Britten-Norman BN-2 Islander, Defender and Trislander

Type Description and Produced Variants

BN-2 and BN-2A Series Islander
BN-2A Series Defender
BN-2A Mk.III Series Trislander
BN-2B Series Islander
BN-2B Series Defender
BN-2T Series Islander
BN-2T Series Defender
BN-2T-4 Series Defender 4000

• BN-2
• 10 seat (pilot + 9 pax) cantilever high wing all-metal monoplane transport. The constant constant chord, two spar wing, with 2 degrees of incidence, is a single continuous structure with separate wing tips, and is fitted with slotted ailerons and single-slotted flaps. Each spar consists of angle section booms with shear webs of 18 s.w.g. L72 sheet which. Over the central area the spar booms comprise three nested angles. They are Radix bonded and reduce in both directions outboard, first to two sections and finally to one. Outboard of these points the spars are of a lighter section, riveted and butt strapped to make up the complete spar unit.The sopars, together with three inter-spar Z section stringers top and bottom and the skin plating, constitute a torsion box.
  The fuselage is a conventional riveted four-longeron semi-monocoque structure of pressed frames and stringers and metal skin, using aluminium alloys. The tail unit is a cantilever two-spar structure, with pressed ribs and metal skin, a fixed-incidence tailplane and mass-balanced elevator. The non-retractable tricycle undercarriage has twin wheels on each main unit and a single steerable nosewheel, the cantilever main legs being mounted aft of the rear spar. Passenger seating is on side by side front seats and four bench seats; there is no aisle. The bench-seats can be easily fitted in a forward or aft-facing arrangement, or can be removed and folded to stow in the baggage compartment when only freight is carried.. Access to all seats being via three forward-opening doors, tthe pilot entry door on forward port side, passenger rows 2 and 3 accessed by a wide door on the forward starboard side, and rows 4 and 5 by a wide door on the aft port side. A baggage compartment is located at the rear of cabin, with a port-side loading door. The prototype first flew in 1966 with two 210 h.p. Rolls-Royce built Continental IO-360-B powerplants, but was later modified with 260 h.p. Lycoming O-540-E4C5 powerplants in revised cowlings fitted further outboard, driving a Harzell HC-C2YK-2B or -2C two-blade constant-speed feathering metal propeller, along with a 4 ft. increase in wingspan and redesigned tailplane, BN-2 production aircraft being to this standard.

• BN-2R
• BN-2 fitted with a Jonas Aircraft developed Rajay turbocharging installation, for improved climb performance in hot climates.

• BN-2S
• A single BN-2 converted for test purposes by FG Miles Aviation at Ford aerodrome in Sussex under contract to B-N. Two Rolls Royce built 300 h.p. turbo-charged Continental TSIO-520-E powerplants.

• BN-2E Mk.II Super
• Insertion of 33 inches in the fuselage forward of the wing, and the removal of the internal baggage area step each gained an extra double seat, increasing the passenger seating to 13 in addition to the pilot. Access to the new passenger row 6 was via a new aft door in the starboard side, and new aft side windows were provided for the extra passenger row. The baggage access door was moved further aft. As this was a prototype installation, it seems unlikely that any attempt was made to recoup lost baggage volume.
  B-N had identified the need to increase engine power for the BN-2 Super in the form of 400hp Lycoming IO-720 engines. However, the BN-2 Super in its initial configuration retained the original 260hp Lycoming IO-540-E4C5 engines. During a brief series of test flights it was found that although the handling was unaffected, the centre of gravity range was somewhat restricted, this being a factor in precluding further development of the BN-2 Super.

• BN-2A
• The BN-2A was fitted with a new square shaped rear nacelle and undercarriage leg fairings of increased chord, under Modifications NB/M/319 and NB/M/358. This resulted in an improvement to the performance and raised the maximum operational weight as far as the single engine performance was concerned to 6,300 lb. This became the definative BN-2 production variant, and spawned a family of sub-variants (see table):

  260 h.p. Lycoming O-540-E4C5	300 h.p. Lycoming IO-540-K1B5	Max AUW	Drooped LE	Drooped Flaps	Increased Span w/ Tip Tanks	Lengthened Nose
  BN-2A		6300
  BN-2A-1					X
  BN-2A-6 & 6R	BN-2A-4*		X
  BN-2A-7 & 7R	BN-2A-5*		X		X
  BN-2A-8 & 8R	BN-2A-2		X	X
  BN-2A-9 & 9R	BN-2A-3		X	X	X
  BN-2A-8S		6600	X	X		X
  	BN-2A-3S		X	X	X	X
  BN-2A-24			X	X		X
  BN-2A-25	BN-2A-23		X	X	X	X
  BN-2A-26 & 26R	BN-2A-20**		X	X	X
  BN-2A-27 & 27R	BN-2A-21		X	X

