Short S.25 & 26 Sunderland

Le gros hydravion britannique raconté sur Wikipedia en anglais :

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The Short S.25 Sunderland was a British [Vous devez être inscrit et connecté pour voir ce lien] developed for the [Vous devez être inscrit et connecté pour voir ce lien] by [Vous devez être inscrit et connecté pour voir ce lien].

Based in part upon the [Vous devez être inscrit et connecté pour voir ce lien] flying boat, the flagship of [Vous devez être inscrit et connecté pour voir ce lien],
the S.25 was extensively re-engineered for military service.

It was one of the most powerful and widely used flying boats throughout the [Vous devez être inscrit et connecté pour voir ce lien], and was involved in countering the threat posed by German [Vous devez être inscrit et connecté pour voir ce lien] in the [Vous devez être inscrit et connecté pour voir ce lien].

It took its name from the city of [Vous devez être inscrit et connecté pour voir ce lien] in northeast England.

Development


The early 1930s saw intense competition in developing long-range flying boats for intercontinental passenger service.

The United Kingdom had no match for the new American [Vous devez être inscrit et connecté pour voir ce lien] flying boats, which were making headlines all over the world.

The powers-that-be in Britain felt that something should be done.

Les photos qui ne sont pas sur Wikimedia proviennent du MoD britanniques, Royal Navy. Merci !

Celle-ci est officiellement australienne : Merci aussi

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In 1934, the [Vous devez être inscrit et connecté pour voir ce lien] declared that all first-class [Vous devez être inscrit et connecté pour voir ce lien] sent overseas was to travel by air,
effectively establishing a subsidy for the development of intercontinental air transportation in a fashion similar to the U.S. domestic program a decade earlier.

In response, [Vous devez être inscrit et connecté pour voir ce lien] announced a competition between aircraft manufacturers to design and produce 28 flying boats, each weighing 18 tons (18.2 tonnes) and having a range of 700 miles (1,100 km) with capacity for 24 passengers.

The contract went almost directly to [Vous devez être inscrit et connecté pour voir ce lien] of [Vous devez être inscrit et connecté pour voir ce lien].

Although Short had long built flying boats for the military and for Imperial Airways, none of them was in the class of size and sophistication requested, but the business opportunity was too great to pass up.

[Vous devez être inscrit et connecté pour voir ce lien], head of the company, began a fast-track program to come up with a design for a flying boat far beyond anything they had ever built.

While the first [Vous devez être inscrit et connecté pour voir ce lien] was under development, the British [Vous devez être inscrit et connecté pour voir ce lien] was taking actions that would result in a purely military version of the big Shorts flying boats.

The 1933 [Vous devez être inscrit et connecté pour voir ce lien] called for a next-generation flying boat for ocean reconnaissance.

The new aircraft had to have four engines but could be either a monoplane or biplane design.

The R.2/33 specification was released roughly in parallel with the Imperial Airways requirement, and while Shorts continued to develop the S.23, they also worked on a response to the Air Ministry's need at a lower priority.

The military flying boat variant was designated S.25 and the design was submitted to the Air Ministry in 1934.

Chief Designer [Vous devez être inscrit et connecté pour voir ce lien] originally intended that a [Vous devez être inscrit et connecté pour voir ce lien] be mounted in the bow with a single
[Vous devez être inscrit et connecté pour voir ce lien] in the tail.

As with the S.23, he tried to make the drag as low as possible.

The nose was much longer than that of the S.23.

[Vous devez être inscrit et connecté pour voir ce lien] also designed a flying boat, the [Vous devez être inscrit et connecté pour voir ce lien], in response to the R.2/33 competition, and prototypes of both the S.25 and A.33 were ordered by the Ministry for evaluation.

Vue d'un S 23 " Empire "

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Design


The S.25 shared much in common with the S.23 but was most notably different in that it had a deeper hull profile.

As construction proceeded the armament was changed to a single [Vous devez être inscrit et connecté pour voir ce lien] in the nose turret and four [Vous devez être inscrit et connecté pour voir ce lien] in the tail.

Then there was a change in the tail turret to a powered version and Gouge had to devise a solution for the resulting movement of the aircraft's centre of gravity aft.

The prototype first flew, without armament, on 16 October 1937.

After the preliminary flight trials the prototype (K4774) had its wings swept back by 4 degrees and 15 minutes by adding a spacer into the front spar attachments.

This moved the centre of lift enough to compensate for the changed centre of gravity.

This arrangement flew on 7 March 1938 with [Vous devez être inscrit et connecté pour voir ce lien] XXII engines of 1,010 hp (750 kW).

Un Bristol Pegasus

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As with the S.23, the Sunderland's fuselage contained two decks with six bunks on the lower one, a galley with a twin [Vous devez être inscrit et connecté pour voir ce lien], a yacht-style [Vous devez être inscrit et connecté pour voir ce lien], an anchoring winch and a small machine shop for inflight repairs.

