“The Seven Crystal Balls” was a mystery in which scientists involved in studying Inca mummies were attacked by a substance which would lead to a mysterious disease leading to hallucinations. Tintin and Captain Haddock decided to unravel the mystery and the book ends with both of them leaving for Peru in a Sea-plane. Why sea-plane? Well this book was published in 1948 and the aircraft of the time did not have very long ranges. So it was safer to cross the Atlantic in a sea-plane. Also, South America did not have very well developed airstrips and airports and it was easier to operate from the sea as one did not need large and complex infrastructure. The sea-plane in which the two travelled to Peru was a Short Sunderland.
The Short Sunderland was developed and manufactured by Short Brothers of UK in response to the British Air Ministry’s specifications R.2/33 of 1933. These specifications were for the development of a long range maritime flying patrol boat bomber for the Royal Air Force. Two companies participated in the competition to develop the aircraft, the Short Brothers and Saunders-Roe. However, the prototype built by Saunders-Roe met with an accident during the initial trials and only the Short Sunderland was left in the fray. The aircraft was named after the port of Sunderland. Design of the aircraft was to some extent influenced by the design of a civilian flying boat called the Short S.23 Empire. This aircraft was being developed in response to the British Post Master General’s decision that all long distance First Class Mail would be transported by air henceforth. In fact, the second prototype Sunderland travelled all the way from the UK to Singapore in 1938 halting at Gibraltar, Malta, Alexandria, Habbaniyah, Bahrain, Karachi, Gwalior, Calcutta, Rangoon and Mergui.
The Sunderland was in service with several armed force like the Royal Air Force, Royal Australian Air Force, Royal Canadian Air Force, Royal New Zealand Air Force, South African Air Force, Norweigian Air Force, French Navy and Portugese Navy. After the war several of these aircraft, like the one in which Tintin and Captain Haddock travelled, were converted for civlian use. They were in service in Argentina, Australia, USA, UK, Uruguay, Norway and New Zealand.
The first Sunderland flew in 1938. It was designed with an all metal fuselage with rivetted construction. The aircraft had a twin deck arrrangement with the flight deck, and weapons and armament on the upper deck and sleeping accomodation for six crew members on the lower deck. It has a toilet and a small galley (kitchen) on the lower deck with kerosene stoves for cooking. The aircraft had a patrolling range of nealry 14 hours. It was armed with sixteen 0.303 Browining machine guns and two 0.5″ Browning machine guns. It could carry up to 2,000 lbs (910 kgs) of bombs, depth charges and mines. These planes played a very important role in the war against the U-boats in the Atlantic and the Mediterranean. Post world war 2 they were used extensively during the Korean War as well as during the air support to Berlin.
The Sunderland was powered by four Bristol Pegasus XVIII, nine cylinder radial engines. Each cylinder had four pushrod operated valves, two intake and two exhaust. The air being sucked into the engine was compressed using two speed centrifugal supercharger. The cylinders were air cooled and used 100 Octane petrol as fuel. Each engine generated 965 BHP at 2,475 rpm for take off at sea level, 835 BHP at 2,250 rpm at 8,500 feet for continuous climb and maximum power of 965 BHP at 2,600 rpm at 13,000 ft for combat emergency. This burst of power was limited to just five minutes of operation.
The Sunderland was 26 m (8′ 4″) in length, 10 m ( 32′ 10.5″) in height and had a wing span of 34.39 m (112′ 9.5″). It weighed in at 26,332 kg (58,000 lbs) when fully loaded. The aircraft carried a military crew of 9-11 personnel. The four Pegasus XVIII engines pushed the Sunderland to a maximum speed of 336 km/h (210 mph) at 6,500 feet. The aircraft had a cruising speed of 285 km/h (178 mph) at 5,000 feet. The Sunderland had a range of 2,848 km (1,780 miles) and a service ceiling of 16,000 ft.
Once converted for civilian use, the plane could carry 22 passengers with 2 tons of cargo or 16 passengers with 3 tons of cargo. Regular services were operated by both the RAF as well as the BOAC to Lagos and Calcutta. The later passenger versions were more luxurious carrying 24 passengers including 16 with sleeping accomodation.