Flight Testing Auto towing with the Antares 23

Auto towing is a much desired option for pilots of Antares 18T and Antares 23T, as it allows for even more independence for these aircraft with home towing. The first extensive test launches in autotow with the Antares 18T have shown that this type of launch can be a useful addition to winch launching or aerotow.
Now we have continued the testing of the autotow in Reinsdorf near Berlin with an Antares 23.
The aim was to investigate whether also the Antares 23 can reach altitudes from which it can continue to fly independently, even with full water ballast. After all, the 23 weighs almost a ton with full tanks.
The data obtained during testing will also be used to verify our mathematical models of aerotow launching for large flight masses. Since the maximum flight mass is identical for the Antares 23T and Antares 23E, it was possible to use an Antares 23E that was just available for testing.
Unlike the flight test with the Antares 18T, the engine remained in the fuselage during the test of the 23. This was because, for certification, the aircraft had to be flown up to the maximum permitted speed for winch launch - which meant well beyond the operating range of the engine.
It became apparent that greater disengagement altitudes were achieved with increasing towing speed. During the first flights with a takeoff mass of 642 kg (1415 lb), i.e. without water ballast, and with flaps set to +1, an altitude of around 280 m (920 ft) was achieved at 140 to 150 km/h (76 to -81 kts) towing speed. At 160 to 165 km/h (86 to 89 kts) it was even 300 meters (984 ft) and that with a headwind of 20 to 30 km/h (11 to 13 kts) coming from the side at about 30 degrees.
The towing vehicle used for the test flights on the good two kilometer long grass field (we did not use the full length of about 2,800m / 9200 ft) was a 258 hp BMW 530d Touring with all-wheel drive. The dyneema rope used had a length of 370 meters (1214 ft).
Flights with full water ballast - the Antares 23E then weighs 901 kilograms (1986 lb) - resulted in significantly lower release heights. Takeoffs with a towing speed of about 140 km/h (76 kts) ended at an altitude of 200 meters (656 ft) , tows with 145 to 155 km/h (78 to 84 kts) at about 250 meters (820 ft). This meager altitude yield speaks rather against the car tow launch with the Antares 23 with water ballast.
Control inputs during the towing procedure was similar to that in the winch launch and brought no surprises. The control forces to be applied were low. No large deflections were required to keep the wings horizontal from the start of the roll. Also, during climb, with slightly tail-heavy trim, there was no particular need to push down.
With the flights, we found: The Antares 23E takes off at 70 to 80 km/h (38 to 43 kts). Further, the speed increases when a clear climb attitude is assumed. In this phase it is important that the tow vehicle continues to accelerate above 90 km/h (49 kts), otherwise the pilot must be careful not to adopt too large a climb angle, as with winch launch. The launch becomes safe and effective at airspeeds of 120 km/h (65 kts) and above. The car must accelerate to around 110 km/h (68 mph) for this. If there is a headwind, a lower speed is of course sufficient. For the tests, the Tost coupling was used again, which can be mounted on trailer couplings without any effort.
Now the certification of the Antares for the launch mode car towing is pending. In order to be able to use it within EASA jurisdiction, pilots need the aerotow license entry and airfields have to include the aerotow launch mode in their permit.