164
edits
Icaro Laminar 13 MRX: Difference between revisions
Jump to navigation
Jump to search
→Tuck avoidance
(→Tuck avoidance: some more slides / one new reference in →References) |
|||
| Line 136: | Line 136: | ||
<br> | <br> | ||
<br> | <br> | ||
Firstly, the analysis of the sensor video (in keywords): | |||
[[File:MomentDiagram AssignmentSensor en.jpg|left|thumb|800px|Assignment of the flight attitude and pilot deflection in the moment diagram (see Sensor video)]] | [[File:MomentDiagram AssignmentSensor en.jpg|left|thumb|800px|Assignment of the flight attitude and pilot deflection in the moment diagram (see Sensor video)]] | ||
<br> | |||
<div style="clear:both"></div> | |||
# The pilot wants to initiate a spin, but does not succeed (Point 1 in the slide). The angle of attack is very high (estimated α>45°). He is probably already in a stall. | |||
# To stop the stall, the pilot pulls in slightly to the trim position (Point 2). The angle of attack is unchanged. The moment is now clearly negative. This leads to the extreme pitch-down. | |||
# In exactly this pilot position (relative to the wing), the system - consisting of wing and pilot - continues to rotate. The angle of attack is continuously reduced. In the diagram, the hang glider moves from the right to the left on the blue curve. | |||
# At point 3, the blue curve intersects CM=0 at alpha=25°. The area under the (negative) moment curve (between point 2 and 3) is a measure of the strength of the rotational excitation. | |||
# for α<25° (to the left of point 3) the moment is now positive. The deceleration of the rotation has started. | |||
# α<sub>0</sub> is reached at point 4. From then on, the lift becomes negative, which results in a reversal of the control effect (see Figure 2). | |||
# '''Up to this point the hangstrap is tight!''' | |||
# If the pilot would remain in this position relative to the wing, it would continue to move to the left on the blue curve. The momentum there is still positive up to α~-15° and the deceleration effect would still be present. However, the pilot now has to grab firmly the basebar because otherwise he would fall into the sail due to the downforce. | |||
# Due to the braking effect, the rotation of the wing is almost stopped at point 5. However, due to the inertia of the pilot, the pilot continues to rotate (relative to the wing), resulting in a shift of the pilot's centre of gravity backwards. This configuration corresponds to the brown curve. | |||
# Since the angle of attack is already less than -2°, the moment becomes negative again, which results in an increase in the (initially stopped) pitch-down rotation. This is the actual tuck. | |||
# Compare the area under the moment curve from point 3 to 5 (deceleration) with the area from point 5 to 6 (excitation), which is a lot larger. This is one of the reasons for the high rotational speed that is often observed in tucks. | |||
<br> | |||
The tuck initiation can therefore be separated into four phases. The initial phase, in which the pitch-down moment is generated and the excitation phase (CM<0), in which the rotation is excited. This is followed by the deceleration phase (CM>0), in which the rotation is slowed down. In the last phase, it is then decided whether a tuck occurs (CM<0) or not (CM>0). | |||
<br> | |||
<br> | |||
The four different phases are shown in detail on the following slide. | |||
<br> | |||
[[File:Definition of the tuck initiation phases.jpg|left|thumb|800px|Tuck initiation: Definition and characterization of the individual phases (Predictable tuck initiation)]] | |||
<br> | <br> | ||
<div style="clear:both"></div> | <div style="clear:both"></div> | ||