Reviewed by R. Silva for F5J Portugal >>> http://sites.google.com/site/f5jportugal/fxj-program-card

In April of 2010 the FAI/CIAM/F5 (Electric Flight) Sub-Committee nominated a Working Group to define a F5J class proposal for thermal duration electric motorgliders. One of the conclusions the WG reached, right or wrongly, was that the height limited “200m” rules were not competitive enough for a FAI formula and similarly to F3J, where a quicker/lower launch possibly gives a longer flight time with greater score to the contestant that takes this riskier option, there should be in F5J a way of rewarding the pilot that launches his motorglider lower (but not quicker as this would mean a “propulsion race”).

The concept the WG proposes is the “Launch Altitude” (incorrectly named as it is not an altitude, as this is relative to the mean sea level, but an height above the launch point), defined as the maximum height reached since the throttle is cut until 10 seconds have passed, these 10 seconds are considered time enough to cancel any advantage of the so called “zooming” tactics (significant climbing after the throttle is cut by trading kinetic energy (speed) for potential energy (height)). To reward the pilot that is able to fly longer, up to the 10 minutes working time, a penalty system is set of minus 0.5 points up to 200m and 3 points above 200m.

Two practical examples:

Pilot A cuts the throttle and his model reaches a “Launch Altitude” of 120m then to his flight time and landing bonus points are deduced 60 points (120 X 0.5).

Pilot B cuts the throttle and his model reaches a “Launch Altitude” of 220m then to his flight time and landing bonus points are deduced 160 points (200 X 0.5 + 20 X 3).

To figure the “Launch Altitude” two different devices are needed, one height logger onboard the model and one electronic “reading” device of the “Launch Altitude” which is connected to the logger after each flight (although it would be possible to read the height versus time graph downloaded to a computer this would be very time consuming).

The object of this review, named “FXJ Programming Card”, is the first such “reading” device commercially available to the Aeromodelling community and it was conceived to work with the RC-Alti #2 logger/height limiter, by far the most popular logger used in “200m” competitions, this enabling the FXJ PC to work both as a “reader” and as a height/time limiter programmer “on the spot”.

The device was kindly sent for review by Ing. Pavol Lishak of RIVA Models, Slovakia, who also provided much needed technical advice.

The first remark is that the FXJ PC is programmed for a slightly different formula from the F5J proposal, defined and trialled in Slovakia in 2010 as the “Red Dot” formula (so named because the start height is marked by a red dot in the height(time) graph); the difference regarding the start height is in the time considered after the motor is switched off, in this case 5 seconds against the 10 seconds proposed by FAI. If F5J as proposed is approved I suppose it will be simply a question of updating firmware and the correct F5J “Launch Altitude” will be read by the FXJ PC.

After downloading and reading the FXJ PC manual from the RC-Electronics’ website it seemed simplicity in itself to use, just plug the FXJ PC to the RC-Altimeter #2 after the end of the flight, press the “Enter” button and read the “StartAlt”. Alas, it showed 0 (zero) meters time and again.

So began a series of e-mails exchanged between me and Mr. Lishak (a.k.a. Palo), he detailed the correct configuration parameters for the RC-Alti #2, another trip to the flying field and again… “0 m”.

In short, for quite a while we didn’t understand what was wrong until Palo asked what personal computer firmware version I was using to program/read the RC-Alti #2 and what was the current .exe file downloaded to RC-Alti #2. I was using respectively files “PC_RC_Altimeter_Logger v1.5.6” and “RC_Altimeter_ v2_11.exe”, the latest files available from the RC-Electronics’ website. These were the problem, Palo sent me the correct files “Logger v1.5.7” and “Altimeter_v003.hex” and finally it worked!

Note that nowhere in the manual there is any reference to the need of updated firmware files and the specific configuration parameters; these are glaring omissions that will lead to much confusion and frustration for the prospective buyers.

These are the RC Alti #2 configuration parameters the user must write and save:

Saving interval: 0.3s (High)
Trigger: ALWAYS ON
FXJ switch enabled: OFF (No cross)
FXJ time enabled: ON (Cross)
FXJ time value: 30s

As the logger starts using available memory as soon as it is powered this means its memory will last nearly 3 hours and this possibly will not be enough for a whole day’s flying. One must connect the FXJ PC after the flight but keeping the RC-Alti #2 powered as otherwise it will reset to a new flight and a 0m “Start Altitude” will be show. Pressing the left (“Enter”) button and the LCD displays “StartAlt x m”; after this readout one must disconnect the power from the RC-Alti #2 for a new flight log. Quite simple.

Another possibility with this device is to program the RC-Alti #2 for variable height and/or time limits, if the option for a motor cut-off time different from 30s seems useless competition wise, the possibility of setting a lower limit than 200m depending on the “pre-launch” lift conditions can be interesting for the devoted competitor as it would automatically insure a smaller “Launch altitude” penalty. This also means that we have several options of setting-up the RC-Alti #2 and the motor ESC (the names were made up by me):

“Manual with timer”: the RC-Alti #2 is connected is series between ESC and receiver, the FXJ switch parameter is off (no automatic cut-off at height x meters), the pilot launches the motorglider and cuts the throttle when he wishes but with a motor runtime limit of 30s. Of course one can climb the model above 200m and this entails a heavy “Launch altitude” penalty according with F5J rules.

“Manual”: the RC-Alti #2 is connected to a free receiver channel and functions simply as a height logger, the throttle channel must be mixed with this free logger channel as this gives the RC-Alti #2 the information about throttle operation for the “Launch Altitude” readout, in this case there is no height or motor runtime limits, it all depends on the pilot.

“Variable Auto Height”: the RC-Alti #2 is connect in series between ESC and receiver, the FXJ switch parameter is off (no automatic cut-off at height x meters) but the pilot programs the RC-Alti #2 with the FXJ PC for an height limit, usually a few meters less than 200m (to avoid the heavier “Launch Altitude” penalty of passing 200m), if lift is looking really good and to ensure a smaller “Launch Altitude” penalty the pilot programs an height limit significantly below 200m, for instance 100m and takes his chances searching for lift during the 30s motor runtime limit, knowing that the motor will be automatically switched-off if the model climbs above 100m.

One of the puzzling rules of the F5J proposal is the single attempt allowed, this is contrary to every motorglider (“200m”, “200W/kg”) or glider (F3J, F3B) formula where the competitor has at least two attempts at the task (the last one being the official), I suppose the problem lies in the necessity of switching the logger off from power between flights for a correct “Launch Altitude” reading, is it difficult to change the software to consider only the last attempt (climb-out) after powering up the logger? This is a software improvement definitively needed.

To conclude this review, I never thought that such a simple device could be so difficult to get to work, fortunately it is only a matter of revising the instructions, making the correct firmware available and after that it’s as simple as it can be.

What is the point of buying the FXJ Programming Card? In my view, individually only if you are a competitor keen on trying (and training for) “Red Dot”, “FXJ” or F5J competitions; naturally if your club wants to organize competitions for such “variable height” formulas then it must have such a device.

Finally, thanks again to Palo Lishak of RIVA Models, who kindly provided us with the FXJ PC for the review and also a big thank you to Palo for all his efforts in the promotion of thermal duration electric motorgliding as a competitive Aeromodelling formula.

FXJ Programming Card specifications:

Size: 58mm x 22mm x 15mm + cable
Weight: 32 grams
Approx. price: €80

Disclaimer – The contents of this review are only the personal opinion of the author, references to commercial products, vendors, services, etc., are only mentioned in an informative basis and are not any kind of endorsement or publicity.