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TOST Weak Link
TOST Weak Link TOST Weak Link TOST Weak Link TOST Weak Link

TOST Weak Link

Sale Price: $7.00

SKU: 4989 - 5052

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Detailed Description

TOST Weak Links

TOST Weak Link

General Description

TOST weak links are required to protect the sailplane against overloading during launch operations. The strength of the spar of an aircraft is calculated on the basis of a given maximum load. The type and rating of the weak link used during the launch must meet the requirements of the sailplane as described in the Type Certificate Data Sheet (TCDS).

Weak links are fitted to aerotow ropes for the protection of both the sailplane and the tug. Apart from the Piper Pawnee 235 (which has a maximum weak link strength of 750kgs), the maximum weak link strength for other tow planes is limited to 450gs. Weak link requirement will be found in the Aircraft Flight Manual (AFM) towing supplement. For sailplanes, this information is found in the TCDS, the sailplane AFM, and the sailplane placards in the cockpit.

If the specified weak link strength for a heavy glider is greater than the specified strength for the tug, the operator is stuck with the weaker of the two values. Remember, sailplane weak link strengths are the maximum allowable to prevent structural overload of the sailplane; a lower strength weak link strength merely provides a higher safety margin. If the specified strength for a light glider is less than that specified for the tug, a separate weak link of the correct glider strength must be inserted at the glider end in addition to the one already in place at the tug end.

If only one weak link is fitted to an aerotow rope, it must be fitted at the tug end. This retains the protection in the event of the tug inadvertently snagging the rope on an obstacle on the final approach. Exception: a tug fitted with a TOST tow rope retraction system will have the weak link fitted at the sailplane end.

It is essential the tow pilot inspects the weak link and tow rope for serviceability before the day’s operation and also after being subjected to a high jolt or load. It is also required that when that weak link fails, the reserve link must also be replaced.

The TOST weak link system is an engineered and approved design which prevents aircraft overloading during winch, autotow and aerotow launching. By using this system, the operator is assured of maintaining the manufacturer’s airworthiness requirements assuring protection to both tow plane and sailplane.

TOST weak links are color coded and are available for loads from 80 to 1000daN with a tolerance of 10%. For conversion purposes, one decanewton is the equivalent of 1 kilogram force.

The GFA recommends clubs and operators use the TOST reserve insert and sleeved weak link system. This uses two weak links in parallel protected by a steel sleeve. Both weak links have attachment holes at each end and are 8 mm in length. The reserve has oval attachment holes and carries no load in normal operations. If the load exceeds the rating, the weak link will fail and the reserve link will take up the load. If the load is more than a momentary jolt both weak links will fail. Source: The Gliding Federation of Australia Inc.

TOST weak links in optimized format combine the following improvements:

• Longer service life.
• Correct marking with load group and manufacturer’s name.
• Made of high-quality certified aircraft steel.
• Clear differentiation from inferior copies.
• Manufacturing tolerance 5% Like our type-approved equipment, also our weak links are manufactured according to the EASA-approved production methods. Each batch is tested on computerized test equipment and the results are documented. This guarantees consistent high quality and traceability.


• Weak links protect your aircraft against overloading.
• Use only the weak links stipulated in your aircraft TCDS or aircraft manual.
• Checking the cable preamble is mandatory according to SBO (German Gliding Operation Regulations); this includes the inspection of weak links.
• Replace the weak link immediately in the case of visible damage.
• We recommend that the weak link insert are replaced after 200 starts: an insert exchanged in time is always safer and cheaper than an aborted launch.
• Always use the protective steel sleeve.
• Use only the correct shackles: they prevent the weak link and the steel sleeve from twisting, leading to an increase of the breaking load.
• Never use two equal inserts, eg, both with round holes, in a reserve system weak link, since this would double the breaking load.

Custom Weak Link

Using combinations of weak link inserts from different manufacturers can double the breaking load because of the elongation of inferior inserts. Refer to our Weak Link Application List for choosing the right weak link.

