SAFA Skysailor Magazine

34 SKY SAILOR January | February 2024 AIRS Safety Wrap-up – December 2023 by Iain Clarke – SAFA Safety Management Officer Greetings fellow pilots. Firstly, congratulations to those who spotted the clanger in the ‘It Happened To Me’ column last issue. Cue Monty Python, “Howls of derisive laughter Bruce” … Low humidity air is of course denser than higher humidity air. Why? Molecular weights. Water (H2O) has a molecular weight of 18.01528g/mol (1.00794*2 + 15.9994). The mo- lecular weight of air, assuming 78% nitrogen and 21% oxygen, is 28.9647g/mol. Therefore, low humidity = denser air. There are a lot more factors to do with atmospheric chemistry and composition, and a search of the interweb will satisfy your curiosity. As for my clanger, I blame the drugs – I wrote that article in the days immediately following my operation. Secondly, we have seen a rise in serious accidents and non-compliant flight opera- tions involving mini/speed wings/para-kites, however named. In this edition of Skysailor, you will find an article on the issue. I would urge all of you who fly these wings, or know someone who does and who may not hold the endorsement, to read and share this article. There are some pretty big implications if you choose to fly these without holding the required authorisation. Now, let’s dive into this month’s reports. We’ll start off with older completed reports and move forward in time. #1166 – PG towing accident, NSW PIC was setting up for a paraglider ground tow relaunch at Boor Hill, near Parkes (NSW). PIC had their wing above their head but had not made the call to commence the tow when they were lifted 3-4m AGL. After lift off, the tow-line unexpectedly broke at the vehicle end. The pilot caught the surge, but due to insufficient altitude for a full recovery, impacted terrain, suffering a stable fracture of vertebra L2, and a fractured pelvis. As per standard practice, the winch was set to a very low tension at the time for the initial phase of a reverse launch, so it came as a surprise to see the wing lift the pilot off the ground. The weak link used was a re-usable German style one, rated at 150kg, with the pilot weight at approximately 100kg. The tow line was 2.5mm Dyneema, with a breaking strain of circa 500kg when new and undam- aged. It is unclear to determine what exactly occurred with any level of certainty, but it can be assumed that the line did break at a tension lesser than the weak link rating, possibly due to damage. The general condition of the line used at the time was good, estimated approxi- mately 25-30% into its usable life. Owners and operators of tow winches are advised to conduct a visual inspection of their entire tow line at regular intervals. Pilots are reminded to always be prepared for unexpected weak link breaks and have the actions to be taken in response at the front of their minds.