  R - Fitted with a Jonas Aircraft developed Rajay turbocharging installation, for improved climb performance in hot climates.
  * Project Only
  ** Projected; -22 appears to be identical to the -20

  The first sub-variant to be introduced was the BN-2A-6, which introduced a larger radius leading edge to the wing between the engine and the fuselage. This drooped leading edge was originally fitted across the whole span of the wing but this resulted in a stall speed only one knot less than that achieved with the droop between the engine and the fuselage. This became a standard fitting on all variants except the Trislanders.
  Next to be intoduced was the BN-2A-7, which added raked tip tanks, to Modification NB/M/364, originally designed to increase the endurance of Islanders equipped with cameras, magnetometers etc. and used for survey flights. These added an extra 59 U.S. gallons and increased the wing span from 49 feet to 53 feet.
  The BN-2A-2 came next, which introduced 300 h.p. Lycoming IO-540-K1B5 powerplants, together with other companion modifications, under Modification NB/M/410. A wing flap droop of 6 deg. was also introduced, helping to improve the attitude at which the aircraft flies in the cruise at maximum weight and helping to concentrate the lift on the inner section of the wing thus enabling the all up weight and the zero fuel weight to be increased. The wing portion between the flap and the aileron was adjusted to fair the two surfaces together and the wing root fillet lowered to align with the flap angle.

• BN-2A-1
• The first Romanian built aircraft was fitted with Micronair spray equipment in July 1970 as the BN-2A-1, under Modification NB/M/408. The installation consists of a 130 Imperial gallon tank, pallet-mounted in the cabin and two wing-mounted external booms carrying wind driven rotary atomiser spray units, and required the tip tank Mod NB/M/364 to be embodied on the aircraft.

• BN-2A-3S
• The BN-2A-8S was later fitted with 300 h.p. Lycoming IO-540-K1B5 powerplants and wing tip tanks as the sole BN- 2A-3S.

• BN-2A-8S
• The BN- 2A-8S featured an extended nose, built by C. F. Taylor (Hurn) Ltd, containing a new baggage compartment of approximately 28 cubic feet, incorporated under Modifications NB/M/548 and NB/M/549, along with an extended flat baggage compartment at the rear of the cabin to Modification NB/M/550. This allowed the carriage of baggage further aft in the fuselage, which enabled two extra seats to be incorporated in a sixth row position. The normal two person bench seat in row 5 was replaced by a single seat allowing access to row 6 from the rear port door, giving maximum seating capacity of 11 persons including the pilot. Despite the increase in capacity, maximum take off weight remained at 6,300 lb. The addition of the extended nose increased the total length of the aircraft from 35 feet 7.75 inches to 39 feet 5.25 inches.

• BN-2A-10
• As BN-2A-8 but fitted with 270 hp Lycoming TIO-540-H1A (turbo-charged, fuel injected) powerplants.

• BN-2A-23
• The BN-2A-24 was later fitted with 300 h.p. Lycoming IO-540-K1B5 powerplants and wing tip tanks as the sole BN-2A-23.

• BN-2A-24
• Identical to the BN-2A-27, but fitted with the long nose of the BN- 2A-8S.

• BN-2A-25
• BN-2A-25, built by Fairey SA at the Gosselies factory in Belgium, was created specifically to meet the configuration requirements for conversion to the BN-2A-41 prototype by B-N Bembridge, and was essentially a BN-2A-26 fitted with the BN-2A-8S long nose. The Turbo Islander project was effectively abandoned in the latter part of 1977, and the aircraft languished, partially dismantled, and was officially categorised as Withdrawn from Use in August 1979. In August 1982 it was dismantled and shipped to the USA, remaining dismantled until shipped to Australia in August 1992, where it was converted to its earlier BN-2A-25 configuration. However, the aircraft could not be registered as such, as this variant had not been officially certified by the CAA. The Australian CAA came up with the BN-2A-27LN designation as a means of certifying the aircraft.

• BN-2A-26
  Agricultural Islander
• A BN-2A-26 fitted with a liquid/powder hopper for up to 1,742 pounds of chemicals on each wing.

