Tour in Tomark Aero factory: how two-seater planes are born (Video)

Tour in Tomark Aero factory: how two-seater planes are born (Video)

Travelling is different when you are an aviation enthusiast. While some are looking for the best places to eat, researching nightlife, trying to list all the must-see places, I am browsing the internet for something else. I like travelling through new airports, I enjoy visiting local aviation museums and I always hope I will get to sit in an aircraft I have never flown in before. However, my latest trip to Slovakia beat all of that, because I got the opportunity to visit an actual plane factory – a place where Skyper GT9 and Viper SD-4 ultralights and EASA certified Viper SD-4 RTC are born.

Visiting industrial sites is not for everyone and I fully understand people who don’t see any value in it. However, I, for once, had never been to any plane factory before, so I was very excited about this opportunity. I wanted to see how a mass-produced ultralight plane is made, what processes does it go through, how are they controlled, what drives the design decisions. So I was really glad I got to visit Tomark Aero – Prešov, a Slovakia based airplane factory.

Tomark Aero is actually part of a bigger company, called TOMARK. Its main business is metal working: manufacturing trailer subassemblies, pressure vessels and a number of other metal components for the heavy industry and agriculture. The CEO of TOMARK has been an aviation enthusiast for years, so one day he decided to form a team that would create the perfect plane for him. Long story short, the design was so good that soon the decision was made –Tomark Aero had to make airplanes for sale.

Tomark Aero factory is located in Prešov, Slovakia.

Viper SD4, the company’s first plane, took off for its maiden flight in 2006. It is a low-wing two-seater – a quite athletic design from where I’m looking. The second plane, the high-wing Skyper GT9 took off for the first time in 2014. It is a faster, more touristic type of a plane, but more about the differences between the two models later.

Viper – is a low-wing two-seater – you can easilly recognize it by its wingtips.

Tour of the Tomark Aero factory

I had never been to a plane factory before so I didn’t really know what to expect. Somehow in my head I pictured almost a laboratory setting with people rushing to complete their tasks in time and partially assembled airplanes moving along on a conveyer. Obviously, that couldn’t be further from the truth as we found out getting a personal tour guided by Tomak Aero airworthiness specialist Robert Benetin.

Skyper is a high-wing model. It is not just the placement of wings, it is an entirely different airplane.

I wanted to see the entire process of the airplane build so the tour started in the point where both TOMARK businesses meet. Sheet metal (mostly aluminium and stainless steel) is cut into shapes using an industrial laser cutter – the exact same machine is used to cut out parts for the trailer subassemblies. The laser cuts out all the holes, so that workers in the assembly line would not have to drill or cut anything. That is pretty much the only area where these two industries meet in the entire site. Interestingly, Tomark Aero always stocks up on parts, so that the manufacturing process would not be hindered by shortages.

Entering into the factory you see an unfinished Viper.

Then these flat parts are deburred and bent into shapes using other machines. Later they form all the needed components for the structure of the plane, including beams for the monocoque construction of the front part of the fuselage of the Viper SD4. The Skyper GT9 is a little bit different, since its front fuselage is actually constructed from thin steel tubes – a common architecture for this kind of plane.

This is where the engine is fitted. You can see the bare metal construction of the Viper.

Of course, before any of these parts get put together to form the basic structure of the plane, they are coated against corrosion and marked so that the assembly line workers would know which part goes where and what process it has to go through. Both Tomark Aero models are basically fully metal, so there are a lot of different parts. I was surprised to see how controlled the process is and to find out that quality check-ups are done at each and every stage.

You can simply feel these people love aviation.

When the basic structure is assembled, the engine is installed on a special frame at the nose of the plane and workers start putting the wiring in. That is a very meticulous task, because not only engine controls have to be installed, but also cables for avionics, whole-plane parachute for emergency landing, fuel tanks switch and many other devices. After that, the outside layer of aluminium is riveted on and the basic shape of the plane is complete.

In the main assembly room the wings of Tomark Airplanes are finished and stored before installation.

At the same time, the wings are being made – also fully metal. Skyper GT9 has slightly thinner wings, but both airplanes have fuel tanks with pretty much the same capacity. Interestingly, Viper SD4 has nice wingtip devices, with a gentle curve going up and back. They are made from composite materials and serve to reduce aerodynamic drag, but, at least for my eyes, they make the entire plane look much more elegant.

Some clips from our visit

When the plane is partially assembled it is time to put it into the paintshop. Tomark Aero has the biggest closed paint booth in Central Europe. Clients can choose from a selection of paint schemes, but, if they think nothing in the catalogue represents their taste, they can opt for a custom paintjob.

Viper with its canopy and engine cover in place.

