Best known for its famous, war-winning World War 2-era fighter, the "Spitfire", Supermarine of the United Kingdom was also a major player in the floatplane / flying boat industry. One of its contributions of the pre-war period became the "Sea Otter" (originally known as the "Sting Ray") which was produced in 292 examples as a biplane-winged "amphibian". This categorization meant that the aircraft was equally-capable of landing and taking off from either traditional runways or from water due to its multi-functional design.
The Sea Otter was developed by the company as a longer-ranged, maritime patrol version of its popular "Walrus" product of 1935 of which 740 were ultimately produced from 1936 until 1944. This aircraft, too, was an amphibian with a biplane wing arrangement and held its engine between the two planes, over the fuselage. The Sea Otter followed suit but installed its sole engine unit within the upper wing mainplane. Unlike the Walrus, which had its propelled driven in a "pusher" arrangement, the Sea Otter reverted to a more traditionally-arranged propeller mounting with the multi-bladed unit held at the front of the engine installation ("puller" arrangement).
It its earliest form, the Sea Otter was outfitted with a Bristol Perseus XI series air-cooled radial piston engine and this was used to drive a two-bladed propeller unit. When this was found to be too weak, a three-bladed propelled was substituted and a first-flight was recorded on September 23rd, 1938. Overheating issues led to a complete powerplant switch, this arriving in the form of the Bristol Mercury XXX series.
With the war in full swing, maritime patrollers like the Sea Otter were soon in high demand as seaways were contested across the globe. The British Air Ministry finally committed to the type through a January 1942 order and the series went on to see considerable wartime service under the banners of both the Royal Air Force (RAF) and Royal Navy (RN). The latter proved the more prolific operator with no fewer than twenty-one squadrons operating the Sea Otter. The RAF utilized the line across nine squadrons as well as one experimental Marine unit.
As designed, the Sea Otter was crewed by four personnel and was given a length of 39.10 feet with a wingspan of 46 feet and a height of 15 feet. Empty weight was 6,800lb against an MTOW of 10,000lb and power from the Mercury XXX radial engine was 965 horsepower. Maximum speed reached 165 miles per hour with a range out to nearly 700 miles, a service ceiling up to 17,000 feet and a rate-of-climb nearing 870 feet-per-minute.
The Sea Otter was modestly armed through 1 x 7.7mm Vickers K machine gun fitted to the nose and 2 x 7.7mm Vickers K machine guns installed in the aft section of the aircraft. Its bombload measured 4 x 250lb drop bombs.
Outwardly, the aircraft was certainly a product of its time. The fuselage was traditionally-arranged with the cockpit seated aft of a nosecone assembly. The front and sides of the cockpit were lined with windows for better viewing by the crew. The biplane wing arrangement consisted of a lower unit fitted to the roof of the fuselage and an upper unit suspended high over the fuselage. The wings were joined by parallel strutworks and cabling. The upper wing unit held the single engine nacelle with the propeller just cleared the fuselage roof. Under each lower wing element were outboard pontoons for water-running / stability. For ground-based running, the aircraft incorporated a conventional "tail-dragge"r stance made up of two main legs emanating from the fuselage sides and a diminutive tailwheel seated under the tail structure. The tail section had a single vertical plane with a pair of mid-mounted horizontal planes.
Two production variants ultimately emerged, the first becoming "Sea Otter Mk I" and this model was used primarily in the reconnaissance and communications role. The follow-up "Sea Otter Mk II" was a dedicated Search and Rescue (SAR) platform. Some 592 units were ordered by the Air Ministry but, in the end, just 292 of the order were realized mainly due to the conclusion of the war in 1945. Global operators went on to include British allies Australia, Denmark, Egypt, France and the Netherlands.
Sea Otters found extended post-war service in both military and civilian markets. In the latter, various facilities were added, including a lavatory and baggage compartment, to better serve passengers.
Australia; Denmark; Egypt; France; Netherlands; United Kingdom
(OPERATORS list includes past, present, and future operators when applicable)
✓Special-Mission: Search & Rescue (SAR)
Ability to locate and extract personnel from areas of potential harm or peril (i.e. downed airmen in the sea).
✓Maritime / Navy
Land-based or shipborne capability for operating over-water in various maritime-related roles while supported by allied naval surface elements.
Used in roles serving the commercial aviation market, ferrying both passengers and goods over range.
✓Intelligence-Surveillance-Reconnaissance (ISR), Scout
Surveil ground targets / target areas to assess environmental threat levels, enemy strength, or enemy movement.
39.9 ft (12.15 m)
45.9 ft (14.00 m)
15.1 ft (4.60 m)
6,834 lb (3,100 kg)
10,020 lb (4,545 kg)
+3,186 lb (+1,445 kg)
(Showcased structural values pertain to the base Supermarine Sea Otter production variant)
1 x Bristol Mercury XXX air-cooled radial piston engine developing 965 horsepower and driving a three-bladed propeller unit in puller configuration.
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