After investigation of the Mantra M7 leading edge lower surface deformation, we now have a better
understanding of the phenomenon and can give an explanation.
Under certain specific circumstances the leading edge plastic reinforcements can remain inverted on the lower surface, even during flight. This is not created by overtight plastics but is caused by a lack of tension in the middle part of the leading edge during the inflation process. If the wing tips are allowed to inflate before the middle section of the wing, the plastics in the centre may become inverted and can remain so even once in the air. This normally only affects the central part of the wing occurring either symmetrical or to just one side, the extent of the deformation or whether it occurs at all depends exactly on how the wing inflates.
To avoid this situation, always ensure the wing is in a good position before inflation. When launching in
wind make sure the wall is well built with the middle higher than the tips, in nil-wind conditions lay the wing in a pronounced arc so the middle is more likely to rise before the tips. We recommend to only take hold of the central A risers, there is no need to hold the outer riser to which AR3 is attached. Whatever the wind conditions or launch method you use, always try to ensure the middle of the wing inflates first, like this the phenomenon will practically not occur. If you do find yourself in the air with inverted plastics, do not worry; the wing can be flown as normal. From the testing we have made we believe it is not a safety concern, the wing can be flown perfectly safely and remedied in-flight. To do so use a short, sharp symmetric jab of the brakes. The action is not the same as the input used to recover from a collapse - a deep long pump is generally not effective - rather, use a shorter, sharper, harder input to provoke the plastics to right themselves. When jabbing the brakes like this, push
your hands to the outside, that way the central brakes are engaged early, this is the most efficient technique to encourage the plastics to pop in the very middle of the wing. When using this method, we have found the plastics can be righted 100% of the time, we have never been unable to right inverted plastics whilst in the air.
We have conducted a thorough flight test procedure with the plastics inverted and have not experienced
any significant detrimental effects to the behaviour of the wing. Parachutal stalls are unaffected, the wing enters and exits a parachutal stall in the same way whether with the plastics inverted or correctly orientated. Collapse recovery is also unaffected.
We do believe however that it will have an slight impact on performance and possibly reduce the inherent stability of the wing, although this is something that is hard to quantify. Even with the plastics inverted, the M7 can be thermalled and ridge soared as normal and when flown actively still remain open in strong turbulent air.
Please watch the video for a clear visual explanation and if you have any questions do not hesitate to
contact one of the test team.