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de
Havilland Hercules
The need of a replacement
for the D.H.10s used on the RAF's air mail service between Cairo and
Baghdad, coupled with an agreement reached in 1925 for Imperial Airways to
take over the service, led to a requirement being issued which was met by
the de Havilland D.H.66 Hercules, a three-engined biplane with a 155 cu ft
(4.39 m³) baggage compartment, space for seven passengers and 465 cu ft
(13.17 m³) of mail and a three man crew.
The prototype flew on 30th
September 1926 following receipt of an order for five aircraft from
Imperial Airways. Such was the speed and comparative simplicity of
procedures in those days that the prototype carried out acceptance
flights, took part in some crew training and was delivered to Cairo by
mid-December. An inaugural flight between Croydon and India left the UK on
27th December and arrived in Delhi on 8th January 1927.
The fifth aircraft was delivered to Cairo in March 1927. The performance
of these aircraft impressed West Australia Airways, then using D.H.50s.
Four examples of the Hercules were ordered, the first flying in March
1929, and the type entered service with WAA on the Perth-Adelaide route on
2nd June. By then Imperial had ordered a sixth aircraft and its seventh
and final aircraft followed in February 1930.
Imperial's sixth Hercules had an enclosed pilot's cabin, a modification
which later became standard on the remaining aircraft. The airline's need
for these last two Hercules followed the loss of three in crashes between
September 1929 and April 1931, but only the first caused fatalities.
Aircraft shortage led to the purchase by Imperial of two WAA Hercules in
1930-1; one of these crashed in Southern Rhodesia in November 1935 and
Imperial eventually withdrew its last aircraft from service in December
1935, having sold three to the South African Air Force. Their eventual
history is not known, but the longest surviving Hercules was probably one
of the two former WAA aircraft, being used in New Guinea between Lae and
Wau and destroyed by enemy action in 1942.
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Design
Company: |
The de
Havilland Aircraft Co Ltd |
|
First
Flight: |
30 September
1926 |
|
DH.66
Hercules: |
11 - de
Havilland Aircraft Co Ltd |
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Type
Specification |
|
Applies
to: |
de Havilland
DH.66 Hercules |
|
Type: |
Three engined
passenger carrying biplane |
|
Wing: |
Equal span
biplane. Two sets of interplane struts on either side of fuselage. Top
centre section carried from fuselage by four steel tube struts. Wing
structure of spruce spars and ribs covered with fabric. Ailerons on
bottom planes only |
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Fuselage: |
Rectangular
structure, of steel tubes. Inside steel frame is a timber framed and
plywood walled cabin and outside steel frame is covered with fabric |
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Tail
Unit: |
Biplane type.
Two fixed horizontal surfaces, the upper one of considerably smaller
chord and slightly less span than bottom. Elevators on bottom surface
only. Three fins interconnect the two surfaces, with three balanced
rudders |
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Landing
Gear: |
Divided type.
Consists of two Vees, attached under wing engine mountings and two
sloping axles hinged to the bottom fuselage longerons |
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Power
Plant: |
Three 450 hp
Bristol Jupiter VI air cooled engines, one in the nose and one mounted
on each lower wing |
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Accommodation: |
Enclosed
pilots cockpit, seating two, behind nose engine. Under wing is main
cabin providing space for fourteen passengers |
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Dimensions |
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Span: |
79 ft 6 in |
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Length: |
56 ft |
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Height: |
18 ft 3 in |
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Wing
Area: |
1,547 sq ft |
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Weights |
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Empty: |
8,890 lb |
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Loaded: |
15,600 lb |
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Performance |
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Max
Speed: |
130 mph |
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Initial
Rate of Climb: |
635 ft/min |
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Absolute
Ceiling: |
13,200 ft |
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