Boulton Paul Balliol
|Balliol T.2 in 1955|
|Manufacturer||Boulton Paul Aircraft|
|Designer||John Dudley North|
|First flight||30 May 1947|
|Primary users||Royal Air Force|
Royal Navy Fleet Air Arm
Royal Ceylon Air Force
The Boulton Paul Balliol and Sea Balliol are monoplane military advanced trainer aircraft built for the Royal Air Force (RAF) and the Royal Navy Fleet Air Arm (FAA) by Boulton Paul Aircraft. Developed in the late 1940s, the Balliol was designed to replace the North American Harvard trainer. It used the Rolls-Royce Merlin engine. The Sea Balliol was a naval version for deck landing training.
Design and development
The Balliol was developed to meet Air Ministry Specification T.7/45 for a three-seat advanced trainer powered by a turboprop engine, competing against the Avro Athena. It was a conventional low-wing monoplane with a retractable main undercarriage and a fixed tailwheel. Pilot and instructor sat side by side ahead of the observer. The first prototype first flew on 30 May 1947, being temporarily powered by an 820 hp (611 kW) Bristol Mercury 30 radial engine. The second prototype, powered by the intended Armstrong Siddeley Mamba turboprop, first flew on 17 May 1948, the world's first single-engined turboprop aircraft to fly. The Air Ministry had second thoughts about its training requirements, and issued a new specification, T.14/47, requiring a two-seat trainer, powered by a Rolls-Royce Merlin piston engine.
The Merlin powered Balliol, designated Balliol T.2, first flew on 10 July 1948, and after extensive evaluation, it was chosen over the Athena, with large orders being placed to replace some of the Harvards in RAF service. The observer's seat of the Mk 1 was removed, the side-by-side seats remaining.
By 1951, however, the Air Ministry changed its mind about its training requirements yet again and decided to introduce a jet-powered advanced trainer, the de Havilland Vampire T.Mk11.
The RAF naming conventions for various types preferred that pure trainers, not conversion type trainers, should have names related to education or places of learning e.g. Airspeed Oxford, Avro Tutor and Athena, the Percival Prentice and Provost and De Havilland Dominie. Balliol is an Oxford University College and it alliterated with 'Boulton Paul'
Pre-production Balliols were delivered to the RAF's Central Flying School in 1950, but with the change in air-training policy, the Balliol was only delivered to one Flying Training School, – No. 7 at RAF Cottesmore, replacing their Harvards. The Balliol later served at the RAF College, Cranwell until replaced there by the de Havilland Vampire T.Mk 11 in 1956. The Balliol also saw limited squadron service from 1953 with No. 288 Squadron RAF based at RAF Middle Wallop. Operations continued until the squadron was disbanded in September 1957.
The Sea Balliols served with 781 squadron at Lee-on-Solent and 1843 Squadron RNVR at Abbotsinch. The last one was delivered in December 1954. Some remained active at Abbotsinch until September 1963.
Two Balliols were used for the testing of radar absorbing coatings.
The only Balliols exported were 12 Mk.2s to the Royal Ceylon Air Force, 7 from RAF cancelled contracts and five from RAF stocks, which were replaced by a further five production aircraft.
- P.108 Balliol T.Mk 1
- Prototypes, 3 built, powered by the Armstrong Siddeley Mamba turboprop engine
- Balliol T.Mk 2
- Two-seat advanced training aircraft for the RAF; 196 built, (166 built by Boulton Paul, and 30 built by Blackburn Aircraft).
- Sea Balliol T.Mk 21
- Two-seat advanced training aircraft for FAA. A total of 30 built by Boulton Paul.
- Aeroplane and Armament Experimental Establishment
- Empire Test Pilot's School
- Royal Air Force
- Royal Navy, Fleet Air Arm
- On display
- Balliol T2 CA310 on display on the parade ground at SLAF Ground Combat Training Unit at Diyatalawa.
- Stored or under restoration
- Balliol T2 CA303 stored by the Sri Lankan Air Force Museum, Ratmalana Air Base.
- On display
- Sea Balliol T21 WL732 former Royal Navy and A&AEE aircraft on display in Hangar 1 as part of the transport and training collection at the Royal Air Force Museum Cosford.
- Stored or under restoration
- Balliol T2 WN149 under restoration to display standard by the Boulton Paul Association at Wolverhampton, West Midlands.
Data from Aircraft of the Royal Air Force
- Crew: 2
- Length: 35 ft 1 1⁄2 in (10.706 m)
- Wingspan: 39 ft 4 in (11.99 m)
- Height: 12 ft 6 in (3.81 m)
- Wing area: 250 sq ft (23 m2)
- Airfoil: NACA 65
- Empty weight: 6,730 lb (3,053 kg)
- Gross weight: 8,410 lb (3,815 kg)
- Fuel capacity: 125 imp gal (150 US gal; 570 L)
- Powerplant: 1 × Rolls-Royce Merlin 35 liquid-cooled V12 engine, 1,245 hp (928 kW)
- Propellers: 4-bladed de Havilland constant speed propeller, 11 ft 3 in (3.43 m) diameter
- Maximum speed: 288 mph (463 km/h; 250 kn) at 9,000 ft (2,700 m)
- Cruise speed: 231 mph (372 km/h; 201 kn) at 5,500 ft (1,700 m) (weak mix)
- Stall speed: 83 mph (134 km/h; 72 kn) 
- Endurance: 3 hr at 220 mph (190 kn; 350 km/h)
- Service ceiling: 32,500 ft (9,900 m)
- Rate of climb: 1,790 ft/min (9.1 m/s)
- Time to altitude: 6 min to 10,000 ft (3,000 m)
- Takeoff distance to 50 ft (15 m): 1,350 ft (410 m)
- Landing distance from 50 ft (15 m): 1,950 ft (590 m)
- Guns: 1 × 0.303 in (7.7 mm) Browning machine gun in port wing
- Rockets: Provision for 4 × "60-lb" rockets
Aircraft of comparable role, configuration and era
- Thetford 1957, pp. 94–95.
- Donald 1997, p. 180.
- Jefford 2001, p. 85.
- "Boulton Paul Balliol T. 21." Archived 10 August 2009 at the Wayback Machine RAF Museum. Retrieved: 10 August 2009.
- Brew, Boulton Paul Aircraft
- "Individual History – Boulton Paul P.108 Sea Balliol T Mk 21 WL732." Archived 5 June 2011 at the Wayback Machine Royal Air Force Museum, 2007. Retrieved: 10 October 2009.
- Ellis 2008, p. 176.
- Ellis 2008, p. 155.
- Bridgman 1953, pp. 52–53.
- Bridgman, Leonard. Jane's All the World's Aircraft 1953–54. London: Jane's All The World's Aircraft Publishing Co. Ltd., 1953.
- Donald, David, ed. The Encyclopedia of World Aircraft. London: Aerospace Publishing, 1997. ISBN 1-85605-375-X.
- Ellis, Ken. Wrecks & Relics, 21st edition. Manchester, UK: Crécy Publishing, 2008. ISBN 978-0-85979-134-2.
- Jefford, Wing Commander C.G., MBE, BA, RAF (Retd). RAF Squadrons, a Comprehensive Record of the Movement and Equipment of all RAF Squadrons and their Antecedents since 1912. Shrewsbury, Shropshire, UK: Airlife Publishing, 2001. ISBN 1-84037-141-2.
- Thetford, Owen. Aircraft of the Royal Air Force 1918–57. London: Putnam, First Edition 1957.
- Thetford, Owen. British Naval Aircraft since 1912, Fourth Edition. London: Putnam, 1994. ISBN 0-85177-861-5.
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