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I’ve used a system on my F1A models for a few years with great sucess. Unfortunately the system I use is no longer available.
All RCDT systems are currently configured to be used in conjunction with an electronic timer running at least one servo to control the tail incidence. Currently I know of no ‘stand alone’ system (ie one that doesn’t use an electronic timer) although people have been muttering about making them for some years.
The only systems I know of are by Aberlenc (France), Van Wallene (Netherlands) and Bauer (USA). The latter system requires a version of a timer sold by Roger Morrell; there may be others of course.
How does one of the new “Spread Spectrum” systems as produced by JR Radio fit into the scheme of RCDT? A ittle weighty with battery, Rx and servo, an option for larger planes?
I was thinking along the lines of a radio bypass to an electronic hot wire timer system. Everything operated by the timer unless you press a panic button that causes an immediate rundown to zero.
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Dennis, Yes, spread spectrum radios will work for FF DT. I have implemented working systems using the Spektrum DX7 radio. Yes, the equipment is fairly expensive, but no more so than the dedicated RDT units built by Bauer and others. You do not need an electronic timer on board the airplane to implement RDT. All that’s required is a receiver, battery, and servo. I use the Spektrum AR6100 receiver; weight 3.5 grams. An important feature of this receiver is that it will operate down to 3.5 volts. Therefore, a single cell lipo battery will work. A 60 mah battery weighs about 1.7 grams. The receiver does not draw much current while idle; and it will only need 150 ma or so when the servo is briefly working. You need a servo that works down to 3.7 volts. Most of the small one’s do. Mine is 4.4 grams. The Spektrum system has built-in fail safe. If the radio signal is lost the model will DT. The Spektrum radio will also work in conjunction with an electronic timer. In this case, I have built a small converter board that transforms the receiver’s servo pulses to logic levels which are sent to the etimer. A radio-commanded logic low overides normal timer functions to drive an instant DT. rivers
Rivers, what kind of range are we talking about with these systems? About how much is the cost for the setup you describe?
Derek
Derek, Range is a debatable issue with these sytems. The DX7 can be used with 3 receivers: AR7000, AR6000, and AR6100. The manufacturer calls the AR7000 “full range” and the AR6000/61000 “park flyer”, meaning small models at moderate distances. However, the AR7000 is too big and heavy for FF. Nevertheless, some R/C users have made carefull range measurements for the various receivers using full scale aircraft and GPS, and this is what I’m relying on, although caveat emptor.
AR6100 5,980 ft.
AR7000 14,341 ft
The list price cost of the DX6 and DX7 systems can be found on the Horizon Hobby website. However, the systems come bundled with servos, harnesses, and, in the case of the DX7, an AR7000 receiver. Remember, this receiver is too big for FF. Therefore, it’s best to shop for the components you want on ebay or on the RC Groups For Sale section. This is what I did, and I got the parts I wanted; slightly used, but lower price. riversI’m interested in the comment about using standard RC equipment with failsafes. Doing that requires the transmitter to be on all the time or esle you’ll DT whilst the ‘commercial’ RCDT systems sold in conjunction with electronic timers do not; you switch on the transmitter and hit a button to DT. The ‘commercial’ systems also use a coded pulse rather than a standard DT pulse so that don’t get intereference that could DT you’re model prematurely unless you do something very clever.
In the UK where RC flying is probably at a greater flyer density than say the US, you’d have to follow RC safety guidelines to use standard RC euipment in FF models or esle you might shoot an RC model down (or even another equipped FF model !) with a continuous transmission system. How is the safety issue covered elsewhere ?
CHE, This is a spread spectrum system, not a standard 72 mhz (USA) or 35 mhz (EU) radio. The frequency band used is 2.4 Ghz. There is no possiblity of interference with standard radios. Also, many flyers can be using spread spectrum radios simultaneously without interference with each other. With the Spektrum system each receiver is bound to it’s transmitter with a coded I.D., and there are billions of code possibilities. I can’t conduct a treatise on spread spectrum theory here, but you should know that these sytems are widely used by R/C’s here in the USA with great success. I would never consider using a standard radio for FF DT for the reasons you state.
Yes, failsafe means the radio transmission is continously on. The model will DT if it flys out of radio range or if the radio is turned off. I consider this an advantage. Also, The system I use is multi-channel. For example, in my electric model I can stop the motor on one channel and DT separately on a second channel. The Bauer system and the others cannot do this.
rivers,
Thanks for your explaination. I’m no radio expert but did I read that there are limitations on the number of 2.4 Ghz sets that can transmit symultaniously or do I have that wrong ? For instance, there are 108 competitors at the Odessa World Champs in a few weeks; could they all transmit at the same time ? For these contests, DTing when out of range would, of course, be a positive disadvantage !
Sadly the system I use isn’t available anymore but has a 10 (or maybe 12) digit PIN number so this would never limit the numbers using the system at any time. It can also perform engine stop and DT functions seperately as can the Aberlenc system (and perhaps others) but as you say the Bauer system can’t.
Is your system commercially available ?
gollywock,
Apologies to M&K who’s RCDT is commercially available as well. of course. It has been used in the past in F1C models so its logical to assume that an engine stop and DT is incorporated.
Also many of these systems have an extend DT function which is very useful in cases where you’re approaching a DT time and there are obstacles or you ar etrimming and want to do an extended flight.
A few commercial systems also have RC trimming of, say, the tail incidence via the servo(s) which of course isn’t legal in FAI contests but is for practice.
CHE, I did a little more research and found that Spektrum 2.4 Ghz R/C radios would not be legal in many European countries. Reason: Peak RF output power exceeds legal limits. So, further discussion is probably moot, now that I realize that you are UK based and you are interested in International competition.
Dennis, Yes, spread spectrum radios are okay in the USA. To repeat: I have assembled working systems for FF DT using off the shelf R/C components. There are two configurations: 1. stand-alone and 2. in conjuction with an electronic timer. I don’t have anything to sell. This is for info only. I use RDT mainly for test flying. Also, very useful to save a model if something goes wrong in the early part of any flight. I would not be using it for extended maxes where the flight distance could exceed 1 mile.
2.4Ghz equipment is legal in the UK but maybe at a lower power rating (I read some discussion about the range of US v’s UK sets and there is a difference).
More importantly, as I noted, I believe you can only operate a limited number symultaniously so general use in FAI FF contests for RCDT is unlikely. This is why the commercial sellers are using coded commands on common frequencies.
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