ETOPS and the ETP
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Waren9
Some B777s have extra Oxygen bottles fitted. I would suggest that the Oxygen time limit would be determined by the number of passengers on board versus the available oxygen.
Some B777s have extra Oxygen bottles fitted. I would suggest that the Oxygen time limit would be determined by the number of passengers on board versus the available oxygen.
Last edited by BGQ; 29th Dec 2013 at 06:19.
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Haughtney the 120/180/240 time is regularly exceeded. The TAS achieved in the critical fuel configuration is most often considerably slower than that used to establish the range circle or area of operation.
For example, the approved TAS for establishing range circles up to 180 mins on a B777-300 is approx 420 kts established at the nominated single engine cruise TAS.
The Critical Fuel scenario is normally ETP1D (single engine depressurised at FL140). The TAS in this configuration is considerably slower than 420kts
This is the most common reason for long diversion times.
As you say wind can also be a factor for exceeding the time.
For example, the approved TAS for establishing range circles up to 180 mins on a B777-300 is approx 420 kts established at the nominated single engine cruise TAS.
The Critical Fuel scenario is normally ETP1D (single engine depressurised at FL140). The TAS in this configuration is considerably slower than 420kts
This is the most common reason for long diversion times.
As you say wind can also be a factor for exceeding the time.
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I cannot verify this but I am informed by a B777 pilot that a standard crew bottle filled to maximum will last a three pilot crew 5 hrs +.
Maybe someone who flies one can verify
Maybe someone who flies one can verify
The Critical Fuel scenario is normally ETP1D (single engine depressurised at FL140)
oh, Scrubber - I quoted the FARs as we'd digressed to show it wasn't an Australianism - and there's an App for them; The rules are pretty much the same and it was much easier than trying to download and search in an appendix to a CAO in commlaw. CASA
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In that case...
CS,
In that case, you (and the App) might be able to clarify something for me about O2 limitations.
From memory, the FARs allow the pax to be carted around DP at F140 without O2 (15-25 min OBOGS) but not FAs, who have to be supplied with O2 after 30 mins between F100 and F125 or at all times above F125 - is that still the case?
If it is, then I also believe that the FA O2 supply would be additional to the first aid oxy which is for the pax rather than the crew. My understanding is that first aid oxygen is like contingency fuel, in that you can't plan to use it for other than its primary purpose.
If all of that is true, do you know how operators carry enough O2 down the back to make the famous "DP @ F140" scenario work?
[I think those operators would be non-EU, since I think they state quite plainly that the DP scenario is at F100/10K']
In that case, you (and the App) might be able to clarify something for me about O2 limitations.
From memory, the FARs allow the pax to be carted around DP at F140 without O2 (15-25 min OBOGS) but not FAs, who have to be supplied with O2 after 30 mins between F100 and F125 or at all times above F125 - is that still the case?
If it is, then I also believe that the FA O2 supply would be additional to the first aid oxy which is for the pax rather than the crew. My understanding is that first aid oxygen is like contingency fuel, in that you can't plan to use it for other than its primary purpose.
If all of that is true, do you know how operators carry enough O2 down the back to make the famous "DP @ F140" scenario work?
[I think those operators would be non-EU, since I think they state quite plainly that the DP scenario is at F100/10K']
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Here's one for new year.
Should you be at right angles to your track for it to be the CP?
How long at normal or S/E cruise at high altitude does it take to turn around??
Allow for a clearance, track incursions in crowded areas.
Where is the REAL CP?????
How much fun to fill in the cruise time to work that out so at the questions which will be asked in the event of.....
You can say "that's why I did>>>>>"
Happy new year if you can.
Should you be at right angles to your track for it to be the CP?
How long at normal or S/E cruise at high altitude does it take to turn around??
Allow for a clearance, track incursions in crowded areas.
Where is the REAL CP?????
How much fun to fill in the cruise time to work that out so at the questions which will be asked in the event of.....
You can say "that's why I did>>>>>"
Happy new year if you can.
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Firstly, oxygen is not an EDTO critical system. Obstacle clearance driftdown, escape routes, and oxygen endurance is a separate issue.
Secondly, the EDTO area is defined by the most limiting of the two cases, not the least limiting. For twin-engined aircraft, the most limiting area is usually the single-engined second case. For quad-engined aircraft, the most limiting area is usually the fire suppression first case. A 777 will not be 4+ hours from an available adequate airport, but a 747 might be.
