By motorized ultralight
Carried out worldwide for Hang Glider as well as for Ultralight Gliders, by Trikes or 3 axis controlled motorized ultralights. Safety is guaranteed by the use of a 90 to 110kg weak link at the end of the tow rope. So any adverse event that may happen is covered: loss of control by the ultralight glider’s pilot, default of the release system, severe turbulence, etc. The takeoff field must be long enough in order to allow an emergency landing should an incident occur just after take off; this is not a strong constraint as usually after 300m the height is more than 15m. Then a safety altitude, allowing both the glider and the tow aircraft to return to the airfield, is quickly obtained, as the rate of climb with 50 to 65HP is well over 2m/s (climb path more than 10%).
There is no special qualification required for the tow pilot, at least in France: for the insurance, the ultralight glider’s towed pilot is considered as a passenger. The use of a weak link clears the tow pilot from any liability.
Due to the unstable (by design) configuration of the tow line – pilot link, flying a hangglider in aerotow may be tricky. But for 3 axes controlled ultralight gliders there is absolutely no lock out hazard.
If the tow ultralight aircraft is a trike (with a pushing propeller), the tow line must be equipped with a little parachute to prevent it to hit the propeller should an unexpected release or weak link brake occur in an unusual relative position.
3 axis controlled Ultralights approved by ADPUL
Phoenix, here is the evaluation report (in french)
Tétras,here is the tests report
Ikarus C42, also able to aerotow rigid hanggliders
Dragonfly, specially designed for hang gliders aerotowing
Dynamic WT9, too fast, restricted to well trained ultralight glider pilots
A22, weak climbing performance.
Rate of climb of those 3 axis controlled Motorized Ultralights aerotowing Ultralight Gliders is higher than with a normal glider, thus, the cost of aerotowing is weaker.
As there are more and more ultralights of those types available, it will be more and more easy to organize ultralight gliders aerotowing
Video of an ultralight trike aerotowing a Swiftlight
Movie of aN A22 ultralight airplane aerotowing an ultralight glider: