The incident or issue
ATA members have reported instances where suzi coil airlines have been used to provide brake air with drawbar trailing units, such as dollies, pig trailers or dog trailers. This use of suzi coils could potentially prevent the timely application of emergency brakes in a decoupling situation.
Incident cause
If a coupling disconnects unintentionally during travel, suzi coils can stretch elastically for several metres and further again as the airline plastically deforms.
This stretching may prevent the quick venting of air from the supply line, extending the time before emergency brakes are activated on the separated trailer.
In addition, the snapped ends of a suzi coil broken in this manner deform plastically, further restricting the air loss from the system and delaying the application of emergency brakes.
Solution
The use of suzi coils with drawbar trailing units is not supported by the ATA. Instead, the ATA’s Industry Technical Council recommends using shorter, non-elastic rubber brake line hoses with approved couplings for these applications.
Follow-up actions
Suzi coils used over drawbar trailing units should be replaced with a non-elastic option.