In 1961, three jet trainers spent two months at Monino airfield near Moscow trying to win the biggest training contract in the Eastern Bloc. One was Polish, one was Soviet, and one came from a Czechoslovak factory that until then had mostly built other people’s designs under licence.

The Soviet-led commission picked the Czechoslovak one. Over the next 13 years, the Aero L-29 Delfín trained a generation of Warsaw Pact pilots. It also made room for its far more famous successor, the L-39 Albatros, the jet MiGFlug customers still fly today.

From licence builder to designer

Aero Vodochody had built thousands of MiG-15s under Soviet licence in the 1950s. By the end of the decade, the Soviet Air Force wanted a jet to replace its piston-engined trainers, and the requirement grew into a single standard trainer for the whole Eastern Bloc. Czechoslovakia, needing a jet trainer of its own, decided to compete.

The design team was led by the engineers Z. Rublič and K. Tomáš. Their brief to themselves was simplicity: one aircraft that could take a student from the first jet lesson all the way to readiness for a front-line fighter. The result had straight wings, a T-tail, manual flight controls, big flaps and perforated airbrakes on the fuselage sides.

The XL-29 prototype first flew on 5 April 1959, powered by a British Bristol Siddeley Viper. The second prototype introduced the Czech Motorlet M-701 turbojet, which powered every production aircraft. It produced 8.7 kN (1,960 lbf), enough for about 655 km/h. The student sat in front, the instructor behind and slightly higher, and the two ejection seats were interlinked to fire in a synchronised sequence, so the crew could not collide after ejecting.

Docile handling was a deliberate choice. The L-29 was designed to be stable and forgiving, which gave it an enviable safety record, and its reinforced undercarriage let it take off from grass, sand and unprepared fields. It was never fast, but it was hard to break, which is exactly what a student pilot needs.

The fly-off at Monino

In 1961 the third prototype went to Monino against the Polish PZL TS-11 Iskra and the Soviet Yakovlev Yak-30. The two-month evaluation went far beyond test flights, scoring everything from cockpit ergonomics to the time needed to change an engine. A commission from all three countries, chaired by a Soviet lieutenant general, ran the contest.

Rex’s Hangar explains why the Soviet Union chose the Czechoslovak L-29 Delfín over its own trainer design.

The Delfín won on reliability, ease of maintenance, ease of manufacture and price. It had no failures during the trials, landed and stalled slowest, and needed the shortest runway on unpaved strips. In one test of continuous training circuits on a single tank of fuel, it flew 15 while its rivals managed ten.

Poland went its own way and stuck with the Iskra. Every other Warsaw Pact country adopted the L-29.

Three thousand Dolphins

Full production started in 1963. According to Aero Vodochody, 3,665 were built by the time the last were delivered in 1974: 1,943 at Vodochody and 1,722 at the LET factory in Kunovice. Around 2,000 went to the Soviet Union, where NATO gave the type the reporting name “Maya”. It let air forces train pilots on jets from start to finish, without a piston-engined stage.

Others went to the Czechoslovak Air Force, East Germany, Bulgaria, Hungary and Romania, and further afield to Egypt, Syria, Iraq, Indonesia, Nigeria, Uganda, China and North Vietnam. Aero also built a single-seat aerobatic version, the L-29A Akrobat, and tested a camera-equipped reconnaissance model, the L-29R, which was cancelled in 1965. Optional pods for machine guns, rockets or small bombs turned it into a light attack aircraft. Nigerian L-29s flew combat missions in the civil war of the late 1960s, and Egyptian ones attacked Israeli ground forces in 1973.

Making way for the Albatros

The Delfín had one problem: it was underpowered. Aero’s answer flew on 4 November 1968, when the X02 prototype of the L-39 Albatros took off with Rudolf Duchon at the controls. It was planned from the outset as the L-29’s replacement, and it was the first jet trainer powered by a turbofan engine.

Through the 1970s, the L-39 replaced the L-29 as the Warsaw Pact’s standard trainer, and nearly 3,000 were built. For a time, many air forces flew the two side by side. Bulgaria retired its last L-29s in 2002, Slovakia in 2003 and Romania in 2006.

A second life with civilians

Like the L-39, the Delfín found new owners once air forces let it go. Many were sold to private operators and fitted with Western altimeters and radios. In 2007, an unmodified L-29 made what Wikipedia calls the world’s first jet flight powered solely by biodiesel, from Reno to Leesburg, Florida. In 2008, two Viper-engined L-29s took first and second place at the Reno Air Races, lapping at more than 500 mph.

A full L-29 Delfín flight from Brno-Tuřany, from taxi and take-off to landing, filmed from the cockpit.

Aero calls the Delfín the first jet aircraft designed in Czechoslovakia. It is a modest title for an aircraft that standardised jet training across half of Europe and laid the groundwork for the most widely used jet trainer ever built.

Sources: Wikipedia (Aero L-29 Delfín), Aero Vodochody company history, MiGFlug L-39 Albatros page