I have just had the pleasure of reading a new book on the Soviet Tu-128 "Fiddler" interceptor by Alan Dawes, Sergei Burdin, and Nikolai Popov. I have written a brief review of the book on Amazon which may be found here: http://www.amazon.com/review/R1WMHLDVQRUJT5/ref=cm_cr_dp_title?ie=UTF8&ASIN=1781554048&channel=detail-glance&nodeID=283155&store=books Having just written a book on its American counterpart, the McDonnell F-101B, I felt that it would be informative to compare and contrast the two aircraft. But before making those comparisons, a brief resume of Soviet all-weather interceptor development is in order.
Experimental work on airborne intercept radars began in the Soviet Union after the end of World War Two. Their first all-weather interceptor, the MiG-17P "Fresco", was fielded beginning in 1952. Armed with a triplet of 27-millimeter cannons and powered by a non-afterburning VK-1 engine, the MiG-17P housed the first successful Soviet intercept radar, the RP-1 Izumrud ("Emerald"), known to NATO as "Scan Odd." Although using an unwieldy dual-antenna design with separate search and tracking dishes, it was capable of automatically tracking a target within 1.1 nautical miles, while the maximum search range was 6.5 n.m. against a bomber-sized target. The Izumrud radar was less sophisticated and had lower performance than the closest Western equivalent, the AN/APG-37 radar of the North American F-86D Sabre Dog. However, following the timeless Russian maxim that "the better is the enemy of the good," The basic Izumrud radar was produced for most first-generation interceptors; the MiG-17P "Fresco-B", MiG-17PF "Fresco-D" with afterburning VK-1F engine, and the supersonic MiG-19P "Farmer-B." The Izumrud also proved capable of being adapted for first-generation "beam-riding" air-to-air missiles with the RP-1U radar of the MiG-17PFU "Fresco-E" and the RP-2U radar of the MiG-19PM "Farmer-E" interceptors, each carrying four RS-1-U or RS-2-U (NATO: AA-1 "Alkali") beam-riding missiles. In both cases, cannon-armed and missile-armed interceptors could only engage targets from dead astern within a narrow 7.5-degree cone. and only from a very close range at that at a maximum range of 1.9 n.m. for the AA-1 "Alkali.". The same held true for a second radar, the RP-6 Sokol (NATO: Scan Three) radar that armed the longer-ranged but slower Yakovlev Yak-25M "Flashlight-A." Well into the 1960s, these interceptors formed the backbone of Soviet Air Defense forces, the PVO Strany. From 1959, they were joined by the Mach-2 Sukhoi Su-9 "Fishpot," equipped with a different radar (TsD-30, NATO: "Spin Scan") but still armed with the beam-riding "Alkali" missiles (modified RS-2-US, in this case), and having a very limited combat radius due to its powerful but thirsty Lyul'ka AL-7F-1 engine. As the 1960s approached, the best distance that PVO interceptors could manage was a combat radius on the order of 200 nautical miles, or in the case of the Yak-25M "Flashlight-A," 500 n.m. Due to common limitations of radar and armament systems, all were limited to rear-quarter, close range attacks against speedy B-47 and B-52 bombers deployed by Strategic Air Command.
The combat radius of existing and projected Soviet interceptors was completely inadequate to provide coverage of the far northern reaches of Soviet territory from austere forward operating bases positioned along the northern frontier. With the conspicuous exception of the Su-9, PVO interceptors lacked the performance to reliably close on fast-moving intruders from the rear, and in all cases the maximum firing ranges of their cannons and missiles were within the defensive ranges of the bomber's gun armament. An ability to be able to engage such targets from the forward hemisphere was deemed to be vital. Compounding the problem was the deployment of new supersonic cruise missiles from late-model B-52s, the North American GAM-77 Hound Dog. Presenting a small, very fast radar target, interception would prove to be difficult, if not impossible. The new interceptor would have to possess sufficient range to not only patrol the approach routes over the Barents and Kara Seas, but to engage bomber targets before reaching their missile launch points within range of vital Soviet targets. Realizing this need for the a long-range interceptor with the ability to engage from the forward hemisphere, Tupolev was charged to develop a new interceptor from a promising (though unsuccessful) tactical bomber design, The Tu-98 "Backfin." Using the latest Soviet radar and missile technology under development, these new features were integrated into one of the first Soviet equivalents of the USAF "Weapon System" concept as the Tu-128S-4 "Fiddler."
