Making Good Better
In the 1970s, the Czech aircraft company Let had a winning aircraft on their hands in the form of the L-410 Turbolet. The Turbolet found popularity with civil and military operators in many countries, that Let continues to produce upgraded versions of the design and find new customers for it in the present day is testament to the design’s good qualities.
The L-610 came about from a combination of Let’s logical desire to create an improved follow on to the L-410 and a late 1970s requirement in the former Soviet Union for a small regional turboprop aircraft with more capacity than the L-410. The two events happened in very close sequence and, as a result, several references on the L-610 mistakenly claim the Soviet requirement to have been the catalyst for the aircraft. In truth, the ground work for the L-610 was already underway before the Soviet requirement was voiced.
While it ultimately never proceded past prototype stage, the L-610 represents an apex of sorts in the story of Czech aviation. It was the largest aircraft designed and built by Czech hands and the first with a pressurized cabin.
The L-610’s is the story of an aircraft which fate seemed to have been against from the very start. Problems hounded the L-610 from a variety of angles. Developmental, economic and political issues all took their turns at stalling the project and it would never know the success of the L-410 which went before it.
Going Nowhere Fast
The beginning of the L-610’s many troubles was directly attributable to the choice of engine the aircraft was to have. The domestically developed Walter M602 turboprop engine was as much a prototype as the aircraft itself was.
At the time the L-610 project started in the late 1970s, the M602 was nearly a decade away from its first running in 1986.
Proposals were made to create a four engined prototype using the proven Walter M601 engine from the L-410 so that the aircraft could begin test flying while waiting for the M602 to become ready. However, such proposals were not followed through with and the L-610 program lost valuable development time to western competitors as a result.
Delays on engine development and delivery meant that the L-610’s first flight was not until 1988. By that time, roughly a decade into the L-610 program, both aircraft and engine had had much ground to make up if they were ever to become a competitive combination.
Over the the same period of time, the Soviet requirement was changed significantly. Without a flyable prototype, Let had no hope of adjusting the aircraft to the changes or keeping up with competitors.
A New Era with New Problems
The L-610 and M602 combination was still in flight testing when 1989 brought an end to Socialism in Europe.
While the aircraft and engine could get off the ground and fly togehter, a number of structural changes were required to the design. These changes were not only to optimise the marriage of aircraft to engine, but also to address additional stresses put on the airframe resulting from the changed Soviet requirements regarding increased maximum takeoff weight.
The 1990s brought difficulties in changing politics, worsening economics and the need to replace old business strategies; all of which had their respective effects on Let and the L-610 project. Through 1990 and 1991, Let saw changes of management and large scale lay offs in its workforce. In spite of displaying the aircraft at the 1991 Paris Airshow, it was not clear where future funding for the L-610 would come from.
Let took the opportunity that the fall of Socialism presented to westernize the aircraft with American engines and avionics. In 1992, two prototypes equipped with General Electric CT7 engines, Hamilton Standard four blade propellers and Rockwell Collins avionics were constructed.
The new, westernised, version was designated as L-610G. At the same time, the original L-610 was retroactively redesignated as L-610M to differentiate the variants.
As it was, the L-610G could very well have been seen as a case of “Too little, too late”. By the end of 1992, several competing designs for the twin turboprop commuter market were well established.
The Curtain Falls
In the late 1990s, after years of struggling, the L-610 looked like it might get the boost it needed. Let was purchased by the American based Ayres Corporation, subsequently, the L-610G was put on a new marketing drive as the Ayres 7000.
On the surface, it looked like a stroke of good luck for Let. However, it proved to be the death blow to the L-610. Despite displaying the Ayres 7000 at several international aviation shows, the new ownership seemed unable to sell a single aircraft. During Ayres’ tenure as owner of Let, much of the working capital promised to be brought to the Czech Republic never materialised. Salaries went unpaid, assembly lines ground to a near halt and several Let employees were forced to leave the company to seek work elsewhere.
Under the burden of heavy debt, Ayres Corporation was forced into bankruptcy by their creditors in 2001.
Let was purchased by fellow Czech aircraft manufacturer, Moravan, following the bankruptcy of Ayres Corporation. The L-610 program was brought to an end under Moravan ownership and the bulk of the toolings and structures for the aircraft were cut up in the 2005-2006 period.
What Remains and Learning More
Ultimately, only 8 complete L-610 aircraft were built.
Fortunately, a few were spared the cutting torch and are accessible to the public in Czech air museums in Kunovice and Koněšín.
For more information on the L-610 project, the Koněšín Air Museum has a summary, the article is in Czech but the site has a translator function:
This website, dedicated to the L-410 Turbolet, has a quite informative section on the L-610 as well:
This retrospective article was written to mark the 25th anniversary of the L-610’s first flight: