Supermarine Seal II
{{good article}}
{{Short description|1920s British flying boat}}
{{Use dmy dates|date=November 2017}}
{{Use British English|date=November 2017}}
| {{Infobox aircraft begin
|name = Seal II |image = Flight International Magazine 1921-11-03-pdf 0004 Seal.jpg |caption = }}{{Infobox aircraft type |type = Reconnaissance flying boat |manufacturer = Supermarine |designer = R.J. Mitchell |first flight = May 1921 |introduced = |retired = |status = |primary user = |more users = |produced = |number built = 1 |unit cost = |developed from = |variants with their own articles = Supermarine Seagull }} |
The Supermarine Seal II was a British flying boat developed by Supermarine after it secured a British Air Ministry order for a prototype three-seater fleet spotter amphibian. The prototype, which had to be capable of landing on Royal Air Force (RAF) aircraft carriers, was designed by Supermarine's R.J. Mitchell, who incorporated suggestions made after the Supermarine Commercial Amphibian achieved second place after it was entered for an Air Ministry competition in 1920.
The Seal II was a biplane with the lower wing mounted on top of the fuselage. Powered by a {{convert|450|hp}} Napier Lion water-cooled piston engine, it was the first British flying boat with the propeller positioned in front of the engine. The pilot was seated forward in the nose with the fuel tanks placed behind him, and a second cockpit was located behind the wing.
The Seal II first flew on 21 May 1921 prior to being assessed by the RAF. After being modified and fitted with a different engine, it was renamed the Seagull prior to being delivered to the RAF two months later. In November 1921 the Seal II was one of a number of aircraft sold to the Imperial Japanese Navy Air Service and shipped out with the British-led Sempill Mission to Kasuimiguara.
Background
The flying boats built by Supermarine at their works at Woolston, Southampton, had a reputation for being seaworthy and solidly constructed. They were considered by Flight magazine to be "always of substantial construction, a proper boat-built job, a boat that will fly rather than an aeroplane that will float".{{cite magazine |title=The Supermarine "Seal" Mark II: An Interesting Deck-landing Amphibian Flet-Spotter |url=https://archive.org/details/Flight_International_Magazine_1921-11-03-pdf/page/n3/mode/2up?q= |location=London |magazine=Flight |publisher=Royal Aero Club |via=Internet Archive |date=3 November 1921 |pages=713{{ndash}}715 |access-date=15 September 2021 }}
Flying boat designs produced by Supermarine's R.J. Mitchell, later to become the chief designer at Supermarine, and shown to the British Air Ministry, together with the good performance of the Supermarine Commercial Amphibian, resulted in Supermarine winning an order for a prototype three-seater fleet spotter amphibian. The Air Ministry produced specification 7/20 around the prototype aircraft,{{sfn|Pegram|2016|p=32}} a biplane that was specified to be capable of landing on Royal Air Force (RAF) aircraft carriers as slowly as possible, with the maximum amount of control.{{sfn|Andrews|Morgan|1981|p=69}}
Design
File:Supermarine Seal general arrangement drawings.jpg
File:Supermarine Seal (front view).jpg
Hubert Scott-Paine, who owned Supermarine, named the aircraft Seal II. Historians have presumed that this happened because the Commercial Amphibian was briefly designated by Scott-Paine as the Seal I.{{sfn|Pegram|2016|p=32}}
Supermarine incorporated suggestions made by the Air Ministry after the company's Commercial Amphibian entered a seaplane competition at Martlesham Heath and Felixstowe in September 1920.{{cite web |title=Type: Supermarine Amphibian (G-EAVE). Location: Bookham. Report No: C35. |url=https://discovery.nationalarchives.gov.uk/details/r/C6576503 |publisher=The National Archives |access-date=4 September 2021}}{{sfn|Pegram|2016|p=30}} Mitchell produced the first drawings for the Seal II, which date from 25 November 1920.{{sfn|Andrews|Morgan|1981|p=68}}
The Seal II was a two-bay biplane with the lower wing mounted on top of the fuselage and the {{convert|450|hp}} Napier Lion water-cooled piston engine mounted below the centre-section of the upper wing. It was the first British flying boat propelled with a tractor configuration (with its engine mounted with the propeller in front so that the aircraft is "pulled" through the air). The wings were rearward folding. The fuselage, of a type designed by Linton Hope during the First World War,{{sfn|Andrews|Morgan|1981|pp=69{{ndash}}70, 81}} was roughly circular in cross-section and was built of planking over a framework of formers and stringers covered with fabric, with the planing surfaces built as separate structures, divided into watertight compartments.
