ShyTorque and K52
Re the “milk run” and “standard flight plan” business. Please let me explain in layman’s terms what I was on about:
You are crossing the sea at low level where it is clear and pleasant towards the Mull;
Your only visual reference ahead is the end of the Mull itself BUT it is so obscured in mist that, at any distance, no useful ground detail is visible;
You want to stick to a popular route for such flights and when you are close enough, you can eyeball the shoreline (which close up is visible because the mist only starts forming as the air rises up the slope);
It is the getting close enough to see the shoreline clearly without creeping cautiously along towards it that is the problem;
With a high speed and weight you need to anticipate the turn somewhat;
Neither the TANS system or the Mk1 eyeball can safely get you close enough to that shoreline for your recognition of small detail that would give you your near field judgment;
Dependence upon the TANS and the Mk1 eyeball would demand prudence and therefore a turn well away from the Mull - spoiling the usual route because of this one aspect or requiring a climb into the world of instrument flying where (being so cloudy) neither the crew nor the passengers would be so comfortable even if this option was possible in the light of the icing limitation;
Given that this was probably a “popular” route and that these conditions would have been a regular occurrence in that area, it had occurred to me that there may have been an established practice to get around that last bit of the approach to the Mull – a bit like knowing the height of lighthouses or similar features can help coastal navigators judge their distance off in the days before radar (ZD576 did not have a radar) or radio/satellite navigation aids – once you are parallel (and close) to the shoreline all is good;
If I had been a thoughtful and responsible planner of operations, I think that I would have suggested something like using the TACAN for that awkward part – perhaps even installing a portable set of DME say at the lighthouse (cheap for the service it would have provided) – for a trial period – even borrow a set from our “friends” – but no! – who would be responsible for its security and monitor its accuracy? – a silly idea – especially as it is so easy to tamper with such ground equipment to give a false reading – it would have been beyond negligent to suggest such a scheme. Anyway, it was just an idea – I wonder what other arrangements could have been made, if any (it could have been left to the pilots all the time)?
I maintain that they demonstrated control at the last moment by starting the evasive manoeuvre which was consistent with either their SEEING how close they were (shoreline passing beneath or mist flitting past windscreen) or when the altitude warning went off suggesting that they were not (successfully) judging their distance off that mist visually; the point at which they had selected their next waypoint, although before the actual waypoint, was already so close in under those conditions that they must have had something else to go on – not the eyeball as explained here.
If not the TACAN then what?