ETOPS divert speed
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ETOPS divert speed
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Are you required to fly the divert speed and make the ETOPS alternate for lets say 120 ETOPS in 2 hours from the ETP/CP or is that only for planning. I see that the worst case scenario out of 3( decompression and engine fail, decompression, and engine fail) is decompression and 2 engines running to alternate.
Why would you burn all that extra fuel for a few minutes earlier.
Are you required to fly the divert speed and make the ETOPS alternate for lets say 120 ETOPS in 2 hours from the ETP/CP or is that only for planning. I see that the worst case scenario out of 3( decompression and engine fail, decompression, and engine fail) is decompression and 2 engines running to alternate.
Why would you burn all that extra fuel for a few minutes earlier.
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tbaylx, Thanks
Then why wouldn't everybody plan to use max divert speed to cover a bigger distance. It appears to me that the distance is different or at least not the same at different airlines. Why would that be.
Is there a reference somewhere that this is for planning only
Then why wouldn't everybody plan to use max divert speed to cover a bigger distance. It appears to me that the distance is different or at least not the same at different airlines. Why would that be.
Is there a reference somewhere that this is for planning only
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If you use a 'divert speed' other than that used for your fuel calculations (which will probably be a good compromise on range/consumption), you might just run out of fuel - simples? Now, should you have an engine failure rather than a depressurisation, it may indeed be that you can safely go a lot faster. That is for you to decide given the info you have in front of you.
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Manufacturers provide tables where to find max 60 minutes distance and max distance in ETOPS environment according to different weights, speed schedule and FL.
Company chooses the worst scenario according it's routing and obtain max planning distance in NM.
Company chooses the worst scenario according it's routing and obtain max planning distance in NM.
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The speed used depends on the route requirements. I may need the greatest distance out of my diversion speed (max) or I may need the lowest fuel requirement (LRC) or there may be other considerations.
Consider a route where the ETP between en-route alternates is at a distance equal to max speed for two hours (ETOPS120 example). Then I have to plan using max speed and start with enough fuel to go to the crit point then divert at max speed.
It may be that if I divert from the same point at LRC I will arrive with more fuel but the diversion will take more than 120 minutes.
So it's not true to say that if you divert at a different speed you always WILL run out of fuel.
However, If your ETOPS distance was based on LRC and you divert with a different speed then you better use the correct speed!
Best bet is to have an idea about your routes and the speeds your company has chosen because it can be completely different from route to route as well as airline to airline.
Consider a route where the ETP between en-route alternates is at a distance equal to max speed for two hours (ETOPS120 example). Then I have to plan using max speed and start with enough fuel to go to the crit point then divert at max speed.
It may be that if I divert from the same point at LRC I will arrive with more fuel but the diversion will take more than 120 minutes.
So it's not true to say that if you divert at a different speed you always WILL run out of fuel.
However, If your ETOPS distance was based on LRC and you divert with a different speed then you better use the correct speed!
Best bet is to have an idea about your routes and the speeds your company has chosen because it can be completely different from route to route as well as airline to airline.
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The threshold time is based on still air and OEI TAS (but not to exceed Vmo. The speed and the distance are to be specified in the OM.
The whole thing is a statistical safety issue i.e. if you have an engine failure what is the probability of having another fail in the following 60, 120 or 180 minutes - set maximum time to acheive required probability of safety.
Having the fuel to divert / continue is a totally separate issue and at planning based on expected conditions i.e. you could find that due to the winds you can not operate at the full 180min ETOPs distance from an alternate and have to route closer or with the winds in the opposite direction you could find that at the max distance you need less fuel than normal thanks to a big tailwind.
So the threshold time is a statistical issue. Having the required fuel to divert from the ETP is a survival issue!!!
The whole thing is a statistical safety issue i.e. if you have an engine failure what is the probability of having another fail in the following 60, 120 or 180 minutes - set maximum time to acheive required probability of safety.
Having the fuel to divert / continue is a totally separate issue and at planning based on expected conditions i.e. you could find that due to the winds you can not operate at the full 180min ETOPs distance from an alternate and have to route closer or with the winds in the opposite direction you could find that at the max distance you need less fuel than normal thanks to a big tailwind.
So the threshold time is a statistical issue. Having the required fuel to divert from the ETP is a survival issue!!!
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This is beyond the discusion stage. Take a look at AC120-42B and you will see 3 and 4 engine aircraft are now included while operating in some regions such as polar and south polar regions. Chapt. 6 is a good reference point.
Last edited by Spooky 2; 27th Nov 2009 at 14:58.
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Am I to conclude that whatever your divert speed is, that is the speed you will have to keep to the alternate from you ETP. I am still confused if it is for planning or for real
Well in the USA the time planning is based on the OEI or depressurized still air flying time ..
but fuel planning takes into account wind with different increases for both forecast or actual winds that reduce tailwind and increase HW. fuel for deterioration of the engine, fuel for general errors but the flying TIME is based on the still air condition
but fuel must be carried for the actual conditions with extra fat,..that but may be greater than the still air time for a TW back does not entirely erase the effects of the HW out and vice versa...I think that section is can be a little confusing
and the AC is also a bit wordy,..but I learned it best to read the FARS very 'face value' likewise the advisory circulars should be read in conjuction with the FARS
PA
but fuel planning takes into account wind with different increases for both forecast or actual winds that reduce tailwind and increase HW. fuel for deterioration of the engine, fuel for general errors but the flying TIME is based on the still air condition
but fuel must be carried for the actual conditions with extra fat,..that but may be greater than the still air time for a TW back does not entirely erase the effects of the HW out and vice versa...I think that section is can be a little confusing
and the AC is also a bit wordy,..but I learned it best to read the FARS very 'face value' likewise the advisory circulars should be read in conjuction with the FARSPA
Last edited by Pugilistic Animus; 27th Nov 2009 at 17:29.
