## Tow Rope ### Length - For aerotow launches, 200ft is considered normal rope length; this is not prescribed by regulation, but is the de facto standard, and recommended by the 2003 edition of the *Glider Flying Handbook* - For ground launches, the longest practical rope/cable length is desirable, with field length typically being the determining factor ### Strength Requirements - Regulatory requirements in §91.309 - Breaking strength is 80 - 200% of maximum certificated operating weight of the glider - A stronger rope or cable may be used IF: glider uses safety link rated at 80 - 200% AND towplane uses stronger safety link (up to 25% stronger, but still <200% glider MOW) ### Materials Many options exist: Nylon, Dacron, polyethylene, polypropylene, etc ![[GFH rope strengths.png]] ### Condition/Inspection - Ensure that the correct tow rope, appropriate to the glider, is being used - The rope must be free from knots: knots reduce breaking strength by up to 50%, and increase wear as a high spot on the line - The rope must be checked for indications of excessive wear: abrasion, broken strands or fraying, damage from the elements or UV, or unsecured splices ## Safety Links/Weak Links May be configured as a single- or double-insert system, with or without a protective sleeve. The single-insert system uses a weak link with round holes. The double-insert system uses two weak links, one with round holes, and one with oval holes. The weak link with round holes serves as the primary weak link, and the weak link with oval holes serves as the reserve weak link; with repeated use over time, the primary weak link may fail at less than the rated strength, so the reserve weak link will take the load for the remainder of the launch. If a protective sleeve is used, the open slot should face towards the glider. The weak links are numbered and color-coded to indicate the rated breaking strength. ![[TOST weak link examples.jpg]] ![[TOST weak link photo.jpg]] ![[TOST weak link load table.png]] ## Tow Rings Two types of tow rings are used, corresponding to the two types of tow hook mechanisms: Schweizer and Tost ### Schweizer Uses a single 2-inch diameter circular steel ring, compatible with Schweizer tow hooks. The Tost tow hook mechanism features a ring cage that prevents Schweizer tow rings from being used. ![[schweizer tow ring.jpg]] ### Tost Uses two interlocked rings: the smaller circular ring fits through the ring cage in the Tost tow hook mechanism, the larger oblong ring is attached to the tow rope. Tost tow rings can be **mistakenly** attached to a Schweizer tow hook, with high risk of the rings becoming stuck and causing a [[Towhook Release Failure]]. ![[TOST tow rings.png]] ### Condition/Inspection - Tow rings must not have any deep scratches, dents, or deformation - The correct tow ring must be used for the type of tow release mechanism installed on the aircraft ## References - FAA, *Glider Flying Handbook* - FAA, *Practical Test Standards for Glider Category* - 14 CFR Part 91 - TOST, *Product Catalog*