Safir 5K/G MI APU
There’s no dispute that this is a top product. It has been one of the workhorses of the aerospace division for more than 15 years, as the entire PBS has been, both in terms of sales and profits. This year alone, more than 40 % of the division’s turnover has been comprised of the “Mičko”. Moreover, every APU (auxiliary power unit) must return to PBS for an overhaul after 8 years or earlier, depending on the number of starts and the number of flight hours. The sales and thus the profit from the overhauls and from the sales of spare parts then also creates a considerable part of the division's economy and for the entire technical lifespan of the APU, which is between 24 to 27 years depending on the type
Despite this, the origins of this sophisticated turbine device were not ideal at all, when it looked like it would be a flop instead of a top product
The MI-171Š Czech Army helicopter
How the Mičko set out West and ended up in the East.
In the 80s, PBS began development of their Safir 5K APU for the L-610 aircraft from LET Kunovice. The development was successfully concluded in 1994, winning certification of the Safir 5K.
Even before that, the former Czechoslovak government recommended the development of a so-called “Western” variation of the aircraft (later designated as L-610G) in 1988, which would also be sold on Western markets. The General Electric CT-7 engine was selected to be the “Western-style” aircraft, ; however, it required a more powerful APU. Thus, the Safir 5K was transformed into the modified Safir 5 K/G, which was once again successfully certified in 1999. However, the L-610 project subsequently failed due to a lack of funds and the stance of the owners aT THAT TIME, LET Kunovice.
Therefore, an APU with very good parameters was created but without a real application and it was in danger of becoming a waste of the time and money invested in it.
However, as is often the case in life, every cloud has a silver lining. In 1999, initial contact was made with representatives of manufacturers of Russian helicopters MIL Moscow and the helicopter plant in Kazan at the MAKS fair in Moscow. At that time, the Russians were looking for a replacement for the Ukrainian AI-9V APU to ensure the startability of the Mi-17 helicopters up to an altitude of 6000 m, which was a requirement of the Chinese customer for the Mi-17 helicopters. A contract was subsequently signed with the Russian group for the supply of APUs with certification in 2000, which were delivered to Russia in 2001. At the time, this was a modified Safir 5K/G MI APU, which was originally intended for the L-610G aircraft for Western markets.
The variation of APUs from PBS
Based on the success of the Mičko in Russia, development started at the ATD on other types of APUs. The APU Safir 5K/G Z8 was developed
for the Chinese AC 313 helicopter. An APU designated Safir 5K/G MIS was created, replacing the direct APU AI-9V APU from a Ukrainian manufacturer.
In the ATD’s selection, there are also simpler APU types intended mainly for smaller sub-sonic training aircraft. They are based on the design of the APU for the legendary Czech aircraft, the L-39 Albatros.
Currently, at the ATD, we are also discussing developing other specific modifications for the current Chinese customer’s upgraded helicopter.
Even the original Mičko is continually being upgraded. For example, between 2015 and 2016, the “Auxiliary certification tests” project was completed based on design modifications. The purpose of this long-term test was to establish the increase of the time limits for the overhaul from the original 750 to 1500 hours and then from the original 2,000 to 3,500 starts.
The total run-time of the APU during the test was 1,548 hours and the total number of successful starts even surpassed 4,000. This year, another increase of 500 hours in the overhaul time limit was achieved for the Mičko and an additional 250 hours for the APU Z8.
The installation of the MI APU in the Mi-171Š helicopter
The very good parameters of our APUs, their reliability, the prolongation of resources, and especially the fact that our APUs are certified by the Russian and Chinese national certification agencies have helped us maintain a lead over our competitors in these markets.
How does an APU work anyway?
As the auxiliary power unit’s name implies, this device serves as an auxiliary source of power for aircraft and helicopters. In the case of the Mičko, it is also a combination of a power and compressed air supply.
Simply put, this is a 60-kilogram turbine engine, which is started with the help of a built-in electrical starter. The running APU generates compressed air and electrical power for the main on-board electrical systems. The pilot starts the main engines after inspection as part of the pre-flight check. The compressed air from the APU is routed to the air-starters of the pair of main TV-3 engines. Each of the engines on the Mi-17 helicopter weighs around 300 kg and provides more than 2,000 horsepower. After starting the main engines, the APU is shut off. If the main engines cut out in flight, the APU is the only chance of restarting the engines.
One of the other functions of the Mičko is supplying clean air for the environmental control system. We have designed the ECS-M1V environmental control system at the ATD for the Russian helicopters, which was successfully certified by the Russians this year. The first 4 units are already cooling or heating Mi-171A2 helicopters.
The Kazan helicopter plant has also successfully finished the certification tests for another of our products this year, the EMG-200 starter generator. As the name once again implies, this is an electric starter and generator in one, intended for the smaller type of Russian helicopters named ANSAT. After initial technical problems, even this product, is faring well on the Russian market and we have sold 37 of them this year. The orders for 2019 have already amounted to 100 units.
There is no profit without risk
The entire team consisting of enthusiastic calculation engineers, designers, skilled production workers and test technicians are responsible for the successes of these products, and they deserve a BIG THANKS, as does the management that gave the green light to these projects. It is necessary to add that if today’s ensured funding and commercial application guarantee requirements were applied at the beginning of the Mičko’s development, we would probably not have any APUs in PBS's offer
funding and commercial application guarantee requirements were applied at the beginning of the Mičko’s development, we would probably not have any APUs in PBS's offer.
Some degree of uncertainty was also present at the beginning of the development of the TJ100 jet engine, which coincidentally will also be celebrating its 900th manufactured piece in a few months.
It cannot be assumed that every development project will be as economically successful, but history has shown that some degree of risk does pay off when developing new products.
Let us wish for a thousand successful starts
With a projected production of more than 90 Mičko units next year, we can anticipate a truly round jubilee of the Mičko with a big one and even more zeroes at the end can be expected in a year and a few weeks.
There is nothing left but to wish a thousand successful starts to its one-year-younger, nine-hundredth little brother, which was finally assembled on Friday, 7 December 2018. Let us also wish that it visits one of the 60 countries in the world to which the Russian manufacturer has historically supplied its helicopters to spread the good name of the PBS brand. Let us also wish that it comes back home in good condition for an overhaul to its “native” little Velká Bíteš, no later than in 8 years’ time.