We can see in film footage that with RAST 2.0 the rear section has hardly any wave action in turbulence and the profile stays clean. Without RAST the profiles become deformed behind the B-hangpoint, try to adjust to the air movement and disrupt the airflow.
It is noticeable that RAST 2.0 prototypes are more likely to generate thrust in turbulence, while their counterparts without RAST have a tendency instead to brief surges and thus lose speed and momentum.
Something which was very apparent to us time and again with both RAST systems during the test flights is this: control through the steering lines is much more direct and more efficient than without RAST. There is hardly any time lag and the whole canopy responds immediately to control input. Where other gliders can hardly be controlled, for example where there are high climb rates, in strong turbulence or when flying at full throttle, the pilot has total control over the canopy. Clearly, the control pressure becomes somewhat stronger with rapid steering movements, but one notices clearly that the entire canopy follows immediately.
There will no doubt be much more discussion about performance and safety with RAST, however the control through the steering lines is definitely convincing.
We have noticed the following difficulties – if you could call them that:
- Collapse simulation is much more difficult and unrealistic. This is a problem particularly in certification.
- RAST calls for a measured launch technique when there is a tailwind.
- When there is a full stall, initially the glider flies backwards noticeably, pitching feels somewhat more dynamic. RAST gliders thrash around much less in very large full stalls though.
Which gliders will have RAST next
Currently our test team is continuously flying RAST prototypes in the high performance class, in order to transfer to high performance gliders the refinements to the design of RAST 2.0 and additional experiences with improved performance through RAST 2.0.
In addition, RAST prototypes are at present flying in lightweight designs and as speedriders. Here, the stabilising effect in particular could prove to be an advantage for the target group.
Besides that, work is underway on the Acro glider TRINITY.