Looking at the basic performance figures, the Tu-128 and F-101B were not dissimilar. The two aircraft had similar combat radii, and although not quite matching the Mach 1.75 placard speed of the Voodoo, the Tu-128 could manage Mach 1.56 with full missile armament. The gigantic RP-S Smerch ("Tornado," NATO: "Big Nose") radar conferred a useful 27 n.m. detection and 21.6 n.m. lock-on range against bomber targets, and was coupled with a pair of semi-active radar homing R-4R (NATO: AA-5 "Ash") missiles of up to 13.5 n.m. range. Two more heat-seeking R-4T "Ash" missiles were also carried to provide a secondary rear-quarter attack capability from up to 6.5 n.m. away. Although the "Ash" missile was more closely equivalent to the US Navy's AAM-N-6 Sparrow III missile and possessed a useful "snap-up" capability to reach higher targets, each radar-guided missile was deemed to have only a 27% kill probability against a B-52 type target, without any electronic countermeasures (ECM) use by the defending bomber. To achieve a 92% kill probability against a single B-52 target, PVO planners anticipated a pair of fully-armed Tu-128s carrying a total of eight missiles to ensure it. In contrast, as what was then the IF-101A in 1955, the intent was to ensure three bomber kills per interceptor through the use of GAR-1 Falcon missiles and new atomic armament, consisting of a pair of MB-1 "Ding Dong" rockets. The MG-13 fire control system for the Voodoo, closely based on the MG-10 system under final stages of development for the Convair F-102A in the mid-1950s, was modified to ensure proper detection, targeting, and fuzing of the MB-1 rockets during forward-hemisphere engagements. The 300-yard diameter fireball and resulting blast from the detonation of the 2-kiloton W-25 warhead of the MB-1 would take care of the rest and go a long way toward meeting the three-kill-per-interceptor design objective. In contrast, the "Ash," a very large and capable missile for its day, had a 118-pound high-explosive blast-fragmentation warhead.
The F-101B had a maximum area intercept radius of 720 nautical miles against a co-altitude target. In contrast, employing a solely forward hemisphere attack at maximum range, the Tu-128 could cover a radius of out to 1,355 n.m. However, if needed to come around for a rear-quarter re-attack, the maximum interception boundary was reduced to 664 n.m. When it first rolled out in the late summer of 1954. the F-101 was by far the largest and most powerful fighter aircraft ever built. It was dwarfed by the Tu-128 when it first flew in March 1961. The two huge Lyul'ka AL-7F-2 engines each produced 15,432 lbs. dry and 22,046 lbs. in afterburner, versus 10,700 lbs./16,900 lbs. for the Pratt & Whitney J57-P-55 engines of the F-101B. However, at "dry" thrust used to maximize area intercept radius, the Lyul'ka engines used nearly 30% more fuel per pound of thrust than the relatively economical J57 engines. Multiply that by 1.44 times greater thrust per engine for the AL-7F, and the math shows that two such engines would suck down fuel in a hurry. To confer the specified combat radius for the new Russian interceptor, it had to carry a prodigious amount of fuel within an airframe to match. While the F-101B tipped the scales at 51,724 pounds at maximum gross takeoff weight, the Tu-128 weighed in at 94,800 pounds. At a total length of 96.8 feet, the "Fiddler" dwarfed the impressively large F-101B, at 71.1 feet long. More than five times heavier and far larger than the MiG-17PF interceptors that preceded it, the penalty paid to carry all of this fuel was a huge parking footprint on austere Soviet airfields and strict "G" limitations on the airframe that drastically reduced maneuvering performance, posing a particular problem in the event that the Tu-128 needed to perform a stern conversion into the rear quarter of the bomber after a failed forward-hemisphere attack. While the relatively primitive Su-9 "Fishpot" could be reefed around the corner at 9 G and maintain pursuit at Mach 2, the Tu-128 was stressed to a maximum of 2.5 G, and a maximum