On Monday, June 8, 2020 at 1:27:57 PM UTC-6, Andy Blackburn wrote:

TAS vs IAS does increase at about 2% per 1,000 ft

Although looking at the data of the protocol and the glider specs, it's really closer to 1.4% per 1000 ft. Certainly 2% is easier to use and 1% is too little. The "10Kft, 2% rule" kind of splits the error. V is too high at 10K and too low at 40Kft. I have to say while it's not accurate enough for the table I will make for my glider, it's a good rule of thumb for on-the-fly estimates.