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Air temperature (ambient air temperature and at the helideck location)
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Barometric pressure (ambient pressure and at the helideck elevation).
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Visibility, and
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Cloud base.
In addition to these basic meteorological parameters flight crews also require accurate measurements of:
Observation and estimation can be used to obtain visibility and cloudbase readings, however the results are often poor. Ideally, specialised equipment should be provided as part of a total aeronautical meteorological measurement, recording and data transmission package.
See also Sections 11.8.3.1 and 11.8.3.2 for information about locating the meteorological equipment and sensors.
11.9.4 Wind Velocity and Direction Measuring Equipment
Obtaining the wind velocity and direction for the general area around the installation or vessel and over the helideck is achieved by installing windsock(s) and anemometer(s).
Essentially, windsock(s) give flight crews an instantaneous visual clue of the immediate wind environment during approach, landing, shut down, start-up and take-off. Anemometers provide an accurate means for the HLO (or Radio Operator) to transmit wind velocity and direction to the flight crews prior to departure and at any stage during the flight.
11.9.4.1 Windsock(s)
At least one, preferably two windsocks should be installed on all installations and vessels.
The windsock(s) should be of suitable size and located in optimum location(s) to ensure they can operate efficiently and do not provide spurious wind speed and direction indications.
Location
One windsock should be located in ‘free air’ at a high point on the installation / vessel where it can operate in windflows unaffected by the structure of the facility and is easily visible to approaching helicopters.
Another windsock should be located in the vicinity of the helideck, without infringing the obstruction free area, to provide an indication of local windflows at the landing site.
(Photograph courtesy of BP plc)
Equipment Specification
Purpose built equipment should be specified that incorporates:
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A folding mast (to assist with maintenance of the swivel assembly, sock and lighting)
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A swivel assembly (designed for long life and low maintenance)
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A windsock (say, 2 metres long x 600mm diameter - coloured international orange)
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A lighting system (to illuminate the sock either internally or externally).
Windsock lighting systems are discussed in more detail in Section 11.3.7. Where integral lighting systems are employed it is imperative that the specification takes into proper account the rating and security of any electrical slip ring arrangements.
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