safe speed of Mach 1.22 at the 44,800-foot combat altitude of a loaded B-52G Stratofortress. Unless a very careful conversion geometry was flown, the Mach 0.87 speed of the B-52G under those conditions and impressive maneuverability at altitude would have made closure and re-attack by the Tu-128 a very tough proposition with a maximum closure speed of 188 knots. The Tu-128 did have good snap-up capability given its relatively low cruise altitude and sheer size, but zoom climbs were intensely disliked by "Fiddler" pilots, who instead would opt to point the nose up at the target and take advantage of the snap-up capability of the "Ash" missile. High performance supersonic targets could, at least theoretically, be engaged in a snap-up attack but this required the interceptor to reverse course to come on the same heading directly beneath the target, but positioned in front of it with the antenna at maximum elevation to reduce lock-on time and engage the target.
The performance of the RP-S Smerch radar was conferred by the sheer size of its antenna. Incorporating transistors in addition to traditional vacuum-tube elements, The basic RP-S radar was probably roughly equivalent to the basic MG-13 units of earlier production F-101B aircraft up through Block 110, which had a maximum tracking range of 30 n.m. They were not equivalent to the upgraded MG-13 units first tested in February 1960 with 40 n.m. tracking range against an F-106-sized target and capable of dealing with closure speeds in excess of Mach 4, entering production with the F-101B in summer 1960. It took some time for Soviet technology to catch up in the Tu-128 when they were retrofitted with a version of the "Fox Fire" radar of the MiG-25 "Foxbat," itself developed from the RP-S radar as the Smerch-A, to the new RP-SM standard. Although testing of the new RP-SM system had been concluded in 1974, it was not until 1979 when the bugs were worked out of the system and operational units began to convert to the upgraded Tu-128M aircraft. Although noted Soviet avionics expert Paul Martell-Mead compares the Smerch-A/RP-SM radars most closely to the AN/APQ-109 unit of the McDonnell-Douglas F-4D Phantom, in my estimation it compares more closely with Project Kitty Car-standard MG-13 units of the F-101B. All F-101B aircraft had been modified to that standard during the latter half of 1961, four years before the Tu-128 entered service and eighteen years before Tu-128M aircraft entered operational service. The F-101B, along with all other Century-series interceptors, underwent a further, radical upgrade of their Hughes fire control systems under the Interceptor Improvement Program. Under this program, the MG-13 units of all USAF F-101B aircraft were upgraded under Project Bold Journey between February 1963 and December 1966. Besides incorporating a number of anti-ECM modifications such as LORO (Lobe On Receive Only) and an anti-chaff switch, the new MG-13 IIP fire control system now had a maximum radar range of 200 n.m, and also incorporated a sensitive infrared search-and-track (IRST) system that allowed upgraded interceptors to detect targets flying in ground clutter, and also introduced much-improved AIM-4D Falcon infrared-guided missiles. These were roughly equivalent to the upgraded "Ash" missiles of the Tu-128M, but unlike the Soviet aircraft could be more effectively employed in the face of jamming or radar failure since they could be cued to the target by the IRST system mounted on the nose. Such systems would not come into use in Soviet service until the mid-late 1970s with the introduction of MiG-23 and upgraded MiG-25 "Foxbat-E" interceptors. By this time, the F-101B had long been retired from active USAF service, although it would soldier on through the mid-1980s with the Air National Guard and Canadian Armed Forces.
In the final analysis, while the Tu-128 offered some very impressive qualities, even by the time of its first flight in 1961 it was already outclassed as a long-range interceptor by the McDonnell F-101B.
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