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ETP

Old 10th Feb 2012, 11:04
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ETP

Last question for today.

How is an ETP displayed on the ND? Do you enter a lat/long fix and put a little ring around it?

Thank you.
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Old 10th Feb 2012, 11:33
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uy,,, the mighty equi time point. well, its dependant on the fmc type . on the honeywell installed on the bae146 you can highlight it from the submenu of nearest airports or the dest/arrival airport.

but remember that at least the bae146 fmc only calculates the distance and does not care about actual winds when it comes to etp.

cheers
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Old 10th Feb 2012, 11:53
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I know I sound incredibly ignorant, and whilst I've gone through the training and studying of this kind of thing (a few years back when I was flying), for commercial operations, it all seems very unnecessary (armour on)

Imagine London to, say, anywhere about 3 hours away, Eastern Europe-ish. ETP, it seems, would be roughly in the middle, dependant on winds. You could plop in (if it isn't provided automatically which helps) a fix about midway (minus all the complex calculation hoohaa, and simply make a decision there and then?

Second, surely it's incredibly unlikely that something will go wrong requiring such a return/continue scenario, but so close the to ETP is even MORE unlikely, statistically speaking. Most things in aviation are based on logic/statistics/likelihood, so it seems to my ignorant non-airliner brain that an ETP point calculation is a little OTT?

Is that how you feel when flying? If a situation arose requiring a turn-back or continue, you could look at DTG to dest, DTG to departure point and make a quick decision without all the calculations!

Is ETP really that important?

Thank you
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Old 10th Feb 2012, 12:28
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hehe-basicly you are pretty right here- the etp has in real life very little value , even when it should be possible to discuss it to death by theroretical means.

i also remember the manual calculation, even considering wind and calculating by nautical air and nautical ground miles and i hated it, further was never in a situation when this would help with a decision.

the pure etp does not take into account if the next airport is your best option in regards to emergency facilities, runway lenght, descend path and much more, it does not take into account if going there will result in an overweight landing, it does not even take into account the wind when calculated by fmc. its just a basic information.

depending on what why and where happened its alsways a manual decision what to do.

cheers !
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Old 10th Feb 2012, 14:55
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When flying around Europe with an airport suitable for any aircraft every 200 nm or so I would agree that ETP's are of little relevance.

Now think about crossing the Atlantic, Pacific, desert region etc et night. There may be no suitable open airport for 2 hours or more.

Believe me, you want to know where you will go at any point of time should a 'Land ASAP' event happen. You will be always aware of the latest wx forecast etc. On the B747-400 the FMC allows you to put in a time as a fix, this then appears on the ND as a circle with the time next to it.

Drawing range circles around airports is also useful, iirc the max range circle on the B747-400 is 511nm and the max range scale on the ND is 640nm.

This facility is also useful for letting you know when it is your turn for the bunk
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Old 10th Feb 2012, 15:53
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Tonic Please . . .

Imagine London to, say, anywhere about 3 hours away, Eastern Europe-ish. ETP, it seems, would be roughly in the middle, dependant on winds. You could plop in (if it isn't provided automatically which helps) a fix about midway (minus all the complex calculation hoohaa, and simply make a decision there and then?
Why would you need an ETP along a route with airports all around....?
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Old 10th Feb 2012, 16:19
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Very good and clear responses. Thanks yet again.

Valid point re. Europe and airports all round. I guess I was talking about distance rather than geographical location.

I guess my absolutely final question would refer to my RTE2 page question but involves the ETP:

Would you constantly update RTE2 as you go on so that it is related in some way to an ETP? Further, can you update an ETP from a new airfield en-route?

I imagine London to Hong Kong or some such - or Japan to New Zeland/Buenos Aires/Rio kind of flights). Could you 'reset' your ETP (along with a revised RTE2 page) on passing a possible en-route alternate and consider that your new 'base' or 'imaginary departure airfield' for want of a better word?

I hope I make myself clear.

Dan
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Old 10th Feb 2012, 16:20
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Believe me, you want to know where you will go at any point of time should a 'Land ASAP' event happen.
Don't you have a FMC page for that with list of the closest airports? The 737 has, including info on mileage, fuel remaining at destination and a one click weather request for any thus selected airport.

However being able to enter a time directly as waypoint can be pretty useful, sadly we do not have that.

Apart from that the fix pages are a nice tool for whatever you want, be it to draw nice circles in the middle of nowhere or remind one of a fuel check/reporting point or of course an ETP if you happen to need that (never did on the 737 in europe/northern africa/UAE).
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Old 10th Feb 2012, 16:59
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An ETP is only relevant in ETOPs or similar operations. Over Europe, I can't fathom why you'd bother/what value it adds. It's just a distraction and would reduce your SA as you'd probably never bother looking at what suitable airports are around you!

