On Wednesday, August 8, 2018 at 1:18:26 PM UTC+1, PGS wrote:
On Tuesday, August 7, 2018 at 10:45:24 AM UTC-4, Steve Koerner wrote:
This subject comes up every few years on RAS and that's a very good thing. Long ago there was a death on tow with a heavily watered ship that I'm pretty sure was caused by this.

I have already posted a couple times in the past about my own near death experiences I have had dangling from a slow towplane at a remarkably low stalled tow position while slamming the stick back and forth against the stops in Ventus 1 and in ASW27. When this is happening at a very low altitude (as it was), then releasing is not an option.

Several have pointed up the necessity of communicating with the tow pilot. I think it preferable to communicate in writing. Except at contests, I always make sure that the tow pilot has been handed my written towing instruction when I have water ballast. Here's a link to my little towing instruction sheet: https://goo.gl/PwVu71

Steve, you should not assume the tow planes airspeed indicator is calibrated or accurate. You might consider modifying your note to say "minimum" or "at least" and once safely on tow ask to slow down if need be.

Even if the tug ASI is properly calibrated by ground testing it may not read accurately in flight because of very poor static inputs or the use of cockpit static. As an ex JS1c 21m owner I got into the habit of not only telling tow pilots the speed I wanted (absolute minimum of 70 knots as read by the glider ASI) but also exchanging ASI readings with them on tow. Every Pawnees I was towed by had an ASI that over-read by 5-7 knots compared to my reading. The same was found using other types of glider behind Pawnees. The Eurofox tugs that are getting popular in the UK has similar errors.

I think that this may be a significant safety issue.

Although perhaps not widely used in the US, Chipmunks and Robins seemed to me to have much more accurate ASI systems.