Glider tow

[EFCY]

Does anyone of you know whether there is a weight limitation for glider tow with the PA 18-150?
There is a pretty heavy glider my flying-club would like to get into the air with our Super Cub, runway length and climb rate should do...but the aircraft manual just doesn´t want to tell me if there is a (legal) maximum weight for the glider I´m towing.
Should anyone of you know, I´d be glad to hear from you...also if someone has had experiences with such tows.
Best regards
Matthias

P.S.: For those who have some knowledge of gliders: its an ASH 25!

 

[sekps]

An ASH-25 shouldn't be a problem. It's a bit heavier than a "normal" two-seater like a Twin-Astir, DG-500 or an ASK-21 so you have to accept slower acceleration. But once airborne the ASH-25 sure got wings to compensate for the higher weight! With an L/D of 57 and max gross weight 750 kg you only need a 13 kg pull in the tow rope to keep it flying...

How long is the runway? Surface?

I have no personal experience from the ASH-25 but I was once towed in an LS-4 behind an 65 hp Cub. That was quite an experience...

/Mattias
(without an "h"..)

 

[cubscout]

Regulations may be different in your country, but in the USA, the only LEGAL restriction is on weak link strength: In the US, 80% to 200% of the gross weight of the Glider, at the Glider end, and a stronger link at the Towplane end, but no more than 25% stronger (FAR 91.309).

That said, the commonly used PA-18 Schweizer tow release mechanism is limited to 1200 pounds at the TOWPLANE end, and the above rope/weaklink strength still applies. The commonly used Tost tow release mechanism is limited to 750 kg/1650 pounds at the towplane end. Appropriate weak link selection can be interesting with the Schweizer release.

In most European countries, this may be different, with a colour-coded glider weak link strength specified by the glider manufacturer, but the towplane release manufacturer's specifications should still be met.

That's just background to your actual question. As a practical matter, the climb performance will be the same as if the operating gross weight of the glider were added to the operating gross weight of the towplane, it's just that the weight is not added to the structural load.
And yes, I've towed ASW-25's at high density altitudes, and they were what we call a "lead sled", but given adequate runway length, and patience for reduced climb rate, very workable. Runway length is really the controlling variable for most operations.

Heck, I've towed some really heavy stuff with a light 105 Supercub, even some double-tows, with OK results.

Just pay close attention to Cylinder head and oil temperatures, and tow at appropriate speeds for each glider, probably 75+mph/65+knots for the heavier ships, maybe even 80mph/70knots, but you lose some climb efficiency if too fast.

Hope this helps in your situation, and let us know how things work out.

Thanks. Cubscout

 

[EFCY]

Thanks for your quick replies!!
Sounds all quite good what you are telling me. Runway is 700m/2300ft long and both paved and grass are available, elevation is just a few hundred feet above MSL, so that shouldn´t be the problem really.
The towing hook we are using - this is the most common one across Europe I guess - is from TOST.
Now, all we got to do is wait for the winter to finally end back here in Germany
I´ll tell you about the results as soon as we have come to do the first tows with the ASH.
Greetings
Matthias

 

[sekps]

For us Europeans this thread gives some information on the Schweizer tow hook (and some more interesting stuff to read):
http://www.supercub.org/phpBB2/viewtopic.php?t=7122

/Mattias