"Tow rings", "connecting rings", etc. are the hardware components that connect the [[Aerotow Rope]] or winch cable, to the glider (and towplane) at the [[Release Mechanisms]]. Two types of rings are commonly used: Schweizer and Tost. ## Schweizer Rings Schweizer rings must be used on aircraft with a [[Release Mechanisms#Schweizer Release Mechanism]] installed. A Schweizer ring is a single 2.25 inch outer diameter steel ring, with a 0.25 inch cross-section diameter (thickness). ![[GFH Schweizer release mechanism.png]] ![[schweizer tow ring.jpg]] ![[Schweizer tow ring and hook.png]] Tost release mechanisms feature a ring cage, that prevents Schweizer rings from being used. ## Tost Rings Tost rings must be used on aircraft with a [[Release Mechanisms#Tost Release Mechanism]] installed. A set of Tost rings consist of two interlocked rings: the smaller circular ring fits through the ring cage in the Tost release mechanism, the larger oblong ring is attached to the tow rope or winch cable. ![[TOST rings and release mechanism.png]] ![[LN 65091 excerpt.png]] \[from *LN 65091*] ![[TOST connecting rings (catalog).png]] Tost rings can be **mistakenly** attached to a Schweizer release mechanism, with a high risk of the rings becoming stuck and causing a [[Towhook Release Failure]]. ## References - FAA, *Glider Flying Handbook* - Wings & Wheels *Tow Ring Schweizer* [Tow Ring Schweizer](https://wingsandwheels.com/tow-ring-schweizer.html) - K&L Soaring, LLC *SAILPLANE FLIGHT MANUAL (SFM) for THE SGS 2-33, 2-33A and 2-33B SAILPLANE* (2022) - TOST, *Product Catalog* (2022) - Aeronautical Standard LN 65091 (2005) ### by Kevin Sakson