WSK-Mielec Lim-6/Lim-6bis/Lim-6M

Continuing from the previous post, about the Lim-5, the Lim-5M was regarded as an interim solution only, and work on a more advanced plane continued testing many different ideas.
In 1961, forty Lim-6 were built with some new features like new blown flaps, but tests showed problems with the modified Lis-6 engine and, therefore the aircraft were not given to the Polish Air Force. Because of that, it was decided to redesign the thick wing sections with fuel tanks, blown flaps, double wheels, RATO system (Rocket Assisted Take Off) and return to the only slightly modified Lim-5 construction, with increased weapon-carrying capability instead.
In 1963 WSK-Mielec started production of the final variant of the attack plane, this time called Lim-6bis. It had standard wings and single wings, like the Lim-5. One important feature was the addition of two underwing weapon pylons close to the fuselage and the fitment of a braking parachute container below the rudder. The Lim-6bis were delivered to the Polish Air Force in 1963 but it wasn't until 14th September 1964 when they were officially adopted.
By 1964 seventy Lim-6bis were built and a number of Lim-5M and Lim-6 were upgraded to Lim-6bis standards, approximately eighty of them. Some few of them were also converted into the Lim-6R reconnaissance variant with an AFA-39 camera under the fuselage.
By 1971, as the Lim-5P fighters were becoming obsolete, they were also rebuilt into Lim-6bis standards, under the designation of Lim-6M. They had their radars removed, however the radar covers in the central air intake remained. They were fitted with additional underwing pylons but not a braking parachute and some of them were also converted into reconnaissance machines with the designation of Lim-6MR.
The Lim-6bis was armed with two NR-23 23 mm cannons and one N-37D 37 mm cannon, just like the MiG-17F, while the Lim-6M was armed with three NR-23 cannons, like the MiG-17PF. It had four underwing pylons and typically, it was armed with two Polish-made Mars-2 launchers for 16 unguided 57 mm S-5 rockets each, or 100 kg bombs. It could also carry 250 kg bombs or launchers on standard outer underwings pods, but usually they were used for 400 L fuel tanks. They were powered by the Lis-5 engine which yielded a thrust power of 5732 lb.
Lim-6bis, Lim-6R, Lim-6M and Lim-6MR were used by the Polish Air Force as their most numerous attack aircraft until the 1980s with the last one being retired in 1992.
They were exported to Algeria, Angola and Bulgaria.

Sources:
1. https://en.wikipedia.org/wiki/PZL-Mielec_Lim-6
2. https://www.valka.cz/WSK-Mielec-Lim-6bis-t80685
3. https://www.valka.cz/WSK-Mielec-Lim-6M-t80672
4. https://www.valka.cz/WSK-Mielec-Lim-6-t80683
5. https://www.valka.cz/WSK-Mielec-Lim-6MR-t80674
6. https://www.valka.cz/WSK-Mielec-Lim-6R-t80686
7. Signal Squadron - Aircraft In action  125 - MiG-17 Fresco in Action

Aero L-29, Part two, Bulgarian and Czechoslovak users

Answering to a sizable requirement for a common jet-powered trainer that could be used by the nations of the Eastern-Block. Aero decided to bid with their own project with a view to suitably satisfying this demand.
On 5th April 1959 the first prototype, name XL-29, flew for the first time. It was selected to be the primary trainer for many Warsaw Pact countries so it was massly delivered from the 1960s onwards.
During the late 1950s the Soviet Air Force started to look for a jet-powered replacement for its piston engined trainers. Over time, the requirement study was widened towards an aircraft capable of overtaking many roles at the same time and could be easily adopted by many Eastern Block countries. Around the same time, Czechoslovakia had been also developing its own jet-trainer that would replace their propeller-powered trainers. To answer those demands, Aero developed a new aircraft, designed by engineers Z. Rublic and K. Tomas. Their work was centered upon a new design based on versatility that could carry the pilots through every stage of training programme as well as frontline duties.
The concept was to create an easy-to-build and easy to operate aircraft. Therefore both simplicity and ruggedness were stressed during development process, leading to the adoption of manual flight controls, large flaps and perforated airbrakes placed on the fuselage sides. Aerodinamically it was designed to be stable and docile. Thanks to that decission, the type was enviably safe. It was able to operate under austere situations such as take-off from grass, sand or unprepared fields. On 5th April 1959 the first prototype, named as XL-29 and powered by a Bristol-Siddeley Viper engine flew for the first time. The second prototype flew shortly thereafter and was powered by the Czech designed M701 engine, which was used subsequently in every L-29.
During 1961 a small pre-production batch was tested against the Polish PZL TS-11 Iskra and the Soviet Yakovlev Yak-30, which were the main rival submissions in the Warsaw Pact main trainer. Shortly after of the completion of the fly-offs, the L-29 was selected as a winner. According to some authors, that outcome caught by surprise to several observers. Regardless of the result, Poland chose to continue the development and production of the PZL TS-11 and the remaining Warsaw Pact and Eastern Block countries adopted the L-29 as their main trainer, under the agreements of the COMECON.
During April 1963 full-scale production of the L-29 started. A total of approximately 3600 exemplars were manufactured on an 11 year production run with some sub-variants being made like the L-29A Akrobat which was a single-seat aerobatics version, a dedicated reconnaissance variant, the L-29R with cameras installed in the rear cockpit position was developed but it was cancelled in 1965. A wide variety of optional armament could be installed in some models like a detacheable gun pod or a pod containing four missiles underneath the wings.
Regarding the drawing, the Aero L-29 was supplied to the Bulgarian Air Force during the 1960s and became its main trainer until the late 1990 when it was completely replaced. The L-39 commenced to replace the type during the late 1970s and for the late 1990s the L-29s was active only with the Aerobatic team.
It was also the main trainer of the Czechoslovak Air Force until it was replaced by the L-39. However, the type was kept in active service until the late 1990s. Apparently on 16th July 1975 a Czechoslovak Aero L-29 shot down a Polish civilian biplane trying to defect to the west.

Sources:
1. https://en.wikipedia.org/wiki/Aero_L-29_Delfín
2. https://en.wikipedia.org/wiki/Bulgarian_Air_Force
3. https://en.wikipedia.org/wiki/Czechoslovak_Air_Force