Quote:
Originally Posted by meritflyer  Loss of airspeed: Expect a pitch down moment as a result of losing some relative wind. Dont pitch up as a decrease in airspeed may result in a stalled condition. Corrective action would be to pitch and power (ie lower pitch and increase power).
Gain of airspeed: Expect a pitch up moment as a result from gaining additional relative wind. Correct your pitch by lowering the nose to the horizon. Correct for the additional airspeed by a reduction in power.
Any thoughts are welcome. |
Flight path control is more important than airspeed control when dealing with windshear. If you encounter windshear at low altitude the last thing you want to do is lower the nose to maintain trimmed airspeed. If it's bad windshear this will almost guarantee a trip into the weeds - at an airspeed well above the stall. Think of that excess airspeed as money in the bank. You don't WANT to spend it but you're going to have to in order to preserve altitude. This usually involves a rather agressive pitch up (we use 15 degrees as the initial target in the Beech 1900 with the idea of increasing pitch until intermittent stick shaker activation occurs) while applying max power. Accept the lower-than-normal airspeed but respect the stall. You want to keep the airplane flying for as long as possible with the hope of exiting the shear. Just remember that even using perfect windshear technique is no guarantee that you're going to make it.
If you encounter a shear that results in an increase in airspeed (let's assume this happens on the approach) you'll see the airplane start to get high on the glideslope in addition to the increase in airspeed. The danger here is correcting by pitching down to get back on glideslope AND pulling power back to get airspeed back on target. Any time you get a performance-increasing shear you must assume that it will be followed by a performance-decreasing shear (aka "the Lord giveth, the Lord taketh away"). You may be better off playing it conservatively and abandoning the approach BEFORE you experience the loss of airspeed/downdraft that may be soon coming (assuming the classic microburst scenario). A less conservative alternative is to pitch down to regain glideslope but leave the power where it is and accept the higher-than-normal airspeed. This excess airspeed is your "money in the bank" which will be used to get you out of any performance-decreasing shear you subsequently encounter. Of course, this may result in the airspeed being too high to stop the airplane after landing - it all depends on the type of airplane and the amount of runway available. In the Beech getting rid of excess airspeed is quite easy.
Here's the link to AC 00-54 which discusses windshear in more detail:
http://www.airweb.faa.gov/Regulatory...LE/AC00-54.pdf