Britten-Norman Islander BN-2T-4S Defender 4000

The BN-2T-4S Defender 4000 is where the BN-2 line strays furthest from its origin. Britten-Norman conceived it as an enhanced version of the BN-2T turboprop Defender intended for aerial surveillance and for ISTAR missions (intelligence, tracking, surveillance, target acquisition and reconnaissance), while keeping weapons carriage and logistics support among its roles. On that basis it stretched the fuselage and took the strengthened wing and undercarriage from the Trislander, with the span increased on each side by a 2 ft (about 0.61 m) insertion between the aileron and the standard wingtip. It added a taller fin, a new nose structure able to house radar, deepened flight deck windows for a better field of view and a greater payload.

The certification basis took 11 January 1994 as its reference date and combined British BCAR Section D and K requirements with parts of the draft European JAR 23 code covering performance, handling, emergency exits and brakes. The British authority, the CAA, issued the type certificate on 15 November 1995 in the normal category. According to the EASA data sheet, the aircraft is a twin-engined, high-wing, all-metal design with fixed landing gear, carrying no more than ten people including crew, a limit set by the space available in the cabin, with a minimum crew of one pilot. It is powered by two Allison 250-B17F/1 turboprops of 400 shp (about 298 kW) each driving three-blade Hartzell HC-C3YF-5F propellers of 78 in (1.98 m). Span is 16.15 m, length 12.20 m and wing area 32.67 m². Maximum take-off and landing weight is 3855 kg, raised to 4048 kg by modification NB-2175.

The cabin accommodates two crew members and six system operators in airline-style seats on sliding rails, so seats and equipment can be placed freely across the cabin. The airborne tactical observation and surveillance system integrates a Seaspray 700E surveillance radar in the modified nose, a passive littoral surveillance system, a Titan 385 multi-sensor turret and a mission management system. According to Jane's 2003-2004, as cited by Wikipedia, empty equipped weight is 2223 kg, maximum take-off weight 3856 kg, cruise speed 280 km/h, range 1863 km with VFR reserves, endurance 8 hours 30 minutes and absolute ceiling 7600 m.

The prototype flew in 1995 and production began in 1997. That same year the aircraft that the Irish Air Corps flew for the Garda Air Support Unit entered service: operational control lay with the Department of Justice while the Air Corps provided pilots and technicians, and the aircraft flew seven days a week with a pilot and two Gardaí. It served until 2023. The Police Service of Northern Ireland retains one, and Hampshire Constabulary and Greater Manchester Police also used Defenders.

In January 2004 the British Army placed an urgent order for four BN-2T-4S aircraft, designated AL Mk 1, for ISTAR missions in Iraq; the first arrived in October 2004 and the last in September 2006. The AL Mk 2 and the T Mk 3 trainer followed from September 2008, with deployments to Iraq until June 2009 and to Afghanistan between 2010 and 2012. In April 2019 the fleet passed to the Royal Air Force, and it was retired on 30 June 2021. Those versions have pages of their own. The britishaviation-ptp production summary, with data to the end of 2023, counts six new-build Defender 4000s and one converted from a BN-2T-4R, separately from the British aircraft, which it lists under their military designations.