Short Empire

https://en.wikipedia.org/wiki/Short_Empire

The Short Empire was a medium-range four-engined monoplane flying boat, designed
and developed by Short Brothers during the 1930s to meet the requirements of the
growing commercial airline sector, with a particular emphasis upon its
usefulness upon the then-core routes that served the United Kingdom. It was
developed and manufactured in parallel with the Short Sunderland maritime patrol
bomber, which went on to serve in the Second World War; a further derivative
that was later developed was the piggy-back Short Mayo Composite.

The development of the Short Empire had been heavily influenced by its primary
customer, Imperial Airways, who had originally developed the requirements to
which it was initially ordered and designed from. Imperial Airways, and its
successor, the British Overseas Airways Corporation (BOAC), along with Qantas
and TEAL, operated the type in commercial service. Upon entering service, the
Empire routinely flew between the British mainland and Australia and the various
British colonies in Africa and Asia, typically carrying a combination of
passenger and mail cargoes; the Empires were also used on various other routes,
such as on the service between Bermuda and New York City.

The Empire also saw military service during the Second World War. The Royal Air
Force (RAF), Royal Australian Air Force (RAAF), Royal New Zealand Air Force
(RNZAF), and briefly the Royal Canadian Air Force (RCAF) used the type to
conduct various military operations, particularly as an airborne platform for
anti-submarine patrols and for general transport duties.

During the 1930s, global demand for air travel was consistently and rapidly
growing. Thus, keen to grow their share of this emerging market, British airline
Imperial Airways was keen to expand and sought the latest technology to do so.
In particular, Imperial Airways' technical advisor, Major Robert Hobart Mayo
developed a specification for a new type of aircraft to serve both passenger and
freight requirements throughout the world. This specification sought an aircraft
that would be capable of carrying up to 24 passengers in spacious comfort along
with adequate room for airmail or freight while simultaneously being capable of
a cruising speed of 170 MPH and a range of at least 700 miles; the capacity for
an extended range of 2,000 miles to serve the North Atlantic route was also
stipulated. According to aviation author Geoffrey Norris, at the time, it was
considered to be impossible to construct a land-based aeroplane of such size and
weight that still possessed acceptable landing/take-off performance, thus it was
determined that a flying boat would be required.

Early on, it was apparent that Short Brothers, who had previously developed and
produced several large flying boats for Imperial Airways and the Royal Air Force
(RAF) which had proven to be sound designs in terms of performance and safety,
would be a frontrunner to fulfil the requirement. However, Shorts was hesitant
to build such an aircraft, due to the necessary advances involved, straight from
the drawing board without the production of a preceding prototype, and thus
requested to be allowed the time to build such an aircraft; this was rejected by
Imperial Airways, stating that such a delay was not permissible. In 1935,
Imperial Airways announced the placement of an order for 28 flying boats of an
as-of-yet undesigned type, weighing 18 tonnes each; the order was reportedly
hailed as being "one of the world's boldest experiments in aviation", while
sceptics referred to the decision less favourably as being a 'gamble'.

A design team led by Arthur Gouge set about designing what would become the
Empire. It was quickly determined that, in order to possess the sufficient
clearance between the tips of the propellers and the water, the wing would need
to be in a high mounted position; initially to be housed in a hump above the
fuselage for sufficient height, the fuselage depth was instead increased,
providing more internal volume than required but enabling a lighter and stronger
integration of the cantilever wing with the fuselage. Shorts' own convention for
wide planing bottomed hulls for their flying boats was overturned as the
18-tonne weight would generate excessive drag with such a configuration;
following a series of water tank experiments, a new type of planing bottom with
a reduced beam deemed suitable. The basic aerodynamic design was derived from
the smaller Short Scion Senior flying boat, which served in all but name as a
half-scale prototype for the Empire and for its sibling, the military-orientated
Short Sunderland.


Role
Flying boat mail and passenger carrier

Manufacturer
Short Brothers

Designer
Arthur Gouge

First flight
3 July 1936

Introduction
Delivered 22 October 1936
First revenue flight 6 February 1937

Retired
1946–47

Status
Retired

Primary users
Imperial Airways/BOAC
Qantas Empire Airways
Royal Australian Air Force
Royal Air Force

Produced
1936–1940

Number built
42

Unit cost

£ 48,830


Variants
Short Mayo Composite

On 8 February 1937, one of the Empire flying boats, Castor, conducted the first
regular flight, flying from Calshot, Hampshire, England to Alexandria, Egypt.
This flight, which covered a distance of roughly 2,300 miles (3,700 km)
non-stop, showing that Britain could move military materiel to its overseas
bases. On 18 February 1937, Caledonia, the first of the Empires built, flew the
same Colshot-Alexandria route; it was able to traverse the route non-stop at an
average speed of 170 MPH.

