Gavin Grimmer
IDENT to RADAR FADE
From the Radar Ident position onwards gets more difficult, but not impossible.
We first need to do a study on what the wind was doing....
WIND REPORTS
Williamtown reported a wind on the ground of Westerly at 20 knots. The wind speed is generally much lighter at ground level due to mechanical interference such as trees, buildings, and the like.
Cessna 206 VH-AZC thought the winds at Coffs Harbour were more likely to be from 220°T than the 240°T as forecast, due to the slower ground speeds and the amount of drift he was encountering. He reported an estimate of wind direction and speed based on the time it took to fly from Taree to overhead Williamtown as 240°M at 40/45 knots. Luckily for us, he reported all the information needed for us to get an accurate direction and speed of this wind....The temperature at Taree at 8000 ft was -2°C. He was at 8000 ft.
His indicated airspeed was 120 knots, so with this temperature and height, it calculates to a TAS of 139 knots. According to the radio transmissions he was overhead Taree at 08:45 and overhead Williamtown at 09:24 = 39 minutes which gives a ground speed (GS) of 100 knots. The distance between Taree and Williamtown Nav-Aids is 64.75 nm and the heading required from TRE to WLM is 212°T. He claimed a heading to make good the track as 215°M (226°T) and this all calculates to a wind of 255°T at 48 knots.
Piper Cherokee VH-CNW is of particular interest as it was the only plane that reported winds basically upwind at similar levels in the general area of Barrington Tops of where VH-MDX is believed to have ended up. Until I did the timeline, I never realised there was a plane in this area! They flew a training flight from Cessnock towards intended destinations of Scone – Merriwa and back to Cessnock, but detoured from abeam Lake Liddell back to Singleton NDB due to what they described as a wall of cloud that could be observed as starting west of Scone and extending to Nelson Bay although I suspect it only appeared from their observation position to go out as far as Nelson Bay as neither VH-ESV nor VH-AZC observed any cloud when they flew through the areas between CRVN - TRE - WLM at virtually the same time. He heard a lot of the transmissions from MDX and was surprised by the calm nature of the pilot's voice given the situation he was supposedly in. He commented on how the pilot's voice became more panicky towards the end - especially the last call of 5000 ft.
The cloud was described as Strata-cumulus 8/8 extending from about 3500 ft up to about 7500 ft. Turbulence was described as ranging from slight to moderate up to a height of 7500 ft and was smooth flying above that. The wind was a direct westerly (181°T) at 50 knots.
The radio transmissions reveal that at 09:37.35 VH-CNW notified a descent to 5500 ft due to cloud and I believe this descent was somewhere near the Singleton NDB.
Piper Cherokee VH-TVK also out of Cessnock on a training flight at about the same time, flew a course of Cessnock – Singleton NDB – West Maitland – Aeropelican – The Entrance - and presumably back to Cessnock (doesn't say), and was flying at 4000ft reporting strong westerly winds necessitating a 50° lay-off heading to maintain the track between Aeropelican to The Entrance. There was no icing and light turbulence.
The 50° lay-off calculates to winds well in excess of 100 kts, so either it was an over exaggeration or as I suspect, the person listening and typing the record interpreted 15° as 50°. At a 15° lay-off, I would say via calculation that the wind was from 248°T at a speed of 48 knots.
Cessna 402 VH-ESV reported a wind of 70 knots at a point at least 25 nm north of RP Craven at an altitude of 9000ft, but as he had only been on the leg from Sandon East to Williamtown for a few minutes, I suspect he calculated this wind on the leg from Toowomba to Sandon East which has a course of 183°T. His calculation was based on a 35/40 knot headwind component. At a cruise speed of 214 knots which converts to a TAS of 252 knots that day at 9000 ft. If the wind was as forecast then the wind would have been coming from 260°T. Hence, having a headwind of 35/40 kts equates to a wind speed of 86/96 knots, so on further calculation to find the wind direction at 70 knots equates to 246°T.
Clip above from Pilot of VH-ESV’s statement
<<<<<Weather areas 20 and 40
Armed with all this information, we can now lay it out on Google Earth and get an idea of what was occurring with the wind that day.... Next Page.....
MDX pg 12