Greybeard, the CP is a preflight calculation based on - largely arbitrary - data and regulations. The PNR is the inflight case based on what you calculate on the spot factoring in all your questions and decisions (what is actually happening).
Happy New Year!
Secondly, the EDTO area is defined by the most limiting of the two cases, not the least limiting. For twin-engined aircraft, the most limiting area is usually the single-engined second case. For quad-engined aircraft, the most limiting area is usually the fire suppression first case. A 777 will not be 4+ hours from an available adequate airport, but a 747 might be.
Greybeard, the CP is a preflight calculation based on - largely arbitrary - data and regulations. The PNR is the inflight case based on what you calculate on the spot factoring in all your questions and decisions (what is actually happening).
Happy New Year!
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separate issue
Hey *Lancer*:
How separate? I would have thought that those issues were a subsequent filter on the overall EDTO route assessment, once the time/distance constraints were identified. 
Firstly, oxygen is not an EDTO critical system. Obstacle clearance driftdown, escape routes, and oxygen endurance is a separate issue.
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Scrubba, for what purpose? There are minimum O2 quantities required for dispatch depending on crew/pax numbers, but only to facilitate descent to 10000'. Oxygen limited routes require more O2 simply because it takes longer to get to 10000' due to terrain.
Sure surplus oxygen may allow a different (to the flight-planned) driftdown/diversion strategy to conserve fuel, but this is an inflight consideration. O2 quantity isn't varied preflight to allow a reduction in fuel burn when CPD limited - more fuel is carried!
Sure surplus oxygen may allow a different (to the flight-planned) driftdown/diversion strategy to conserve fuel, but this is an inflight consideration. O2 quantity isn't varied preflight to allow a reduction in fuel burn when CPD limited - more fuel is carried!
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Oxygen can be limiting in a two engine aircraft.... HKG-LHR would be a case in point.
There is a requirement for pax oxygen at FL140 but not at 10000ft.
It is up to the operator whether they carry the Oxygen for FL140 or just for descent to 10,000.
Clearly if terrain requirements necessitate the use of Oygen it must be considered.
There is a requirement for pax oxygen at FL140 but not at 10000ft.
It is up to the operator whether they carry the Oxygen for FL140 or just for descent to 10,000.
Clearly if terrain requirements necessitate the use of Oygen it must be considered.
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There is a requirement for fixed pax oxygen above 14000, and supplementary pax oxygen above 10000.
O2 quantity is definitely considered in FCOM/DDG, route requirements and design (L888 for example). If an operator wants to reduce CPD fuel and standardise diversions at 14000 to the limit of crew oxygen endurance, it will be based on a set minimum dispatch quantity (specified in FCOM/DDG).
In any case, it does not alter the EDTO area, it is considered separately. Happy to be corrected if I'm missing something!
O2 quantity is definitely considered in FCOM/DDG, route requirements and design (L888 for example). If an operator wants to reduce CPD fuel and standardise diversions at 14000 to the limit of crew oxygen endurance, it will be based on a set minimum dispatch quantity (specified in FCOM/DDG).
In any case, it does not alter the EDTO area, it is considered separately. Happy to be corrected if I'm missing something!
Last edited by *Lancer*; 3rd Jan 2014 at 05:09.
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flight attendant o2
Compressor stall or Lancer,
Understand that the EDTO area is unrelated to O2 in the first instance. But on the day, can you launch knowing that you have insufficient O2 on board to cover your contingency planning?
I think that was what raised the question about continuing depressurised at FL140 provided you had sufficient flight crew O2. I think the question that has been ignored is what O2 do the FAs need at FL140?
Understand that the EDTO area is unrelated to O2 in the first instance. But on the day, can you launch knowing that you have insufficient O2 on board to cover your contingency planning?
I think that was what raised the question about continuing depressurised at FL140 provided you had sufficient flight crew O2. I think the question that has been ignored is what O2 do the FAs need at FL140?
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Prince Niccolo,
No you can't launch with less oxygen than what is required for dispatch.
At 14000' the FAs have access to portable oxygen bottles (supplementary oxygen) in accordance with CAO 20.4 8.6. The number of bottles available is determined by 8.8.
No you can't launch with less oxygen than what is required for dispatch.
