I have difficulty understanding why they continued past the PNR/PSD without requesting - and getting - the latest wx report
There is no indication that the pilots calculated a PNR/PSD. The ATSB calculated several, in order to place the receipt of the weather in context, and they asked the Captain
how he would calculate one - but there is no indication that the crew did, or were aware.
Originally Posted by ATSB report, page 185
Some Westwind pilots reported they routinely used how-goes-it charts for relevant flights. However, most pilots, including the captain of the accident flight, reported they did not use the charts and had not been taught how to use them.
The OM indicated a how-goes-it chart could be used to calculate a CP, but there was no mention of such charts in relation to a PNR. The standards manager agreed that such graphs are used for calculating PNRs rather than CPs.
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The captain of the accident flight reported that, for a situation involving an off-track alternate aerodrome, he would initially work out if he could fly from the destination aerodrome to the alternate aerodrome with the required fuel reserves. If not, he would identify the last waypoint he could reach and still divert with the required fuel reserves. He would then know that the PNR was beyond this waypoint. This involved using the aircraft’s GPS to determine the distance and/or flight time to the last waypoint he could reach, and charts to determine the distance from that waypoint to the alternate aerodrome.
After the captain had passed the last waypoint he could reach, his method involved conducting periodic checks of whether he was still able to divert from his current position. This involved using the aircraft’s GPS to calculate the distance to the alternate aerodrome.
The captain reported that when checking his capacity to divert, he would use the aircraft’s current fuel flow and his best estimate of the expected groundspeed, given the aircraft’s current groundspeed and what information he had regarding the winds if he diverted. For the accident flight, the captain stated he would have based his diversion wind estimates on the current wind he was experiencing. Given that he did not have the current TAFs and NOTAMs for Nadi and Noumea, he would have based his estimations of the PNR on the assumption that these aerodromes were suitable for landing (that is, not also affected by adverse weather).
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The first officer stated she knew how to do PNR calculations, and she reported she had done calculations on some flights. However, she could not recall doing PNR calculations on the accident flight.