• BN-2A-26
  Firefighter Islander
• A BN-2A-26 fitted with fuselage tanks for 211 U.S. gallons of water or fire retardant. The Water Bomber Modification NB/M/852 introduced 4 internally mounted fuselage tanks with a total capacity of 800 litres(176 Imp Gal). Filling of the water tanks was accomplished by use of a single large diameter filler which is connected to all four tanks, access to twhich was gained through the port rear baggage door.

• BN-2A-41 Turbo Islander
• As the BN-2A-26, but fitted with two Lycoming LTP-101 powerplants, spaced about 6 inches outboard in comparison with the standard Lycoming piston engine installation, along with the long nose of the BN-2A-8S. The production aircraft was to have a seating arrangement for pilot plus 11 passengers, presumably via additional rear fuselage seating as used in the BN-2E Mk.II Super, although the sole prototype aircraft did not feature this modification.

Military development of the Islander for roles such as such as search and rescue, internal security, long-range patrol, forward air control, troop transport. logistic support and casualty evacuation. Four underwing hardpoints for pylons for various types of ordinance. Basic changes included the introduction of wing strengthening modifications to allow the mounting of two wing mounted pylons outboard of each engine nacelle, together with an external sight fitted to the leading edge of the port wing tip, and weather avoidance radar fitted in a nose radome, which has the normal Islander nose profile. In addition, 700 x 6 main wheel tyres are fitted in place of the normal 600 x 6. Produced in five variants:

• BN-2A-3 Defender
• BN-2A-3 Islander converted to Defender configuration under Modification NB/M/???.

• BN-2A-7 Defender
• BN-2A-7 Islander converted to Defender configuration under Modification NB/M/486.

• BN-2A-9 Defender
• BN-2A-7 Islander converted to Defender configuration under Modification NB/M/560.

• BN-2A-21 Defender
• Production Defender variant based on the BN-2A-21 Islander airframe.

• BN-2A-21
  Maritime Defender
• Armed maritime reconnaissance and patrol variant of BN-2A-21 Defender. Similar to theDefender, except overall length is increased to 36 ft 3 in due to a modified nose housing larger Bendix/King RDR-l400 search radar. The interior layout provides for pilot and co-pilot, radar operator and two observers. Equipment generally includes search radar, forward-looking infrared (FLIR) capability, sonobuoys, a magnetic anomaly detector, and acoustic processors. Two Sting Ray torpedoes, four Sea Skua anti-ship missiles, or variety of other systems may be carried on the four wing hardpoints.

• BN-2A Mk.III Trislander
• BN-2E Mk.II modified with the fuselage insertion forward of the wing of 33 inches being replaced by one of 90 inches, adding a total of four additional seat rows over the BN-2A, for a maximum of 17 passengers. A new, wider, pilot entry door, moved to the starboard side, provided access to seat rows 1 and 2, and a new port side door gave access to seat rows 3 and 4. The original Islander doors provided access to seat rows 5 to 8 and the rear door of the Mk.II provided access to seat row 9. The aircraft featured a strengthened rear fuselage, a third engine on the fuselage centre line atop a new fin, a strengthened wing with the extended wingtip fuel tanks as introduced on the BN-2A-7 and drooped flaps of the BN-2A-2. A variable-incidence tail plane and new main landing gear with larger diameter wheels and tyres were also fitted. Three 260 h.p. Lycoming O-540-E4C5 powerplants.

• BN-2A Mk.III-1 Trislander
• As BN-2A Mk.III with higher operating weight.

• BN-2A Mk.III-2 Trislander
• As BN-2A Mk.III-1 with the lengthened nose of the BN-2A-8S.

• BN-2A Mk.III-3 Trislander
• BN-2A Mk.III-2 with an automatic feathering system for the propellers.

• BN-2A Mk.III-4 Trislander
• BN-2A Mk.III-2 fitted with rocket-assisted takeoff equipment. The tail mounted rocket motor installation utilizing a Bristol Aerojet 12NS-350CBA motor of 350 lbs thrust, mounted in the base of the tail mounted engine..

