The de Havilland Canada DHC-7, popularly known as the Dash 7, is a
turboprop-powered regional airliner with 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. Design and development
In the 1960s, de Havilland Canada was already well known worldwide for their
series of high-performance STOL aircraft, notably the very popular 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 and 600, and Hawker Siddeley
748. The de Havilland Canada company 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. 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.
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 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 there is no
need to have the blade tip reach near the speed of sound, and the RPM can
therefore be reduced without sacrificing thrust. In reducing the RPM this noise
is reduced substantially. The Dash 7 often landed with only 900 RPM, and took
off at only 1,210 RPM. The propellers on the Dash-7 allow for feathering, a
change in the blade angle to push more or less air as needed. This can be used
to increase airspeed and climb rate while maintaining a constant RPM.
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, most details of the cockpit and nose profile.
Changes included the addition of cabin pressurization, 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 takeoff.
The Twin Otter incorporated "flaperons" that drooped the ailerons as part of the
flaps, but these were not included in the Dash 7 due to weight and complexity.
Instead, the ailerons were reduced in size to allow more flap area, and were
augmented with two sets of roll spoilers, or "spoilerons". The inboard
roll spoilers operate at all speeds while the outboard roll spoilers only
operate at speeds less than 130KIAS to allow for more roll control at slower
speeds. Upon touchdown, both the inboard and outboard roll spoilers extend in
unison to aid in destroying lift created by the wing. Each wing also includes two
ground spoilers which only extend on touchdown. Most of the trailing edge is
spanned by a complex double Fowler flap arrangement for high lift at low speed.
During a typical STOL landing, flaps are selected to the 45° position allowing
for steeper descents and slower approach speeds. Depending on weight, the VREF
speed with flaps at 45° is between 70-85 knots. On touchdown, through "squat
switches" in the main gear, the flaps automatically retract to the 25°
position and thus reduce lift once on the runway producing better braking
performance. The flaps also retract to 25° when engine power is increased
during a go-around procedure. The four-engine layout aids lift at low
speeds due to the wide span of the propellers blowing air over the wing.
When reverse thrust is selected on landing, the props reverse pitch, push
air forward and slow the aircraft very effectively along with the anti-skid
wheel brakes. More importantly, if an engine fails, the asymmetric thrust is
much less than on a twin-engine layout, thereby increasing safety and allowing
for a lower VMC with an engine inoperative .
Operational history Development started in 1972 and the
prototype first flew on March 27, 1975. Testing went smoothly, and the first
delivery took place to Rocky Mountain Airways on February 3, 1978. The Dash 7
enabled Rocky Mountain Airways to operate scheduled passenger air service
from Denver into the Avon STOLport in Colorado which was controlled by the
airline. The Avon STOLport was located in a mountain valley in close proximity
to the Vail ski resort. Another close-in ski resort airfield served by Rocky
Mountain Airways with Dash 7 flights from Denver was Steamboat Springs
Airport in Colorado. With a relatively short runway length of 4,452 feet and an
airfield elevation of 6,882 feet, the Dash 7 was well suited for operations
from this airport located in the Rocky Mountains.
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 -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 tankage and an
improved interior in the -150 and -151. There were plans 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
feederliners into large airports, where the STOL performance wasn't considered
important. In comparison to other feederliners, 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 the airport needed a larger plane to serve its customer base,
they would have built larger runways. One exception to this was operations at
London City Airport which, upon opening in 1987, was capable of handling few
other aircraft types besides the Dash 7 due to its relatively short runway as
well as steep approach. The runway at London City Airport was subsequently
lengthened and now accommodates jet operations including scheduled airline
flights operated with Airbus A318 and British Aerospace BAe 146 jetliners.
The Dash 7 also gained a number of military orders. The first of these was
for two aircraft for the Canadian Armed Forces, who 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 under the Airborne Reconnaissance Low
program. Transport Canada operates a single
DHC-7-150IR aircraft to conduct maritime surveillance, pollution and ice patrols
as part of the Transport Canada National Aerial Surveillance Program. The
aircraft's home base is Ottawa, Ontario, Canada. During the summer months this
aircraft conducts patrols throughout the Canadian Arctic, Alaska and Greenland.
During the fall and winter months this aircraft conducts patrols of the Great
Lakes and east or west coasts of Canada as required.
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.
Variants DHC-7-1
Prototypes, two built. DHC-7-100
Production passenger variant with a maximum of 54 passengers.
DHC-7-101 Production passenger/cargo variant with
a maximum 50 passengers and a left hand forward cargo door.
DHC-7-102 Production passenger variant with a
maximum of 54 passengers. DHC-7-103
Production passenger/cargo variant with a maximum of 50 passengers and a left
hand forward cargo door. DHC-7-110
DHC-7-102 certified for use in the United Kingdom.
