Autotow Antares 23

At 13:29 14 September 2016, wrote:
Andor, what altitudes were achieved and what was the runway/cable length?
Would it be possible to deploy the (sustainer) engine after the tow and
climb away further?


Hi,
We used a 370 m /1214 ft dyneema rope and 2 km / 1.24 miles of runway.
With no water, we reached some 300 m / 980 ft altitude in a combination of
fast tow (160 kph / 100 mph) and some headwind (20/30 kph / 10-16 kts)
At 902 kg / 1988 lbs, we maxed out at 250 m / 820 ft).
A hard runway would probably improve these values. Friction on grass is one
of the determining factors with regards to runway length vs. altitude.

The idea is to get a safe semi-autonumous launch. The testing with the 18T
idling during tow showed that cutting the engine mid tow still left the
pilot with enough altitude for a shortened circuit and normal landing.

We also view it as important to get the self-sustainer (which is not
certified for launching) above minimum legal altitude from ground, so that
no aviation authority can (rightly) claim that we use a self-sustainer
engine for self launching.

Applying engine power during the tow mainly led to issues with overrunning
the tow rope and similar. It is therefore advisable to have an engine with
throttle control (and a starter motor for safe ground starting).

We are now in the process of getting our home airfield certified for
car-towing, and I believe that being able to flight-test non-self launchers
without getting a tow-plane in will be a nice in-house bonus.

Andor

On a side-note
I think that the idea of "helping" an aero-tow by deploying a conventional
self-sustainer is a bad one. If the engine quits, then the extra drag of
the engine can pull down both sailplane and tow-plane. With a jet, it may
be less critical. However, the jet noise at low altitude may lead to
trouble with otherwise peaceful neighbors.