SAFA Skysailor Magazine

25 September | October 2020 SKY SAILOR Winds were ESE at 10-12kt with rain showers in the area. As one shower hit, most pilots in the air at the time came in to land. The PIC was PG2 and approached the southern end of the Blow with a strong tailwind, encountered strong mechanical turbulence and the wing took a partial collapse causing a ground impact. The pilot was taken to hospital by helicopter with fractured ribs, collarbone, pelvis, and internal bleeding. Rainbow Beach’s recommended wind direction is NE; flying in an Easterly is possible, but any South component in the wind makes it an unfavourable place to fly. With anything other than a NE, care needs to be taken on the southside of the Blow as you will usually get rotor there. Careful monitoring of the wind while in flight is always necessary as a wind shift to an unfavourable direction or strength will likely necessitate a landing. With rain around, squalls can make those effects on the wind quite pronounced. Bear in mind possible sources of rotor when coming in for top-landing if the wind direction has changed. Pay attention to all of these details when getting a site briefing. Finally, do not fly in the rain. Rain can adhere to the exter- nal surface of modern glider fabric and disturb the boundary layer of airflow, lowering the stall speed of your wing as well as accumulating internally. The effects of wind over topography played a part in AIRS #1268. A PG2 pilot was scratching low at Spring Hill (near Canberra, ACT), after flying for over an hour. The pilot had pushed out to the west and was returning to the main ridge, attempting to scratch back to the top. Unfortunately, the pilot hit a pocket of sink and had nowhere to go other than the ground, landing backwards into rocks and being dragged uphill a short distance, luckily only suffering some bruising. It appears the pilot had encountered a well-documented Venturi effect that occurs in the saddle to the right of launch. You can read about this feature in the Spring Hill site guide . An unfavourable wind direction at Crackneck Lookout (NSW) led to an extremely narrow lift band when a PG4 pilot was flying there in February this year (AIRS #1223). This, combined with the increased speed on the down- wind leg while attempting to get back to lift, led to a high speed ground impact. A witnessing pilot commented that PIC lost a portion of altitude due to what could be consid- ered rotored/non-laminar airflow that follows the shape of the terrain situated to the south of launch. The pilot required helicopter extraction from a precarious position and was transferred to hospital where fractured vertebrae and pelvis were diagnosed. Unfortunately, we see fractured vertebrae quite often in the reports. Thankfully, not too many result in long-term neurological damage. My relief is always huge when I learn the pilot is okay. Fortunately, this was also the case for the PG pilot in AIRS #959 who suffered fractured L2 and L3 vertebrae requiring surgical stabilisation but with no neurological damage. The pilot had launched from Beechmont (QLD/S), on a cross-country flight with two other pilots in January last year. The day was mildly thermic, with a northerly airflow which was causing some turbulence close to the terrain. Approaching the NSW border, the pilot was getting low and was going to have to land, so headed for the site of a previous landing; even though it was tight, it was achievable. With legs out of the pod and set up for landing, the wing took an asymmetric collapse at tree-top height when hit by turbulence. The pilot recovered the collapse, but then felt as though the wing had gone into a parachutal stall. The pilot then looked up and lost situational awareness of the remaining height from the ground and did not have legs fully down, impacting the ground on his back and requiring a helicopter extraction. We’ll look at a couple of equipment related incidents to wrap up this issue. In the last edition, I touched on the issues of currency and preparing to return to flying after a break. A change of instruments used can also lead to problems through unfamiliarity. This was the case in AIRS #1264. A PPG pilot flying in the Northern Beaches area of Sydney noticed a very large commercial jet some distance away on a converging course at approximately the same altitude. The pilot immediately moved to reduce altitude and called me after landing to discuss the flight. It transpired that the pilot’s usual vario was out of action and instead, the pilot relied on a mobile phone app. However, the display was configured to show altitude above ground level (agl), not above sea level (asl), resulting in the pilot being higher than intended. A review of the available flight data for the time period concerned showed the jet was a Boeing 777 out of Los Angeles and at a lower flight level than the lower limit for that area (quite okay if directed by ATC). The message here is clear. Ensure you know how new or different instruments work and that they are configured correctly for your operations. A warning to the unwary: do not rely on GPS-only mobile phones, these can suffer from significant inaccuracies in the vertical plane, in the order of metres or tens of metres. It is all too easy for poor reception or constellation alignment to blow out the position calculations. If relying on a mobile phone app, your phone must have an internal barometer or is taking barometric input from an external barometric vario. As always, calibrate your vario to local QNH (Query Nautical Height) or your launch elevation before flight. Finally, we turn to an accident that occurred in March. A PG5 pilot was thermaling in light thermals at Mt Tambo- rine (QLD/S) when the right-hand carabiner attachment loop on his Supair Strike harness failed, resulting in the wing riser detaching. The pilot made a safe descent under his reserve. SAFA sent the harness to the Australian Transport Safety Bureau (ATSB) for an independent inspection. They found that the carabiner attachment loop had failed at a stitching point, but made no finding as to whether there was a defect in design, materials, or manufacturing process. We advise all owners of Supair Strike harnesses to inspect the stitching at the carabiner loop attachment points. A copy of the ATSB’s report can be found here. Stay safe.