PART-1
Air Defense of Pakistan is duty of Pakistan Army Air defense and Pakistan Air force.FM-90 was acquired after events of Ops Neptune.Pakistan was satisfied with quality and performance of FM-90 system as an close range air defense SAM.The duty assigned to this SAM in Pakistani service is defense of Air fields,command nodes,moving mechanized columns,vital civilian infrastructure against cruise missiles,choppers and Fighters.The version delivered to Pakistan has been developed with close help of Pakistani Defense organizations, It is being operated by Air Defense Units of PA,it is configured according to Pakistani needs.Here is technical Database of FM-90
FM-90 at 2015 Pakistan Day Parade....
CPMIEC HQ-7/FM-80/FM-90 / CSA-4/CSA-5 Sino-Crotale SelfPropelled Air Defence System
Pakistani system is designed to work in intense and very hostile EW.It has new and more powerful radar and more secure datalink.Missiles are likely to have more range and kill capicty then original cortala and FM-90
HQ-7/FM-90 / Sino-Crotale Technical Analysis
The HQ-7/HHQ-7 SAM systems are often described as “based on” and “derived from” the Crotale. Close inspection of the wealth of detailed HQ-7/HHQ-7 imagery suggests that the first generation of the HQ-7/HHQ-7 system are almost exact clones of the French originals, with differences which at best qualify as cosmetic, such as the headlight arrangement on the P4R, or the shape of the frangible launch tube covers. The changes observed in newer FM-90 system appear to be primarily in the replacement of the acquisition radar, replacement of the P4R vehicle, and internal enhancements to the system electronics. The Chinese have published very little of substance on the Crotale, in comparison with other indigenous weapons systems.
Accordingly, this technical analysis will be based on the original baseline French Crotale, with the caveat that the PLA may have made numerous incremental detail improvements to the internal design of the system, as has been observed with reverse engineered Russian weapons.
The best single discussion of the design rationale behind the original Crotale is the excellent 1970 Interavia/International Defense Review analysis “Design Philosophy of the Crotale AA System”, authored by le Sueur, who was a design engineer at Thomson CSF involved in the definition and development of the Crotale[2].
The imperative for the development of the Crotale was the emergence of terrain avoidance and terrain following radar as penetration aids for tactical aircraft, permitting them to penetrate especially hilly terrain, abundant in Europe, by using terrain masking to conceal their approach. The combination of transonic or supersonic speed and altitudes between 150 and 330 ft AGL typically results in targets which pop-up above the radar horizon a mere 15 to 25 seconds away from the target. Such short reaction times are a genuine challenge for most SAM systems, and typically beyond the capabilities of 1950s and early 1960s SAM designs which dominated NATO air defences during that period. The then new Soviet MiG-23BN/27 Flogger, Su-7/17/22 Fitter and Su-24 Fencer would this be capable of bypassing most NATO IADS components no differently than USAF F-105D Thunderchiefs and F-111 Aardvarks sliced through North Vietnamese defences.
Figure 1 Low level penetration envelope [2].
Figure 2 Crotale threat engagement requirement [2].
Design requirements for the Crotale were detailed by le Sueur thus [cited][2]:
Design principles
A multi-capability solution to the low altitude problem should therefore provide the following:
1.
Radar detection in all weathers of a 1 m2 fluctuating target flying at speeds up to Mach 1.2, amongst ground clutter and fixed echoes of 105 m2 equivalent area (corresponding to a collection of large buildings seen against a rock face 1,500 metres taller).
2.
Tracking of the target accurately in this environment, even if it flies at ground level, hugs the side of a hill or valley, or passes through a nodal point close by.
Guidance of the missile accurately under whatever conditions the target imposes.
3.
Fast reaction, so that the following operations can take place whilst the aircraft in question (flying at Mach 1.2) travels no more than 4 km, allowing an intervention time of just under 10 seconds:
- detection of the target as soon as it appears,
- determination of its type (single or multiple),
- identification friend or foe (with the possibility of interrupting the acquisition/firing sequence at any time in case of a belated 'friendly' response),
- determination of its course parameters,
- automatic tracking lock-on,
- firing of one or several missiles,
- interception.
