Aerotow ropes: short or long, breakable or unbreakable?

On Thursday, November 14, 2013 11:36:01 AM UTC-6, son_of_flubber wrote:

That the probability of a PTT is currently high enough to justify the risk of PTT simulation is part of my motivation. Can the probability of a PTT be lowered to the point that the risk of PTT simulation is no longer justified? How far can better rope material choice and better (practical) inspection go towards eliminating the possibility of PTT?

In over 2500 hours of glider flying, and maybe 700 towing, I've never had a rope break.

As a tow pilot, I inspect the rope at the start of the day, and when there is a break in the action (as part of laying out the rope behind the towplane to get it out of the way).

I've had two (2) PTTs in that time - neither caused by a rope breaking. One was an incorrectly hooked up Schweizer to hook (muddy) that gave me a PTT at about 200' in a loaded 2-32 (quick 180 and rolled back to the doofus who had hooked me up and made him do it again, correctly) and once when the tow pilot ran out of gas and released his end without telling me (but the funny thing was that it happened at exactly 3000' agl and I released at the same time - we never did find that rope!).

And all this at glider fields all over the US.

So I really think our procedures are pretty sound. Can ropes break? Of course. So can tow releases, weak links, etc...

As far as PTT training being dangerous - you can tow with a steel cable and still get a PTT. So yes, it is very important. And really, it's not a Chuck Yeager bit of airmanship, after all...spinning off a PTT is remarkably bad flying - and probably the sign of someone who was scared of stalls or steep banks at low altitude and didn't really know how to fly to the limits of his glider. You want to worry about something, worry about the currency and proficiency of your fellow glider pilots!

Kirk
66

Tow ropes do break, but in my experience it’s pretty rare. I’ve been soaring for only 8 years, primarily off of grass fields, and out of about 20,000 tows that have occurred during that time at the two sites I’ve flown from, I know of only 6 rope breaks. Four of those breaks occurred above 2,000 feet AGL, during slack line removal practice. One break occurred above 1,000 feet AGL, when a glider got high and upset the tow plane. One break occurred at about 10 feet AGL, when the tow rope came apart in its middle via unraveling.

The first four breaks don’t really bother me at all. The fifth break bothered a whole bunch of us, but not from a tow rope standpoint! The sixth break was initially disturbing, but we quickly discovered that a poorly manufactured batch of rope had been imported into the country (the substandard nature of the rope was pretty obvious simply by running the line through your hand).

Most of our tow rope wear occurs where the line is wrapped twice through the round part of the Tost ring. Pilots and line men see this area “growing hair” at the inspection done just before hook-up, and a worn tow rope gets rejected quickly. Our line men use a short stick with a metal hook in its end to guide the rope as the tow plane taxis into take off position. The feel of the rope going through this hook is a virtual mini-inspection, and has resulted in our finding knots as well as rope damage caused by trees and rocks.

-John, Q3

On Thursday, November 14, 2013 1:27:22 PM UTC-5, kirk.stant wrote:
after all...spinning off a PTT is remarkably bad flying - and probably the sign of someone who was scared of stalls or steep banks at low altitude and didn't really know how to fly to the limits of his glider.

I agree that it "should not have happened", but the pilot in the front seat had thousands of hours over decades of flying in multiple gliders. He had been a top glider pilot at one time. He put off his retirement from flying for too long.

I'm confident flying after a PTT if there is a place to land, but as Evan notes there are fields where the options after a PTT at 50-300 AGL are limited. I fully subscribe to Evan's emphasis on pre-flight inspections.