Ergonomic divergence

30th Jul 2010


We are still in Townsville sorting out a few issues so this is one for technically minded.

In aviation, the possibility of an autopilot taking uncommanded hold of the aircraft, is a routinely address possibility even though it happens rarely. In fact, it was long ago that the ergonomics ( the human machine interface) of flight deck layout became a hot topic as pressing the wrong button or switch etc at the wrong time, could (and in the old days did) cause a major problem when airborne. Such knowledge is now an integral part of modern aviation but not, it seems, in the yachting world.

While coming into port at Townsville, as we rounding the outer breakwater, we needed to follow a dredged path to the marina entrance. This had a published depth of 1.1m. Pilgrim draws 1.7 but, the 1.1 refers to the depth at the lowest possible tide. As it was we had a tide of 0.8 so do the sums and one concludes that we should have, as a minimum, 0.2 under the keel. Not a lot but enough! None the less as we slowly motored in we watch the sounder closely as did the depth alarm. This I have set to 1.0 m under the keel and at that depth a alarm sounds on both the sounder and the plotter. The reset for the alarm is also on both but the plotter is the easier to use. With the alarm silenced by the reset, and further reduction in depth reactivates this useful but penetrating siren. The routine then is for one of us, me in this case, to sit at the plotter constantly silencing the alarm. Now what button might you imagine, is right beside the ‘silence’ button? Yep, the autohelm engage button!!!

A moment of distraction on my part, almost instantly had Paul yelling that the boat was turning by itself and (naturally) into shallower water! It took me half a heart beat to figure all this and to drop the autohelm but half a heart beat is a long time when things suddenly decide to turn pear shaped. Ergonomics indeed!