The crew was originally intended to be seven but increased in later versions to 11 crewmembers or more.

It was of all-metal construction (a lot flush-riveted) except for the control surfaces that were of fabric-covered metal frame construction.

The flaps were [Vous devez être inscrit et connecté pour voir ce lien] that moved rearwards and down, increasing the wing area and adding 30% more lift for landing.

The thick wings carried the four nacelle-mounted Pegasus engines and accommodated six drum fuel tanks with a total capacity of 9,200 litres (2,025 [Vous devez être inscrit et connecté pour voir ce lien], 2,430 U.S. gallons).

Four smaller fuel tanks were added later behind the rear wing spar to give a total fuel capacity of 11,602 litres
(2,550 Imperial gallons, 3,037 U.S. gallons), enough for eight- to 14-hour patrols.

Impressionnante réserve de fioul

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The specification called for an offensive armament of a 37 mm gun and up to 2,000 pounds (910 kg) of bombs, [Vous devez être inscrit et connecté pour voir ce lien] or (eventually) [Vous devez être inscrit et connecté pour voir ce lien].

The ordnance was stored inside the fuselage and was winched up to racks, under the wing centre section, that could
be traversed out through doors on each side of the (bomb room) fuselage above the waterline to their offensive position.

Defensive armament included a [Vous devez être inscrit et connecté pour voir ce lien] FN-13 powered turret with four [Vous devez être inscrit et connecté pour voir ce lien] in the extreme tail and a manually operated .303 on either side of the fuselage, firing from ports just below and behind the wings.

Much later a twin gun turret was to be dorsal mounted on the upper fuselage, about level with the wing trailing edge, bringing the total defensive armament from three to 18 machine guns. This was more than any other aircraft during the war.

Portable beaching gear could be attached by ground crew so that the aircraft could be pulled up on land (beached).

The gear consisted of two, two-wheeled struts that could be attached to either side of the fuselage, below the wing, with a two- or four-wheel trolley and tow bar attached under the rear of the hull.

Equipment and on-water management


Like all water-based aircraft there was a need to be able to navigate on water and to control the craft up to and at a mooring.

In addition to the standard navigation lights there was also a demountable mooring mast that was positioned on the upper fuselage just aft of the astrodome hatch with a 360 degree white light to show that the aircraft was moored.

The crew were trained in common marine signals for watercraft to ensure safety in busy waters.

The craft could be moored to a [Vous devez être inscrit et connecté pour voir ce lien] by a [Vous devez être inscrit et connecté pour voir ce lien] that attached to the [Vous devez être inscrit et connecté pour voir ce lien] under the forward fuselage.

When the craft was off the buoy the forward end of the pendant was attached to the front of the hull just below the bomb aimer's window.

For anchoring there was a demountable bollard that fixed to the forward fuselage from where the front turret was
retracted to allow an airman to man the position and pick up the buoy cage or to toss out the anchor.

A standard stocked anchor was stowed in the forward compartment alongside the anchor winch.

However, depending on the operating area, a number of different kinds of anchor might be carried to cope with, for example, coral, sand or rock anchorages.

For taxiing after landing, the galley hatches were used to extend sea [Vous devez être inscrit et connecté pour voir ce lien] that could be used to turn the aircraft or maintain its across wind progress (by deploying the drogue on one side only), or to slow the forward motion as much as possible (both deployed).

When not in use the drogues were hand hauled back inboard, folded and stowed in wall-mounted containers just below the hatches.

Operation of the drogues could be a very dangerous exercise if the aircraft was travelling on the water at speed or in strong currents, because the approximately three ft (one metre) diameter drogue would haul up on its five tonne attachment cable end inside the galley very sharply and powerfully.

Once deployed it was normally impossible to recover a drogue unless the aircraft was stationary relative to the local tidal flow.

Another means of direction control on the water was by application of the flight controls, rudder and ailerons.

The ailerons would cause asymmetric drag from the airflow and, ultimately, drop a float into the water to cause drag on that wing.

Otherwise the pilots could use variable engine power to control the direction and speed of the aircraft on the water.

In adverse combinations of tide, wind and destination this could be very difficult.

By the time a buoy approach was being made, upwind and uptide, the speed of advance could be brought to a stop by shutting down the inboard engines and blipping the magneto switches on the two outboard engines so that they were, effectively, idling at 250-350 rpm, instead of the 750-800 normally.

Otherwise the best that could be done was to attack the mooring buoy with the minimum speed that allowed control of the aircraft and hope that the bow crewman could manage to grab the buoy cage going by and temporarily attach to the aircraft's bollard with a painter.

A permanent attachment to the buoy's pendant was then quickly made after the aircraft was bought to a halt on its overrun and while it was being blown or washed back but before reaching the full extent of the mooring lines and the buoy's anchorage.