Flying the Flag, Far and Wide
The Czech Republic has a remarkably colourful history in aviation that dates to before the first Czechoslovak aircraft company, Letov, was founded in 1918. The small nation has given the world a wide range of capable aircraft in categories including aerobatics, agriculture, general aviation, gliders, trainers and transports among others.
As Czech aircraft manufacturers go, Let is a relatively young company. Founded in 1936 in the south eastern Czech town of Kunovice, Let started as a maintenance branch of the much older Avia company. It would not be until after the Second World War that Let would come into its own as a company after the Communist government that took over the former Czechoslovakia in 1948 nationalized the contry’s industries. It was at that point in time that Let was split from Avia and made into a separate company.
In April of 1969, the prototype of a new aircraft rose from the Kunovice runway into the air for the first time. Designated the XL-410, it was the beginning of a long lived family of transport aircraft that would grow to not only serve as the flagship product of the Let company for over five decades, but also a global symbol of Czech prowess in aircraft design: the L-410 Turbolet.
Upon first impressions, the L-410 Turbolet may seem nothing more than one of the many twin turboprop powered commuter aircraft types out there. Its unassuming appearances belie an aircraft of robust construction, remarkable flexibility, cost effectiveness and short take of and landing (STOL) performance that few aircraft in its class can match.
Still in production five decades after its first flight, used by air arms and civilian operators in over 70 countires across five continents and still going strong; the L-410 is without a doubt the most succesful of Czech aircraft.
Let’s spend some time with the L-410 Turbolet:
A Hard Act to Follow
From the outset, the Turbolet was intended to be a very self-sufficient aircraft that could operate in extremes of temperature and from rough or completely improvised airstrips in very remote regions. These specifications were arrived at as one of the aircraft the L-410 was designed to replace was the venerable and legendary Antonov An-2.
The Antonov An-2 is in the history books as the largest single engine biplane ever put into production. Being a biplane first flown after World War Two, the An-2 was something of an anachronism when it was introduced. However, the aircraft had a very unique set of flying characteristics that would make the job of any aircraft intended to replace it a very high order indeed. The An-2 was an extremely self-sufficient aircraft noted for its tough-as-nails construction and STOL performance that has been next to impossible for any other fixed wing aircraft to match.
While the Turbolet certainly has never been able to equal the An-2’s STOL capabilities, in its STOL optimised form it does possess the performance to give it a place among a small handful of aircraft in its class that are capable of operating from the Tenzing-Hillary Airport in Lukla, Nepal.
Tenzing-Hillary has a long standing reputation as one of the most demanding and dangerous airports for any aircraft and pilot to operate from. This comes from the high altitude the airport is situated at, its short runway length and the unforgiving mountainous terrain that surrounds the airport. Any aircraft and pilot must hold special certifications to fly into and out of the airport. Along with the DeHavilland Canada DHC-6 Twin Otter and the Dornier Do-228 from Germany, the Turbolet is among those few aircraft in its class to be certified for operations from this airport.
As with its nearest contemporary designs, the Turbolet is built relatively low to the ground with its wing set high on the fuselage. This configuration allows good access to critical areas of the aircraft for servicing while still allowing maintenance crews to stand on the ground or require nothing more advanced than a basic stepladder to do their jobs. The configuration also allows for easy loading of cargo or passenger boarding as no specialized airstairs or cargo lifting machinery are required to load the aircraft.
Certified to operate in temperatures that range from -50C (-58F) to 50C (122F), there are very few environments on Earth where the Turbolet would be unfit to work.
With a take off run of around 510 metres (1,673 feet) and a landing run of around 500 metres (1,640 feet) in its STOL optimised versions, there are very few places in the world the Turbolet could not get into or out of.
A Bit of East and a Bit of West
Studies for the aircraft that would become the L-410 started in the 1966-1967 timeframe. In the same period of time, the domestically designed Walter M601 engine that would eventually power the L-410 was under development.
