JulianUK From United Kingdom, joined Apr 2006, 105 posts, RR: 0 Posted (7 years 4 days 19 hours ago) and read 7336 times:
Trying to understand the Equi Time Point feature on FMS systems, and got totally confused, so need some help! Can someone explain it in non technical terms please! Thanks, J
Gordonsmall From UK - Scotland, joined Jun 2001, 1995 posts, RR: 24 Reply 1, posted (7 years 4 days 19 hours ago) and read 7335 times:
An ETP (equal time point) is basically the point at which it'll take a shorter time to continue to the next suitable diversion airfield than to turn back to the last one.
There are many ways of calculating the ETP besides using the FMC, some complex and accurate, others simpler but not quite so accurate.
When I was studying the relevant module of my ATPL exams, I would always forget to take into account the time taken to reverse course when calculating them!
EDIT: Spelling.
[Edited 2006-05-21 13:51:03]
Statistically, people who have had the most birthdays tend to live the longest.
CosmicCruiser From United States of America, joined Feb 2005, 2214 posts, RR: 16 Reply 2, posted (7 years 4 days 1 hour ago) and read 7310 times:
Quoting Gordonsmall (Reply 1): An ETP (equal time point) is basically the point at which it'll take a shorter time to continue to the next suitable diversion airfield than to turn back to the last one.
Unless I'm a lot more tired than I think EQUAL Time Point means EQUAL time. Therefore, AT the ETP it's EQUAL time to either alternate. That's the point, before the ETP you turn back, after you continue, generally speaking.
Gordonsmall From UK - Scotland, joined Jun 2001, 1995 posts, RR: 24 Reply 3, posted (7 years 3 days 21 hours ago) and read 7303 times:
Quoting CosmicCruiser (Reply 2): Unless I'm a lot more tired than I think EQUAL Time Point means EQUAL time. Therefore, AT the ETP it's EQUAL time to either alternate. That's the point, before the ETP you turn back, after you continue, generally speaking.
Common sense would suggest that you are correct, and I have queried this very issue on more than one occasion with more than one instructor, however the UK CAA are absoloutely insistent that the the decision to turn back should be made BEFORE you reach the ETP and that AT the ETP you continue by default, at least that's what I've been told they expect me to say in my written exams.
I've already had enough run-ins and cross-words with the CAA in my short aviation career, so I'll leave any further arguing to those with more faith in the Campaign Against Aviation .... I'm quite willing to tell them the earth is flat if it'll help in my quest for an ATPL!
[Edited 2006-05-22 11:43:02]
Statistically, people who have had the most birthdays tend to live the longest.
CosmicCruiser From United States of America, joined Feb 2005, 2214 posts, RR: 16 Reply 4, posted (7 years 3 days 19 hours ago) and read 7283 times:
I was afraid that you would be looking at it from that point, meaning that yes, to be technically correct, if you turn back EXACTLY at the ETP you would have further to go just by the shear nature that you must do a 180 ( ok 135, 155, etc) and would travel past the ETP. I was just pointing out that the ETP means exactly that...CC
Gordonsmall From UK - Scotland, joined Jun 2001, 1995 posts, RR: 24 Reply 5, posted (7 years 3 days 19 hours ago) and read 7280 times:
Quoting CosmicCruiser (Reply 4): I was just pointing out that the ETP means exactly that...
Indeed! I agree completely that in it's literal sense it is an EQUAL time, and if it was up to me common sense would prevail!
Unfortunately the UK CAA are not known for their appreciation of common sense or simplicity, and it's them I have to convince that I know what I'm talking about - even if it is wrong!
Statistically, people who have had the most birthdays tend to live the longest.
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