Saturday, November 20, 2010

F-7BG of Bangladesh Air Force

F-7BG Multirole Fighter Aircraft

The F-7BG is a multirole capable aircraft manufactured by Chengdu Aircraft Corporation, China. It was especially built to meet Bangladesh Air Force's requirements for a cost-effective multi role fighter. It is said to be the most advanced version of the F-7 combat aircraft to date.


Dubbed “F-7BG” the fighter is capable of performing all weather, day/night air defence operations and ground attack with a new range of armaments and avionics that set it apart from the other F-7MBs that have been in service since 1989.

At present 16 F-7BGs are in the BAF’s inventory and have been in service since 2006 though it intends to procure up to 70 more BVR-capable F-7BGs in total to strengthen its interception capabilities.

Compared to the older generation F-7MBs, the F-7BGs feature a large array of improvements as listed below.

Major improvements

The F-7BG airframe has essentially the same F-7MB fuselage, inner wing portion, tail plane and fin. The outer wing section incorporates the major change, with a reduced 42 deg sweep and automatic manoeuvring flaps. The F-7BG is powered with an improved and more powerful WP-13 engine, Liyang (LMC) WP-13F (R-13-300) turbojet rated at 44.1kN dry and 66.7kN with afterburning. Additionally, cockpit layout, avionics and several ancillary systems have been changed, in line with modern trends. The important systems that remain unchanged (compared to the J-7E) are the fuel system, weapons payload capacity and internal guns.

Double Delta Wings

Like the Su-15, the Draken J-35, as well as the more modern X-31 post-stall manoeuvring demonstrator, the F-7BG has a double-delta wing plat form, which offers an excellent solution to a slender delta`s inherent low aspect ratio problem. The aspect ratio of conventional deltas is, at best, of the order of about 2.4, with the low end notched up, surprisingly, by India`s LCA - at 1.75 it stands behind the bat-winged double-delta Saab Draken, whose very low aspect ratio of 1.8 was considered to be a convenient remedy to the transonic CP shift, albeit at the expense of overall aerodynamic efficiency.

Aspect ratio & aerodynamic effeciency

Creating lift in an aircraft incurs an unavoidable penalty in the form of induced drag. Aerodynamic efficiency is achieved by designing a wing that produces maximum lift for the least drag. This is done by having a high “aspect ratio”, which is the ratio of the square of the wingspan to the wing area. Since induced drag is inversely proportional to the aspect ratio, greater the wingspan, lower the induced drag. A high aspect ratio is thus an important factor in combat, as it helps in sustaining turn rates. High aspect ratio also improves endurance and ceiling and, shortens take-off/landing distances.

As fighters become faster, their aspect ratios have to be reduced to minimise supersonic wave drag. This is done by presenting a smaller frontal area to the supersonic airflow with the help of a smaller wingspan, besides other profile streamlining techniques. It can thus be seen that the conflicting requirements of high-speed flight and subsonic manoeuvring flight have a bearing on the aspect ratio and, compromises invariably result.

Wingtip stalling has never been an issue on the F-7BG, but the double delta wing brings with it an added bonus in this respect. The strong vortex of the inner wing re-energises the boundary layer of the outer wing, preventing span-wise flow towards the tips. This allows even more-carefree manoeuvring at ultra-low speeds.

Flying controls

Manual operation, with auto stabilisation in pitch and roll, hydraulically boosted inset aileron, plain trailing-edge flaps, actuated hydraulically, forward-hinged door type airbrake each side of under fuselage below wing leading-edge. Third, forward-hinged airbrake under fuselage forward of ventral fin. Airbrakes actuated hydraulically, hydraulically boosted rudder and all-moving, trimmable tailplane and leading/trailing-edge manoeuvring flaps are featured on the J-7BG.


All-metal, wings have two primary spars and auxiliary spar, semi-monocoque fuselage, with spine housing control pushrods, avionics, single-point refuelling cap and fuel tank. Blister fairings on fuselage above and below each wing to accommodate retracted main wheels.

Landing gear

The F-7BG aircraft have inward-retracting main wheels, with 600 x 200 mm tyres (pressure 11.50 bars--167 lb/sq in) and LS-16 disc brakes.

