UAVOS convert Pipistrel Sinus into an RPA

Aliaksei Stratsilatau, UAVOS Lead developer, is sharing UAVOS’s experience of the conversion of a manned aircraft the 2-seat Pipistrel Sinus

Where did the idea to convert manned aircraft into UAS originate?

From one of our customers, we received an order for the manufacture of heavy UAS. That customer needed unmanned vehicles of this type for commercial use. When we calculated the cost of developing and manufacturing a heavy UAS from a scratch, the cost of the flight hour was too high, much higher than the cost of the flying hour of a conventional manned aircraft. High production costs are the result of the small series. Then we offered our customer to expand the range of required commercial UAS by converting, and chose for this purpose Pipistrel Sinus.

Why was the Pipistrel Sinus aircraft chosen as the aircraft to convert?

Pipistrel Sinus is a motor glider and, as a result, has a long flight duration, namely, about 25h with 88 lb (40 kg) payload. In addition, these aircrafts are available in the secondary market, which significantly reduces the prototype production both at cost and in terms of time. Another remarkable feature of this aircraft is the availability of a parachute ballistic rescue system in the standard configuration.

The advantage is also the high wing position and the lack of wing struts, which allowed us to place on the wings beam supports for fixing the payload. In place of the pilot seats, additional tanks of 21 gallons (80 litres) capacity were installed.

I would also like to note that this aeroplane has been manufactured for a long time, well tested, and quite reliable. In addition, we have a good partnership with the manufacturer – Pipistrel Sinus, which is located in Slovenia.

How long did it take to develop the unmanned aerial complex based on the Sinus light aircraft?

The conversion of the first aircraft was completed in 8 months. In view of the fact that this version had an intermediate version, namely, it was optionally piloted (it can fly on its own and at the same time it can be controlled by a pilot). Now, on average, the conversion cycle with the modification of the aircraft takes 3-4 months.

What was the biggest challenge that you all encountered during the conversion process?

The main challenge required additional calculations to reinforce the fuselage – that came together with the installation of additional fuel tanks. Also, a large amount of work was done on the control system by our programmers – the problem of landing the aircraft with a strong side wind (about 46ft/s [14 m/s]) in fully automatic mode was solved.

What are some of the advantages of converting manned aircraft into UAS, as opposed to developing heavy UAS from scratch?

Creation of a heavy UAV from a scratch, its development, prototype production, testing without a pilot, preparation of all operating documents, training of technical personnel – all this requires a huge amount of time and resources. The possibility of losing a prototype during tests is also high.

For us, it was quite tempting idea to use ready-made, certified, tested and mass-produced aircrafts with customized systems and guaranteed parameters for a symbolic price. And the ability to test the autopilot’s performance and its setting on board together with the test pilot, especially when performing automatic take-off and landing, is simply invaluable.

Who do you envision benefiting the most from these types of heavyweight UAS?

Heavy UAV weights about 1 ton and more. In this weight category, all manned aircraft (light aircraft) are piloted according to the rules of open visibility, i.e. the pilot must observe the horizon (direct vision). Thus, flights in bad weather conditions and at night can only be performed by vehicles equipped with special equipment and a specially trained crew. This automatically affects the cost of flying hours, making it more expensive. At the same time, a UAS with a mass of about 1 t or more allows performing routine monitoring tasks not only in complex meteorological conditions, but also over zones with no emergency landing: the ocean, the forest. An important point is that there is no danger of losing people.

Why is this capability — the conversion of manned aircraft to UAS — is important to the unmanned systems industry?

First, it drastically reduces the cost of flying hours, thereby opening up a commercial market for heavy UAS.

Secondly, the reliability of certified devices increases the reliability of the entire UAV system as a whole.

In addition, the conversion reduces the production time for an UAV – one of the important conditions for any customer; and the funds don’t freeze.

An important point is the availability of a large network of dealer centers and spare parts stores of the UAV donor, which, again, reduces downtime and reduces the cost of flying hours.

Are there any plans to convert other types of manned aircraft outside of the Sinus light aircraft into UAVs? If so, what types of aircraft are they, and what does that timetable look like?

Yes, we are completing the conversion of the Robinson 22 helicopter and proceeding to a project to convert a helicopter with a payload capacity of 1 ton. In addition, we paid attention to the hydroplane segment. Now we are testing the altimeters above the water. There are problems with this as for now.

By Taisia Vasiukovich

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