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Overview
The TS-11 Iskra (spark) bis is a Polish jet trainer/ light multirole aircraft. Poland’s first indigenous jet aircraft, it was developed from 1957, first flew in 1960, and entered service in 1964. The Iskra bis B was the second model, featuring a more powerful engine (introduced in the last batch of As) and four underwing hardpoints. These hardpoints allowed for more advanced training as well as providing a secondary role as a light strike aircraft.
Note on engines: the first two batches of Iskra Bs, for a total of 51 aircraft, were powered by the SO-1 engine. The remaining 3 batches of 73 aircraft total were powered by the more reliable SO-3, and the SO-1s were gradually replaced by SO-3s. Additionally, Iskra Bs were often later refitted with more powerful SO-3Bs or Ws. This suggestion will specifically be looking at SO-3-powered aircraft as these were more common than the SO-1 and to differentiate the Iskra B from the following D.
History
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Development
Poland’s first jets were a trio of Yak-17s and 11 Yak-17UTI trainers purchased in 1950. As the Siły Powietrzne (Air Force, from here on abbreviated SP) acquired more jet aircraft (Yak-23s in 1951, production of MiG-15s in 1952) the need for a new basic jet trainer arose. In 1956, project requirements for the new TS-11 (named for lead designer Tadeusz Sołtyk) were laid out- the aircraft was to be of all-metal construction with a low, straight, thin wing, a top speed of Mach 0.8 and a conventional tandem cockpit layout with the student in the front and the instructor behind. The TS-11 was to be armed with a 23mm cannon for gunnery training or to allow the aircraft to operate as a fighter should global war break out.
A full-scale wooden mockup was built in late 1957. This was followed by a static test airframe in March 1959 and three proper flying prototypes from December 1959, all mounting the British Viper 8, acquired from Yugoslavia. The TS-11 made it first flight on 5th February 1960, being publicly debuted on 11th September 1960 in Łódź. The three prototypes underwent extensive testing late 1960 through 1961, proving easy to fly, agile, stable, reliable, and simple to maintain- in short, exactly what you’d want in a training aircraft.
Competition
So in August 1961 when the TS-11 was put up against the Soviet Yak-30 in a competition to become the standard jet trainer for Soviet allies, it dominated, outperforming the Yak in essentially every metric. This would be a massive deal for the Polish aviation industry.
However, there was a third contestant in the competition- the Czech L-29 Delfín. The L-29 was very similar to the TS-11 and nearly matched it in performance, all at a lower cost than the Polish aircraft. Because of this, the L-29 was selected as the standard primary jet trainer, and it and the subsequent L-39 were used by all close Soviet allies- except Poland, who continued forward with the TS-11.
Iskra A Into Service
Production of the TS-11 Iskra bis A began in 1964. Production aircraft were fitted with the HO-10, a copy of the Viper 8 with slight improvements that boosted its continuous power to 7.84kN. The first batch of 10 aircraft were handed over for trials in 1964. This was followed by two batches of 22 each in 1964 and 1965 respectively. Finally, in 1967, the last batch of 15 Iskra bis As (powered by the improved SO-1 as mentioned in the intro) entered production.
These aircraft had relatively uneventful service lives in SP service. The Iskra A was the least reliable of the family due to the HO-10, but still had a low accident rate.
The Iskra bis A achieved a series of four closed-circuit speed records for an aircraft in the 3000kg class.
Upping the Standard- the Iskra B
During this period the idea of a trainer/light attack aircraft was becoming very popular. Such an aircraft would provide increased strength in the event of war while being cheaper than separate trainer and light strike aircraft. Additionally, combat-capable trainers made training more realistic, allowing live-fire of actual weapons in service instead of simply simulators.
To this end the TS-11 Iskra bis B was developed with four underwing hardpoints for carrying ordinance, for training or combat. This aircraft had the SO-1 engine initially, later replaced by the more reliable but equally powerful SO-3.
The Iskra bis B entered service in 1968. Like the Iskra A, it was popular among pilots because of its good handling and easy flying. The Iskra B mostly replaced the Iskra A, becoming the primary jet trainer for all SP pilots. Pilots would fly the TS-8 for basic training, then the TS-11 for jet training, then the Lim-2SB (licensed MiG-15UTI) for advanced training, then straight to combat units for Lim-series aircraft or to Su-7U, MiG-21UM, MiG-23UB, or MiG-29UB for pilots bound for the Su-7/20/22, MiG-21s, MiG-23MF, and MiG-29 respectively. Pilots were also given regular refresher training in Iskras to ensure top performance.
Almost Immortal Spark
The TS-11 had an extremely long service life, the longest for any armed single-engine jet in service of the country of origin. Simply, nothing could replace it. The first attempt to build a successor came with the TS-16 Grot of 1963, a supersonic aircraft (only the second supersonic trainer aircraft design in the world, preceded only by the T-38). This aircraft never saw production due to ballooning costs. The next attempt to replace the TS-11 came in 1976 with the I-22 Iryda. The Iryda was a subsonic twin-engine aircraft comparable to the Alpha Jet. This aircraft was actually produced and even entered service, and proved reliable, agile, and easy to fly just like the Iskra, while having substantially improved performance. However, the end of the Cold War and subsequent budget cuts killed the I-22 program in 1999 after only 28 built and 5 years of service. The I-22 would be the last indigenous Polish combat aircraft design. The next attempt to replace the TS-11 came in 2010, with the SP looking to purchase and license-produce the L-159 Albatros 2. This purchase was not pursued. The TS-11 would only begin being replaced in 2017, with the controversial purchase of the M-346 Bielik. While originally offered the M-346LCA, a modified version the the M-346FT, Poland instead opted for an unarmed version of the aircraft. This meant that many pilots were being deployed to their operational units without any actual weapons training, a significant issue only resolved in 2023 with the purchase of the FA-50GF. The final TS-11s were retired in 2021, 64 years after their first introduction.