On 5 July 1937, the first crossing of the Atlantic by an Empire flying boat was
conducted. On an experimental basis, Caledonia, piloted by Captain W N Cummings,
flew a 1,993 miles (3,207 km) route from Foynes on the River Shannon west to
Botwood, Newfoundland. On the same day, an American Sikorsky S-42 flying boat
flew the opposite direction.Caledonia took just over 15 hours (including a
period spend searching for a landing spot), flying at an altitude of 1,500 to
5,000 ft (460 to 1,520 m) to cover 1,993 miles (3,207 km)—an average speed of
about 130 mph (210 km/h). On its return flight, conducted on 22 July 1937,
Caledonia flew the same route in the opposite direction in a time of 12 hours;
in comparison to the competing Sikorsky S-42, the Empire was able to traverse
the overall route faster.

In an attempt to manage the Atlantic crossing, an alternative 'piggy-back'
approach was trialled. This concept had been strongly advocated for by Imperial
Airways' technical advisor, Major Robert Hobart Mayo, as a means of
significantly increasing both range and payload, and had been well received by
both the airline and the British Air Ministry, the latter of which placed an
order with Shorts. Using the S.21 design (based on the S.23) as the carrier, a
smaller four-engined floatplane, the Short S.20, was mounted upon its back; the
most obvious difference between the S.21 and regular S.23 aeroplanes was the
additional superstructure to carry the floatplane. Only a single example was
built of the S.21 carrier aircraft, named Maia, and of the S.20, named Mercury.
Together, they were known as the Short Mayo Composite.

On 21 July 1938, a successful mid-air launch of Mercury was executed off the
west coast of Ireland while carrying a 600 lb payload of mixed cargo and mail;
it arrived at Montreal, Canada, 2,860 miles (4,600 km) 22 hrs 22 min later,
having achieved an average speed of 141 mph (227 km/h). In further flights, the
Empire-Mercury combination went on to set a number of long distance records; one
such flight was conducted on 6 October 1938, flying from Dundee, Scotland to
Orange River, South Africa, covering 6,045 miles (9,728 km) in 42 hrs 5 min.
However, in spite of the demonstrated merits and workability of the concept, the
outbreak of the Second World War resulted in the effective termination of all
development work. During wartime, there was interest in the concept using
alternative land-based aircraft to deliver Hawker Hurricane fighter aircraft for
aerial protection over the mid-Atlantic.

After Italy entered the Second World War in June 1940, it became impossible for
mail to be safely flown between Britain and Egypt (and thus onto Australia) via
the Mediterranean. Accordingly, a new "Horseshoe Route" was established that ran
from Auckland/Sydney via Cairo (following the old "Eastern Route") to Durban,
South Africa, and thence by sea to Britain. This was restricted after the loss
of Singapore in February 1942 to being between Durban and Calcutta, India.

Wartime experience in operating the type at overload weights resulted in the
realization that the Empires could take off at considerably higher weights than
the conservative maxima provided by Shorts and, although the last Empire
crossings to America were made in 1940 (by Clare and Clyde), many more flights
were made on the long, demanding and vital over-water Lisbon-Bathurst flights.

Specifications (Short S.23)

General characteristics
Crew: 5 (2 pilots, navigator, flight clerk and steward)
Capacity:
24 day passengers or 16 sleeping passengers
1.5 ton of mail

Length: 88 ft 0 in (26.82 m)
Wingspan: 114 ft 0 in (34.75 m)
Height: 31 ft 9 3/4 in (9.696 m)
Wing area: 1,500 sq ft (140 m2)
Empty weight: 23,500 lb (10,659 kg)
Gross weight: 40,500 lb (18,370 kg)
Powerplant: 4 × Bristol Pegasus XC radial engines, 920 hp (690 kW) each

Performance
Maximum speed: 200 mph (322 km/h; 174 kn)
Cruise speed: 165 mph (266 km/h; 143 kn)
Range: 760 mi (660 nmi; 1,223 km)
Service ceiling: 20,000 ft (6,100 m)
Rate of climb: 950 ft/min (4.8 m/s)