Boeing Simulation / Mitchell Analysis
Isn’t it odd how Boeing and MoD place such unerring faith in a system (RNS252 / GPS) when, just a few months earlier, both were content that the Release to Service warned aircrew that it should not be trusted. Not to use it as the sole NavAid. To ignore Error messages as “meaningless”. That GPS hadn’t been granted Initial Operating Capability and its performance couldn’t be guaranteed. Its rubbish, just rely on the other NavAids – but we’ll let you know in due course if we decide to clear them for use.
May I suggest it may have helped matters to simply follow the regulations, establish an installed performance and give the aircrew some meaningful assistance through an unambiguous clearance or limitation, instead of just saying the system produces “meaningless” messages. If that was a TV you wouldn’t buy it in the first place. This was an aircraft for God’s sake. But no, MoD blithely ignored their own regulations and told the aircrew to suck it and see.
And, while it appears the system was being used as Waypoint A was approached, the AAIB’s opinion was that at impact the RNS252 was switched off. Not by impact, but at impact. What happened in between these events regarding a system the aircrew did not trust?
Speaking of the AAIB, Boeing’s report clearly assumes that organisation is an agent of the MoD and privy to all relevant information – information that Boeing state was not available to themselves as the Aircraft Design Authority. But, as we know, the AAIB was kept even more in the dark by MoD. I’ve read hundreds of such ADA reports – this one is so full of caveats and get-outs as to be completely meaningless. Just like RNS252 messages. Without first addressing the above issues the true context can never be understood. Which is why MoD don’t want to go there.