While I've been told that the HGFA has or will come out with new towing rules, I haven't seen them yet, but will publish them when I do get them. In the meantime let's look at the existing rules in the HGFA towing manual which you can find here.

Section 3.2 of the HGFA towing manual states:

Weak links built into the bridle which trigger the release are not recommended.

The "Moyes" type system - uses a motorcycle type lever fitted to the control frame of a hang glider which operates a remote release via a wire cable. These systems are suitable, though care must be taken to ensure the release is correctly adjusted and maintained.

These are in fact contradictory statements. Let's look first at what they mean (and try to understand them).

The pro tow type barrel release system (see here) has a weaklink connected to one end of the bridle and that weaklink is connected to a loop on the harness near the shoulder. The other end of the bridle is connected to the barrel release. It is also possible to use use two barrel releases, one on each end of the bridle. The weaklink is then connected to one end of the bridle and then to the barrel release. It is also possible to put weaklinks on both ends of the bridle used in a pro tow system.

When and if the weaklink breaks the pilot is released from the tow line if and when the bridle goes through the "snap link," "light weight non locking carabineer," ring, "screw type gate" or whatever is on the end of the aerotow line. The pilot also releases themselves from the tow line in a similar fashion by pulling back on the barrel release allowing the bridle to thread through the "ring type" device at the end of the tow line.

I understand the first line above from the HGFA manual in Section 3.2 to mean that the HGFA wants the weaklink to be between the bridle and the tow line and to not require that the bridle has to take an action (thread through the "ring") before the pilot is released, although I'm not completely sure that that is what they mean. I will ask them and hope to get a better answer.

I understand the reason that the HGFA tow manual includes the first line above is "because these systems have been known to fail due to the release failing to operate." I don't have a record of this being the case, but I ask anyone who have information to support this belief to provide it to me.

The "Moyes" type system has a weaklink (or two) built into the bridle(s). There is a weaklink at the end of the V-bridle that is connected to the spinnaker release that is connected to the keel. If this weaklink breaks the pilot is released when the V-bridle threads through the "ring" at the end of the tow line.

Often a second weaklink is also used on the shoulder to shoulder line (i.e. the pro tow part of the V-bridle) at one end of the bridle. If this weaklink breaks, it threads through the loop at the end of the V-bridle line going to the keel and releases the pilot.

Even through the "Moyes" type system is accepted by the HGFA it appears to contradict its own recommendations in the same section.

The "Moyes" type system is widely used especially for pilots who are less experienced (and just beginners) and not ready to use a pro-tow which can require greater pilot skills to control the hang glider. The "Moyes" type system, and any other systems that tow the glider partly from the keel and partly from the keel, can reduce the bar pressure that the pilot experiences while towing making it safer for less experienced pilots, or safer when towing single surface gliders which have high bar pressures at the speeds required by trikes and Dragonflies.

I look forward to any response from the HGFA or other interested persons. Again, I have a direct personal and minor financial interest in the issues raised by this discussion.