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Icaro Laminar 13 MRX: Difference between revisions
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→Impact of gusts on pitch-stability
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This can also be seen clearly on the next slide, where the gust with the highest possible change in angle of attack is shown in the moment diagram for the two flight speeds. A gust with an upward component increases the angle of attack and with a downward component reduces it (simply mirrored). | |||
For α<α<sub>0</sub> downforce (negative lift) occurs, which leads to a ‚wire-slap‘ or slack hang strap. A 5m/s gust can be sufficient for this regardless of the flight speed. | |||
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The influence of flight speed is much more different with gusts that increase the angle of attack. The huge impact of a strong gust at the low flying speed can be seen very clearly. This can increase the angle of attack far into the stall range. The maximum angle of attack with a 5m/s gust is already similar to that AoA reached by the Sensor before the pull-in. With the 10m/s gust, the angle of attack is so high that the moment coefficient CM is in the order of magnitude than that for the Sensor after the pull-in. Although the absolute moment is reduced by a factor of approximately 2 (due to the decreasing inflow velocity), it is nevertheless likely to be just as large or even larger compared to the Sensor, where the airspeed was also relatively low due to the stall. | |||
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That demonstrates that '''at low flight speeds, gusts have the power to trigger 'tucks out of the blue''''. | |||
[[File:Gust Change in AoA en.jpg|left|thumb|800px|Maximum Change in Angle of Attack due to Gusts]] | [[File:Gust Change in AoA en.jpg|left|thumb|800px|Maximum Change in Angle of Attack due to Gusts]] | ||
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If you now think you have understood the influence of gusts, you are terribly mistaken. | |||
The curves only give a rough indication of the change in moment caused by a gust. | |||
However, so far we have not taken into account that the temporal characteristics of the gust also have a major influence on the flight path. | |||
The time in which the gust builds up, the duration and the decay all play a role. | |||
It is also important to note that the decay of a gust has exactly the opposite effect to that of its build-up. For example, a gust from below (+90°) is equivalent to a gust from above (-90°) when it decays. | |||
Tests with FlightGear show that the whole process is extremely unsteady and that the reaction to a gust can be different from what the curves suggested so far. | |||
This is highlighted in the following video. Here, the influence of a 10m/s gust is examined for different gust directions. All other parameters remain constant: the airspeed is approx. 45km/h in all cases, the gust build-up lasts 0.5s, the duration is 2s and the decay 0.5s. | |||
It should also be noted that initially no attempt was made to compensate for the gust by steering. In reality, the change in attitude is of course not so extreme, as the pilot will compensate for the gust by (instinctive) controlling. | |||
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The inflow is visualized by the displayed red vector. The length of the vector represents the inflow speed and the angle in relation to the keel tube represents the angle of attack. | |||
[[File:Flight Dynamics.jpeg|left|thumb|400px| | [[File:Flight Dynamics.jpeg|left|thumb|400px| | ||
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Examples of a gust from above at a | In the following, the complexity of the flight dynamics will be explained in more detail using two examples from the video. | ||
==== Gust directly from the front ==== | |||
--- TBD --- | |||
==== Gust directly from above ==== | |||
--- TBD --- | |||
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Examples of a gust from above at a high flight speed: | |||
{{#ev:youtube|https://youtu.be/seCr0SS2GyE | 500 | inline | with Atos Hangglider in violent turbulence in Gnadenwald / Austria|frame|start=22&end=44&loop=1}} | {{#ev:youtube|https://youtu.be/seCr0SS2GyE | 500 | inline | with Atos Hangglider in violent turbulence in Gnadenwald / Austria|frame|start=22&end=44&loop=1}} | ||