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Aviation History
1978
1978 - 0071.PDF
FLIGHT International, 14 January 1978 Austere THE Peruvian Air Force is dis appointed with the avionics fitted to its newly acquired Su-22s, according to a report in the Defence & Foreign Affairs newsletter on Latin American Affairs. The aircraft are Atoll-equip ped and carry the I-band High Fix ranging radar, which, the report claims, is considered inferior to the Aida II set carried by Peruvian Mirage 5Ps. The Service was "aghast" to find how basic were the Russian avionics. The IFF equipment fitted is not compatible with the Russian-supplied SA-3 SAMs which were acquired last year, while the VHF and UHF radios are not interoperable with current Peruvian AF communications gear. Navigation aids are virtually non existent—the operator will have to install Vortac, ILS and LF aids. High Fix is thought to be standard on all the Su-17/-20/-22 family, and the navigation/communication prob lems may reflect the inevitable diffi culties which any Third World operator might experience when shop ping for an advanced combat aircraft. One reported deficiency does sug gest however that the Peruvian Sukhois have a somewhat austere avionics fit. Peru seems to have ex pected the Su-22s to carry the Sirena III radar-warning receiver—an omni directional unit fitted to the latest generation of Russian aircraft in place of the limited-coverage Sirena II carried by most older types such as the Tu-16, Yak-28 and MiG-19. Warsaw Pact Su-17/-20s are under stood to be1 Sirena Ill-equipped, con firming that the equipment is available for export, but the Russians seem to have omitted to install such recent technology in aircraft based so close to the USA. A precedent for such a downgrading of the avionics was set in 1975 when Libya received the first export MiG- 23s. Soviet AF Flogger Rs carry the High Lark fire-control radar—a J- band set with a maximum search range of 85km and able to track tar gets at up to '55^111. Flogger Es sup plied to Libya were fitted with the smaller Jay Rird radar originally developed for use in late-model MiG- 21s. Although operating at a similar frequency to High Lark, Jay Rird has maximum search and tracking ranges of 30km and 20km respectively. Most of the other "deficiencies" listed in the US report will come as little surprise to readers of our annual surveys of the world's military air craft. Like the original Su-7 from which it was developed, the Su-22 is a little short of internal fuel and cursed with a rather thirsty power- plant. During the 1965 war between India and Pakistan a number of Su-7 drivers were reported to have paid Sukhois the penalty for being over-keen to en gage the afterburner, when their mounts ran out of fuel on the wrong side of the border while returning from strike missions. Internal fuel capacity of the Su-7 was 7,0001b, and it is difficult to see how the variable-geometry version could carry substantially more. According to some reports, the Lyulka AL-7F-3 in the Su-17 series has a lower specific fuel consumption (s.f.c.) than the earlier AL-7F-1, but the improvement is unlikely to be of any great magnitude. It has been sug gested that the Su-20 and/or -22 is fitted with the lower-thrust -7F-I, but the effect on fuel consumption of the lower-thrust engine will be partly off set by the increased s.f.c. The Su-22 flies badly with external loads, the US newsletter claims, so the carriage of external tanks is un desirable. Several current Russian aircraft have balance problems—the MiG-21, for example, is almost un controllable at low speed when the internal fuel load is down to 30 per cent. Flight has received no reports so far on Su-17 handling characteristics, but the earlier Su-7 is regarded by the Egyptiani Air Force as being stable and easy to manoeuvre. The com mander of an Egyptian AF Su-7 squadron told Flight that the aircraft could be violently manoeuvred at a height of only 20m (see Flight for March 13, 1975, page 422). It is possible that the modification of this relatively simple fighter- bomber into a variable-geometry type has upset the handling qualities^ but Warsaw Pact Su-17/-20 pilots seem Sky Flash trials TRIALS of the Sky Flash air-to-air missile have been completed at the Pacific Missile Test Centre, Point Mugu, Calif. More than a third of the rounds fired scored direct hits, with a similar number passing within lethal range of the target. Ry using the proven motor, air frame and warhead of the US AIM-7E Sparrow, Rritish Aerospace has been able to complete the trials programme in only 22 firings. This is a far cry from the pioneering days of missilry, when, for example, the Germans fired about a third of total V-2 production in tests. The high-speed Sky Flash trials pro gramme was made possible by mathe matical modelling. US Sparrow test results allowed the British design team to use a computer to build up a mathematical model of Sky Flash. As the trials proceeded, the resulting data were used to modify the model, which was then used to plan other reluctant to stray too far from the airfield boundary fence without two large underwing drop tanks, undesir able or not. As with the MiG-23, wing sweep is controlled manually rather than automatically as on Western types like Tornado and F-14. The Defence & Foreign Affairs report remarks: "A fighter pilot twisting and turning in combat will have another lever to operate to get the best from the air craft." MiG-23 pilots select an inter mediate but fixed angle of sweepback before engaging in combat, leaving the extreme wing positions for take off and landing (forward) or high speed dash (backward). Since the Su-17 series are basically strike air craft, with only a secondary air-to-air role, the lack of automatically varying wingsweep is unlikely to be a great handicap. One minor mystery remains un solved. Russian fighters have tradi tionally been allocated odd numbers as service designations, the bombers even numbers. Although the designa tion Su-17 fits this pattern the alloca tion of Su-20 to most export versions and Su-22 to the Peruvian aircraft does not. In a cynical moment Flight Soviet-watcher Bill Sweetman sug gested that the Russians have prob ably changed the system just to confuse the West, but the allocation of a separate type number to the Peruvian order probably indicates that these carry simpler avionics than the export model supplied to Egypt and Russia's Warsaw Pact allies. completed trials and to explore the behaviour of the weapon under different simu lated conditions. The targets for the firing trials represented a range of hostile air craft. Some were enhanced to repre sent the radar echoing area of speci fic aircraft, while others were ad justed to produce high values of radar glint. The latter phenomenon causes the apparent position of the target to jitter, with the result that the ap proaching missile wastes energy on altering course to cope with the illu sory movements. Some firings were made against un- augmented targets, several of which had only a small echoing area, and others against multiple or manoeuvr ing targets and in the presence of electronic countermeasures. Low- flying aircraft pose a major threat, so some of the firings were carried out as snap-down attacks against low- level targets.
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