by Norman Sanders
Consider the hard working and unsung windsock. On duty, rain or shine, 24/7. The windsock is one of the two most identifying features of an airport. The other is….a runway of some sort. (And tall trees, and power lines.)
The windsock has a valuable story to tell for those willing to listen (or look). The windsock is automatically the first thing that an experienced pilot notices upon arrival at the airfield. What is the wind direction? Steady or variable? Speed? Gusty or smooth?
There are actually standards for windsocks so that they indicate pretty much the same all over the world. The FAA in the US spells out the mechanical requirements for construction, along with calibrations.
Per FAA standards attached, a 15-knot (28 km/h; 17 mph) wind will fully extend the properly functioning windsock. A 3-knot (5.6 km/h; 3.5 mph) breeze will cause the properly functioning windsock to orient itself according to the wind. If the windsock has blown away, the wind is greater than the 75 knot design limit.
In general, the primary windsock at an airfield will be white in color, secondary windsocks will be yellow. However, many fields have only one yellow windsock, which is acceptable considering the alternative which is no windsock at all or maybe an old bedsheet tied to a pole. Windsocks ideally should be located away from buildings and trees. At Tyagarah, both the windsocks are somewhat compromised. The yellow one by the Club is only even vaguely accurate in westerly winds.
The windsock design has the bigger, open end facing into the wind which may seem a bit illogical to some. In fact airports used to have big tetrahedrons mounted so they could swing into the wind with the pointy end to windward. This had the advantage that all you had to do was land in the direction the tetrahedron pointed. With a windsock, of course, take offs and landings are in an opposite direction from the way the windsock is pointing (just like a flag.)
All this fancy windsock technology is only of any value if it is used. People generally don’t have trouble with determining wind direction for takeoff, but a surprising number make mistakes on landing. These are of two kinds:
1. Not understanding how to read the windsock (fairly common) and
2. Not checking the windsock before entering downwind. Pilots may assume that the active runway is the same one they took off from a half hour ago. At Tyagarah, a southwesterly favoring 23 can easily be suddenly overpowered by a sea breeze blowing down 05. The other trap at Tyagarah is the fact that the Caravan jump plane will almost always land on 23 no matter what the wind direction so he doesn’t have to taxi very far. His ground speed may be high, but he has the option of reversing the pitch on his prop and screeching to a halt. (Unlike the “brakes” on Motorfalkes.)
If altitude permits, overflying the field to view the windsock is good practice. A good habit to develop is to check the windsock on downwind no matter what.
A windsock is one of the few items in aviation which is free. Use it wisely, and often!
Windsocks_150_5345_27d.pdf is available from the downloads page.