Failsafe: Fact and Fiction
by Tony Holden

     How many of us who own a Pulse Code Modification (PCM) computer radio can honestly say that we have thoroughly read and understood the manual that comes with it? If it was anything like the manual that came with my Futaba 8UAPS it was about as an inviting read as the Greek classics in Latin, and made as about as much sense. I have been told that the JR manual is written better, but in either case help is at hand.
     Harry Higley publishes an excellent book covering the basic set up for both the Futaba 8UA and the JR XP8103 for airplanes. Unfortunately, the book makes little mention of failsafe, and in fact leaves you with the impression that if you do not program this menu then there are no parameters set in this function or that this function is even activated. WRONG!
     A large number of PCM radio owners are under the same impression. After a recent fatal accident in the United Kingdom a survey of the clubs PCM users showed that 80% did not know that they had active failsafe and/or what those parameters were. If you operate in PCM mode you have active failsafe, period!
     If you have not gone in to the program menu and entered your own parameters then your model will default to the factory settings if the signal is lost. Do you know what these are? If you don’t you could be in for a nasty surprise if you ever suffer interference.
     First, understand that failsafe is not going to stop your model from crashing if the signal loss is long enough. What it will do is allow you to program parameters in to the menu that will help keep damage to the rest of the equipment to a minimum, and, from a safety standpoint, stop your model from coming out of the sky at full bore pointing at who knows what.
     Let’s start at the beginning of the menu. I have both the JR347 and Futaba 8UAPS and the menus are set up the same way, just the button(s) you push to enter the information are different.
    First choice is the amount of time delay from the loss of signal to entering the failsafe mode. The choices are in fractions of a second, and I don’t really think it makes a big difference which one you use. I personally use the longest one.
     Next is the choice of the position of the servos should the model go into failsafe. The factory setting is normally hold last known position, not good if you happened to be in the middle of a snap roll at the time! In the case of Futaba the throttle will go to 50%, still a hard way to hit the ground! To enter your own settings in most cases just hold the control surface where you want it to go and press the data enter button(s). To check the function and to see if the inputs you programmed are correct just turn on the transmitter and receiver, wait one minute, turn the transmitter off and see what happens.
     Why wait one minute? The transmitter sends the failsafe information you programmed to the receiver automatically once every minute, try this before then and you get the factory setting. 
     One of the last functions that falls under this section is battery failsafe. There is nothing to program here, just be aware of it and how it operates. When the airborne battery (in the case of Futaba) drops below a preset voltage the failsafe function moves the throttle to a predetermined position or to the position you programmed in the failsafe menu. In the case of Futaba you may temporarily reset the function by moving the throttle stick back to idle which will give you about 30 seconds of control before the battery function reactivates.
     It is as simple as that, so are most of the other functions once you have been through the menus a few times. Play with your setup at home on the bench. If you really mess things up there is always the Data Reset function, which will put everything back to the original factory settings. Try to learn as much as you can about your own radio. I am always happy to give advice or lend a helping hand to programming the Futaba 8UA, but don’t just hand the radio to someone and expect them to program the whole thing for you. You may not have to build or cover your own models in this hobby anymore, but knowing how to set up your computer radio properly can make all the difference in the world as to how your aircraft will fly and handle in the air.

from The Slow Roll
Sun Valley Flyers
Bob Purdy, editor
Phoenix, AZ

     Until next month, please fly safe!
Bill

     The next meeting of the MMRCC is scheduled for October 6, 2005 at 7:00 P.M. The meeting will be held at the Northrop Grumman facility. Personnel are required to sign-in and sign out for security purposes.

See you at the meeting............Will