Then the airplane is taken to a nearby airfield for final assembly and flight testing. At first, the plane is finished – all devices are installed, seats, cabin upholstery are put in and temporary number for testing is pasted onto the fuselage. Initial testing is done on the ground – quality control experts look over the entire airplane checking for defects. Then all controls and avionics devices are inspected and after that the plane is prepared for its maiden flight.

Preparation for the paintjob – planes are painted in-house and customers are allowed to choose whatever paint schemes they like.

This job belongs to a test pilot. He follows instructions about what manoeuvres he has to do in the first flight and registers all the defects if there are any. Then they are immediately corrected so that the customer would get his/her plane in perfect condition.

Tomark Aero planes have an emergency landing system – a parachute that shoots out of the plane in case of a technical problem or other potentially catastrofic issue.

Finally, when the customer decides to ship his/her airplane to aforeign country, the wings are taken off, the plane is packed into a crate and shipped to its owner. It is also possible to fly-over finished airplanes directly to the customers and there is also the option to pick-up the airplane at Tomark Aero test airfield. It typically takes around four months from order until delivery, but, in some cases, Tomark Aero can deliver an airplane quicker – stocking on parts allows for some flexibility in manufacturing time. Delivery time also depends on the customer paint-job scheme, whether it is one already available or if it is customized.

Skyper’s cabin is constructed from tubes.

Both Skyper GT9 and Viper SD4 look mighty impressive for an outsider like me, but how do you chose which one to buy?

Tail structure of the Skyper.

Skyper GT9 and Viper SD4

Skyper GT9 is a high-wing airplane, designed mostly for touristic-type of flying. Because its wings are mounted on the top of the fuselage, the ingress is simple, the luggage compartment is easily accessible from the outside and the plane sports an impressive performance. Meanwhile, the Viper SD4, although a bit slower, is a more robust airplane, which will appeal to more passionate pilots. It is more athletic looking and it is EASA certified to be used in pilot schools – that is a big part of its appeal.


Differences of variants of individual Tomark Aero Airplanes

  „Viper SD-4 RTC“ „Viper SD-4 LSA“ „Viper SD4 UL“ „Skyper GT9 UL“
Wing span 8,4 m 8,4 m 8,4 m 9 m
Length 6,4 m 6,4 m 6,4 m 6,3 m
Height 2,2 m 2,2 m 2,2 m 2,1 m
Engine Rotax 912 S / ULS (100 HP) Rotax 912 UL/A/F (80 HP)

Rotax 912 S / ULS (100 HP)

Rotax 914 UL / F (115 HP)

Rotax 912 UL/A/F

(80 HP)

Rotax 912 S / ULS

(100 HP)

Rotax 912 UL

(80 HP)

Rotax 912 ULS

(100 HP)

Maximum take-off weight 600 kg 600 kg 472,5 kg
Cruise speed 195 km/h 195 km/h 195 km/h 220 km/h
Maximum speed 240 km/h 240 km/h 240 km/h 250 km/h
Ceiling 4 725 m 5000 m
Runway (take off/landing) 240/ 176 240/ 176 150/140 m 120/80 m
Fuel tank capacity 100 l 70 / 100 l 70 / 100 l 88 l

In LSA specifications both planes are heavier (maximum weight reaches 600 kg), which means that a bit-longer runway is required. Also, instead of the 70l fuel tank LSA specified the Skyper GT9 and Viper SD4 get 100-litre fuel tanks.

In short, Skyper GT9 is easier to use and maintain and to live with. It is also faster than Viper SD4, although a little less rigid. Meanwhile, Viper SD4 is a sportier airplane. It is strong, reliable and looks good. It is also very easy to fly – a perfect choice for pilot schools. Viper SD4 can be also used as a great towing machine for gliders or banners. Ideal for flight clubs.

Wingtips of the Viper look very elegant, but are also functional – they reduce aerodynamic drag.

By the way, I asked about the safety record of these planes. This really not-polite question was met with a smile – while there have been several crashes, none of them were caused by mechanical faults nor factory defects.

Summing up

It is the first airplane factory I’ve ever been to. While I was expecting a busy and almost laboratory-like setting, it was much simpler – just an industrial site where everyone fulfils their functions. There are no robots as far as I could see and every plane was caressed by human hands on every step of the way. Kind of a romantic image, to be honest, but it is very technical.

Assembly is completed in a nearby airfield where flight testing is done as well.

Everything regarding the airplane manufacturing is done to the highest possible standards. The quality control is meticulous and watches over every airplane at every stage. However, make no mistake – Tomark Aero airplanes do have some passion about them. They appeared in this world because the CEO of the company simply loves aviation and this sense is visible throughout the factory. I saw posters with fighter jets in one of the stations where the cabin and interior get installed – these people just love what they are doing. And I loved visiting the factory, learning a lot about manufacturing of ultralight airplanes and seeing these birds before the wind touches their wings.