More on Engines
Interestingly, the SO-1 engine was always intended to propel the Iskra, being developed in 1956, even before the Iskra itself. However, the engine had serious vibration and seizing issues that would take some to resolve. So the Viper 8 and HO-10 were introduced as an interim measure. The SO-1 would enter production in January 1966 for the final batch of Iskra As.
But the SO-1 was still seen as unsatisfactory in terms of service life, at only 200 hours between refits and 800 hours total. New specifications for a variant of the SO-1 with 400 hours between service and a lifespan of 1,000 hours. This resulted in the SO-1-III (the SO-1-I was the troubled prototype and SO-1-II was the production model), entering production as the SO-3 in 1969 for the third batch of Iskra Bs.
Further Developments
The Iskra B was followed by the unsuccessful photoreconnasaince Iskra bis C, with instructor’s flight controls replaced by a reconnaissance suite. This was the least-built Iskra model at only 5 aircraft. The Iskra bis D was essentially identical to the B, but with a more powerful SO-3B engine. The bis D was developed into the bis DF with further refined SO-3W engine and reconnaissance capabilities. The D and DF were the only Iskra models to see export with 76 purchased by the Indian Air Force.
Finally, in 1991, small numbers of DFs were rebuilt to the navalized Iskra bis R standard.
One interesting prototype model of the Iskra was the BR 200, a single-seat dedicated attack aircraft that wasn’t accepted into service due to the availability of the superior Su-20.
The Iskra B was also modified to create the Iskra bis MR, an unarmed model with ICAO-compliant avionics for use by the Red-White Sparks aerobatic team.
Specifications
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Airframe
Length: 11.25m
Span: 10.60m
Height: 3.50m
Empty Mass: 2,560kg
Loaded mass: 3,734kg
Wing Area: 17.50m^2
Crew: 2
Propulsion
1x SO-3 turbojet
Max thrust: 9.8kN
Internal Fuel: 1,200L across 4 self-sealing tanks
Flight Performance
Max Speed: 750km/h (Mach 0.61)
Climb Rate: 14m/s
Armament
1x NS-23 23mm cannon
23x115mm
115 rounds
600 RPM
720m/s
or, interchangeably (can be swapped out in <30 minutes)
1x NR-23
23x115mm
150 rounds
900 RPM
720m/s
I’d have the NS-23 stock and NR-23 as a Rank I/II modification
Underwing hardpoints x4:
1x OFAB-100 100kg bomb
1x Mars-2 launcher (4x S-5)
1x Mars-4 launcher (8x S-5)
1x Zeus-1 gun pod
Pretty much every source mentions the Zeus-1 gunpod. However, the only information on the pod is that it has a calibre of 7.62mm
Systems
RW-UM radar altimeter
Engine fire suppression system
KAP-3 ejection seats
The TS-11 Iskra bis B in-game
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The TS-11 has pretty poor performance for an aircraft of its time because of its role as a trainer. However, it performs decently compared to first-gen jets. The Iskra would be a central part of a Polish air tree, helping to bridge the gap between wartime western equipment and post-cold-war western equipment. Compared to the preceding Iskra A, the Iskra B offers improved performance in air battles due to its more powerful engine. The SO-3 produces more peak thrust than the HO-10, without the latter’s limited duration. The suspended armament would be a great boost for ground battles, though it’s too light to be particularly effective in air battles.
Pros:
- Agile
- Decently fast
- Moderately powerful engine
- Decent rocket load for CAS
Cons:
- Poor climb rate
- Limited armament- NR-23 is an effective cannon but only a single cannon is rather poor
- Insufficient suspended armament for base bombing
Placement in a hypothetical Polish air tree
Gallery
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The Iskra bis B standard introduced four underwing hardpoints for suspended armament- rocket pods, small bombs, cluster bombs, and gun pods. This feature would be present on all following models
The Iskra carried two indigenous rocket pods- the Mars-2 and Mars-4 with 4 or 8 S-5K/Ms. These rockets would make the TS-11 rather formidable as a CAS aircraft
^on BR 200, just to show the Mars-2 and Mars-4 side-by-side
The elusive Zues-1 alongside other Polish suspended weapons, this photo is apparently from a Polish military magazine that unfortunately isn’t available anywhere I can find
TS-11 undergoing maintenance
TS-11s (likely Ds) doing a live fire exercise
The SO-1 engine, a much improved version of the HO-10. It would be replaced by the more reliable SO-3
There’s also the lovely livery of the Red-White Sparks aerobatic team. They operated the special TS-11 MR, based on the TS-11 B but upgraded with more powerful engines as they became available. I believe this is justification enough for this skin for the B, D, and DF
Sources
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Polskie Skrzydła- Polish Wings 36 TS-11 Iskra- Dariusz Karnas and Artur Juszczak
PZL TS-11 Iskra. 2008. - Polot
PZL TS-11 Iskra. 2009. - Polot
PZL TS-11 Iskra. 2010. - Polot
PZL TS-11 Iskra. 2011. - Polot
PZL-Mielec TS-11 Iskra two-seat low-wing jet trainer
Also check out the other members of the TS-11 family!
Iskra A
Iskra C
Iskra D
Iskra DF
Iskra R
Iskra BR 200