After take-off, a helicopter encounters windshear with a decreasing headwind. As a result…
Refer to figures.
Windshear could be defined as an abrupt and localized change of wind velocity, that is strength, direction or both.
There can be several causes of low-level wind shear:
- The passage of the front in which the isobars change direction;
- A marked temperature inversion;
- Sea breeze;
- Topography and large buildings;
- Surface friction; and
- Cumulonimbus clouds, and their associated weather of heavy rain and hail, which can give rise to the phenomenon known as Microburst.
The primary methods a pilot can employ to avoid a potentially dangerous encounter with wind shear:
- Acknowledge the presence of wind shear;
- Ascertain the extent of the change;
- Stay ready to promptly rectify the situation or execute a go-around maneuver.
Therefore, for a safe escape, the pilot must initiate a "go-around" by:
- DISengaging the autopilot;
- Applying full power;
- Establishing the "best climb speed".
In addition, wind shear can manifest in both vertical and horizontal forms, affecting a helicopter during takeoff, descent, or horizontal flight. Specifically, regarding an approach:
- In cases where a headwind diminishes and begins to shift into a tailwind, there is a sudden reduction in airspeed. Consequently, lift decreases, and the helicopter may descend below the correct glide slope if the pilot does not take corrective action
- Conversely, when a headwind increases due to a decreasing tailwind, the result is an accelerated airspeed. This increase in airspeed leads to greater lift, potentially causing the helicopter to surpass the correct glide slope.
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