From the outset, the aircraft was designed as a short haul machine that could carry between 12 and 19 passengers or 1850 kg (4079 pounds) or cargo into or out of a wide variety of airport and runway types. The aircraft was designed to operate from airstrips made of grass, sand, gravel, clay or snow at rudimentary airfields with equal ease as it would operate from a well prepared asphalt runway at a fully equiped airport.
The reason for designing this level of versatility into the aircraft was to ensure it had a chance of meeting specifications put forth by the former Soviet Union for a new aircraft requirement of the state airline, Aeroflot. The airline needed a modern, well built, durable and dependable aircraft to replace the older types they had to serve the communities on their more remote routes.
The former Soviet Union was the world’s largest nation, a distinction that contemporary Russia still holds today. Outside of the major cities, there are wide tracts of less developed areas with far flung communities that can only be reached with aircraft. Typically, these regions have climates that are harsh and unforgiving on man and machine alike. Needless to say, the bushflying art is alive and well in these remote corners of the world.
The turbolet met the specifications and many of the type were exported to the former Soviet Union and quickly gained popularity among those who worked with it. It still enjoys a good deal of popularity in Russia.
While the former Czechoslovakia was solidly within the Socialist sphere of influence at the time the Turbolet was being developed, there was a western component to the prototypes and earliest production versions in the form of the Pratt and Whitney Canada PT6 engine.
The choice of the PT6 came about from the fact that the Walter M601 would not be ready for flight at the time the prototype Turbolets would be completed, so a substitiute engine was required to make sure the prototypes got airborne on schedule. The PT6 was a proven engine that was a close match for the sort of performance the M601 would provide later versions of the Turbolet.
Let also considered Garett engines from America and Turboméca engines from France before settling on the PT6.
Refining the Machine
From the first flight of the XL-410 in April of 1969, it was clear that the Turbolet would be a solid performer and worthy of further development. However, as it is with all machines, the prototype and production versions can differ quite a lot.
This is a general overview of the Turbolet family development across major production models:
The prototypes of the Turbolet line were designated as XL-410. Three XL-410 prototypes were built, the first and third were flying prototypes while the second was used for stress testing.
The first production series of the family was the L-410A. Like the prototypes, aircraft of this series were powered by the PT6 engine.
The L-410A line differed from the prototypes by having a completely redesigned main landing gear as well as structural reinforcements nose to tail. Other differences included a small stabilizing fin being added to the underside of the rear fuselage as well as changes to the propellers and aircraft de-icing system.
A total of 31 aircraft were made to L-410A standards. Significant among them was the L-410AS, a specialized version for the Soviet Union that proved the Turbolet’s excellent performance in climatic extremes and rudementary airport and airstrip conditions.
The second production Turbolet series, the L-410M, debuted in 1973 and is the series that defined the Turbolet family on the world stage.
The L-410M was the first series of the family to be powered by the Walter M601 engine. Most of the development that took place between versions of the M model concerned the fitting of improved versions of the M601.
An offshoot of the L-410M, the L-410UVP is different enough to be considered the third production series of the Turbolet family.
While all members of the aircraft family are capable of STOL performance, the UVP versions were optimised to bring those qualities of the aircraft to the fore.
The UVP versions had more powerful engines as well as increases to the wingspan and tail area. All of this was to meet a STOL specification set out by the Soviet Union. While the UVP met the specification, it turned out to be a machine of compromises.
The increases in wingspan and tail surface area translated into an increase in overall weight in the UVP versions and corresponding decreases in performance as far as payload, range and economy of operation were concerned.
Beyond the basic UVP version, this branch of the family includes:
L-410UVP-S: VIP transport version with an executive interior fitted.
L-410UVP-E: Improved version with more powerful engines, five bladed propellers and wing tip fuel tanks.
L-410T: A cargo optimised version with a larger cargo door.
L-410FG: A specialised version with a glass nose for aerial mapping and survey work.
