeoff weight of 43,000 lb (20,000 kg).

• DHC-7-101: A production passenger/cargo variant, it could accommodate a maximum of 50 passengers and featured a left-hand forward cargo door, also with a takeoff weight of 43,000 lb (20,000 kg).

• DHC-7-102: This model was another production passenger variant, similar to the -100, but with a slightly higher takeoff weight of 44,000 lb (20,000 kg).

• DHC-7-103: Functioning as a production passenger/cargo variant, this version also featured a left-hand forward cargo door and had a takeoff weight of 44,020 lb (19,970 kg).

• DHC-7-150: An improved version from 1978, it boasted a higher gross weight, increased fuel capacity, and enhanced passenger amenities.

Technical specifications

Current operating countries

Country		Units
	United States	4

Numbers in parentheses, e.g. '(+5)', indicate units ordered but not yet delivered.

All operators

Canada • United States • Venezuela