In the later half of 2007 the SLAF acquired a number of J-7G aircraft from the Chengdu Aircraft Corporation in China, to give the SLAF a genuine All Weather Day/Night Air Combat Fighter to counter the aerial threat posed by the Air Tigers. The aircraft (dubbed the F-7GS) in SLAF service, has in addition to its primary air defence role, a secondary precision munition delivery capability, and as a result has some additional features not common to the standard J-7G in service with PLAAF.

Here is a brief overview of the air crafts capability.

**NOTE: Some of the information in this article has been obtained from a personal source within the SLAF.**

[TYPE: Fighter and Close Air Support Aircraft]

[DESIGN FEATURES]

- Diminutive tailed double-delta, with clipped tips to mid-mounted wings.

- Circular-section fuselage with dorsal spine.

- Nose intake with conical centrebody.

- Swept tail, with large vertical surfaces and ventral fin.

- Wing anhedral 2 deg from roots, incidence 0 deg, thickness/chord ratio approximately 5% at root, 4.2% at tip, quarter-chord sweepback at 49 deg, reducing to 42 deg on the outer panels. No wing leading-edge camber.

The aircraft in (Fig: 1.0) is labeled accordingly:

A - Angle of Attack (AoA) Sensor.
B -- SE-2 Airborne Missile Approach Warning (MAW) Sensor.
C -- KLJ-6E Pulse-Doppler Radar Unit.
D - UHF/VHF Multifunction Communication Antennae.
E -- KJ8602A Airborne Radar Warning Receiver (RWR).
F -- Type 602 `Odd Rods` IFF.
G -- Liyang WP-13F Afterburning Turbojet.
H - Anti-Flutter Weights.
I - Location of the GT-1 chaff/flare dispenser.
J - 30mm Type 30-1 cannon.
K - UHF Aerial.
L - VHF Aerial.

--Major Improvements--

The F-7GS airframe has essentially the same F-7BS 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-7GS 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-7GS has a double-delta wing planform, 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 EFFICIENCY--

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 maneuvering flight have a bearing on the aspect ratio and, compromises invariably result.

Wingtip stalling has never been an issue on the F-7BS, 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 autostabilisation in pitch and roll. Hydraulically boosted inset ailerons. Plain trailing-edge flaps, actuated hydraulically. Forward-hinged door type airbrake each side of underfuselage 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. Leading/trailing-edge manoeuvring flaps on J-7GS.

[STRUCTURE]

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 mainwheels.

[LANDING GEAR]

Inward-retracting mainwheels, with 600 x 200 mm tyres (pressure 11.50 bars--167 lb/sq in) and LS-16 disc brakes. Forward-retracting nosewheel, with 500 x 180 mm tyre (pressure 7.00 bars--102 lb/sq in) and LS-15 double-acting brake. Nosewheel steerable +/-47 deg. Minimum ground turning radius 7.04 m (23 ft 1{1/4} in). Tail braking parachute at 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. Maximum internal/external fuel capacity 4,185 litres (1,105 US gallons--920.5 Imp gallons).

--New Engine--

The WP-13F engine of the J-7GS produces 1,200 lbs of more thrust than the F-7BS`s WP-7B, 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-7BS. Go-arounds are also prompt and a bad landing is actually a thing of the past on the GS. 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-7BS, the F-7GS`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-7GS 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-7GS has increased by 43%, and the combat effectiveness has increased by 84% compared to the F-7BS.

[ACCOMMODATION]

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.

[AVIONICS]

The F-7GS 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. (See Fig: 2.0)

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 - See Fig: 2.1) in the F-7GS 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-7GS 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 ...