"Blue Fox wave off and keep out twenty miles, We have a blue screen error and aren't sure we turned off the Phalanx. You'll have to wait till we reboot the servers and stations here, should be about 50 minutes. Conserve your fuel because we can't get a gas bird off the deck either. Communications out while we reboot."
But as I picked up the Aug/Sep issue of Professional Mariner( which I just noticed has a website. I can't check it out just now as I am on the palm) to check out the Maritime casualties column, I became concerned about fly by wire in general. For those of you (probably most) who don't know already, The maritime casualties column is a place where they detail as much of every commercial marine accident they can with causes and conditions. The intent is to provide a sort of "forewarned is forearmed" prophylactic effect and prevent repeat accidents. This time around I noticed two accidents DIRECTLY caused by fly-by-wire failures.
The worst one had one of the sleazy/slick casino gambling boats in Miami. They rammed a ro/ro( rollon-rolloff, they sacrifice capacity and stability for WAY convenient loading). They lost their engine AND steering controlls upon leaving the dock and the Princesa kept right on steaming in the direction and throttle position she last had. Right in to the ro/ro Seaboard Venture which was moored the the Dodge Island terminal. Both vessels were damaged, no fuel leaked and no injuries reported.
Now here's the deal:
The controls (Kobelt, who unfortunately had the quarter page ad only a few pages away) run on a 24 volt DC system, pretty much standard stuff. They will operate normally with voltages as low as 16 volts but when the voltage drops below that the units default to what ever rudder and throttle position they last recieved. In Kobelt's defense the units can be manually overridden in in the engine room by the engineer who can recieve voice communication from the skipper (pretty much the way ships have been doing it since we first put engines in them(or for that matter even before that, the work was done in the rigging instead of the engine room)). Princesa's skipper just didn't happen to do that( I suspect that he had no one in the engine room). On Princesa the switch controlling the battery charger for that particular bank was in a broom closet. Yup, a broom closet. Have any of you out there every carelessly chucked a broom into a closet and not payed attention to any switches it may have flipped. I know I have. Pretty stupid design. Somewhere there is a Naval Achitect whose feelings are hurt by that statement. Tough. Any way the controls happened to have just enough voltage left to get away from the dock and get her pointed at Seaboard Venture. The investigating Coast Guard officer reported that this was the company's ninth incident in 18 months.
The other incident was a board a twin Z-drive Tug in Anchorage. Z-drives are an Incredibly cool innovation in the towboat industry. They provide a prop with however many thousands of horsepower behind it with the ability to swivel a full 360 degrees. You can put the power in what ever direction it is most needed( incidentally this issue also has a lenghty and informative article on deciding just that). The cold hard fact of Z-drives is that they have to be fly-by-wire. There really isn't any other way to do it. In this particular incident two wires came loose and the Stellar Wind backed into and destroyed an unoccupied catwalk in the harbor. No apparent harm done the vessel in fact the picture shows the wheelhouse virtually unscratched. The wires were terminated on the block with spade-type terminals. Very convenient terminals in that they can be slid in to place easily. However the reason that they are specifically Forbidden by the ABYC is that they can slip out almost as easily. They have since switched all of the terminals to much more sensible ring terminals. Had Stellar Wind not been designed to hit things hard and repeatedly there would have been much worse trouble from two little wires.