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If there is way to attach a PDF file a post I will send you a Boeing (Non Proprietery) document on ETOPS. It covers just about all operational issues one could ever imagine. Well written and an excellent source of information. Otherwise, send me a pm with your email address on it.
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NO, 737ng - you can fly any speed you are able. It is entirely down to the Captain.
If, however, you either run out of fuel going flat out or alternatively spend so long in the air that your cargo hold fire burns through the floor then you will look a little foolish. Have a look at my post #4 again?
It is purely for planning BUT that is the speed for which your planning programme calculated the CP fuel requirement. Remember also that is for the 'worst case' diversion - ie highest fuel requirement - which is depressurised.
If, however, you either run out of fuel going flat out or alternatively spend so long in the air that your cargo hold fire burns through the floor then you will look a little foolish. Have a look at my post #4 again?
It is purely for planning BUT that is the speed for which your planning programme calculated the CP fuel requirement. Remember also that is for the 'worst case' diversion - ie highest fuel requirement - which is depressurised.
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ETOPS attachment
Gents and ladies as well,
I'm having problems sending this attachment via Gmail. It's a 13,749.00K PDF file so I would think it should go through but so far no luck. Not sure how to break it into smaller bites
Spooky
I'm having problems sending this attachment via Gmail. It's a 13,749.00K PDF file so I would think it should go through but so far no luck. Not sure how to break it into smaller bites
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I'll try to explain again.
The rules require that the aircraft be a maximum of xxx minutes from either departure, destination or alternate.
This time is a statistical based figure. It can be longer if one can comply with certain requirements / have reliable equipment and procedures etc.
Having set the time with the authority, then in order to draw some circles on a map, a speed must be used. Clearly the higher the speed then the bigger the circles. The rules limit the maximum speed that can be used. The speed used must be shown in the ops manual.
So we have our chart with some circles. The position of the aircraft can never be at a place that is outside of all the circles drawn. i.e. one can end up with no-fly zones.
---------- end of that issue---------
When it comes to the pratical operation of the flight then the flight will be planned based on not just the winds and OAT but also the payload and MEL issues. The route will never be through the no fly zone mentioned above. However, the enroute alternates will be selected to provide for the aircraft to arrive at the alternate in the expected conditions with the required fuel reserves when the aircraft is diverted from the ETP.
There will be several ETPs and the operational flight plan will show how the fuel is calculated when flying from the ETP to each of the alternates. This will include winds, level, TAS/Mn and usually fuelflow/eng etc.
If conditions are as expected then fly as per the operational flight plan and you will (should) arrive at the alternate with the expected fuel reserves.
If conditions are different then make adjustments to arrive at the alternate safely or fly to a different alternate (the ETP may have moved if the conditions are different).
---------------
So I hope that you can see that there is the statistical calculation that determines if ther are some no-fly zones / the size of those zones. Separate to that is the practical operation of the flight which is no different from any other flight with enroute alternates.
The rules require that the aircraft be a maximum of xxx minutes from either departure, destination or alternate.
This time is a statistical based figure. It can be longer if one can comply with certain requirements / have reliable equipment and procedures etc.
Having set the time with the authority, then in order to draw some circles on a map, a speed must be used. Clearly the higher the speed then the bigger the circles. The rules limit the maximum speed that can be used. The speed used must be shown in the ops manual.
So we have our chart with some circles. The position of the aircraft can never be at a place that is outside of all the circles drawn. i.e. one can end up with no-fly zones.
---------- end of that issue---------
When it comes to the pratical operation of the flight then the flight will be planned based on not just the winds and OAT but also the payload and MEL issues. The route will never be through the no fly zone mentioned above. However, the enroute alternates will be selected to provide for the aircraft to arrive at the alternate in the expected conditions with the required fuel reserves when the aircraft is diverted from the ETP.
There will be several ETPs and the operational flight plan will show how the fuel is calculated when flying from the ETP to each of the alternates. This will include winds, level, TAS/Mn and usually fuelflow/eng etc.
If conditions are as expected then fly as per the operational flight plan and you will (should) arrive at the alternate with the expected fuel reserves.
If conditions are different then make adjustments to arrive at the alternate safely or fly to a different alternate (the ETP may have moved if the conditions are different).
---------------
So I hope that you can see that there is the statistical calculation that determines if ther are some no-fly zones / the size of those zones. Separate to that is the practical operation of the flight which is no different from any other flight with enroute alternates.
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Well I may not understand you advice. The document is on my desk top as it was downloaded from a Boeing source for which I do not have access to at this moment. Boeing is eager to share ETOPS information so I'm surprised it's not directly available from a source such as Google. Obviously My Boeing Fleet would be a source but that is propietary in nature. The best I can offer is to wait until next week when I can do further checking.