In addition the forward-retracting nose wheel measurements are 500 x 180 mm tyre (pressure 7.00 bars--102 lb/sq in) and have LS-15 double-acting brake. The Nose wheel is steerable to +/-47 deg, while the minimum ground turning radius is 7.04 m (23 ft 1{1/4} in). Tail braking parachute is located at the base of vertical tail.

Power plant

One LMC (Liyang) WP-13F (44.1 kN--9,921 lb st dry, 64.7 kN--14,550 lb st with afterburning).

Total internal fuel capacity 2,385 litres (630 US gallons--524.5 Imp gallons, contained in six flexible tanks in fuselage and two integral tanks in each wing. Provision for carrying a 500 or 800 litre (132 or 211 US gallon--110 or 176 Imp gallon) centreline drop tank, and/or a 500 litre drop tank on each outboard underwing pylon. The maximum internal/external fuel capacity is 4,185 litres (1,105 US gallons--920.5 Imp gallons).

New engine

The WP-13F engine of the J-7MB produces 1,200 lbs of more thrust than the F-7MB`s WP-7BM, giving it a thrust-to-weight ratio of about 0.9 compared to 0.8 of the latter in clean take-off configuration. A 50% improvement in spool-up time is a welcome feature, particularly on final approach and landing where a sudden gust of wind has resulted in many a tail scrapes on the F-7MB. Go-around’s are also prompt and a bad landing is actually a thing of the past on the BG. Use of titanium alloys in compressor blades and an increased TBO are indicators of improvements in Chinese jet-engine technology.

All improvements were verified and were found to be as advertised or even better. Even more remarkable was the fact that these trials took place in hot and humid weather, well outside the 15 C, 1013 hP environments in which the specifications are usually engineered.

The aerodynamic performance of the aircraft is further improved by the introduction of a more powerful WP-13F turbojet. The thrust increase was evidenced by a 25% improvement in acceleration time from 500 kph to 1100 kph and an equally impressive time-to-climb to 36,000` AMSL. Compared to the F-7MB, the F-7BG`s sea-level climbing rate has increased from 155m/s to 195m/s. The internal fuel capacity has increased from 2,080kg to 4,165kg. The ferry range has increased from 1,500km to 2,200km. The G limit has increased from 7 to 8. The maximum instantaneous turn rate of the J-7BG is 25.2 deg/s, and the maximum sustained turn rate at 1,000m altitude is 16 deg/s. According to CAC, the overall aerodynamic performance of the F-7BG has increased by 43%, and the combat effectiveness has increased by 84% compared to the F-7MB.


Pilot only, on CAC zero-height/low-speed ejection seat operable between 70 and 459 kt (130 and 850 km/h--81 and 528 mph) IAS. One-piece canopy, hinged at rear to open upward.


The F-7BG has several modern avionics upgrades. These include a new head-up display (HUD) with a new Stores Management System, which is essentially a useful cockpit-pilot interface to help establish the status of stores including configuration, fusing and weapon codes etc. A voice warning system, colour video recorder, elaborate cockpit lighting (Night Vision Goggle Compatible) and a more precise and jitter free AOA probe, GPS and inertial navigation system (INS), and a New Pulse-Doppler fire-control radar based on Russian and Israeli technology.

Comms: GMAv AD 3400 UHF/VHF multifunction com, Type 602 (`Odd Rods` type) IFF.

Radar: I/J-band KLJ-6E Lieying (`Falcon`) pulse-Doppler fire-control radar. This Radar has a Search Range of 30km, with Target Tracking Range of 26km.

Flight: WL-7 radio compass, 0101 HR A2 altitude radio altimeter, LTC-2 horizon gyro, XS-6 marker beacon receiver, VOR, Distance Measure Equipment (DME), Instrument Landing System (ILS), tactical aircraft navigation (TACAN) system and an improved Type 8430 air data computer with HOTAS.

Instrumentation: A new HUD (made by the Xian Sicong Group) in the F-7BG provides pilot with displays for instrument flying, with air-to-air and air-to-ground weapon aiming symbols integrated with flight-instrument symbology. It can store 32 weapon parameter functions, allowing for both current and future weapon variants. In air-to-air combat its four modes (missiles, conventional gunnery, snapshoot gunnery, dogfight) and standby aiming reticule allow for all eventualities. VCR and infrared cockpit lighting on the F-7BG is to be used with a Chinese (Cigong Group) Helmet Mounted Sight (HMS) slaved to the PL-9 AAM. The new air data computer coupled with the new HUD in the air-to-ground mode is capable of projecting both Constantly Computed Impact Points (CCIP) and Constantly Computed Release Points (CCRP) - which will use internal GPS and INS.

