In the 1950's and 1960's, the development of rotorcraft technology took other directions, and helicopter derivatives often took a different form than what the world is mostly used to today. Few people, even insiders, realise today that it was rotorcraft with jet rotor propulsion that first exceeded 300 km/h, and that this category was at one time the absolute top performer. It comes as a surprise to many that several hundred of these machines in various weight categories were produced and operated.

The largest rotorcraft for passenger transport with a capacity of up to 50 passengers (2 crew, 48 passengers) was the British Fairey Rotordyne. It was a truly impressive machine with unprecedented agility for such a large machine, excellent climbability and a top speed of over 300 km/h. Unfortunately, it was a victim of backroom political and commercial intrigue, not a technical failure. In the upcoming upgraded version, its reactive rotor drive was to have a much lower noise footprint, which bothered ecocritics. Unfortunately, this has not been implemented. Fairey Rotodyne - Wikipedia. The manufacturer arrived at this large machine by gradual evolution from the single-seat Fairey Ultra-light Helicopter - Wikipedia.

The four-seat American XV-1 helicopter achieved similarly high performance in terms of top speed, climb rate or agility. McDonnell XV-1 - Wikipedia.

In this brief list we must not miss the rotor tip jet helicopters - French SNCASO SO.1221 Djinn - Wikipedia, Sud-Ouest Ariel, VFW-Fokker H3, Dornier Do 32/ 132, Fiat 7002, Percival P.74, Nagler - Honcho/Voljet, Doblhoff WNF 342, Hughes XH-17 but also others using both Cold and Hot Tip Jet technology.

A unique feature of these machines is the fact that, despite the number of types and number of machines produced, there is no traceable accident with damage to health or death of the crew.

NA Engineering has been involved in the development of this rotor technology for a long time, benefiting from the knowledge gained from its own development work in the field of hybrid-compound helicopters. NADC - composite technology.

Currently, three tip-jet rotor helicopters are realized by NAE in this category - single-seat PitPit, two-seat Nyala and unmanned container CargoPit.

These have identical propulsion and rotor system functional units. The rotor blades developed in the project are identical for all machines, but due to the different take-off weights of the different machines they are suspended at different radii, thus achieving different rotor diameters with the same blades. One of the keys to the success of this category is the optimization of the efficiency of the whole system and this is achieved, among other things, by the very specific aerodynamic concept of the blades and the multiple thrust generating nozzles themselves.