Not sure what you mean by fails open, I suspect you mean fails "closed". The Fromeco units do not rely on physical contact actuation to supply main PWR, but rather electronic means by transistor/FET. The flag/pin negate main current flow by holding the (electrical) junction open. When the pin is removed, essentially current flows until either the system's (electronic switch in this case) current capabilities are exceeded or the pack/lead material dies.
On some HLG's folks employ miniature speaker phone jacks to make/break contact to supply PWR to the control system. In this example current flow is relatively low, so one can get away with it (most of the time). On larger aircraft, where there is a definite spark as contact is made or broken, carbon build-up (or even material transfer) occurs which makes the area of actual contact a hit-or-miss scenario. A cycle-up on one flight might make adequate contact...while on another it may only supply enough current to move the control surfaces while still on the ground. Once under load, like during launch, the contact area may fail...and down goes your pride and joy. The slider switch normally used by pretty well everyone has a wiping action as contact is made and broken. It is this wiping action that not only ensures adequately cleaned surfaces, but also adequate contact area to flow it's rated current specification. This is precisely why employing rocker switches or phone jacks, with no wiping action, that gets folks into trouble...don't employ them if you value your aircraft!!! There are significant electro-mechanical reasons they are not used. Quoting Rob Davis <[EMAIL PROTECTED]>: > To add to Simon's note. I normally build / buy my batteries with dual leads. > One lead is used to charge and the other plugs into the switch. Charging > through a switch is normally a bad idea. > > I like the idea of a switch that fails open. I've used Fromeco's pin flag > switches on other aircraft and wonder why I've not seen any saiplanes using > them. The switch has a pin that you remove to turn on the aircraft. The pin > (2-3 inches in length) normally has the proverbial "Remove before flight" > streamer attached to the pin requiring a 2-3mm hole in the canopy of fuse to > allow the pin access to the switch. It ought to lead to fewer failures to > turn on the plane prior to launch. But then again a quick control check would > accomplish this task as well. > > Rob > Simon Van Leeuwen PnP Systems - The E-Harness of Choice Radius Systems Cogito Ergo Zoom RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
