PPRuNe Forums - View Single Post - Revised Bristol/Cardiff airspace/SIDs/STARs
Old 11th Oct 2006, 14:03
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Rev Thrust
 
Join Date: Sep 2006
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I'm curious... what reason would sensibly account for BRI not being in the FMC? Surely, BRI is part of the BRI1C STAR, and as such, should be expected to be called for, in normal circumstances?

Obviously, I fully appreciate that 'normal' actually often consists of radar vectoring by ATC once you're past POMAX, and that overflight of BRI is in fact very rarely used, but my point is, because it's part of the STAR, the presumption ought to be that it will be used... not the other way round.

Not trying to tell busy (and highly respected) busdrivers how to do their jobs, nor imply knowledge that I simply don't have on a working level... but I am rather curious, all the same.

Are there any other places in the UK where the last half of a STAR is 'optional' in terms of setting up the FMC?

It would seem (to my simplistic mind) that if BRI was routinely entered into the FMC, instead of 'as needed', then the system becomes 'fail-safe' again... viz:

Case 1: BRI in the box, radar heading off POMAX to straight in (or downwind and vectors to CF27) = no reprogramming necessary, the work is done on HDG SEL or manual after POMAX, until LLZ is captured (wherever that may be) = no problem, nor even a need to reprogram the box.

Case 2: BRI in the box, radar down, procedural approach = box takes you all the way to BRI, you fly the IAP on HDG SEL or manual to CF27 = no problem, no reprogramming either. Heck, you might even be lucky enough to also have the entire IAP procedure available as a "BRI Transition" (as my armchair B737 does), so the thing will fly the whole 107deg 8DME and proc turn onto LLZ without you even having to lift a finger until its time to flick over to VOR/LOC and APP when cleared to intercept/descend on the ILS?

Case 3: BRI in the box, radar having a bad day, late call, whatever, ATC gives you straight in under own nav from POMAX to CF27 without having initially vectored you from POMAX = a quick downselect of CF27 into the scratchpad, followed by LSK1L next to the top line and you're going direct CF27. Two button pushes. Providing you make the descent to CF27 okay, no problems with the box thinking you've passed the field.

Opposite Case X: BRI not in the box, and the situation is different. Pass the field at low-level (because you've been routed in procedurally instead of straight in)and the box says 'end of route' and leaves you high and dry. At the very least, you'll either have to fly manual or HDG SEL headings to get to BRI, if it's not in the box and ATC calls for it, or bung it in as a manually-typed 'Bee Arr Eye' LSK1L sequence into the box, to put it above the CF27 that you previously had. Four buttons, and a consequent route disco, and other things to possibly contend (such as recalced VNAV descent issues) at the busiest stage of your entire route.

I'm just a humble armchair driver, when it comes to flying buses, but I have got a lot of hours in, all the same, and albeit it simulated. There must be a reason, other than the simple human approach of 'save ourselves a minute but cost ourselves ten later when the plan doesn't pan out', as to why you'd deliberately not program the full, official STAR, only to have things potentially go pearshaped (FMC-end-of-route-wise), when things turn out to be different that one time?

Isn't it precisely because of situations like this, where we cut a corner to save a moment, but risk far worse when the other thing happens, that the fail-safe principle was invented?
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