11.9.4.2 Anemometers
At least one fixed anemometer should be installed on all installations and vessels. In addition, a hand held anemometer should be provided to allow the HLO to acquire actual helideck deck wind velocity readings, when required. The instrument should be located at a convenient control point adjacent to the helideck.
Sensor Location
A fixed anemometer should be provided and located in ‘free air’ at a high point on the installation or vessel where it can operate in windflows unaffected by the structure of the facility.
Locating anemometers on DP (Dynamically Positioned) vessels is a particularly important exercise because the outputs are often linked to the DP system.
It is vital to pick sensor locations that ensure an accurate readout of the wind conditions over the vessel but at the same time the sensors do not pick up helicopter ‘downwash’, etc. that may spuriously affect vessel heading control.
Indicator Location
The wind speed indicator should be located at a suitable control point where the HLO and / or Radio Operator can easily obtain readings to transmit to the flight crews (See Sections 11.8.3.1).
(Photograph courtesy of John Burt Associates Limited)
11.9.5 Air Temperature Measuring Equipment
Ambient air temperatures taken at least 10 metres above sea level and the air temperature immediately over the helideck are required by the HLO to pass operational information to flight crews.
The ambient air temperature is required for flight crews to compute aircraft payload, etc. Any significant temperature variation (from ambient) over the helideck (e.g. resulting from exhaust plumes) should be recorded and the information passed to the flight crews by the HLO.
Either digital or analogue readout systems are acceptable. To be effective, the sensors and temperature indicator should provide a rapid response to temperature changes.
11.9.5.1 Sensor Locations
Locations selected for the sensors should take full account of the operating conditions likely to be experienced on the installation or vessel with respect to obtaining accurate and steady readings. In particular the sensor for obtaining ambient air temperature should be sited where it is unaffected by transient operating conditions.
11.9.5.2 Indicator Location
The temperature indicator(s) should be located at a suitable control point where the HLO and / or Radio Operator can easily obtain readings to transmit to the flight crews (See Sections 11.8.3.1).
11.9.6 Barometric Pressure Measuring Equipment
Barometric Pressure is used to provide information to flight crews for them to accurately establish their correct altitude relative to the fixed elevation height of the helideck at the destination installation or vessel. It is imperative that the information (QNH is essential, QFE is optional), when given to the flight crews, is both accurate and current.
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