Let L-13 Blaník – Gliding Globally

Team Blanix, a pair of L-13 Blaník gliders operated by Red bull. Seen at Zeltweg, Austria in 2022.

A Sailplane for the Masses 

To travel aloft in a glider and be kept airborne by nothing more than thermal updrafts, no engine or fuel to worry about, is an experience quite different from flying in any sort of powered aircraft and likely as close as humans will ever come to flying as the birds do.

The sense of freedom that comes from gliding has made it a very popular activity worldwide and the Let L-13 Blaník and its variations have been catering to the training needs as well as touring and aerobatic desires of sailplane clubs and pilots in almost every corner of the globe since the late 1950s.

From it’s first flight in 1956 and subsequent production starting in 1958, the Blaník had a quick rise to popularity thanks to its durable construction, affordability and ease of handling both on the ground and in the air. It was extensively exported and became the stalwart of gliding clubs in many countries.

In its lifetime, the Blaník has held many records for two seat sailplanes. With over 3000 built, the Blaník still holds the record for the world’s most produced glider of post World War Two design.

An L-13 AC engaged in aerobatics and showing the varied shades of the type’s all metal construction. Brno, Czech Republic in 2022.

A Breed Apart 

Designed and built by the Let aircraft company of Kunovice, in the south east of the Czech Republic, the Blaník was in several key ways a radical departure from sailplane designs which had gone before it. Chief among those departures was the extensive use of metal in the Blaník’s construction; with the exception of the elevators and rudder, the aircraft structures were entirely of metal.

The Blaník was designed from the outset with training in mind; to this end, it incorporated a semi retractable main landing gear with a strong shock absorption system which would allow the aircraft to withstand gear up landings and such similar beginners’ mistakes with little to no ill effect on the aircraft.

With a high level of durability afforded by its all metal construction, the Blaník proved particularly popular as a training aircraft in gliding clubs for its ability to withstand heavy handling that would do serious damage to more expensive and modern types made of composite materials. Beyond civilian groups, the Blaník also served as a military trainer; it was known as the TG-10 series in U.S. Air Force service.

Baseline L-13 at Brno, Czech Republic in 2022.

Clipping the Wings 

In spite of its durability, the Blaník is not unbreakable. Following a fatal crash in 2010 of a Blaník in Austria, baseline versions of the aircraft were grounded in many countries when the cause of the accident was attributed to metal fatigue in the wing spar area.

The grounding was controversial in many quarters for a variety of reasons, not the least of which was that it affected all baseline L-13s even those with total flight hours well short of the aircraft’s fatigue life.

Interestingly, while other nations scrambled to find a fix to the fatigue problem, Australia had already come up with a Blaník life extension solution in the 1980s known as the “Llewellyn Modification”; aircraft which received the modification were re-designated L-13 A1 and not affected by the grounding. While this modification did keep some L-13s in Australia flying, it was not approved as a valid fix outside that country.

In the time that has passed since the accident in Austria, some modification packages have become available to enable Blaníks affected by the grounding to possibly be made flyable again as L-13 A models.

L-13 AC at Brno, Czech Republic in 2022.

Variations on a Theme 

Naturally, with the popularity that the baseline L-13 enjoyed, Let and others set about on developing and improving the aircraft. In 1988, the L-23 Super Blaník was introduced; the L-23 incorporated changes to save weight and improve cockpit ergonomics and outward visibility among others. The L-23 served as the basis for the L-33 Solo single seat glider which was introduced in 1992. Like the original L-13, the L-23 and L-33 are of primarily metal construction.

Another variation is the L-13 AC, a development intended to increase the Blaník’s flight parameters so it could be used to train pilots to a higher level. The L-13 AC, generally speaking, can be described as the cockpit and wings of the L-23 married to the rear fuselage and slightly modified tail of the L-13.

The most visible external features differentiating the L-13 AC from the baseline L-13 are a small extention at the base of the vertical tail fin and less support framing on the cockpit canopy.

An L-13 Vivat seen at Brno, Czech Republic in 2018.

Motoring Along 

As was the case with many sailplanes, attempts were made to motorize the Blaník in order to make it self-launching and independent of tow planes and launching winches.

The earliest motorized version of the Blaník was the L-13 J variant which had a specially built three cylinder engine built by the Jawa company, best known for their motorcycles, mounted on struts above the wing spar. The first flight of the L-13 J took place in March of 1968.

A more meaningful development in terms of self launching abilities was the L-13 Vivat series of aircraft. The Vivat took the wings, rear fuselage and tail of the L-13 Blaník and connected them to a newly designed forward fuselage and cockpit. Most Vivats have a retractable single wheel main landing gear with outrigger wheels at the wingtips, though a small number were also made with a fixed two wheel main landing gear arrangement.

An L-13 TJ seen at Brno, Czech Republic in 2018.

The Vivat keeps the Blaník’s two seat arrangement, but has the seats side by side rather than tandem thus creating a much more roomy cockpit. The Vivat can be fitted with a Czech made Walter Mikron engine, a German made Limbach engine, or a Rotax engine from Austria.

Construction of the Vivat was undertaken by Aerotechnik, also based at Kunovice, and over 150 of the type were completed before production ended in the late 1990s.

Other attempts to motorize the aircraft were done on a much more limited scale.

The L-13 B Bačostroj first flew in 1979 and has only ever existed as a single example. The concept of the L-13 B was to create a single seat motorized version of the Blaník by removing the front seat and placing the engine there.

2006 saw the first flight of the L-13 TJ, a jet powered version of the Blaník. Two L-13 aircraft were modified to be fitted with small jet engines and were used to set new records for sailplanes in speed and time to height.

The L-13 B Bačostroj at Brno, Czech Republic in 2017.

The Blaník Today 

In spite of the groundings that affected the baseline variant, popularity and numbers are still very much in the Blaník’s favour and its name is still respected.

Blaník Aircraft, a company established in Prague in 2014, currently holds the certificates for all Blaník types and has actively been pursuing life extension programs for existing L-13 Blaníks as well as the possibility of restarting production of the L-13.

While some Blaníks have found their way into museums, it is safe to say that members of this aircraft family will be flying for several years to come.

Learning More

This link will take you to the Blaník Aircraft company website where you can find the latest developments regarding the L-13 and it’s family

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