Should the attack be of large proportions, this sequence must still take no longer than for a single attacking aircraft. In addition to the above requirements, the weapon system should:
- classify targets by the urgency of the threat which each represents whenever a fresh attack is detected,
- engage targets in this order of priority classification,
- be capable of co-ordinated engagement of several targets on different bearings simultaneously.
4. Firepower sufficient to ensure a kill probability of 90%. This involves:
- highly accurate missile guidance,
- a high-acceleration, high-speed missile,
- missile manoeuvrability, even at maximum range,
- controlled detonation of the warhead for maximum effect in a position relative to the target's leading-edge and engine infrared sources,
- a proximity warhead, the destructive range of which is considerably greater than the missile's miss-distance,
- the possibility of firing several missiles at the same target if needs be, without starting the acquisition sequence again; immediate, automatic realization of the need for this without human intervention; the automatic firing of such a salvo.
5. Mobility comparable to that of the combat formations which the system will protect, particularly cross-country, without degradation of its detection capability; self-propulsion; self-contained operation and air-portability.
6. Maximum reliability in spite of enemy electronic countermeasures. Detection of faults the moment they occur and not when the approach of an enemy aircraft sets off the full operating sequence.
7. Simplified training of operating and maintenance crews.
These design requirements are not dissimilar to such a requirement were it drafted today, indeed the principal differences would be in more challenging specific requirements for ECCM capability and detection performance against low signature targets in clutter.
The design strategy defined for the Crotale was detailed by le Sueur thus [cited][2]:
The following are the solutions which have been adopted to fulfil the stated requirements:
1.A fully coherent [Mirador IV] pulse Doppler
surveillance radar. This will detect aircraft of an area equivalent to a 1 m2 fluctuating target flying at radial speeds of 35 to 440 m/s (156 to 890 mph) at altitudes from 0 to 3,000 m (0 to 10,000 ft) and ranges up to 18.5 km (11.5 miles). At maximum range the probability of detection is 90% with each antenna revolution. The chances of a false alarm are low and radar visibility through the fixed echoes is so good that even when Crotale was tested in the most difficult conditions, no ground shadow whatever appeared on the screen. A computer logic circuit correlates the data gathered on each antenna revolution, rapidly extracting all but the useful information and allowing automatic tracking of any aircraft within detection range. So as not to lose the benefits of the fast reaction time, information is renewed at the very high rate of one antenna revolution per second. Using a pulse Doppler radar, this antenna revolution speed is incompatible with precise target definition and suppression of ambiguities and 'blind speeds' within the range limits imposed by the terrain, unless the S-band is used for the surveillance role. The radar coverage is so designed that it immediately provides not only the bearing of the target. but also a first indication of its range and elevation (high, medium or low).
2.
Tracking of the target is carried out by a Ku band [Castor 2] monopulse radar, the narrow beam and short pulse of which give very high definition; the use of multiple frequencies gives good protection against jamming as well as very smooth tracking. The tracking radar antenna has been separated from the co-axially mounted missile launchers, in order to reduce its inertia to a minimum. Missile guidance is accurate to within 0.1 milliradians, this unequalled performance being the result of using the beam-riding guidance technique in direct combination with the target tracking technique described above. This process eliminates the mechanical and electronic errors common to systems with separate target tracking and missile guidance equipment.
3. The very
fast reaction time required of the system necessitates total automation. Crotale is the first example of a weapon system to be so designed. A computer mounted in the surveillance/target designation vehicle determines whether the target is approaching or receding and its nature (one or several aircraft); it processes the data provided by radar, initiates tracking of each aircraft, and classifies it in terms of immediacy of the threat in relation to other targets already being tracked. After identification of the aircraft as hostile, the computer communicates with its counterparts in the firing unit vehicles, before assigning the target to whichever of the latter is best placed to deal with it. This causes all the uncommitted tracking radar/missile launcher mountings to turn towards the target. The designated fire unit then receives an accurate bearing on the target, together with its approximate elevation and height. The fire unit computer then guides the tracking radar within these limits, by continually updating target elevation and height data (Fig. 3), until the automatic tracking mode locks on. During this period of search, the fire unit computer remains under the overall control of the computer in the surveillance/target designation vehicle. It calculates the interception possibilities and decides when target engagement becomes possible. Once the order to fire is given, several irreversible missile launching procedures take place: internal power is switched on, the autopilot is activated, the missile container is opened, and the missile is fired. At any time between tracking lock-on and interception of the aircraft, a 'friendly' IFF response, however belated, will automatically interrupt the intercept sequence; if this occurs during missile flight, the latter will destroy itself.
