Visibility and Illusion
Walter,
I have never presented my interpretation of events as facts. I have never said that Waypoint A has to be the lighthouse.
It is just that I have never seen any evidence to support a planned approach to the Mull. As I have said "in my opinion", and that of my Puma and Tornado friends, the failure to insert a Waypoint between Belfast and the Mull suggests no planned accurate or precise approach. The BOI, FAI and HOL seem to agree, as this issue seems never to have been considered.
On my "coarse TP" theory, why did they in the then "visual conditions", approach so close to the Mull?
What "visual conditions" were those then?
Full and honest answer. I don't know.
Do I have a theory. Yes.
Visibility is infinately variable. It is common to have four different visibilities in four different directions. Change height by a few feet, it changes. Change heading, it changes.
Visibility is difficult to assess over land and impossible over the sea.
I will use simple figures to demonstate a possible scenario.
When you leave Belfast, the forecast visibility is say 3nms at the Airfield and the Mull. You plan your "coarse turn" at 2 nms from the coast.
Once airborne you assess the visibility as 3nms, same as the Met.
By coast out, the visibility may have changed little.
As you fly North the visibility slowly decreases, but you probably will not notice. You have no reference points.
You see Mr Holbrooks boat, still to you the Vis seems 3nms. But is it a 30, 40 or 60ft boat?
One minute later the clincher. The lighthouse appears in the gloom. You check the TANS. 3 nms to run. You have been right all along, the Vis is 3nms, exactly what you expected.
Hit the real or mental stopwatch. Check groundspeed. 120 kts. Thirty seconds to turn.*
What if the TANS is lying? What if the accurate range is 1.5nms. Where will you be 30 seconds later? When will your brain register the error?
Big tree little tree, big cliff little cliff, big lighthouse little lighthouse. All you RAF types have seen the films.
So what have we now. "Gross negligence" or "error of judgment" partly induced by equipment error.
Did this happen? No idea.
Could this happen? Yes.
It is more likely than an experienced crew planning to skim a ridge by 300ft IMC.
And it is about as likely as a UCFM at a precise moment in time.
* Spot the deliberate mistake
Last edited by dalek; 24th Jun 2009 at 19:15.