SAFA Skysailor Magazine

22 SKY SAILOR July | August 2021 Recently, we have had a couple of AIRS reports involving PG pilots come across the desk where the pendulum effect has come into play and had either not been considered or been forgotten about. This in turn set me off thinking about landings generally and these in particular,… and then it’s 3am, and I’m still awake, which is why you’re all reading this. In my opinion, landings are the most dangerous phase of flight – you are intentionally coming in close proximity to the ground – Pilot Enemy #1. Hopefully, this is a planned landing, but sometimes it may not be. You may be forced from the sky for some reason and have not had enough time to assess the landing area fully and what is going on down there – you are heading to the ground and that’s all there is to it. The PG swing cycle in a turn Some specifics for PG pilots first (HG & WM folk, I beg your indulgence). It’s important to remember that in our aircraft we control the aircraft from the harness through our inputs on the wing via manipulation of the brake lines and appli- cation of weight-shift. But equally important is our role as the weight beneath the wing in maintaining the shape of the wing, via the internal components and attachment points through the lines to the risers and carabiners. Our weight also opposes the force of lift generated by the aerofoil shape. As opposed to a hang glider where the pilot is suspended very closely to the centres of force and weight of the aircraft, this configuration means that PG pilots are at the end of a very long lever arm. Because of this we are subject to pendular motions. When the brakes are applied, the wing slows and falls behind the pilot before the pilot swings back underneath the wing. If the brakes are released, the wing surges forward and the pilot then swings forward. This also occurs when applying one brake to initiate a turn. The brake applied slows that wing and the other wing continues flying faster around the inner wing. The pilot continues flying forward, but is then pulled into the turn, swinging outside the centre of the wing. When the turn is exited, the pilot swings back in towards the centre of the wing. In all of these cases, when a swing back towards beneath the centre occurs, you can expect some overshoot, depending on the magnitude of the action of the wing. It is worth getting an idea of the degrees of pendular movement when in the air. When in stable flight and safe to do so, look up at the wing as applying the brake inputs and releasing. You will be able to see the degree of movement with respect to the wing centre quite clearly. So, how does this relate to what occurred in the AIRS reports? In the first case a PG2 pilot, while setting up for landing after flying at Beechmont (SE QLD), performed a series of turn reversals to lose altitude. The pilot appeared to lose track of their turning sink rate and be unaware of the pendular acceleration on the return cycle. As a result, on the second turn they impacted the ground while in the return cycle and suffered stable injuries to vertebrae. Executing low PG turns Sometimes, it is necessary to execute a turn when low on approach, but I personally try to avoid these. You’re in a situation where you have no recovery room if you experience a problem, such as a collapse, down low. If you have trees or obstacles lining the landing area, you may be subjected to mechanical turbulence from wind blowing around trees, or alternately, entering wind shadow; executing a turn in those circumstances could initiate a collapse. You really need to be lined up and carrying as much speed and energy as you can. As Phil Hystek says, you need altitude, energy (speed) and ideas. Take one away (altitude) and you stand a good chance of getting out of a problem. Take two away though… Reflections on landings by Iain Clarke, SAFA Safety Management Officer