BN-2A Mk.III-1 Trislander Specification
Span	Length	Height	Wing Area	Empty Wt	Max AUW	Cruise Speed	Maximum Speed	Range	Service Ceiling
53 ft 9 in	43 ft	14 ft 2 in	337 sq ft	5745 lb	10000 lb	160 mph/ 139 kn	180 mph/ 156 kn	1000 mi	14600 ft
16.38 m	13.11 m	4.32 m	31.31 m2	2606 kg	4536 kg	257 kph	290 kph	1609 km	4450 m

As BN-2A with higher max landing weight and improved interior design. Features included a range of passenger seats and covers, more robust door locks, improved door seals and stainless steel sills, redesigned fresh air system to improve ventilation in hot and humid climates, smaller diameter propellers to decrease cabin noise, and redesigned flight deck and instrument panel. Three-blade propellers available giving quieter noise signature. Produced in five variants:

• BN-2B-20
• As BN-2A-20 with Model B improvements.

• BN-2B-21
• As BN-2A-21 with Model B improvements.

• BN-2B-26
• As BN-2A-26 with Model B improvements.

• BN-2B-27
• As BN-2A-27 with Model B improvements.

• BN-2B-27R
• As BN-2A-27R with Model B improvements.

BN-2A & -2B Islander Specification (260 h.p. Lycoming O-540-E4C5)
Span	Length	Height	Wing Area	Empty Wt	Max AUW	Cruise Speed	Maximum Speed	Range	Service Ceiling
49 ft	35 ft 8 in	13 ft 9 in	325 sq ft	4114 lb	6600 lb	150 mph/ 130 kn	170 mph/ 148 kn	578 mi	17200 ft
14.94 m	10.87 m	4.19 m	30.19 m2	1866 kg	2994 kg	241 kph	274 kph	930 km	5243 m

• BN-2B-20 Defender
• Military development of the BN-2B-20 Islander (see BN-2A Defender).

• BN-2B-21 Defender
• Military development of the BN-2B-21 Islander (see BN-2A Defender).

• BN-2B-21
  Maritime Defender
• Armed maritime reconnaissance and patrol variant of BN-2B-21 Defender (see BN-2A-21 Maritime-Defender).

• BN-2T
• Turbine Islander based on BN-2B series, fitted with two 320 s.h.p. flat rated Rolls Royce Allison 250-B17C turboprops, each driving a Hartzell three-blade constant-speed fully feathering metal propeller. It lacked the earlier aircraft's drooped leading edge and extended wingtip fuel tanks, but introduced new tip tanks inside standard wing span, 42.5 US gal per side, to Modification NB/M/1153. The outer, between spar, bays of the wing were modified to accommodate an extension cell bolted to the attachment rib of each detachable wing tip, forming a partialty integral. and partially separate tank unit. MTOW was increased to 7000 lb.

• BN-2T-2
• As BN-2T with 400 s.h.p flat rated Rolls Royce Allison 250-B17C turboprops and a MTOW increased to 8500 lb.

• BN-2T Islander AL.Mk 1
• Twin-engined communications and reconnaissance BN-2T variant for the British Army, built as Defenders (though designated Islanders), but with provision for only two under-wing pylons. They lacked the sliding door but were given provision to accept a wide variety of mission equipment items.

• BN-2T Islander CC.Mk 2
• Twin-engined communications BN-2T variant for the RAF.

• BN-2T Islander CC.Mk 2A
• Civilian BN-2T converted to BN-2T Islander CC.Mk 2 standard.

• BN-2T-4S Defender 4000
• An enhanced version of the BN-2T Defender intended for ISTAR (Intelligence, Tracking, Surveillance, Target Acquisition and Reconnaissance) missions, weapons carrying and logistics support missions. It features a stretched fuselage, the strengthened wing and undercarriage from the Trislander, with span increased both sides by means of a 2 ft insertion between the aileron and the standard wingtip, a taller fin, a new nose structure capable of accommodating radar, flight deck windows deepened for enhanced field of view and an increased payload. The new cabin can accommodate two crew members and six system operators, with airline style crew seats and sliding seat rails for the flexible placing of seats and equipment across the cabin. The aircraft features an airborne tactical observation and surveillance system. The system integrates the Seaspray 700E surveillance radar in the modified nose, a passive littoral surveillance system, Titan 385 multisensor turret and a mission management system. Two 400 s.h.p. Allison 250-B17F1 turboprops.

• BN-2T-4S Defender AL.1
• Defender 4000 configured for reconnaissance missions.Fitted with an array of sophisticated surveillance equipment such as low light level television (LLLTV) camera in a turret mounted under the nose, a number of cabin-mounted cameras or COMINT (COMmunications INTelligence) equipment for listening in on radio signals. Infrared jammers and other defensive systems can be carried in pods under the wings in order to defend against surface-to-air missiles.

