de Havilland Canada Dash 7

https://en.wikipedia.org/wiki/De_Hav..._Canada_Dash_7

The de Havilland Canada DHC-7, popularly known as the Dash 7, is a
turboprop-powered regional airliner with short take-off and landing (STOL)
performance. It first flew in 1975 and remained in production until 1988 when
the parent company, de Havilland Canada, was purchased by Boeing and was later
sold to Bombardier. Bombardier sold the type certificate for the aircraft design
to Victoria-based manufacturer Viking Air in 2006.

In the 1960s, de Havilland Canada was already well known worldwide for their
series of high-performance STOL aircraft, notably the very popular DHC-2 Beaver
and DHC-6 Twin Otter. However, these aircraft were generally fairly small and
served outlying routes, as opposed to the busier regional airliner routes which
were already well served by larger, higher-performance turboprop aircraft such
as the Fokker F27, Fairchild F-27, Convair 580, Convair 600, and Hawker Siddeley
748.

The de Havilland Canada company personnel felt they could compete with these
designs in a roundabout way. With their excellent STOL performance, their
designs could fly into smaller airports located in city centres and smaller,
outlying, more austere airports having runways that the other aircraft could not
easily use (unpaved, unimproved). The original specification called for a
40-passenger aircraft with a fairly short range of 200 statute miles, operating
from runways only 2,000 ft long (610 m).

With new noise restrictions coming into effect throughout the 1970s, an aircraft
tailored for this role would also have to be very quiet. Propeller thrust is a
factor of blade length and chord and the speed at which it rotates. To meet
these new regulations, the new design used much larger (oversized) propellers
geared to rotate at a slower speed than is normally designed. Much of the
problem sound from a typical propeller is generated at the tips of the blades
which are rotating just beneath the speed of sound. By using overlarge propeller
blades, no need exists to have the blade tip reach near the speed of sound, and
the speed can therefore be reduced without sacrificing thrust. In reducing the
speed, this noise is reduced substantially. The Dash 7 often landed at only 900
rpm, and took off at only 1,210 rpm. The propellers on the Dash-7 are
constant-speed propellers which change the blade angle to push more or less air
as needed. This can be used to change power while maintaining a constant (and
lower) speed.

In other respects, the new DHC-7 was essentially a larger, four-engine version
of the Twin Otter: the general layout remained similar, with a high aspect
ratio, high-mounted wing, and similar details of the cockpit and nose profile.
Changes included the addition of cabin pressurization (requiring a switch to a
fuselage with a circular cross-section), landing gear that folded forward into
the inner engine nacelles, and a large T-tail intended to keep the elevator
clear of the propwash during take-off (the Twin Otter's empennage was a
cruciform arrangement).


Role
STOL regional airliner

National origin
Canada

Manufacturer
de Havilland Canada

First flight
March 27, 1975

Introduction
February 3, 1978

Status
In service

Primary users
Various airlines
Canadian Forces
United States Army
Venezuelan Navy

Produced
1975–1988

Number built
113

Developed from
de Havilland Canada DHC-6 Twin Otter

Developed into
Bombardier Dash 8

The Kapalua Airport on the island of Maui in Hawaii was constructed specifically
with Dash 7 operations in mind. According to state of Hawaii historical records,
Hawaiian Airlines built this airfield and then initiated scheduled passenger
flights with new Dash 7 turboprops on March 1, 1987. The airline owned this
private airport, which is also known as Kapalua-West Maui Airport, until 1993,
when it was acquired by the state of Hawaii. The 3000-foot runway length at
Kapalua was well suited for Dash 7 operations. The three-letter code for the
Kapalua Airport, JHM, stands for John Henry Magoon, who was president of
Hawaiian Airlines when the airfield and terminal were constructed by the air
carrier. Kapalua is currently served by Mokulele Airlines with Cessna 208 Grand
Caravans.

One hundred Dash 7 turboprops were delivered by 1984, when the production line
was put on hold in favour of the Dash 8. Another 13 were delivered between 1984
and 1988, when the production lines were removed when Boeing bought the company.
The last Dash 7 was bought by Tyrolean Airways.

The original Series 100 represents the vast majority of the aircraft delivered,
and came in two models; the DHC-7-102 passenger version and -103 combi with an
enlarged cargo door. These were followed by the Series 110 which met British CAA
requirements, including the -110 and -111, and finally the Series 150 which
included additional fuel capacity and an improved interior in the -150 and -151.
Plans were made for a Series 200 with the new PT6A-50/7 engines which improved
hot-and-high power, but these plans were shelved when Boeing ended production of
the design.

The mixture of features on the Dash 7 met with limited commercial success. Most
commuter airline turboprop operators used the aircraft as feeder liners into
large airports, where the STOL performance was not considered important. In
comparison to other feeder liners, the Dash 7's four engines required twice the
maintenance of a twin-engine model, thereby driving up operational costs.
Finally, those airports that did require a high-performance STOL operation were
generally small and well served by the Twin Otters; had an airport needed a
larger plane to serve its customer base, they would have built a longer runway.
One exception to this was operations at London City Airport (LCY), which upon
opening in 1987, was capable of handling few other aircraft types besides the
Dash 7 due to its relatively short runway and steep approach. The runway at LCY
was subsequently lengthened, and the approach angle reduced somewhat and since
accepts airliners such as the Airbus A220, Airbus A318, British Aerospace BAe
146 and Embraer 190 types. Noise criteria remain strict in comparison with other
international airports.

The Dash 7 also gained a number of military orders. The first of these was for
two aircraft for the Canadian Armed Forces, which needed them to transport
high-ranking passengers and freight around Europe. These aircraft received the
CF designation CC-132 and were delivered to 412 Transport Squadron at Canadian
Forces Base Lahr, in West Germany.

The United States Army operates several Dash 7 aircraft as surveillance
platforms with the designation EO-5C (RC-7B before 2004) under the Airborne
Reconnaissance Low program.

The design of a much more "conventional" twin-engine design commenced at de
Havilland in 1978, resulting in the extremely popular Dash 8. The DHC-7
production line eventually delivered 113, of which six have been lost and one
scrapped. Many of the rest remain in service.

Specifications

General characteristics
Crew: 2
Capacity: 50 passengers
Length: 80 ft 7?3/4 in (24.58 m)
Wingspan: 93 ft 0 in (28.35 m)
Height: 26 ft 2 in (7.98 m)
Wing area: 860 sq ft (79.90 m2)
Aspect ratio: 10:1
Empty weight: 27,690 lb (12,560 kg)
Max. takeoff weight: 44,000 lb (20,000 kg)
Powerplant: 4 × Pratt & Whitney Canada PT6A-50 turboprops, 1,120 shp (835 kW)
each

Performance
Maximum speed: 231 knots (266 mph (428 km/h))
Range: 690 nm (795 mi, 1,279 km) (with 50 passengers and baggage)
Service ceiling: 21,000 ft (6,400 m) (25,000 ft without passengers)
Rate of climb: 1,120 ft/min (6.2 m/s) (en-route, flaps and landing gear up)




*