Lim-5 – The Troubled Polish Built MiG-17
For a large part of the Cold War, the Lim-5 and Lim-6 series served as the flagship fighter aircraft of the Polish military. Based on the Soviet MiG-17, the Lim planes would have a rocky developmental phase that was made even more challenging by the limits to innovation imposed by the Russians, who in jealously guarding the integrity of the original design only hampered Polish efforts to improve upon it.
In 1955 the blueprints for the Soviet-made MiG-17F were transferred to Polish manufacturer WSK-Mielic, who was to produce their own version of it called the Lim-5.
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The first Lim-5, emblazoned with serial number 1C00-0 and pieced together from parts imported from the USSR, was rolled out on November 28th 1956 just as the production of its predecessor, the Lim-2, was being phased out.
Interestingly, this earliest model would become the personal aircraft of General Frey-Bielecki, commander-in-chief of the Polish Air Force before becoming a teaching aid for trainee pilots in Dęblin during the 1980s. By 1957 222 Lim-5s, which had the factory codename IC, had been ordered, but 477 were built overall.
Over half of these Lim-5s served in the Polish Air Force until the 1990s, while 120 were sold to East Germany, 20 to Indonesia, and 29 to Bulgaria. The last Lim-5 was assigned to the Polish military on June 30th 1960, but by the middle of the decade, they had largely been replaced by the MiG-21.
In 1960 for example, 253 Lim-5s were registered as military planes used by the Air Force, whereas only 2 could be found by 1996, 3 years after its last flight on July 12th 1993 by a pilot of the 45th Aviation Experimental Squadron in Modlin.
There were also a couple of different iterations of the Lim-5 including a reconnaissance variant known as the Lim-5R, which was already well underway at the same time as the original Lim-5 was leaving the assembly line.
This new model, given the serial number IC-02-01, was evaluated between February 8th and April 19th 1957, when it was flown by pilots Z.Stręk, Z. Korab and M.Skowroński.
Further examinations were carried out at Warsaw’s Bemowo Airport between March 1958 to December 1959 at the Air Force Scientific and Research Institute under the guidance of lead engineer Major Andrzej Siemiątkowski. Following the construction of the first model between 1959 and 1960, a total of 36 Lim-5 aircraft were converted into the Lim-5R which, unlike its predecessor, included a stand for the AFA-39 camera.
The Lim-5M fighter-bomber version was developed in 1958 under the stewardship of Chief Engineer Major Zymunt Pojda and featured a raft of additional features such as doubled wheels in its undercarriage and a PT-19 braking parachute.
However, since the Lim-5M strayed considerably from the original schematics licensed to Poland by the USSR, on September 27th 1958 Alfred Baron and Tadeusz Kostya had to attend a series of 7 meetings in Moscow to get permission to carry out modifications from the Committee for Aviation Technology and from Artem Mikoyan himself, who was present at 5 of the discussions.
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Although getting some concessions, the Russians displayed a lukewarm attitude, refusing to provide detailed engineering documentation relating to the airframe and engine and barring the Lim-5M engineering team from making any major changes to the original MiG-17 design.
In particular, the Committee criticized the planned addition of fairing tanks, which were never added as a result. Consequently, the Lim-5M featured only minor changes, including a strengthening of the airframe only where rocket engines and breaking parachutes were installed, while the antennas of the RW-2 radio altimeter were moved from under the wings to the bottom of the fuselage.
Flight analysis of the first prototype was commenced on July 2nd 1959 at an airfield in Nadarzyce, where the sturdiness of the landing gear and the efficacy of the breaking parachute was tested. It was here under the supervision of Stanislaw Kruk that the parachute was found to shorten the landing run by 250 meters, while the landing gear was deemed strong enough.
Another wave of follow-up tests with the express purpose of determining the craft’s military application was conducted from August 19th 1960 with the assistance of aviators Andrzej Dobrzeniecki, Józef Menet, Zbigniew Słonowski, and Andrzej Natkaniec.
After being officially inaugurated into the Polish military following the issuance of the Order of the Minister of National Defense No. 035/MON on July 5, 1961, the earliest production version of the Lim-5M with serial number 1F 01-01 was unveiled on November 30th 1960.
In total 60 Lim-5M Mark I, Mark II, and Mark III editions, the latter two of which included aerodynamic shields on the antennas of the RW-2 radio altimeter, were produced until May 10th 1961.
By 1964 however, mainly as a result of Russian restrictions, the Lim-5M was found to have very poor handling characteristics, which were further compounded by problems relating to the automatic release of the braking parachutes and the unsealing of laminate fairing tanks.