On the standard version of the Crotale system, the intervention of human operators has been kept to two levels:
- In the surveillance/target designation vehicle, an operator assigns the target classified as top priority to the fire unit indicated to him by the computer as being that best capable of dealing with it.
- In the fire unit, an operator presses the firing button when it illuminates.
These two functions - as we have seen - are not essential, and when the computer calculates that the available reaction time offered by a priority target is incompatible with the real time constants of the human operator, it deprives him of his authority to intervene in the operational sequence.
The attachment of several fire units to the same surveillance unit allows the most flexible and economic defense of various types of point targets. One surveillance unit will therefore be under-utilised in many cases if it is linked with only one firing unit. But more important still, if the fire of the various units co-operating to protect the same target is not co-ordinated, then there is nothing to prevent those fire units whose operating envelopes overlap engaging the most urgent target simultaneously, leaving the field wide open for following aircraft. By ensuring the co-ordination of several firing units against a large-scale attack therefore, the Crotale organisation optimizes their performance.
4.The firepower of Crotale results from the combined effect of several devices which have been incorporated in the system. An advanced operational research study showed that, faced with the threat posed in the next decade and taking account of the restricted range of fire compatible with terrain limitations, the beamriding guidance technique with continuous deviation correction offers a cost-effectiveness ratio superior to any other. Designed and produced by Engins Matra with the assistance of several divisions in the Thomson Brandt group for in particular, the propulsion unit,, the warhead and the transponder, the Crotale missile is gathered by the radar in under 500 metres. Its single-stage motor propels it to Mach 2.3 in 2.3 seconds. and at the limit of its range its speed is still supersonic.
The missile is roll-stabilized in order to allow a high degree of guidance precision and to provide the ability to absorb the high load factors imposed by crossing targets. Canard-type surfaces provide the required manoeuvrability with a minimum of drag, and at the limit of combat range, the missile still has a manoeuvrability of 7 g which allows it to cope with fluctuations and evasive manoeuvres of the target.
The 15 kg warhead was specially designed for high efficiency: its detonation produces a burst of fragments moving at over 2,000 m/sec localised in space and time, the fragments retaining the same lethality to a distance of 8 metres. The warhead is detonated by an infra-red proximity fuze in the standard version (an electromagnetic fuze is optional) at a point determined by the ground-based computer as a function of the relative positions of the missile and its target.
The flexibility of the digital computer allows full simulation of the firing and intercept sequence before it takes place. This permits, for example, the avoidance of a situation in which a missile could be fired at an aircraft which would be masked by terrain at the theoretical point of interception: a firing lock avoids waste of this missile. In the same way, if it appears that an airborne target will present itself in conditions which would make interception difficult (very high speed, very brief appearance within the limits of action of the missile) so degrading the hit probability, the computer will give authority to launch a salvo of two missiles the moment the operator presses the firing button.
All these provisions have allowed verification during the firing trials that the 90% destruction probability indicated by the design calculations can, in fact, be achieved in reality.
5.To conform to the requirement to support mobile combat forces, it was necessary that the surveillance radar be capable of giving the alarm whilst on the move, so as not to lose the advantage of the very short reaction time by a long detection period. Without this capability, it would be necessary to resort to the classic “leapfrogging” technique with the slowness of movement and the doubling of surveillance equipment which it involves.
The stable oscillator of a pulse Doppler radar is sensitive, in certain frequency ranges, to the mechanical vibrations of vehicles. These generate false alarms which the computer confuses with the actual signal of an airborne target. To eliminate these vibrations, mechanical transmission has been dispensed with and a very flexible suspension adopted for the thermal [internal combustion engine in P4R] motor. The power supplied by this motor, converted into electrical energy, is fed via cables to electric motors on each wheel. The missile launch vehicle uses the same system.
The first military application of a principle already proven commercially, combined with a very elaborate hydropneumatic suspension system, ensures a smooth ride for the Crotale vehicles on varied terrain, and a high initial starting torque [characteristic of DC electric motors], well above the usual norms for a four wheeled air transportable vehicle of 13 tonnes powered by the 230 SHP motor.
