Originally Posted by
Dora-9
Can I ask some questions here please, just to clarify this in my own mind?
1. What type of INS did the DC10 have?
2. Did it have a triple-mix function?
3. How were the waypoints loaded? Individually as Lat/Longs by the crew or was it already pre-loaded by (say) the Nav Dept?
4. Was the CFP also changed on the day or was the infamous altered waypoint only changed? What I'm getting at here is would the crew have been able to pick up that there'd been a change by cross-checking the tracks/distances or even Lats/Longs?
Thanks.
I don't think anyone answered. I'll answer question 3 and 4 for you. The procedure was that the waypoints were keyed into the INS before take-off by Cassin by reading from the flight-plan they had been issued that morning, with Collins checking the numbers had been keyed in correctly. This was unusual as the data for all the scheduled flights was normally on cassette and did not need to be keyed in. In that respect the accident could've happened by the digits not being entered correctly, in the same way we see incidents todays where the take-off weight is not keyed in correctly and not picked up by double-checking.
Would the crew have been able to pick up a change? at the RCU a few weeks prior they had the opportunity to read a sample flight-plan. That flight plan had the slightly different co-ordinates, track distance, and heading for the final leg, but still had MCMDO MCMURDO as the label, and in the final error by the nav department, no entry to indicate a recent change to draw attention to the entry as there should have been.
MCMDO MCMURDO 188.9 (track)
7753.0S16448.0E 357.4 (dist)
versus
MCMDO MCMURDO 188.5 (track)
7752.7S16658.0E 357.0 (dist)
The crew did not have the opportunity to directly compare the two flight plans, but if as widely believed at the RCU briefing they wrote down the co-ordinates from the first flight plan into a private notebook, they might have had the opportunity to pick-up the difference between what was in their notebook (and plotted on their personal map), versus what was in the flight plan. Thats why the notebook and its missing pages was crucial evidence. Also Cassins notes from the briefing which he accidentally left at home disappeared as well after the event.
In hindsight it would have been prudent to check the line you have drawn on a map versus what you've entered into the computer, but that wasn't something an Air NZ pilot was expected to do on any other flight.