Impuls

The Impuls project was to be the successor flagship project of Lambach Aircraft, then still referred to as SSVOBB. It was started in 1994, while the HLII build was still ongoing. It was to be a two-seater aircraft with a pusher prop configuration that would provide a spectacular view. It would be built using (for the time) novel composite materials.

The conceptual design was soon finished and in 1996 production was started. Design and production continued alongside each other, however the project experienced many setbacks, culminating in it being halted in 2009.

A model of the Impuls fuselage in the low turbulence (LTT) wind tunnel of the TU Delft.

 The Problems

Some of the encountered problems were:

  • The CS regulations were used incorrectly, appendix A was used while the aircraft did not qualify for this.
  • The aerodynamics were not improved after wind tunnel tests showed that the expected values were not reached. This was mainly caused by airflow disturbances from the engine cowling.
  • The mass budget was very tight, this problem was further exacerbated by the extra resin that was absorbed by the foam cores in the wing, which had not been taken into account.
  • 14 years after the start of the project the hull design is outdated, full composite fuselages are now producible. Additionally the tube frame was too complex.
  • The certification specifications changed during the design/production. FAR became JAR which in turn became CS. This was not adequately incorporated into the design.
  • The first engine choice was a Rotax engine. This was later changed to Midwest, Which then sadly went bankrupt. The decision to go back to Rotax was made too late which caused large changes in (amongst others) the performance calculations.
  • Insufficient systems engineering caused some design decisions to be driven by the parts that had already been produced. This involved some weird solutions and workarounds that could easily have been avoided. It also caused problems to pile up instead of axing them at their source.
  • Insufficient documentation caused information deficits between different generations of volunteers. This meant that some systems had to be redesigned purely because the knowledge of the original had been lost. This created a lot of unnecessary extra work.

It was thought that it would be easier to start over with a new aircraft design. This resulted in the S-Vision project.

A piece of the fuselage mold next to a model of the Impuls.