Heavily disliked by pilots, a decision was made to withdraw it from use in fight-assault regiments in 1964 after a series of accidents. In the end, 51 Lim-5Ms were converted into Lim-6bis variants between 1964 and 1965 after 9 units were lost in crashes between 1961 to 1964.
With the Lim-5M proving a total and utter disaster, a much-improved version called the Lim-6 was, fortunately, being developed in tandem. In comparison to its crash-prone contemporary, the container housing the breaking parachute was moved above the engine nozzle at the base of the vertical stabilizer, the construction of two internal combs was adjusted to accommodate slotted flaps, and the engine was tweaked to supply air to the flaps.
Designated the Lim-5M-II during trials, the Lim-6’s maiden voyage occurred in January 1961, during which its new air intakes were shown to be inadequate, resulting in a reversion back to the design used on the Lim-5.
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Despite unsatisfactory results, the production version of the Lim-6 was launched before the conclusion of testing with 40 machines being made, but unhappy with its low level of stability and persistent engine-pumping troubles, the Polish Air Force refused to accept them until further improvements had been made.
Between July 6th and July 8th 1961, thanks to the redesign of the valves used to funnel air to the slotted flaps, the engine problems were finally solved. The fixes however had come at a cost, for soon after high gas temperatures were detected behind the engine turbine in a further spate of tests carried out by pilots Józef Menet and Zbigniew Słonowski from December 23rd 1961 to January 18th 1962.
The failure of the modification was confirmed on March 26th 1962 when testing was discontinued and the Lim-6 was judged inoperable in its current state, with engineers citing poor stability and low elevator effectiveness as the key reasons.
Between April 6th 1962 and May 24th 1962 with the fairing tanks disassembled, the fairings on the doubled wheels of the Lim-6 were analyzed to similar disappointment.
A flight on April 8th revealed that the fairings were causing the craft to vibrate, leading to the abandonment of the entire program. The 40 Lim-6s prematurely assembled would later be reconfigured into the Lim-6bis.
On April 24th 1962 a new of specifications were released for the Lim-6bis: the fairing tanks and slotted flaps that had caused so much trouble previously were to be removed, the doubled wheels, breaking parachute, and rocket accelerators were to stay, and a boom was to be added to each wing.
Overseen by T. Stępczyk, flight trials began on June 19th 1962 where various landing gear, armament, and container placement layouts were explored. After ascertaining optimum configurations, trials were wrapped up on August 6th 1962, with the doubled wheels of the landing gear most notably shelved following the discovery that they had been negatively impacting high-speed flight characteristics.
Next on June 26th 1962, the Ministry of Defense approved the construction of two Lim-6bis prototypes, namely a reconnaissance version equipped with the AFA-39 camera and a fighter-assault variant.
Following the announcement, the Lim-6bis was subject to a gauntlet of additional weapons tests, including the launching of FAB-250 explosives, OFAB-100 bombs, and S-5 missiles on August 28th 1962 in its first practical military run.
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Furthermore, at the end of 1963, the planned rocket accelerators were officially scrapped, while during state trials lasting between April 15th and June 27th, 1964 evaluators were left disheartened by poor operational results. However on December 1965, with a further rejigging of the airframe and other modifications, the final armament configuration was confirmed and the Lim-6bis was green-lit for production.
By 1966, 155 Lim-6bis units were serving in the Polish military, by 1975 there were 197, but by 1992 there was only a significantly reduced force of 24.
- Crew: 1
- Length: 11.264 m (36 ft 11 in)
- Wingspan: 9.628 m (31 ft 7 in)
- Height: 3.8 m (12 ft 6 in)
- Empty weight: 3,919 kg (8,640 lb)
- Max takeoff weight: 6,069 kg (13,380 lb)
- Powerplant: 1 × Klimov VK-1F afterburning centrifugal-flow turbojet engine, 26.5 kN (6,000 lbf) thrust dry, 33.8 kN (7,600 lbf) with afterburner
- Maximum speed: 1,100 km/h (680 mph, 590 kn) M0.89 at sea level
- 1,145 km/h (711 mph; 618 kn) / M0.93 at 3,000 m (9,800 ft) with reheat
- Range: 2,020 km (1,260 mi, 1,090 nmi) at 12,000 m (39,000 ft) with 2 × 400 L (110 US gal; 88 imp gal) drop-tanks
- Service ceiling: 16,600 m (54,500 ft)
- g limits: +8
- Rate of climb: 65 m/s (12,800 ft/min)