The ETP is important in ETOPs planning (usually the last ETP on a route, if more than one exist, has a fuel requirement associated with it - the Critical Fuel Requirement. We must have enough fuel at this point, on our airfraft type, to depressurise and fly to a suitable alternate, in the prevailing weather, at 10,000', with enough for 15 minutes holding at 1500' overhead).

It's also useful in the air - it gives you an awareness of whether you're carry-on-minded or turn-back-minded in a time-critical scenario over lots of water. We put the lat/long as a 'floating waypoint' on the end of the route so it displays on the ND/HSI.

aerobat77,

A proper ETP, rather than just a 'halfway point' will take in to account the wind.

Hey Denti,

Isn't there a predicted ETA line on your fix pages to put times in? I'm surprised - thought the 737 and 757 FMCs shared a lot of commonality. We don't get the 1-click weather reports though - very decadent!

Cheers!

B&S
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Old 11th Feb 2012, 05:25
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Denti
Don't you have a FMC page for that with list of the closest airports? The 737 has, including info on mileage, fuel remaining at destination and a one click weather request for any thus selected airport.
No!

I remember that FMC page from my days on the 737-400 20 years ago and thought that it was cool, albeit iirc, just giving DTG and fuel on arrival, uncorrected for wind, so not really ETP information.

As I said before, there is also airport opening hours to consider, something not usually an issue in European daytime flying which the majority of it is.
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Old 11th Feb 2012, 08:08
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Very interesting and informative. Thank you to all. I shall now try it out for a tad more realism.

Floating fixes - nice terminology
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Old 11th Feb 2012, 08:37
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Certainly on the A320 there is an ETP page under the DATA menu. You can select any two airports and it will display a ring on the green line at the appropriate point. When I flew in Europe the ETP had little relevance at all due to the abundance of suitable airports everywhere.

Now that I frequently fly across the Pacific 'ETP's' become very, very important. The big difference though is at the flight planning stage ETP's are worked out taking into account, winds, fuel, engine out scenarios, depressurisations etc and a list of ETP's published for your flight in the form of LAT's and LONG's. These are then entered as new waypoints and placed into the flight plan. It is amazing how much these differ from the FMGS calculated position which assumes programmed winds and two engines operating.
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Old 11th Feb 2012, 15:12
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Hi,

May I ask how and who works these out for Pacific flights? What about West Coast to Hawaii?

Thanks
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Old 11th Feb 2012, 15:32
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On The B777 on the FIX pages in the FMC I just enter range rings that correspond to the data supplied on our flight plans....and as if my magic they intercept our track, however ETOPS planning is just an excuse to get airborne, normally in flight any major emergency Fire/Failure etc. our QRH says.."Land at the nearest suitable airport"..this does not mean fly for another 3 hours to a planning airport if a suitable airport is closer, who knows it might nearly be below you!...North Pacific Operations can be a little tricky, I operated out to 207 minutes using say RJCC & PANC with a previous operator and sometimes nothing else was suitable.....
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Old 11th Feb 2012, 15:33
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West coast to the Hawaiian islands require 180 ETOPS. (2 Eng.) If your departing Southern California your ETP airports will usually be KSFO and PHTO but there is always the exception with unusual winds that might bring you back to KLAX. Leaving KSEA or KPDX you would have KPDX as your first ETP alternte and then for a period time KSFO would be the active alternate. Finally PHOG would show up as the final ETP alternate. Again unusual winds can cause these alternate to chnange.

Some Honeywell FMC's will allow you to display the Lat/Long on the FIX page, others will not. You can always build the ETPs on the ROUTE Page 2 in that case. The 737 uses a Smiths FMC so I don't know what works best for that airplane.

Use of a plotting chart is beneficial in plotting both the ETPs along with the ETP entry points.

Last edited by Spooky 2; 11th Feb 2012 at 18:47.
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Old 11th Feb 2012, 18:10
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On the 737 we simply enter EEP, EXP and CP1 in as a temp nav data. I've heard some airlines just put them in as legs after a disco after the dest airport.
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Old 11th Feb 2012, 18:46
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Yes, putting the ETP at the very end of the LEGS page, after a discontinuty works as well.
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Old 13th Feb 2012, 07:53
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All very insightful. Thanks very much!
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Old 13th Feb 2012, 09:32
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Go take the ETP from your Flight Plan. Create a waypoint in the FMC along with the Etops Entry point, and Exit point, insert them in the legs page, have a look in plan mode if it all makes sense, and ready.
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Old 13th Feb 2012, 09:34
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It shows up in the legs and prog page as another waypoint. Do not forward your estimates to ATC though.
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