Huge THANKS to Tomark Aero for allowing us to visit their factory. Definately visit their website –

Bell P-39 Airacobra fighter plane recovered from the bottom of the lake in Russia (Video)

Bell P-39 Airacobra fighter plane recovered from the bottom of the lake in Russia (Video)

It‘s been more than 70 years since the Second World War ended. However, traces of the biggest humanity‘s conflict can still be discovered. Just recently a Bell P-39 Airacobra fighter has been retrieved from the Lake Shukozero in Russia and a year ago a couple of Sherman tanks have been recovered from the bottom of the sea almost in the same place.

Bell P-39 Airacobra was mid-engined and therefore required a long shaft to spin its propeller. (US government, Wikimedia)

Bell P-39 Airacobra is a peculiar airplane. It took off for its amiden flight back in 1938 and entered service in 1941. It featured one unusual construction solution – its engine was mounted behind the pilot, which meant that a long shaft was required to spin a traction propeller. However, it was a good fighter plane – it is often said that together with P-63 Kingcobra, the P-39 was one of the most successful fixed-wing aircraft manufactured by Bell. But it did have one issue – its engine was not turbocharged or supercharged.

It is likely that the plane will go to the museum as is – it is just more authentic that way. (Минобороны России)

It meant that it could not operate at high altitude very well and therefore RAF did not want it. Meanwhile soviets took it gladly – 4,746 P-39s Airacobras were sent to Soviet Union to aid its efforts of fighting Nazi Germany. However, this one did not fall into a lake because of some intensive fighting – this accident occurred on a training mission.

As it was said, Fyodor Varavik lost control of his airplane and crashed into Shukozero Lake in northern Russia. Since it was March of 1945, lake was covered with ice so it could’ve been that Varavik performed emergency landing, but at the result is clear – P-39 Airacobra sunk to the depth of 45 metres. Recently this plane has been discovered and Russian Navy personnel assigned to the Northern Fleet organized the recovery operation.

Divers reached the plane, but no human remains were found – only a boot of the pilot was inside of the plane, together with 37 mm ammunition and oxygen tanks. Bell P-39 Airacobra was retrieved and now will find its way in a museum. Very likely, it will not be restored – it will remain authentic with its own story.

Plane was found in a lake in Murmansk region. Not too far away last year Russian Navy recovered a couple of American Sherman tanks. They went down with the SS Thomas Donaldson ship, when it was torpedoed by a German U-Boat.  Tanks were also meant to help Soviet Union – in total 4,102 M4 Sherman medium tanks were sent to the Eastern Front. Interestingly, despite spending 71 years in salty water, tanks were in decently good condition. Some say it is because they were packed very good and could resist water damage for some time.

People love stories about tanks and planes sunken to the bottom of the sea and later discovered by some enthusiasts. But the truth is that most of it is just some legends and myths that are completely made up or got distorted through the years of going from one person to another. However, it is very satisfying to see these gracious machines emerge from their watery grave, because some more years and nature will claim what is hers. Soon all of the lost WW2 weapons will simply be rotten away.

What is this strap for on the doors of the plane? (Video)

What is this strap for on the doors of the plane? (Video)

If you fly a lot you might have noticed a strange looking detail on all of the main doors of the plane. There is a bright red strap going diagonally across the tiny window in the door. You might have also noticed that when the plane is stationary and the door is open this strap is moved away, leaving the window unobstructed. Why? What is its function?

This red strap is used in Boeing 737 and many other planes. It is usually attached to the window as soon as the plane starts moving towards the runway and is put away as soon as it reaches its final destination. People have guessed before that this strap might be some sort of handle or even have something to do with structural integrity of that little window. However, it is just a sign.

At the bottom of the door there is a large box with a slide mechanism inside. This slide is automatically inflated in the case of emergency and allows people to evacuate quickly and safely. However, this slide can be quite dangerous itself, because it inflates very quickly and violently. Basically, imagine an airbag, but much bigger and much more powerful. That red strap tells fire brigade that the slide is on.

Red strap on the door of Boeing 737 – when the slide is not armed, the strap is moved away from the window. (Vasyatka1, Artem Katranzhi, Wikimedia)

Rescuers can get inside of the plane from the outside, but they have to know if the slide is armed. They will adjust their strategy according to this information. Slide is actually always armed as soon as the plane leaves towards the runway. So why this strap is not left there permanently? Fire brigade professionals know that the plane has been moving, so they must know that the side is on.

In case of emergency the slide might be disarmed from the inside. For example, if plane has to land on its belly and the door gets damaged, flight crew may disable the slide so that fire brigade can open the door safely. But in most cases the strap does stay on from the moment the plane starts moving until it stops at the airport of destination.

