A comprehensive test campaign was performed in the Politecnico di Milano wind tunnel to compare the aerodynamic performances of the ERICA engine air-intake. Indeed, several operating conditions were tested i.e. cruise, conversion and hovering, with and without blade stubs for several values of flow rates of the principal and by-pass duct.

...As a matter of fact, a remarkable total pressure saving was found with the stubs-off model.

Unfortunately, the presence of the rotating hub significantly reduced the gain. In fact, the total pressure is 6% higher with the optimized duct, but it must be considered that the stub blade makes much more disturbance that the real complete one as the tip of the stub, and consequently the tip vortex , is very close to the duct inlet.
https://cordis.europa.eu/project/id/619949/reporting

The three rotor head configurations are designated: H.1 - without blade stubs but with spacers; H2 - including both stubs and spacers; and H3 - including blade.

https://www.google.ru/search?newwindow=1&biw=1067&bih=750&tb...

Ref. also to:

- https://www.google.ru/search?newwindow=1&biw=1067&bih=750&tb...

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Note added at 9 час (2020-02-10 08:13:25 GMT)
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В некоторых случаях при изготовлении сварных рабочих колес с целью получения высокопрочного соединения применяется электро-шлаковая приварка лопасти не непосредственно к ступице, а к пенькам, отлитым на ее поверхности, при этом шов оказывается в зоне, достаточно удаленной от места наибольших напряжений. Но при совмещении лопастей с пеньками их профили часто не совпадают и пеньки приходится подрубать или наплавлять. Кроме того, омываемую поверхность ступицы не удается обработать на станке.
https://mash-xxl.info/info/337198/