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Canadian Forces Aircraft — DeHavilland Canada CC-138 Twin Otter |
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Update – 21 Aug 2008:
According to the Ottawa Citizen, the Harper government has rejected a proposal for 4 new
northern utility aircraft. Instead, 440 Squadron's Twin Otters will be re-winged – no other major
upgrades are planned – so that they can continue to fly until 2017.
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"...'Thought I should find you here all right,' said the Otter..."
The short field performance of the Twin Otters is partly due to their light weight [2] and the
fully-reversible Hartzell propellers tranforming propulsion into braking power. A Twin Otter is the
antithesis of a modern aircraft in many ways. Unpressurized and having fixed undercarriages, CC-138s combine
turboprop power with the structural techniques of another era. An unpressurized aircraft has a lighter airframe and
can fly with its doors removed (useful for supply drops since the air- craft has no rear ramp). That simple but
rugged undercarriage also keeps the CC-138's weight down.[3]
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CC-138 Twin Otter
Specifications
| Name: |
DeHavilland DHC-6-300 |
Dimen:
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Span 19.8m, wing area 39
m2,
length 15.1m, ht 5.66m |
Power:
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2x P&WC PT6A-27 turbo-
props , 507 kW
(680 shp),
3-blade Hartzell propellors |
| Ceiling: |
Service 8230 m (27000 ft) |
| Range: |
1427 km (769 nm) max [4] |
| Payload: |
2999 kg or 20 passengers |
| Weight: |
5600kg empty, 7600kg max |
Speed:
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337 km/h (181 kts) max
274 km/h (145 kts) cruise |
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Twin Otter's Future: "... quid turpe, quid utile, quid non"
The Feb. 2005 budget included funding for a "light utility" aircraft to replace the high-hour
CC-138s. A difficulty was that no direct replacement for the Twin Otter existed. This left open the
expansion of the Fixed-Wing SAR program – for much
larger aircraft. Fortunately, the situation has now changed – the Twin Otter is back in production and main- taining claims to Arctic
sovereignty has greater emphasis. Despite this, new Arctic utility aircraft are no longer a government
priority. The four CC-138s will be re-winged [5] and serve until 2017.
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[1] There have been nine CC-138s in total (see Bill Walker's Canadian Military Aircraft Serial
Numbers for a complete listing). In June 1986, 13807 crashed killing all eight 418 Sqn crew aboard.
In 1971, Twin Otter 13808 was destroyed on the ground in Kashmir at the outbreak of the India-Pakistan war.
That CC-138 was in Kashmir on UN assignment at the time and was strafed in error by an Indian Air Force
fighter.
[2] The CC-138s supply Regular Force outposts like CFS Eureka on Ellesmere Island but the Twin Otter
is also the only CF aircraft able to operate from unprepared sea-ice or small, rough-surfaced gravel airstrips in
support of Canadian Ranger patrols. Lightness and compact size are only part of the equation.
'Twotter' STOL characteristics are enhanced by ailerons that droop along with the flaps to
increase lift.
[3] A non-retractable undercarriage means that the Twin Otter is no speed demon but that landing gear is
remarkably robust. The CC-138s can be fitted with high flotation 'tundra tires' for rough ground, skis
or, in the past, with twin floats (these are no longer used by 440 Sqn).
[4] The CF list the CC-138's maxium range as 1427 km (886 statute miles or 769 nautical miles). Standard range
for the DHC-6-300 is usually listed at 920 nautical miles (1050 miles or 1705 km). With a 1450kg payload, range is
150 nautical miles (172 mi / 276 km) with VFR reserves.
[5] Viking Air of Sidney, BC owns the Twin Otter wing jigs and has been manufacturing new wings
for this aircraft for more than 15 years.
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DeHavilland Canada's 'Twotter' – A STOL for Arctic Utility
CFB Namao for search and rescue duties – one CC-138 being lost on SAR duty.[1] In 1994,
the remaining 'Twotters' moved north to Yellow- knife, supporting Canadian Ranger and
Regular forces in the Arctic. [2]