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Icaro Laminar 13 MRX: Difference between revisions
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And this is what the pilot himself says about his stunt:<br> | |||
https://forum.hanggliding.org/viewtopic.php?p=150334#p150334 <br> | |||
Also read his following posts in this thread. The last one ends with the sentence:<br> | |||
''"Im pretty sure if i were on the basetube and just put hte bar to my knees i would have just stopped at "s---"''<br> | |||
How true. | |||
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The initiation of the tucks or near-tucks in the other videos can also be subdivided into the 4 phases. The individual phases are just more or less pronounced. | The initiation of the tucks or near-tucks in the other videos can also be subdivided into the 4 phases. The individual phases are just more or less pronounced. | ||
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The fifth video (Hang glider Tuck and in air collapse Tolmin Slovenia) is a very rare documentation of a tuck out of the blue. In contrast to the previous videos, in which the tuck initiation is predictable (either due to the high angle of attack and/or the pilot's deliberate control input in phase 0), here the hang glider tucks suddenly out of a normal gliding attitude. | |||
Jesper's video seems to be “the film to the book”, i.e. Adam Parer's report from 2009. I have the impression that Adam describes exactly the same tuck initiation that can be seen on Jesper's video. Adam also mentions Andreas Orgler's tuck, which seems to have a similar initiation: | |||
(1) http://ozreport.com/13.238 (2) https://ozreport.com/docs/AdamParerAccidentReport.pdf (3) https://xcmag.com/news/there-i-was-h...v=79cba1185463 | |||
Jesper writes in his comment on his YouTube video:<br> | |||
„''For an in-depth look, check out the [IGC Replay]( https://replay.flights/1z9CGwY ). I've reviewed the footage extensively but cannot identify any clear mistakes or preventive actions. I'm seeking insights and detailed analyses from experienced pilots to understand what might have caused this incident and how to avoid such situations in the future.''“<br> | |||
And further on:<br> | |||
„''Please review the video and share your expert thoughts in the comments. Let's ensure safer flights for all.''“<br> | |||
How right he is! Hence the detailed analysis below. I am only focusing here on the tuck initiation (until the hang glider flies inverted). Although the following in both Jesper's video and Adam's report is also super interesting and quite spectacular, it is explicitly not part of this analysis, as from this point onwards the pilot is only a passenger and can no longer intervene in the steering. You are then helplessly at the mercy of what follows. | |||
This tuck initiation can also be broken down into the four phases described above. The only difference is in phase 0, where the high angle of attack is generated by a strong gust that must have come from behind below (The influence of gusts on longitudinal stability is described in detail later in a separate chapter). Phases 1-3 then proceed in the same way as in the previous videos. | |||
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The following are the most important findings from the data analysis in bullet points:<br> | |||
# Turbulent air. In the last ½ minute before the tuck, the vario displays values between +4m/s and -5m/s. In the last 5 seconds before the tuck, the sink rate decreases from -5m/s (t_Replay=14:26:06) to -2m/s (t_Replay=14:26:11). | |||
# t_Video=0s: Straight flight, maybe with a slight right turn. The hands are relaxed on the speedbar. The pilot's position is centered in the trim position. The VG rope is symmetrically aligned (symmetrical airflow from the front). | |||
# t=2:20-3:00s: The hang glider begins to yaw to the right (see VG rope deflection to the right). The wing is banked slightly to the right. However, there is no rotation around the longitudinal axis. | |||
# Jesper corrects a left-side lift (?) several times and with increasing intensity: first with half, then with full weight shift to the left and finally he shifts his legs as far as possible to the left (more is not feasible, as the space is limited by the left rear wire). By the way: a perfect control technique! The left-side lift must have been caused by a gust/turbulence. The gust can also be recognized by the change in wind noise. However, I myself cannot judge with 100% accuracy whether the wind speed is decreasing (which would be the