• BN-2T-4S Defender AL.2
• (Re-designated Defender R.2 in 2019) As BN-2T-4S Defender AL.1 with different sensor fit.

• BN-2T-4S Defender T.3
• Training variant of BN-2T-4S Defender AL.1

BN-2T-4S Defender 4000 Specification
Span	Length	Height	Wing Area	Empty Wt	Max AUW	Cruise Speed	Maximum Speed	Range	Service Ceiling
53 ft	40 ft 7 in	14 ft 5 in			8500 lb	174 mph/ 151 kn	196 mph/ 170 kn	1863 mi	25000 ft
16.15 m	12.37 m	4.39 m			3856 kg	280 kph	315 kph	2998 km	7620 m

Projected Variants

• BN-2A-11
• As the BN-2A-10 with added raked tip tanks.

• BN-2A-3x Series
• As the BN-2A-20 series fitted with twin floats, attached to the undercarriage legs and some of which incorporated retractable landing gear. Mockup created. See table.

260 h.p. Lycoming O-540-E4C5	300 h.p. Lycoming IO-540-K1B5	Max AUW	Drooped LE	Drooped Flaps	Increased Span w/ Tip Tanks	Float Type
BN-2A-30	BN-2A-32	6600	X	X		amphibian
BN-2A-31	BN-2A-33		X	X	X	amphibian
BN-2A-34	BN-2A-36		X	X		floatplane
BN-2A-35	BN-2A-37		X	X	X	floatplane

• BN-2A-4x Series
• A new family of landplanes, floatplanes and amphibians fitted with two Lycoming LTP-101 powerplants with Auto Feather propellers, spaced about 6 inches outboard in comparison with the standard Lycoming piston engine installation. A seating arrangement for pilot plus 11 passengers, presumably via additional rear fuselage seating as used in the BN-2E Mk.II Super. One prototype developed (see Produced Types). See table.

Type	Drooped Flap	Max AUW	Increased Span w/ Tip Tanks	Lengthened Nose	Float Type
BN-2A-40	X	7300		X	none
BN-2A-41	X		X	X	none
BN-2A-42	X				amphibian
BN-2A-43	X		X		amphibian
BN-2A-44	X				floatplane
BN-2A-45	X		X		floatplane

• BN-2A Mk.III-5 Trislander
• As BN-2A Mk.III-2 with sound-proofed cabin, modernised cockpit/interior and new engines.

• BN-2A Mk.III Trislander M 
• Proposed military version, capable of carrying 17 equipped troops over 220 n.m., 13 troops over 650 n.m. or up to 16 parachutists. For maritime roles, it would capable of carrying a range of maritime patrol and search and rescue equipment.

• BN-2C
• Upgraded model with Hartzell three-bladed scimitar propellers, an enlarged baggage door and avionics upgrades.

• BN-2T-1
• As the BN-2T but powered by two 320 h.p. flat rated Rolls Royce Allison 250-B17F/1

• Agricultural Islander
• BN-2 with cockpit for single pilot moved to a location above the wing, internal fuslage hopper and redesigned nose.

• Mosquito
• COIN Defender based on the BN-2T featuring a raised cockpit and retractable undercarriage.

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Production Summary

Notes

1. All aircraft are Islander unless noted.
2. Aircraft build code as follows:
   B-N - Britten-Norman Aircraft, Bembridge, IoW.
   BNB - Britten-Norman (Bembridge), Bembridge, IoW, from October 1971.
   FBN - Built by Fairey Britten-Norman, Gosselies from August 1972, completed at Britten-Norman (Bembridge), Bembridge, IoW.
   PBN - Pilatus Britten-Norman, Bembridge, IoW from 1978. Includes aircraft built at Gosselies and finished at Bembridge while under Pilatus Britten-Norman ownership.
   BNG - Britten-Norman Aircraft Ltd from mid 1998, and as part of the BN Group from May 2000.
   IRMA - Built by Intreprinderea de Reparatii Material Aeronautic (IRMA) of Bucharest, Romania. Renamed IAvB - Întreprinderea de Avioane București (Bucharest Enterprise Aircraft) in 1978, rebranded as Romaero S.A. in 1991.
   PADC - Built by the Philippine Aerospace Development Corporation (PADC) from kits supplied from FBN, Gosselies.

Production References

1. Islander 2023, B-N Production History (B-N Historians, available on request)
2. BNAPS News (various issues)
• BNAPS (Britten-Norman Aircraft Preservation Society) publications are available at https://www.wightmagic.com/bnaps.htm

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