An EFIS display can be found in the upper starboard corner of the Flight Instrumentation panel. It can display heading and navigation sub-systems like ADF, VOR, TACAN, ILS etc.

Self-defence: South-West China Research Institute of Electronic Equipment KG-8602 RWR interfaced with the South-West China Research Institute of Electronic Equipment KG-8605 internal radar noise jammer and China National Import and Export Corporation GT-1 chaff/flare dispenser, and Type 602 'Odd Rods' IFF.

The F-7BG also comes with SE-2 Airborne Missile Approach Warning (MAW) Sensors located at the rear and port and starboard sides.

HMS: The HMS helmets are supplied by the Cigong Group, further upgrading the F-7s mission capabilities.


Fixed weapons include One 30mm Type 30-1 belt-fed cannon, with 60 rounds, in a fairing on the starboard underside of the front fuselage just forward of wingroot leading-edges. Four under-wing stores stations can carry up to 2,000kg of disposable stores (each unit rated at 500kg). Two hardpoints under each wing, of which outer ones are wet for carriage of drop tanks. Centreline pylon used for drop tank only.

Each inboard pylon is capable of carrying a PL-2, -2A, -5B, -7 and -9 missile or, at customer's option, an R550 Magic.

One 18-tube pod of Type 57-2 (57 mm) air-to-air and air-to-ground rockets. One Type 90-1 (90 mm) seven-tube pod of air-to-ground rockets. Or a 50, 150, 250 or 500 kg Guided/Unguided or Custer Bombs. Each outboard pylon can carry one of above rocket pods, a 50 or 150 kg bomb, or a 500 litre drop tank.

All Bangladesh Air Force F-7BGs are also equipped with 250~500 kg LS-6 laser guided munitions. The PGMs provide capabilities that are roughly comparable to US JDAMs.

Both weapons will be capable of using three systems the US GPS, the Russian Glonass and China's own Beidou System. The architecture for this system eventually foresees using five satellites in geosynchronous orbit (GEO) and up to 30 non-GEO platforms. The LS-6 has a maximum launch range of around 60 km.

Unconfirmed reports also suggest that by 2010 according to the Bangladesh Air Force plans the F-7BGs will be upgraded with KLJ-6F BVR-capable fire control radar and PL-12 medium range air to air missiles, which have a range of 70 km.


F-7BGs were inducted in the Bangladesh Air Force in 2006. The new generation F-7BGs are likely to replace all existing F-7MBs in the future with the procurement of additional units as a gip filling measure if later generation fighter aircraft are not procured in time.bangladesh has total 16 F-7BG in it's inventory.But they are not armed with SD-10/PL-12 BVR missile.


General characteristics

  • Crew: 1
  • Length: 14.885 m (48 ft 10 in)
  • Wingspan: 8.32 m (27 ft 3½ in)
  • Height: 4.11 m (13 ft 5½ in)
  • Wing area: 24.88 m² (267.8 ft²)
  • Aspect ratio: 2.8:1
  • Empty weight: 5,292 kg (11,667 lb)
  • Loaded weight: 7,540 kg (16,620 lb) (two PL-2 or PL-7 air-to-air missiles)
  • Max takeoff weight: 9,100 kg (20,062 lb)
  • Powerplant:Liyang Wopen-13F afterburning turbojet
    • Dry thrust: 44.1 kN (9,921 lbf)
    • Thrust with afterburner: 64.7 kN (14,550 lbf)



  • Guns: 2× 30 mm Type 30-1 cannon, 60 rounds per gun
  • Hardpoints: 5 in total - 4× under-wing, 1× centreline under-fuselage with a capacity of 2000 kg maximum (up to 500 kg each)
  • Rockets: 55 mm rocket pod (12 rounds), 90 mm rocket pod (7 rounds)
  • Missiles:
  • Bombs: 50 kg to 500 kg unguided bombs


  • FIAR Grifo-7 mk.II radar



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