This information was revealed in the video in Mentour Pilot’s YouTube channel. Here you can see the video:

Mentour Pilot’s creator also debunked an old Hollywood myth – main doors of the airline plane cannot be opened mid-flight. They are held in position by the pressure inside of the cabin – no locks are needed. So you cannot just throw out bad guys from the plane that easily.

Is it possible to retract the landing gear accidentally while the plane is standing on the ground? (Video)

Is it possible to retract the landing gear accidentally while the plane is standing on the ground? (Video)

Piloting a large airlines plane is a very responsible job. However, sometimes small mistakes happen, making people wonder what if a pilot accidentally hits a wrong button at a wrong time? For example, what would happen if one of the pilots would move landing gear lever while the aircraft is stationary? Would the plane simply flop to the ground on its belly?

This did happen in a popular TV series “The Simpsons”. Homer was mistaken for a pilot, since he was actually dressed as one, and was pushed into the cockpit. Soon he found himself pressing random buttons in an attempt to fly the plane. One of them actually retracted landing gear, making the plane flop on its belly. Probably causing some serious damage in the process. But is that possible in real life?

Well, the short answer is no. Modern airplanes have something called “Squat switch”. Essentially it is a sensor, which can tell if a plane is still standing on the ground. That is why it is called squat switch – it senses when the landing gear is still squatting under the load of the plane. When the squat switch is activated, meaning that the plane is still on the ground, it is physically impossible to retract the landing gear.

In “Simpsons” homer just pressed a switch and the incident happened. In real life landing gear is controlled by a lever. When the squat switch is activated, a special rod in the mechanism physically prevents the landing gear lever from moving. In other words, pilots cannot push it forward even if they want to. When plane is off the ground, squat switch is off and the lever is free to move.

You may say that sensors can fail and you’d be right. However, engineers made sure that the squat switch would fail in “on” position if it happens at all. In this case pilots would not be able to retract the landing gear even when already flying. Plane would have to return immediately, but it would not be an extremely dangerous situation.

Also, don’t forget that airline pilots are highly trained – it is hard to believe that they would make such mistake. And planes have some impressive safety tech nowadays. But some mistakes similar to this may happen.

Sometimes pilots may retract landing gear a little early when they are taking off. As soon as the plane is lifting itself from the ground and the landing gear gets extended, they can move the lever and wheels go in. However, at this point nothing serious can happen, since the plane is already taking off anyway. Unless the pilot gets scared of his own mistake and decides to land on the belly immediately.

In conclusion, mistakes related to landing gear are very rare. Pulling it up too early or deploying a little too late is very likely to never happen to you, regardless of how often you travel. However, it did make for a funny scene in “The Simpsons”, even if not possible in real life.

What are those little rods at the trailing edge of the wing? Those are NOT antennas (Video)

What are those little rods at the trailing edge of the wing? Those are NOT antennas (Video)

If you‘re not so much into aviation or technology in general, while flying you notice many little details of the plane that you don‘t know the purpose of. For example, have you noticed that at the trailing edge of every wing there are some weird little rods sticking out? While walking around the plane you might have noticed that there are rods like this on the plane‘s tail too. Why? What do they do?

These are static wicks – they allow electrons with negative charge to dissipate from the airplane’s body. Dennis N., Wikimedia

Some guess those rods are some kind of antennas and they really do look like they could be. However, antennas are situated on the underbody of the plane instead. Those little things you see are actually static dischargers, often known as static wicks. And you have some on your body also.

When you walk across the carpet, you get charged with negative electrons. And then a single touch to something or someone may cause a little electric shock. In fact, in dark you can even see it. This happens because your negative electrons have to equalize with whatever you are touching. Sharp points on your body, such as fingers (or nose, for that matter) are perfect for this negative charge to dissipate from.

Large airplanes fly through the clouds and are constantly rubbing against some particles in the air. Naturally, they get this negative charge also, which can cause a variety of problems, such as poor radio communication or imperfect function of navigation equipment. It is because radio antennas are perfect spots for these negative electrons to collect.

Solution – many little sharp points on the airplane that provide a way for these negative electrons to dissipate. Works well – this negative charge is just given back to the surroundings of the airplane. This explanation is provided by the creator of the YouTube channel Captain Joe and you should check this video out, because it gives a more detailed explanation of how it works:

Captain Joe has been featured in a couple times before. Do you know what those little loops on the wings of the plane are? And what do those numbers mean on the end of every runway in the world?

Coming back to static wicks, you should watch them if you’re flying at night in close proximity or in a thunderstorm – you might notice sparks flying off of them if you’re lucky.

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