case with a gust directly from behind) or increasing. But I have the feeling that the wind noise tends to increase. The replay didn't show any significant change in speed immediately before the tuck. However, this may be due to the measurement method and evaluation (time-averaged speed). The right hand rests rather relaxed on the control bar the whole time. For me, this is a sign that he is close to the trim position (neither pulled-in nor pushed-out). | |||
# With the pilot in this sideways deflected position and in this yaw attitude, the hang glider begins to pitch down. The pitching and the rotational speed can be well recognized by the relative movement of the right corner of the controlbar to the trees in the background. Tests with ''FlightGear'' show that a '''gust from behind and below''' at a speed of approx. 15-20m/s is sufficient to trigger a tuck. | |||
# At t=3:24s the downward rotation comes to a brief stoppage (see right speed bar in front of the background; you have to look very closely; frame by frame analysis!) I do not yet have an explanation for this behavior. Immediately afterward, however, a much more pronounced pitch-down occurs (pilot is still on the very left; VG rope is still blown out to the right). | |||
# t=4:12s: The yawing has stopped (VG rope is centered again). The main suspension begins to become slack (first visible at the top of the hang strap). The arms are already slightly pushed-out. The lateral pilot deflection remains unchanged to the left. This situation corresponds to point 4 in the diagram. The nose of the hang glider is not yet pointing exactly vertically downwards. | |||
# t=4:15s: Jesper is still on the far left. His arms start pushing-out. It would be important to know whether he has actively pushed-out or whether the control bar has only moved forward without his intervention and how the bar pressure has changed in direction and strength. In this phase there is no slowing down of the rotation of the wing observable (in contrast to the tuck of the Sensor). It looks rather similar to the tuck of the U2. | |||
# Then, due to the rear center of gravity position (fully stretched arms), an extremely fast rotation begins. Jesper drifts from the sideways deflected position to the center. The right hand no longer rests relaxed on the control bar (is this an indication that he has pushed-out deliberately?). | |||
# t=5:08s: At this point, the harness/legs fall symmetrically into the rear wires. The negative lift forces are now only transferred to the pilot via the rear lower wires and the hands at the control bar. The nose of the hang glider points vertically downwards. | |||
# t=4:18s to 5:18s: Continuous increase of the negative dihedral (increasing negative air force). | |||
# t=5:16s to 5:18s: The left and right uprights bend symmetrically outwards. The hands are still holding the controlbar and the feet are still resting on the lower rear wires. | |||
# t=5:19s: Breakage of the right upright. Right hand loose (?). t=5:20s: Right hand back on the controlbar but further left. t=5:21s: Right hand loose again. Left hand continues to clutch the control bar. The hang glider is approximately inverted (see alignment to the horizon). | |||
[[File:Analysis Tuck Jesper Diagram.jpg|left|thumb|800px|Time sequence of Jespers tuck using the moment diagram]] | [[File:Analysis Tuck Jesper Diagram.jpg|left|thumb|800px|Time sequence of Jespers tuck using the moment diagram]] | ||
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[[File:Tuck initiation; Definition and characterization of the individual phases.jpg|left|thumb|800px|Tuck initiation; Definition and characterization of the individual phases]] | [[File:Tuck initiation; Definition and characterization of the individual phases.jpg|left|thumb|800px|Tuck initiation; Definition and characterization of the individual phases]] | ||
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Could Jesper have avoided the tuck?<br> | |||
Yes, that is possible!<br> | |||
Either he could have flown a little faster (pulled-in slightly). This would have made him less susceptible to gusts or, ideally, he should have been in the maximum possible forward pilot position at point 5 in the diagram (at the very latest at α=-4°; CM=0 of the yellow curve, but only if the rotation had stopped completely by then). Admittedly, the time window for pulling-in is very small (approx. 1s). It is therefore important to be mentally prepared in advance and to have “automated” control reflexes. You can practise this with ''FlightGear'', for example. ;-) | |||