Debuting in in 2015, the L-410NG “New Generation” is at once a member of the Turbolet family and a substantial departure from what has gone before it in the lineage.
The NG was developed from the UVP-E and maintains the spacious passenger cabin the aircraft family is known for as well as the robust construction and mission flexibility.
Where the NG differs is in a redesigned wing that allows for more fuel to be carried and has resulted in a significantly increased range for the NG model. The NG also can carry more cargo in a lengthened nose and has a fully modern cockpit and avionics suite.
Additionally, the NG has more powerful engines from General Electric. In fact, the new engines are a development of the M601 and bear General Electric branding due to the Walter company becoming subsidiary to General Electric in 2008.
The L-410NG has been in series production since 2018.
Flexing to Function and Fun
As mentioned in previous sections of this article, the Turbolet was designed with a good amount of mission flexibility in it. This is thanks largely to its spacious cabin area.
Beyond standard passenger and cargo variations, the cabin can be fitted with air ambulance or emergency medical service interiors. It can also be fitted with an executive interior for VIP or corporate flying.
Along with the roomy cabin, the L-410 has the power and range to make it useful for aerial survey and mapping work as well as patrol and surveillance work. Special modifications for aerial mapping and photogrammetry created the L-410FG version with its distinctive glass nose.
The flexibility of the Turbolet was further tested in Russia in 2017 when experiments were carried out to test the type’s suitability for ski and float landing gear.
It’s not all work and no play for the Turbolet. The aircraft is very popular worldwide as a platform for skydiving. With a good climb rate and the roomy cabin, it lends itself very well to getting larger groups to jumping height efficiently.
If you’re a more intrepid holiday maker who looks for more exotic and remote locales to visit, you may very well find yourself on a Turbolet for at least part of your journey. As mentioned earlier, the Turbolet is one of the few aircraft types of its class that could get you to Nepal’s Tenzing-Hillary Airport.
Come aboard, It’s Perfectly Safe
In some quarters, the Turbolet has been branded an unsafe aircraft. However, this is quite unfair and borders on the ridiculous.
The fact that more than 1,200 examples of the Turbolet have been built over the years and it’s still in production more than five decades after it first flew is testament to the soundness of the design and the competence of its designers.
On the surface, it would seem the Turbolet is an accident prone machine. It’s been involved in over 100 accidents that have resulted in over 400 fatalities. However, before one judges the accident record of an aircraft like the Turbolet, one must keep in mind a few things about it:
A vast majority of accidents the Turbolet has been involved in were traced back to human error rather than any issues inherent to the design of the aircraft.
Very few aircraft can operate in places where the Turbolet can and many of those places are inherently risky to fly in even for the most rugged of aircraft and most seasoned of aircrew. Accidents are bound to happen in such places even under the most ideal of circumstances.
Turbolets are often operated in developing or underdeveloped nations where regulations are poorly if at all enforced. That in combination with many operators of the aircraft being small and remotely located has often lead to poor quality control in both ground maintenance and aircrew training.
The L-410 Today and Learning More
While some Turbolets have found their way into museums, the type is still very much an active flyer earning its keep in air arms and on civil registers worldwide. As such, your chances of seeing one in action aren’t particularly scarce.
Without a doubt, the best place to see the bulk of the Turbolet family line in one place is Kunovice, in the south east of the Czech Republic. Kunovice airport is home not only to the Let company, but also the Kunovice Air Museum. The museum dedicates most of its activities to preserving the aviation history of Kunovice. In the museum collection, you will find the first and third XL-410 prototypes as well as early production Turbolet models. A visit to Kunovice could also see you in a position to watch resident Turbolets operating at the airport.
Still in production more than fifty years after it was designed, the Turbolet shows no signs of slowing down any time soon.
This link will take you to a website with a wealth of information on all aspects of the Turbolet and its development. The site is in Czech, but responds well to online translator functions.