Abstract
The UL-39 Albi university's all-composite ultralight aircraft project, powered by a piston engine and ducted fan, continues at the Department of Aerospace Engineering at Faculty of Mechanical Engineering CTU in Prague and its partners ZALL JIHLAVAN airplanes, s.r.o. and LA composite, s.r.o. by developing its new generation. The article is a follow-up to a contribution from 2017, where the entire genesis of the first prototype was described. The introduction summarizes the experience of the prototype operation and analyzes the deficiencies that required a major redesign of the propulsion unit. Aspects leading to the choice of another propulsion unit arrangement and changes in the ducted fan, airframe and systems are described. The fuselage of the airplane has undergone a dominant change. The paper describes not only structural changes leading to the reduction of the width of the fuselage and its wetted area, but also the changes in manufacturing process of composite parts leading to weight reduction. Following the changes in the fuselage design modifications of the wing (mainly high lift devices) and modification of the horizontal tail plane are described. At the end there is a plan of further development described, which should ultimately lead to the commercialization of the project.
Highlights
The UL-39 Albi university©s all-composite ultralight aircraft project, powered by a piston engine and ducted fan, continues at the Department of Aerospace Engineering at Faculty of Mechanical Engineering CTU in Prague and its partners ZALL JIHLAVAN airplanes, s.r.o. and LA composite, s.r.o. by developing its new generation
The unconventional type flight tests have a important role in obtaining airworthiness, the design of which could not be based on previous experience of similar conceptual, constructional or technological solutions. This was confirmed for the UL-39 Albi, which, thanks to its unconventional propulsion unit, stands out of all established design conventions in the category of ultralight aircraft
All changes of the original design resulting from the solution of Albi deficiencies were applied in the design of Albi II
Summary
In the first phase of the aircraft reconstruction, the development work focused on the design of a new propulsor - inlet duct, fan stage (Fig. 6), outlet channel with cooling bypass, nozzle and the modification of the engine itself. Thanks to the more compact engine arrangement and the fan drive shaft directly connected to the crankshaft without further gearing, the inlet duct could be tightened around the engine. This made it possible to reduce its curvature, which contributed to reducing losses compared to the original solution. From the pre-stator - rotor configuration to the pre-stator – rotor – stator This arrangement allowed the entire rotor to be accommodated in a smaller bearing in the stator, and at the same time an easy installation of the outlet cone to the fixed stator to reduce the base drag behind the fan stage. The original intercooler, using the water the scooter is moving in, has been replaced by air one because of the weight and the difficult availability of a sufficiently cold liquid
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