The ACU S-band pulse Doppler Mirador IV acquisition radar is designed to reject 60 dB of ground clutter, and performs a single scan per second. Two stacked beams for heightfinding are produced by a pair of feeds on a boom, with a third feed for the IFF channel. The digital data processor can concurrently track up to 12 targets on different bearings.
The HQ-7/FM-80 ACU antenna is of a similar configuration to the Mirador IV, with a feed boom and rear V-shaped structural frame which appear identical. The sculpted Mirador IV reflector is replaced by a truncated concave mesh and frame reflector, which permits a HQ-7 ACU to be easily recognised when compared to the Thomson-CSF original product.
The digital data processing system communicates with the Fire Units through a datalink interface, which employs either cable or radio link channels. The cable allows communication between the ACU and a fire unit up to distances of 400 metres. The alternate VHF-band radio datalink permits communication over distances of 50 to 5,000 metres.
The Fire Unit Thomson-CSF Castor 2J/C pulse Doppler engagement radar employs a circular parabolic reflector with splayed monopulse feeds on a characteristic four spoked strut frame, which appears identical on both HQ-7 Type 345 systems and French built Crotales. The radar operates in the Ku band producing a 1.1° circular pencil beam for target tracking. Three channels are used to permit tracking of a single target and one or two outbound missile round Ku-band transponders, the arrangement intended to minimise the relative angle errors between target and missile tracks. An X-band missile uplink is employed. Frequency agility is employed to minimise susceptibility to jamming. For a more detailed discussion refer
HQ-7/FM-80FS/FM-90FS/Type 345 Crotale Engagement Radar.
An infrared tracker with a ±5° FOV is employed to ensure that the antenna boresight is aligned with the missile flightpath vector immediately after launch, before the missile is captured by the guidance command link 500 metres after launch.
Most Crotale systems, including the HQ-7, employ a TV telescope to provide ECCM capability, and redundancy in the event of radar failure.
The Fire Unit digital mission computer is employed to calculate the parallax offset relative to the ACU, acquisition and tracking algorithms, speculative intercept parameters against possible targets, command uplink instructions for missile capture and command link guidance to intercept, fusing control calculations, and missile self destruct commands.
Crotale engagement envelope [1].
Conceptually the HQ-7/Crotale radar suite most closely resembles its Soviet/Russian analogues, the Land Roll system in the 9K33 Osa / Romb / SA-8 Gecko, and the later 9K331 Tor / Tor M/M1 / SA-15 Gauntlet. The French design is cleaner and more compact, and shares the antenna across multiple functions, whereas the Soviet/Russian designs employ additional function specific antennas.
Figure 3, reproduced from le Sueur's paper, shows the transfer of the target track from the ACU to the Fire Unit. The Mirador IV localises the target into an angular box cited at 4 milliradians, which falls well inside the 20 milliradian mainlobe angular coverage of the engagement radar. This permits the Castor 2 to acquire and lock very rapidly, as the acquisition and lock process primarily involves driving the antenna boresight to null the initial angular error, and establishing range and velocity tracks. There is no need for the Castor to perform a search to place the target into the mainlobe.
What specific changes the Chinese may have made to the Mirador IV and Castor 2 in the process of reverse engineering the Crotale has never been disclosed. Given the good quality of the original Thomson-CSF design, there would be few useful optimisations possible to improve upon the basic functions of these radars.
Unvalidated Chinese Internet claims are that the FM-90 is fully digital, and the engagement radar operates in two bands to improve ECCM capabilities - the Russians employed a dual band engagement radar in this class in developmental variants of the 96K6 Pantsir S - and that the FM-90 is intended to engage cruise missiles, ASMs, anti-radiation missiles and aircraft.
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Figure.3 [cited] “Diagram showing the interface between the two radars, and automatic tracking lock-on. Key: A - designated tracking envelope; the volume of this envelope depends on the elevation bracket, range bracket and the bearing, which is always given by the surveillance radar to within 4 milliradians. The accuracy of the given bearing obviates the need for a three-dimensional target search by the tracking radar, B - target; C - radar echo on the PPI; D - bearing vector, E - tracking radar beam.”[2]
Figure 4, 5, 6 Crotale engagement sequences[2].
