The Impuls project represents a large and important piece of history within SSVOBB Lambach Aircraft, running from 1994 to 2010. During this period the project saw a lot of changes within the aviation world. Examples are the introduction of the JAR and CS certification base, the introduction of LSA and VLA as new aircraft categories and the upcoming usage of composite materials. Although work progressed and many students gained valuable experience while working on the Impuls, the cancellation of the project in 2010 did not come as a surprise. The change from FAR-23 to CS-23, an engine change and an uncompleted aerodynamic study had made it virtually impossible to continue with this rather unconventional aircraft.

The Impuls concept consisted of a 2-seat FAR-23 certified aircraft, because VLA and LSA didn’t exist yet, propelled by a 100HP Wankel engine in a pusher configuration. Other distinctive characteristics were the two tail booms and the large windows ensuring a broad view. Materials characterising the Impuls, were the back then state of the art glass fibre composite used in wing, tail booms and outer fuselage shell. The inner fuselage however, still consisted of a load carrying steel inner frame as monocoque composite constructions were still very rare back in the ‘90’s.

In 1994 a group of five students started designing the Impuls as a bachelor end project at Delft University of Technology.  The project was initiated to fill the gap the Lambach HL-II left within the design department of the society. This new project would redirect the attention from building to designing, another important goal of Lambach Aircraft and more in the field of what the faculty is teaching their engineers-to-be.

During the period from 1994 to 2003 not only the preliminary design (structural, aerodynamic and performance) was completed, but also some detailed design was finished (internal frame, initial wing design, engine cooling, etc.). From 2003 until 2008 the frame, wing moulds and wings and the outer shell of the Impuls were constructed. The fact that it took so long to produce these parts was that during this period some issues arose. Examples were the change in certification base, the slow progress in mould building and the bankruptcy of the engine manufacturer, leading to a reduction in the amount of volunteers, resulting in an even lower progress. A small team of ten persons however, managed to complete the design of landing gear and tail booms as well as the production of the frame, chair and the upper wing skins.

The period 2008-2010 is characterised by new blood that tried to do everything possible to save the project from cancellation.  They mainly worked on the fuel tank, control system, the engine mount of the newly chosen engine (Rotax 912) and the reorganization of the paperwork. Eventually however, it was decided with current and old Impuls volunteers to cancel the project, because of the problems already stated, and use the learned lessons to start something fresh.

Major principle learned from the Impuls is to do things as simple as possible.  Members of the society are still students, which will not suddenly solve problems that trouble even the most experienced aeronautical engineers. Second important principle is to talk more to the experts to gain insights in problems and let them overlook the design for flaws.  Last important principle, dare to take decisions and to fully commit to your decision!

SSVOBB Lambach takes these lessons serious as it would be stupid to make the same mistakes again. This way, the Impuls project will not only have  given students, working on it from 1994 to 2010, valuable insight in the practical design of aircraft, but also will it help future students to create a successful project which will give them lots of experience to be used during their  future careers.

Delft University of Technology