I don't doubt that 10% number for a minute! It certainly squares with what I have seen. Looking at the archived survey data from the Pacific Puddle Jump would gives a number at least that high and likely higher.
When we bought Harmonie she had two autopilots and two drives installed in the usual Amel configuration of a linear drive at the quadrant and a chain drive at the wheel. They were, however, not switchable. One drive was wired to one computer. If there was a failure, you would have to do some rewiring to swap drives from one pilot to the other. It was also possible to inadvertently turn both on, which would lead to same serious problems with the steering gear as the two drives fought each other.
I installed a pair of 4-pole, double throw, Form C, switches. Now with two toggles over the sink I can hot swap either computer to be the active one, and use either drive, with no risk that both can be turned on at the same time. I very much like this arrangement, because the two computers have different strengths, as do the two drives. Being completely separate, systems all parts are duplicated.
It is really helpful to my piece of mind that the entire "spare" autopilot system is installed and exercised on a regular basis. I know it will work when it stops being the "spare" and starts being the only one!
SM #160 Harmonie
Providenciales, Turks and Caicos Islands.
, wrote :
Bill Kinney referred to my mention of "10% of autopilots fail on ocean crossings." Maybe there is some doubt that this number is accurate.
I should have given everyone more information about where this 10% number comes from. The 10% agrees with my experience with other
boats crossing at the same time as we did. Many times while you are circumnavigating, you will cross in the loose company of
others...seasons cause the migration at certain times.
I also asked the founder of the ARC and the ODYSSEY, Jimmy Cornell. In his vast experience, 10% of the boats crossing will have an autopilot failure.
I strongly recommend having a backup for each component of your autopilot system during ocean crossings. Normally this includes:
- Course Computer
- Control head
- Electronic compass
- Rudder reference
- Drive unit
I also recommend a backup GPS and any component such as an antenna.
There is a way to "rent" these backups for very little money. Buy them and sell them after your crossings are complete. I bought ours from Dan Gerhardt mydurango.net>. Dan sells new old stock and refurbished Raymarine components...and will repair anything Raymarine. I believe that a number of Amel owners have used Dan with complete satisfaction.