DHC-7-111 DHC-7-103 certified for use in the
United Kingdom. DHC-7-150
Improved 1978 version with higher gross weight, increased fuel capacity and
improved passenger amenities, DHC-7-150IR
One series 150 modified in 1986 for Transport Canada for ice/pollution
patrols of the Canadian Arctic. CC-132
Canadian military designation for the Series 102/103
O-5A ARL-I Converted by California Microwave
Incorporated 1991-92 EO-5B ARL-C
United States military designation for Series 102
EO-5C ARL-M Converted by California Microwave
Incorporated 1996 RC-7B ARL-M
Redesignated EO-5C in 2004. Accidents and incidents
The de Havilland Canada DHC-7 has been involved in six accidents with a total
of 68 fatalities. April 28, 1982 - Aerovías Nacionales de
Honduras DHC-7-103 hijacked at Le Ceiba-Goloson International Airport in
Honduras with no loss of life May 9, 1982 - Alyemda DHC-7-103 crashed
into sea near Aden International Airport in Yemen killing 23 of 49 on board.
June 23, 1982 - Henson Airlines DHC-7 hijacked at Staunton-Shenandoah Valley
Airport, in Virginia with no lives lost. February 15, 1983 - Rio Airways Flight
252 DHC-7-102 hijacked at Nuevo Laredo, Mexico with none of 20 on board injured.
May 6, 1988 - Widerøe Flight 710 DHC-7-102 crashed on a hillside during
poor weather near Brønnøysund Airport in Norway, killing 36 on board.
November 28, 1998 DNK Aviation Leasing Group DHC7-102 crashed after engine
failed during a test flight near Ashburton, United Kingdom killing the
crew of 2. July 23, 1999 - US Army DHC-7-102
crashed into mountain near Orito in Putumayo province in Colombia killing
all seven on board. September 7, 1999 - Skyline DHC-7-102
damaged from belly landing at Port Harcourt Airport in Nigeria with 19 on
board. September 4, 2002 - Asian Spirit Flight
897 DHC-7-102 slid off runway at Manila-Ninoy Aquino International
Airport with 49 on board. May 1, 2006 - Trans Capital Air for
United Nations Mission in Liberia DHC-7-102 crash-landed at Zwedru Airport
in Liberia after landing gear failed to extend, with 40 on board uninjured.
Operators = Airline and other operators=
As of April 27, 2012, a total of 47 Dash 7 aircraft remain in airline and other
services. Canada
Air Tindi Trans Capital Air
Transport Canada Voyageur Airways
Egypt Petroleum Air Services
Indonesia Pelita Air Service
Kenya Airkenya Express
Malaysia Berjaya Air
United Kingdom British Antarctic Survey
Venezuela Linea Turistica Aerotuy
= Former operators= Australia
Jetcraft Aviation Austria
Tyrolean Airways Canada
AirBC City Express
Time Air Wardair
Colombia Helicol
Guatemala Aviones Comerciales de Guatemala
Aéro Ruta Maya Honduras
Sahsa Israel
Arkia New Zealand
Ansett New Zealand Nigeria
Skyline Norway
Widerøes Flyveselskap DNK Aviation Leasing Group
Papua New Guinea Air Niugini
Philippines Asian Spirit
Zest Airways Slovenia
Adria Airways Tanzania
Regional Air Services United Kingdom
Brymon London City Airways
United States Air Pacific
Air Wisconsin Atlantic Southeast Airlines
Continental Express Delta Connection and Rio Airways)
Era Aviation Farwest Airlines
Golden Gate Airlines Golden West Airlines
Hawaiian Airlines Henson Airlines
MarkAir Express Maverick Airways
Pan Am Express Paradise Island Airlines
Ransome Airlines Rio Airways
Rocky Mountain Airways - worldwide launch customer
Ross Aviation Trans World Express
Venezuela Conviasa
Yemen Alyemda
= Other civilian operators= The British Antarctic Survey operates a
single Dash 7 in support of its research program in Antarctica. The aircraft
undertakes regular shuttle flights between either Stanley on the Falkland
Islands, or Punta Arenas in Chile, and the Rothera Research Station on Adelaide
Island. It also operates to and from the ice runway at the Sky Blu Logistics
Facility on the Antarctic mainland. A single DHC-7 150IR is owned and operated
by Transport Canada conducting coastal pollution and ice patrols across the
Canadian Arctic. = Military operators=
Canada Canadian Forces
United States United States Army
Venezuela Venezuelan Navy
Specifications Data from Jane's All The World's
Aircraft 1982–83 General characteristics
Crew: 2 Capacity: 50 passengers
Length: 80 ft 73⁄4 in Wingspan: 93 ft 0 in
Height: 26 ft 2 in Wing area: 860 sq ft
Aspect ratio: 10:1 Empty weight: 27,690 lb
Max. takeoff weight: 44,000 lb Powerplant: 4 × Pratt & Whitney Canada
PT6A-50 turboprops, 1,120 shp each Performance
Maximum speed: 231 knots) Range: 690 nmi
Service ceiling: 21,000 ft Rate of climb: 1,120 ft/min
See also Related development
de Havilland Canada DHC-6 Twin Otter de Havilland Canada DHC-8 Dash 8
Aircraft of comparable role, configuration and era
Antonov An-24 ATR 42
Convair 540600/640 Dornier 328
Fokker F27 Hawker Siddeley 748
Saab 340 Related lists
List of STOL aircraft List of airliners
References = Notes=
= Bibliography= External links
The Dash 7 Homepage de Havilland DHC-7 Dash-7