Programming the Futaba 7UGFS

Mike Shellim, c. 1998

The Futaba 7UGFS may not be the latest in radios, but it's still a good set of gear and can even be used on F3F models with crow mixing.

The transmitter has mechanical trims - which I prefer to the new style ones on the 8U - and all the basic glider functions we need to set up an F3F ship.

In the mixer...

First, I'll review the requirements of a typical F3F/F3B model. If we take the Ellipse V or Calypso V as examples, we have

4-servos in the wing operating outboard ailerons, and inboard flaps.
2 servos operating V-tail.

To get all the bits working together we need:

V-tail mixing
Aileron-flap mixing - provides progressive camber change when applying ailerons.
Aileron to rudder mixing (the Calypso requires a small amount of Aileron/rudder coupling!).
Crow brakes - flaps down, ailerons up for landing.
Elevator-flap mixing (snap flap)

The 7UGFS Glider can certainly provide all these functions, so no problem here.

Five flight modes?

The Calypso instructions describe five flight modes: Normal, Launch, Duration, Speed, Distance. However, the 7UGFS can only store three using the default, STAT and SPED programs, so we have to discard two of them. I figured that Distance is reasonably similar to Speed, and Launch is not required from the slope. That left three - Normal, Duration, and Speed.

Configuring flight modes

Flight modes is selected via the three position switch labelled Speed / Normal / Start. Normal is the default mode.

The second and third flight modes are programmed by means of the STAT and SPED programs. Each of these extra flight mode stores the neutral positions of the flap, aileron and elevator servos. You cannot save mixing schemes with each flight mode, only servo offsets.

I won’t go into programming the various mixing programs - it's all in the manual, or get Don Edberg's book (which I haven't seen, but a lot of people swear by it - see below). I'll just to mention one or two tips for programming the 7UGFS for this application.

7UGFS Programming Tips

Order of programming

This rough sequence worked for me when setting up the Calypso.

DIFF - enable aileron servos
FLTR - disable flap knob (see below)
STRM - adjust neutral on each servo
ATV - adjust travel range for each servo
VTAL - configure V Tail
A->F - aileron to flap mixing (see below)
BFLY - configure crow brake
1 -> 4 - aileron to rudder mixing

Setting ATV

There are two techniques for adjusting servo travel. You can either use the ATV function, or you can just leave ATV at the default 100% and adjust the movement via special programs like DIFF and VTAIL. Which method to use? The advantage of setting your ATVs is that you can prevent gross over-travel of the servos which might damage your linkages if you make a mistake. You can still use the special programs for fine tuning.

How to disable the flap knob.

I recommend disabling the flap knob since camber presets can be stored with the flight modes. Disabling the knob also has another great advantage - it establishes a fixed neutral for the flap servos. Here's how to disable the flap knob:

Enable Flap Trim using the FLTR program.
Set the flap trim range to zero

Aileron/flap mixing

Something which is not mentioned in the 7UGFS manual: the Aileron/flap mixing ratio is controlled not only by the A->F program, but also ATV. Here's how it works:

A->F controls the amount of flap movement in both up and down directions.
The relative amount of up/down mixing is governed by the relative amount of up/down ATV for servos 5 and 6.

An example of poor interface design - the user has to edit one parameter (in this case ATV) in order for an unrelated feature (A -> F) to work properly.

In order to get aileron/flap mixing sorted, you'll probably have to configure similar values for up and down ATV for flap. However, you'll then find that if the flap knob is enabled, it would be possible to dial in around 35 degrees of up flap - not good for the linkages and another reason to disable the flap knob altogether!

Crow brake mixing

Crow brake involves the ailerons going up while the flaps go down. In an ideal radio, deploying crow brake would progressively disable aileron-flap mixing, thus preventing possible over-travel of the flap servo. This is not possible on the 7UGFS, so when setting up the flap movement don’t forget to allow for extra movement induced by application of the ailerons.

The BFLY program is used to configure crow.

Summary

The 7UGFS may be the latest set, but it’s still perfectly capable as an F3F/F3B glider guider. The limitation of just three flight modes makes it better suited to F3F and slope flying than F3B, though.

The key to programming it effectively is

Define three flight modes in terms of aileron/flap/elevator neutrals, and configure them via the default, STAT and SPED programs as described above.
Disable the flap knob.

So if you’ve been put off flying a plastic ship for lack of a suitable radio, and don’t want to buy a Multiplex, why not give your old Futaba 7UGFS another look, or perhaps even get hold of a second hand one.

Digging deeper...

Don Edberg has written the standard text on setting up the Super 7. It's well thought of by pilots as it goes into the system in more detail and clarity than the manual.

The book is called "Programming the Futaba Super 7 for Aircraft and Sailplanes". (For more details see the review...)

Happy flying!