Windshear, A Phenomenon to Watch Out For All Pilots

Windshear is something that every aviator needs to be mindful of when flying any airplane. Windshear has been found to be cause on many mishaps in the aviation history, and therefore this meteorological event needs to be properly studied and understood by every pilot who intends to take an aircraft up in the air. Windshear is particularly dangerous when the aircraft is very close to the surface of the earth, thus aircraft either taking off or attempting to land are at the highest risk. The proximity to the ground during take-off and landing phases of flight means that there is very little margin for the pilot to react and recover the aircraft from such a low altitude in case it is caught up in a wind shear.

Wind shear has been defined as the rapid change in the direction and strength of the wind that tends to displace the airplane from its flight path, and requires considerable effort on part of the pilot to control the abrupt displacement. Wind shear usually occurs over a small area but has significant strength to disrupt normal flying.

Causes of wind shear, and Other Factors Associated with It

Topography and Jetstreams also cause windshear, this factor is more profound and evident near hilly areas and high elevation airports. Variations in the severity of the wind, and changes in its direction are always happening in the atmosphere. However, for heavy passenger jets, normally a horizontal change in wind speed of 45 knots or more and for smaller aircraft that are light in weight a change of 30 knots or more, coupled with a vertical velocity change of 4.9 knots is considered a wind shear of importance. Other meteorological factors that are often associated with wind shear include:

• Cumulonimbus clouds and thunderstorms
• Thermal and temperature inversions
• Fronts and their movements
• Severe updrafts and downdrafts
• Microbursts and turbulence are also associated with Windshear

The potential risk posed by wind shear for the aircraft

Windshear should never be thought of as a normal change in wind velocity, the severity and abruptness of a strong shear is such that even very experienced pilots cannot maintain control of the aircraft. One may lose a lot of altitude before being able to regain control, and then physical damage may occur to the exposed parts of the airplane like landing gears, rudders, and flaps. Severe turbulence may be associated with the Windshear, which has a prominent role in the development of thunderstorms and other adverse weather conditions.

The most risky areas to encounter a windshear are takeoff and landing phases of the flight, where you are flying at a low level very close to the ground. An aircraft on an approach speed of 120 knots and a headwind component of 30 knots at 300 feet AGL, may find itself facing a 10 knot headwind at 200 feet AGL, a sudden loss of 20 knots of airspeed on the final approach. This will require very quick addition of power to regain and maintain the airspeed, any delays may taper off more speed; risk of stalling the aircraft in landing configuration may become a possibility in such an eventuality, since you are required to maintain altitude and pitch the nose up. Many more difficult situations that are potentially dangerous for the safety of the aircraft may be encountered due to Windshear, and anyone who has experienced this phenomenon would tell you that it is an extremely uncomfortable event to go through during flying.

How to Deal With Windshear

Every pilot should be aware that if thunderstorms are being reported in an area then the chances of windshear are there, therefore he/she should be mentally prepared to deal with a potential windshear. The best way to deal with a windshear is to avoid it altogether, however if you have to make an approach in a likely windshear area, the best thing to do is to keep the approach speed a little bit on the higher side to have a safety margin in case of sudden loss of airspeed on finals. The problem may be compounded due to a sudden increase in the rate of descent of the aircraft coupled with the drop in airspeed during the final approach path. This warrants prompt actions by the pilot to arrest the rate of descent by pitching the nose up and at the same time not lose any more speed, rather gain speed to or above the normal approach speed by immediately adding power. This can be tricky since at the critical stages of landing and taking off, the landing gears and flaps etc add to the drag and make sudden acceleration a difficult task. However, with proper knowledge, mental alertness, and correct timely actions, one can overcome the challenges posed by low level windshear encountered during takeoff and landing.

Cory Doggett invites you to read more aviation related articles at his aviation blog at http://www.flightlearnings.com/category/aviation-blog/.

Source: http://toddsblogs.com/referenceandeducation/2012/07/21/windshear-a-phenomenon-to-watch-out-for-all-pilots/

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