At 14000' the FAs have access to portable oxygen bottles (supplementary oxygen) in accordance with CAO 20.4 8.6. The number of bottles available is determined by 8.8.
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now I'm confused
*Lancer*,
Serves me right for trying to clarify someone else's questions
So, we agree that you can't launch with less O2 than required for your plan.
We most certainly do not agree on the relationship between paragraphs 8.6 and 8.8 of CAO 20.4
You said:
First, for the EDTO ops under discussion, the normal supplemental O2 is provided by plumbed in O2 bottles or OBOGS designed to cater for the depressurised descent to a cabin altitude of 10K', where after it is not required. Your basic OBOGS provides 15 minutes and most gaseous O2 tables tell you how much you need to provided the 10 mins for the pax, with the FAs generally being covered the same way. Keeping First Aid O2 out of it (it is a mutually exclusive requirement with a totally different flow rate specified), there are generally no portable O2 bottles on board. So a decision to fly a DP diversion above 10K' would require a conscious decision to add portable bottles suitable for the purpose.
Second, paragraph 8.8 is titled "Supplemental oxygen for passengers" and it is quite separate and distinct from the requirement set out in paragraph 8.6 which is titled "Supplemental oxygen for other crew members".
Now, for me the conundrum is this: how do you calculate the requirements of subparagraph 8.6(a), should you plan a DP diversion at FL139.99?
Unlike subparagraphs 8.6(b), 8.8(a)(i), 8.8(a)(ii) and 8.8(b) which are easily calculated, how much is enough when you merely need to provide a supply?
Serves me right for trying to clarify someone else's questions
So, we agree that you can't launch with less O2 than required for your plan.
We most certainly do not agree on the relationship between paragraphs 8.6 and 8.8 of CAO 20.4
You said:
At 14000' the FAs have access to portable oxygen bottles (supplementary oxygen) in accordance with CAO 20.4 8.6. The number of bottles available is determined by 8.8.
Second, paragraph 8.8 is titled "Supplemental oxygen for passengers" and it is quite separate and distinct from the requirement set out in paragraph 8.6 which is titled "Supplemental oxygen for other crew members".
Now, for me the conundrum is this: how do you calculate the requirements of subparagraph 8.6(a), should you plan a DP diversion at FL139.99?
Unlike subparagraphs 8.6(b), 8.8(a)(i), 8.8(a)(ii) and 8.8(b) which are easily calculated, how much is enough when you merely need to provide a supply?
Last edited by Prince Niccolo M; 6th Jan 2014 at 09:02.
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Prince, I can assure you that supplemental oxygen is absolutely provided by portable oxygen bottles on many airliners (e.g. 767, 737, a320). Their fixed oxygen system is chemicallly generated and not capable of extended use. Aircraft with bottled emergency oxygen (e.g. 747, a380) still carry supplementary portable bottles.
Preflight, 'enough' supplementary oxygen is defined by the manufacturer, whereby the DDG may allow a reduction in accordance with the CAO 20.4 8.8 limit. Post dispatch, flight at 14000' is only limited by flight deck crew oxygen endurance. Bit of a thread drift, happy to chat over PM!
Preflight, 'enough' supplementary oxygen is defined by the manufacturer, whereby the DDG may allow a reduction in accordance with the CAO 20.4 8.8 limit. Post dispatch, flight at 14000' is only limited by flight deck crew oxygen endurance. Bit of a thread drift, happy to chat over PM!
Last edited by *Lancer*; 6th Jan 2014 at 16:19.
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Lancer,
Not all airliners use Oxygen generators for passenger Oxygen. Those that do would have to carry supplemental oxygen for flight at 14000.
Oxygen can be a limiting system on some routes. One operator ensures there is enough passenger O2 prior to departure for 4 hours flight at 14000. In terms of EDTO beyond 180 they assume flight beyond 3 hours 45 will be at 10000ft (4:00 hrs minus 15 mins)
Not all airliners use Oxygen generators for passenger Oxygen. Those that do would have to carry supplemental oxygen for flight at 14000.
Oxygen can be a limiting system on some routes. One operator ensures there is enough passenger O2 prior to departure for 4 hours flight at 14000. In terms of EDTO beyond 180 they assume flight beyond 3 hours 45 will be at 10000ft (4:00 hrs minus 15 mins)
