The envelope must have means to allow for rapid deflation after landing. The system must be designed to minimize the possibility of inadvertent operation. If a system other than a manual system is used, the reliability of the system used must be substantiated. (See AMC 31HB.55(a)).
If a mixed balloon is equipped with a lateral rapid deflation means, a device must be installed to align the balloon during landing in order to turn the rapid deflation means into its designated position. (See AMC 31HB.55(b))
AMC 31HB.55(a) Rapid deflation means
ED Decision 2009/005/R
The installation of turning vents or a drag rope is considered as a suitable device to align the balloon
during landing in the sense of this subparagraph.