We manufacture to your requirements custom made weak links with defined breaking load in the load range of 10 daN to 50 kN. Testing on computerized test equipment. Material: plastic, stainless steel, steel. Application examples: bracing of antennas, retaining of flagpoles, Off-Shore-operation, testing of parachutes, test racks, food industry.

TOST Weak Link price varies depending on selection.
Use dropdown box above for selection and final price.


• BGA Approved Winch Launch Weak Link Strengths STX 165 User Manual

Weak Link Load Table for Winch Launch or Aero Tow

Insert No. Color Breaking Load daN
1 Black 1000±100
2 Brown 850±85
3 Red 750±75
4 Blue 600±60
5 White 500±50
6 Yellow 400±40
7 Green 300±30

Load Table for Kites, Hang Gliders or Ultralights

Insert No. Color Breaking Load daN
8 Mauve 200±20
9 Grey 150±15
14 Turquoise 120±10
11 Orange 80±10

Tost Weak Link Examples

Tow Cable and Fan Assembly


Using combinations of weak link inserts from different manufacturers can double the breaking load because of the elongation of inferior inserts. Refer to our Weak Link Application List for choosing the right weak link.

FAR Rules on Glider Towing

FAR 91.309 Towing: Gliders: (3) The towline used has breaking strength not less than 80 percent of the maximum certificated operating weight of the glider and not more than twice this operating weight. However, the towline used may have a breaking strength more than twice the maximum certificated operating weight of the glider if-

(i) A safety link is installed at the point of attachment oh the towline to the glider or unpowered ultralight vehicle with a breaking strength not less than 80 percent of the maximum certificated operating weight of the glider and not greater than twice this operating weight;

(ii) A safety link is installed at the point of attachment of the towline to the towing aircraft with a breaking strength greater, but not more than 25 percent greater than that of the safety link at the towed glider end of the towline, and not greater than twice the maximum certificated operating weight of the glider.


Why Buy From Us?

Wings & Wheels has been serving the sport aviation and soaring community for more than 20 years.  We have the largest and most comprehensive inventory of sailplane and soaring supplies.  Nearly everything you find here is in stock and can ship the same day.  We are here for aviators, businesses, mechanics and government.  Our goal is to fulfill your order promptly and as conveniently as our resources allow.

Wings & Wheels is proud to be the American representative for HpH Ltd, producer of the finest quality 304 sailplanes.

Our staff has over 8,000 hours of flying experience in gliders and airplanes. Wings & Wheels is staffed by Sean, Garret, Miki, Matt and Linda. You will have a friendly voice pick up when you call. Our staff is trained to promptly take your orders and ship your products.

Shipping Information

Same Day Shipping

Orders placed by 3:00 pm PST Monday-Friday for “off-the-shelf“, in-stock items are normally shipped same day by UPS.  Although we stock the vast majority of the items on our online store, we cannot assure that they will all be on hand at all times. We ship every order as quickly as possible, and in the event of a delay, be assured that we are working hard to get your order shipped promptly. Due to order volume during holidays, we cannot guarantee that all orders placed can ship on the day after the holiday closure. 

Orders for special cut products may take a few days to ship depending on order volume. Special order products ship based on the lead times of each manufacturer. 

Shipping Service

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UPS orders will need to be placed before 4:00 pm EST and 4:00 pm PST Monday-Friday to ship out the same business day.  We apply UPS retail rates to calculate shipping costs.  Packages may not qualify for actual wieight due to size.  If dimensional weight is applied by UPS your shipping & packing rate will be adjusted.  Packages are only insured aganst theft if signature delivery is accepted.  Request signature delivery.


Priority Mail & 1st Class order has to be placed by 11am. We will use the flat rate box service if your parts fit in the box and the service cost is less than USPS Priority Mail. USPS may not always have tracking information available.  If you request lower cost USPS shipping you agree to accept all responsibility for lost, stolen and damaged packages.

Delivery Timing

UPS Ground Delivery

USPS Delivery Timing

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