What is a wind cone made of?
A mast, a swivel, a yoke, a frame ring and a fabric cone: five working parts that let the sock turn into the wind and show its direction and strength.
A wind cone assembly is the complete mechanical windsock: a mast, a swivel, a yoke, a frame ring and the fabric cone. The ring holds the large end open, the swivel lets the cone turn through 360° so it always points downwind, and the wind fills the large end and leaves by the open small end. How far the cone lifts gives a general idea of the wind strength, not a measurement.
ICAO Annex 14 recommends a truncated fabric cone at least 3.6 m long and 0.9 m across the large end, in colours that show clearly from 300 m above: one colour, preferably white or orange, or five alternate bands with the first and last the darker. FAA AC 150/5345-27 defines two sizes: Size 1 (8 ft long, 18 in throat) and Size 2 (12 ft long, 36 in throat). The AC prints the metric values as 2.5 m and 3.75 m, but the English dimensions govern and 12 ft is 3.66 m. Only Size 2 meets the ICAO recommended minimum. The assembly has to turn freely and keep its shape, because a stiff swivel, a bent ring or a torn cone gives a false wind reading. An aerodrome must have at least one wind direction indicator. Annex 14 requires it to be sited where it is visible from aircraft in flight or on the movement area and clear of air disturbance from nearby objects, and recommends lighting at least one where the aerodrome is used at night, either inside the cone or from floodlights above it, but the mechanical assembly is the same.
Frequently Asked Questions
Q1What is a wind cone assembly?
The whole mechanical windsock: a mast, a swivel, a yoke, a frame ring and a fabric cone. Together they let the cone turn into the wind and fill, so it points downwind and shows the wind direction and a general idea of its strength. Lighting is added to the assembly for night use but is not part of it.
Q2What does each part do?
The mast lifts the cone into clear air. The swivel lets it turn through 360 degrees. The yoke carries the frame ring from the swivel. The ring holds the large end of the cone open. The fabric catches the wind, and the open small end lets the air out, which keeps the cone pointing downwind.
Q3How big should the cone be and what colours should it be?
ICAO Annex 14 recommends a truncated fabric cone at least 3.6 m long and at least 0.9 m across at the large end, in colours that can be seen from 300 m above. A single colour, preferably white or orange, is used where practicable. Where two colours are needed they are preferably orange and white, red and white or black and white, in five alternate bands with the first and last the darker. Follow the aerodrome authority and the manufacturer for the size and colours at a given site.
Q4Why must the swivel turn freely?
A stiff or seized swivel makes the cone lag behind the wind or hang in the wrong direction, which gives the pilot a false reading. Dirt, corrosion, worn bearings and ice are the usual causes. Service the swivel as the manufacturer instructs.
Q5What should be checked on a wind cone assembly?
That the swivel turns freely with no rough spots; that the frame ring is round and firmly fixed to the yoke; that the fabric is clean, not torn, frayed or faded, and the bands are clear; that the stitching and fixings are sound; and that the mast, hinge and fastenings are secure and free of corrosion. Use safe access or the tilting gear, and isolate any lighting supply before working on the assembly.
Q6Where is the wind cone placed, and does it have to be lit?
An aerodrome must have at least one wind direction indicator. ICAO Annex 14 requires it to be sited so it is visible from aircraft in flight or on the movement area, and free from the air disturbance of nearby objects. The location of at least one indicator should be marked by a circular band 15 m across and 1.2 m wide, centred on the support and preferably white. At an aerodrome used at night, at least one indicator should be lit. Confirm the site arrangement with the aerodrome authority.
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