RAST in practice |
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There is a principle in science known as falsification, which says that the accuracy of a statement cannot be proven, but only its invalidity.
We were breaking new ground in paraglider design with the RAST system, so this concept saw us encounter curiosity and interest on the one hand, and understandably, on the other hand, scepticism and reservation as well.
There have been attempts from many quarters to refute the effectiveness of our new technology, by applying time and again the same existing standards used for paragliders without RAST, so as then to compare the results despite the fact that there are different preconditions. What’s more, at the same time the preventative effect of RAST is constantly disregarded.
Adopting such an approach can hardly be considered as evidence that RAST is ineffective.
Our test pilots soon realised during testing that the advantages of RAST were much more apparent under real conditions than in simulation.
It is thus not possible to draw adequate conclusions in relation to the safety of paraglider designs featuring RAST from simulation alone, which is why testing also involved hundreds of hours of airtime in a great range of conditions with independent pilots. Pilots all agreed that RAST proved truly effective in practice and that this system is one of the biggest innovations in paraglider development.
With other new designs, such as 2-liners or paramotor gliders with reflex profiles, safety assessment beyond the pure simulation of collapses has already reached its limits. However, in practice these designs have proved themselves in their areas and today are “state of the art”.
The principle mentioned above means it is impossible to prove that RAST is effective without fail. However, we are able to provide actual examples of canopy stability problems with RAST, which satisfied pilots have passed on to us.
These practical examples demonstrate convincingly how RAST counter-acts any deformation of the canopy and prevents it from spreading back to the trailing edge. However under no circumstances should pilots be tempted by this into switching too soon to gliders with a higher classification because of RAST, as major collapses spreading beyond RAST cannot be completely ruled out, and the glider would then exhibit behaviour typical for its category, to which a pilot must be able to respond.
Besides that RAST still offers so much more:
» The comprehensive RAST special issue with all information, Magazine test reports, pilot feedbacks and FAQs about the “Ram Air Section Technology”. – PDF (59mb)
Not long after the pilot launched in Annecy, he flew his Arcus RS into an area of very strong turbulence generated by thermals.
The resulting collapse initially starts as a frontal collapse, which spreads from the right side of the wing across to the left and changes into a massive asymmetric collapse on the left side.
It is clearly evident how the front stall is stopped at the partition, even without any pilot input, and the asymmetric collapse is then prevented from extending over into the right half of the wing.
Whilst deformation of the canopy affects approx. 80% of the wing at its leading edge, its trailing edge is not affected until well over into the left half of the wing.
The fact that the canopy does not completely empty behind the RAST system means that it re-opens extremely rapidly and there is little loss in altitude (due also to thermal assist).
Pilot’s comment: “It all happened so quickly that I didn’t have any time to react! “
Jeffrey Griffioen was flying out of a thermal in Greifenburg, Austria when he experienced a front stall on his Arcus RS XL (take-off weight: 121kg, harness: Lightness 2).
RAST stops the symmetrical front stall, thereby preventing it from spreading further into the wing’s rear section.
There is thus no risk of a front rosette and the glider opens extremely quickly, without any significant loss of altitude.
The pilot himself reported that he did not respond to the front stall by braking.
Pilot’s comment: “A front stall on an Arcus RS – a non-event!“
The Arcus RS pilot was coming in to land in Austria’s Tannheim valley when he experienced an asymmetric collapse shortly before touching down in the intermittently turbulent valley wind.
In this case too, RAST effectively prevents the collapse from spreading further, and the folding line runs practically parallel to the leading edge.
The glider reopens extremely rapidly and there is a flat folding angle, so it doesn’t turn away and there is very little loss of altitude.
While testing the Nyos RS, the Italian XC-pilot and photographer Gianni De Zaiacomo flew with a tow camera he had built himself (image frequency of 1 sec.). This produced this photo of an asymmetric collapse. The photo shows the image with the most extreme features of the collapse.
It can be seen clearly from the distortion of the right SWING arrow on the bottom surface how the collapsed section of the wing (buffer zone) literally “wraps” around the partition.
Behind the RAST-system, the wing remains stable and filled with air.
Pilot’s comment: “I’m happy to see the effectiveness of RAST in that picture. RAST works very well!”
