<<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>>
         <<  Lancair Builders' Mail List  >>
         <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>>

Time to add more fuel to the connector fire.  I spent some years working on MIL-SPEC electronics packages in land-sea-air applications.  There you learn that solder has NO fatigue resistance (none, nada, zero, zip) and is thus totally unacceptable to carry loads of any type, particularly in a flexing or vibration environment.  On printed circuit boards there are standards for how large a component can be and how long its leads can be before the component must be supported.  Fatigue failures on solder joints in printed circuit boards were so common years ago in the days of larger components that conformal coatings were used to seal and reinforce components to minimize transfer of mechanical loads to the solder.

Brent is right: every connector is a failure waiting to happen.  Minimize or eliminate connectors wherever possible.  However, any unsupported solder joint that can flex or is subjected to vibration is a failure guaranteed to happen.  Soldering of connectors is  notapproved for aircraft.  Good crimps provide the mechanical integrity required.  These can then be soldered to provide some additional electrical pathway and to seal the copper against possible future corrosion.  But if you solder, remember that the joint should have lots of shrink tubing go help carry the loads and reduce flexing, and the wire must be strapped down well on either side to prevent any motion. I also agree that Fast-on connectors do not belong in a high vibration environment forward of the firewall although they are widely used in automotive engine applications (which vibrate much less than aircraft).  However, their long term reliability (assuming you use top quality, dimpled units) has been excellent in marine, truck, and automotive applications, frequently better than ring terminations that are subject to screws coming loose over time.  They maintain a high local spring pressure, lock in place well (if you get the good ones), and are used by the millions in places that are quite hostile.  Good quality, sensible application, good crimping, and use of shrink tubing as strain relief are more important to reliability.

At the end of the day I believe that Fast-ons are just fine in the right location (clean, low vibration environments aft of the firewall, to be doubly safe).  Your reliability will depend much more on your workmanship, crimps, application of shrink tubing, strapping of cable bundles, and good practice than on whether you use Fast-on or ring connectors (assuming you use all your components appropriately).

Fred Moreno

LML homepage:   http://www.olsusa.com/Users/Mkaye/maillist.html