Windsock Compliance Requirements
In the UK, the requirement to have a windsock, and the specification it must meet, depends on the type of site you operate. There is no single universal windsock law. Instead, the obligation arises from a combination of aviation licensing requirements, industrial safety regulations and environmental permitting conditions.
This page explains which framework applies to your site and what it requires.
Licensed aerodromes: CAA CAP 168
CAA CAP 168 Licensing of Aerodromes is the UK Civil Aviation Authority’s standard for licensed aerodromes. Chapter 7 covers visual aids including wind direction indicators, referencing ICAO Annex 14 for the physical specification.
CAP 168 requires a wind direction indicator to be installed, sited correctly, maintained to a serviceable standard, and illuminated where the aerodrome operates at night. For the physical specification, ICAO Annex 14 sets a minimum sock length of 3.6 metres (12ft) with a mouth diameter of at least 0.9 metres (36 inches), in international orange.
CAP 168 applies to all civil licensed aerodromes in the UK. Non-compliance is a finding at aerodrome licensing inspection and can affect the licence itself.
Offshore helidecks: CAA CAP 437
CAA CAP 437 Standards for Offshore Helicopter Landing Areas covers offshore helidecks on the UK continental shelf. It requires an internally illuminated windsock on any helideck used for night operations, with all electrical components ATEX/IECEx certified to the zone classification of the platform.
CAP 437 is enforced through the helicopter operator’s own safety management system and through CAA oversight of offshore helicopter operations. It is internationally recognised as best practice beyond UK waters.
COMAH regulated sites: HSE and environmental agencies
The Control of Major Accident Hazards (COMAH) Regulations 2015 apply to UK sites storing or processing hazardous substances above threshold quantities. Most oil and gas facilities, chemical plants, EfW sites, large water treatment works and some waste facilities are COMAH-regulated.
The Health and Safety Executive and the relevant environmental agency enforce COMAH jointly. Wind direction indicators are embedded in COMAH compliance through two routes: the safety report (which must document meteorological monitoring for hazard dispersion scenarios) and the emergency response plan (which must address evacuation routing, which depends on knowing which way the wind is blowing).
COMAH does not specify a windsock standard in the way aviation regulations do. The requirement emerges from the obligation to have appropriate wind direction monitoring in place, which in practice means a permanently installed, continuously visible windsock maintained to a reliable standard.
Environment Agency permit conditions
Many waste, chemical storage, water treatment and industrial sites operate under Environmental Permitting (England and Wales) Regulations permits. These permits have historically included a standard condition requiring a wind direction indicator to be permanently displayed on site. This obligation exists independently of COMAH tier status and applies to a wide range of permitted facilities.
Check your specific permit conditions as the first reference point. Non-compliance with a permit condition is an enforcement matter.
ICAO Annex 14: the international baseline
ICAO Annex 14 is the international standard for aerodrome design published by the International Civil Aviation Organisation. It underpins CAP 168 and is the recognised best-practice benchmark for unlicensed aviation sites worldwide. Its physical specification for windsocks, minimum 3.6m length, 0.9m mouth, international orange, extending at 3 knots and fully extended at 15 knots, is the reference against which compliant windsocks are designed.
ATEX and DSEAR: classified electrical zones
Where a windsock installation includes electrical components (illumination) and is sited in an ATEX-classified electrical zone, the ATEX Directive 2014/34/EU and DSEAR Regulations 2002 apply. All electrical components must be certified to the appropriate zone classification. This applies to offshore helidecks and to onshore oil, gas, chemical and other sites with classified zones.
Which standard applies to your site?
UK licensed aerodrome: CAA CAP 168 + ICAO Annex 14
UK military aerodrome: MAA regulations + ICAO Annex 14
Unlicensed airstrip or gliding site: ICAO Annex 14 (best practice)
Onshore licensed heliport: CAA CAP 168 + ICAO Annex 14 Vol II
Offshore helideck: CAA CAP 437
Upper-tier COMAH site: COMAH 2015 / HSE guidance
Lower-tier COMAH site: COMAH 2015 / HSE guidance
EA permit regulated site: Environment Agency permit conditions
ATEX classified zone: DSEAR / ATEX Directive 2014/34/EU
For more detail on specific industries see our aviation, heliports, oil and gas and chemical processing pages.
Piggotts can supply product specification sheets and certificates of conformity at the point of ordering. Contact our team to discuss documentation requirements for your compliance file.
FAQ's
Is there a legal requirement to have a windsock?
It depends on your site type. Licensed aerodromes must comply with CAA CAP 168. Offshore helidecks must comply with CAP 437. COMAH-regulated industrial sites must address wind direction monitoring in their safety reports and emergency plans. EA-permitted sites may have an explicit permit condition. In practice, most regulated sites in the UK are required to have one.
What specification does a compliant windsock need to meet?
For aviation sites the specification follows ICAO Annex 14: minimum 3.6m (12ft) length, 0.9m (36 inch) mouth, international orange, extending at 3 knots and fully extended at 15 knots. For industrial sites the specification is less prescriptive but the sock must be permanently installed, clearly visible and maintained reliably.
Can Piggotts provide compliance documentation with orders?
Yes. We can provide material specifications, certificates of conformity and product data sheets at the point of ordering. Contact our team with your specific documentation requirements.
What happens if our windsock fails a CAP 168 inspection?
A non-compliant or degraded wind direction indicator is a finding at aerodrome licensing inspection. Depending on severity, this can require immediate remediation and may affect the aerodrome’s licence until the finding is closed. Keeping a spare sock on site and maintaining a documented inspection regime is the practical way to prevent this.