The second cockpit of the Seal was located behind the wing, and the undercarriage retractor system was of a new design so that the need for cables was avoided.{{sfn|Pegram|2016|p=31}} The pilot, who was protected in his cockpit by a cover, was seated forward in the nose with the fuel tanks placed behind him and in front of the other crew members.{{sfn|Andrews|Morgan|1981|p=70}}
Operational history
The Seal II prototype was allocated the serial N146,{{sfn|Andrews|Morgan|1981|p=356}} and first flew on 21 May 1921. It was officially handed over to the RAF on 2 June 1921, who flew the aircraft to the Isle of Grain to be assessed.{{sfn|Pegram|2016|pp=32, 42}}{{sfn|Andrews|Morgan|1981|p=68}} Following the trials, which were generally satisfactory, the RAF recommended a number of modifications to be made that included moving the position of the fuel tanks from inside the hull to the upper wing, and increasing the size of the rudder and the fin.{{sfn|Pegram|2016|p=42}} The aircraft was re-engined with a {{convert|480|hp}} Napier Lion II power unit.{{sfn|Andrews|Morgan|1981|p=72}}
Mitchell made further modifications to the Seal II after two prototypes (of specification 21/21) were ordered by the Air Ministry at the beginning of 1922. He lengthened the hull by {{convert|2|feet}}, modified the tail surfaces, and amended the shape of the wings to correct the aircraft's balance.{{sfn|Pegram|2016|p=42}} The prototypes were designated N185 and N159,{{sfn|Pegram|2016|p=42}} and renamed as Seagulls on 4 July 1921 prior to being delivered to the RAF.{{sfn|Andrews|Morgan|1981|p=71}} A Seagull was exhibited at the annual RAF Aerial Pageant at Hendon in June 1922.{{sfn|Thetford|1994|p=292}}{{cite magazine |title=The R.A.F. Aerial Pageant |url=https://archive.org/details/Flight_International_Magazine_1922-06-22-pdf/page/n1/mode/2up |location=London |magazine=Flight |publisher=Royal Aero Club |via=Internet Archive |date=22 June 1922 |page=351 |access-date=18 September 2021 }} A variant of the Seal, the Fleet Spotting Gunnery Amphibian, was designed by Mitchell, but not built.{{sfn|Pegram|2016|p=32}}
Both a Seal II and a Seagull were sold to the Imperial Japanese Navy Air Service when it acquired aircraft after a fact-finding mission in Britain. The aircraft were shipped out with the British-led Sempill Mission, arriving in Kasuimiguara, {{convert|40|miles}} north-east of Tokyo, in November 1921.{{sfn|Peattie|2007|p=19}}{{sfn|Andrews|Morgan|1981|pp=71, 355{{ndash}}356}}{{cite magazine |title=The British Aviation Mission for the Imperial Japanese Navy |url=https://archive.org/details/Flight_International_Magazine_1924-04-10-pdf/page/n9/mode/2up?q= |location=London |magazine=Flight |publisher=Royal Aero Club |via=Internet Archive |date=10 April 1924 |pages=209{{ndash}}210 |access-date=15 September 2021 }} It was acquired "with a view to experimenting with it under actual service conditions".
Specifications (Seal II)
{{Aircraft specs
|ref=Supermarine Aircraft since 1914{{sfn|Andrews|Morgan|1981|p=81}}
|prime units?=imp
|crew=3
|length ft=32
|length in=10
|length note=
|span ft=46
|span in=0
|span note=
|height ft=14
|height in=10
|height note=
|wing area sqft=620
|wing area note=
|aspect ratio=
|airfoil=
|empty weight lb=4100
|empty weight note=
|gross weight lb=5600
|gross weight note=
|max takeoff weight lb=
|max takeoff weight note=
|fuel capacity=
|more general=
|eng1 number=1
|eng1 name=Napier Lion
|eng1 type=W-12 water-cooled piston engine
|eng1 hp=450
|eng1 note=
|prop blade number=4
|prop name=wooden fixed-pitch pusher propeller
|prop dia ft=
|prop dia in=
|prop dia note=
|max speed mph=112
|max speed note=
|cruise speed mph=
|cruise speed note=
|stall speed mph=
|stall speed note=
|never exceed speed mph=
|never exceed speed note=
|range miles=
|range note=
|combat range miles=
|combat range note=
|ferry range miles=
|ferry range note=
|endurance= 4 hours
|ceiling ft=
|ceiling note=
|climb rate ftmin=
|climb rate note=
|time to altitude={{cvt|10000|ft|0}} in 17 minutes
|lift to drag=
|wing loading lb/sqft=
|wing loading note=
|fuel consumption lb/mi=
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|more performance=
}}
See also
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References
{{reflist}}
Sources
{{commons category|Supermarine Seal II}}
- {{cite book |last1=Andrews |first1=Charles Ferdinand |last2=Morgan |first2=Eric B. |title=Supermarine Aircraft since 1914 |url=https://books.google.com/books?id=p3NTAAAAMAAJ |date=1981|edition=|publisher=Putnam |location=London |isbn=978-03701-0-018-0}}
- {{cite book|last=Peattie|first=Mark R|author-link=Mark Peattie|title=Sunburst: The Rise of Japanese Naval Air Power, 1909-1941|publisher=Naval Institute Press|location=Annapolis, Maryland|year=2007|isbn=978-1-61251-436-9}}
- {{cite book |last1=Pegram |first1=Ralph |title=Beyond the Spitfire: The Unseen Designs of R.J. Mitchell |date=2016 |publisher=The History Press |location=Pegram |isbn=978-0-7509-6515-6}}
- {{cite book |last=Thetford |first=Owen |title=British Naval Aircraft Since 1912 |location=London |publisher=Putnam |year=1994 |isbn=978-0-85177-861-7}}
{{Supermarine aircraft}}
Category:1920s British military reconnaissance aircraft
Category:Single-engined tractor aircraft
Category:Single-engined piston aircraft
Category:Aircraft with retractable conventional landing gear