Like many of my threads/posts in this section, readers could easily/readily dismiss the highlighted pieces of equipment as piffling/puny/inconsequential in the overall scheme of things ..... not so ..... take a look at the importance of the siting of anemometers on ships not yet even built.
Head-on-view-of-Type-26-left-and-Type-23-right-showing-positions-of-main-anemometers.jpg
4.Assessment of air flow at anemometer positionsAs well as impacting directly onto the helicopter, the disturbed flow of the ship’s airwake also affects the accuracy of the ship’s anemometers. As shown earlier in Figure 1, the safe operational envelope for the helicopter is defined by the SHOL. The boundaries of the SHOL are determined by at-sea flight trials where test pilots fly repeated deck landings at differentwind angles and wind speeds to find the limiting conditions at which it is safe for a fleet pilottolaunch and recover the helicopter. While the wind speed and direction during the trials are usually measured by dedicated temporary anemometers mounted on tall masts at the bow of the ship, in an attempt to avoid the ship’s airwake, the readingshave to be correlatedwith the ship’s own anemometers, and for every sortie afterwards it will be the ship’s anemometers that measure the wind speed and direction. If the ship’s anemometers are incorrect or unreliable, then the SHOL will not be correctlyspecified in the first instance, and neither will the wind condition be reliably measured for every sortie conducted thereafter.Accurate readings from the ship’s anemometers are therefore essential for a reliable SHOL.The operational parameters for the anemometers are prescribed by Defence Standard 00-133 (2015), extracts from which are shown below.
Anemometers shouldbe:
-positioned in clearair above the edge of the boundary layer created by theship’s superstructure
-located as high aspossible on separate port and starboard yard arms
-in aspace uncluttered by adjacent equipment, facing forwardwith at least 3.0m radius free air space around each anemometer
Accuracy of Indicators should be as follows:
-Wind Speed ± 5% error
-Wind Direction ± 5 degrees error
As was seen earlier in Figure 4, finding a locationon the ship that isoutside of the airwake is difficult, and the trend towards bulky enclosed masts will significantly distort the flow at the traditional anemometer locations on the main mast. Figure 9 showshead-on views of the Type 23 and Type 26 ships, with their anemometer locations identifiedby red squares. The perspective viewsof the two ships are different and in practice the two sets of anemometers are approximately the same height above sea level. The Type 23 anemometerscan be expected to be in less distorted air flow because of the more slender mast and longerforward-facing yardarms on which they are mounted. The larger mast of the Type 26, however, as well as the bigger deck house and the additional equipment ahead of and in the vicinity of the anemometers,can be expected to have a greater influence on the air flow.A more detailed discussion of the aerodynamics of a bulky ship mast has been given by Mateer et al. (2016).
Excerpt copied from page 7 of 11 of the PDF paper titled:-
Superstructure Aerodynamics of the Type 26 Global Combat Ship
RMateer, Dr. SAScott,Prof. IOwen*, Dr.MDWhite
School of Engineering, University of Liverpool, UK
*Corresponding author. Email:
i.owen@liv.ac.uk