SM4 Pirate
My alternate figures, both fuel plan and FTI, are based on diversion from the MAP’t. This is the figure I have on my flight plan, and is I believe, universal practice.
Scenario 1
If I am 200 nm north of SYD coming down from BNE. Things start to turn ugly and in the spirit of timely advice and desiring to preplan your sequences, you advise me:
“expect significant delays, when ready, go ahead with your Latest Divert Time.”
I will use the MAP’t as the basis for my LDT.
Logic: it’s the only point I can reasonably expect to fly over, and I already have all the data from that point.
Scenario 2
If I am somewhere on an ATC guided tour of the Blue Mountains, Woolongong or perhaps doing a bit of impromptu fish spotting out in the Tasman, and you advise me that things are getting uglier:
“you are still number 10 in the sequence, advise your Latest Divert Time”.
I will use the MAP’t as the basis for my LDT.
Logic: it’s the only point I can reasonably expect to fly over, and I already have all the data from that point.
Scenario 3
I am being held at XXX. You feel the need for information and request an LDT.
I will use the MAP’t as the basis of my LDT
Logic: it’s the only point I can reasonably expect to fly over, and I already have all the data from that point.
I have no idea what your sequencing plans are. You may shift my hold or you make take me on a scenario 2 guided tour. I don’t know. The one constant in each scenario is the MAP’t. If the logic holds for scenarios 1 & 2, why would it not hold for scenario 3?
If you ask me for a DT from a particular point, different story. Ask for any particular time and I will do my best to give it to you.
The time/calculation you nominate in your example is a DT from the hold but it is not an LDT. Internationally it is referred to as an EFC, or in this case a Latest EFC. It is a generally pointless to hold beyond that time as nothing more than a diversion can be undertaken, but it is not an LDT. In high density areas it is conceivable that ATC might require a hold beyond a latest EFC, to facilitate traffic flow to a popular alternate.
In the absence of a specified point for a requested LDT, I will give you a time based on the MINMA, planning a latest possible time to be at the bottom of the hill, and still be able to divert. If at any time in the sequence, it becomes obvious to me that you will not get me to the minima by the nominated time I will initiate a diversion immediately, to maximise my options at the alternate. In my experience this is the international standard.
Some have suggested that such an interpretation is narrow and, by inference a bit anal. However it should be remembered that we work in an international environment. SYD as an international airport deals with legions of crews for whom English is a second language. Equally we, as aircrew must deal with ATC’s from a wide range of backgrounds. It has been my experience that when a non native speaker is asked a question in a language in which he is not fluent, he will take a literal interpretation of the individual words, rather than an overall view which may be tinged with local influence. Hence, if you ask a Japanese or a Columbian or an Egyptian, for a LATEST time he will almost certainly give you a figure from the MAP’t, as that is the true, latest, time.
If due to local custom you wish to use DT in lieu of the international standard EFC, may I suggest it is essential that you specify the point from which you want the DT calculation made.
In the incident that sparked this thread (according to the report), the pilot was asked for and gave a Latest Landing Time. For him to continue as he did he must have believed his LLT, was an LDT aligned with your interpretation, which as I have pointed out is not an LDT. If a native English speaker can be sucked in to this sort of error, what is the possibility of a non native speaker making a similar error?
This incident, in my view highlights the need for global standardisation in radio procedures, and the necessity for both sides of the radio to understand which page they are working on.
Although I have not seen an Aust. AIP for many years I suspect it is silent in this area, as are Jepps.
Personally, I don’t give a rats what time you want, ask for it and I will give it to you, but only if the request is precise can we all be sure that the response is appropriate.
TAC On