ETOPS divert speed

[737ngpilot]

.

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.

[tbaylx]

The ETOPS speed is only for planning purposes. In an actual diversion you can fly whatever speed you think is best given the situation.

[737ngpilot]

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

[BOAC]

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.

[Henry VIII]

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.

[FE Hoppy]

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.

[BOAC]

you always WILL run out of fuel - did someone say that?

[DFC]

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!!!

[Sir George Cayley]

Have I read somewhere, or did I hear that ETOPS is to be renamed EROPS?

The R standing for Range.

Sir George Cayley

[FE Hoppy]

Quote:
Originally Posted by FE hoppy
you always WILL run out of fuel

- did someone say that?

Yes me.:ok:

Chill out man.

[Grasscarp]

It is talked about becoming LROPS - Long Range Operations - and applying to 3 and 4 engined aircraft. This is still at the discussion stage.

[Spooky 2]

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.

[737ngpilot]

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

[Pugilistic Animus]

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

[Spooky 2]

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.

[BOAC]

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.

[Spooky 2]

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:confused:

Spooky

[DFC]

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.

[vapilot2004]

Mister Spooks, try linking the original source rather than uploading it. :ok:

There's a good publication from Airbus on this too.

[Spooky 2]

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.

[737ngpilot]

Thanks for all the valuable info.
Spooky 2 is there a link or ref. where you got your file.

[BOAC]

I'm not sure how up-to-date this is, but Smartcockpit has the Airbus ETOPS pdf (http://www.smartcockpit.com/pdf/flightops/navigation/1)(18.8MB) and also has a bit on ETOPS/LROPS changes

[737ngpilot]

BOAC... Thats a great link.... The best info so far.... Thank you

[Spooky 2]

No linky. Just have acess to certain stuff!

[737ngpilot]

OK...here we go again...my flight ops tell me that on 737-800 all our divert scenarios are based on LCR with 1185NM 180 ETOPS. To me this does not seem realistic. Where am I going wrong here.
My understanding is the circles are depended on the divert speed .
Obviously with LRC the speed varies with wight and how many engines are turning.
We are told to fly the FMC at all times.

[A Comfy Chair]

The planned divert scenarios are just that... planned. An arbitrary speed is chosen, and for simplicity is turned into a distance based on still air. That distance is what is used on all your charts to draw the circles etc. It is usually not realistic to what you would do in real life, with most operators basing it on a very fast speed (to give bigger circles).

If, in real life, you have an ETOPS failure then you fly whatever speed YOU deem best (which is likely to be FMC speed). You do not have to be on the ground within 180mins.

[bucker1973]

As you said the operators will use a very fast speed to give bigger circles. My flight ops use the Vmo=0.82 (737-800)
This is not very realistic because it should be a speed based upon the true airspeed that the aeroplane can maintain with one engine inoperative (EU-OPS 1245 b). But the thing is that I don´t know where to find a performance chart to determine the one engine maximum cruise speed.
Thanks for the help!!

[waren9]

bucker1973

Dont confuse Mmo with Vmo.

Both of these speeds (Mach No. and IAS) will be nominated and promulgated by your company to derive the range circles.

I would say that your aircraft is indeed quite capable of drifting down at Mmo and MCT on the live engine untill you reach the nominated diversion IAS. That may or may not be Vmo.

Whether or not the Captain elects to fly that fast is quite another matter. But if these speeds are nominated to achieve the desired range circles then the fuel to fly at those speeds must be carried.

[Mansfield]

There is of course a direct relationship between the engine-out divert speed and the altitude you are able to maintain. The faster you fly, the lower will be the maximum single engine altitude. Boeing applies some pretty hefty icing penalties in the performance manual. It is quite possible in the 767/757 fleets, if the TAT falls within the correct range, to have a published single engine capability of less than 10000 feet at higher divert speeds after the icing penalties are applied.

So one question worth considering is the temperature/moisture content at the diversion altitudes and the obstacle clearance requirements. A higher diversion speed results in a higher TAT but a lower altitude; the inverse may be a more desirable option in some cases.

[Jim Croche]

BOAC,

I would suggest that you're not entirely correct. The worst case is Depressurisation plus Engine Failure is it not?

For all the others, yes you can divert at any speed you like but as BOAC says don't run out of fuel. You can also divert to any alternate you wish - not necessarily the planned ETOPS ones. And your actual divert time may well be greater than the ETOPS time that your company has approved. Remember, in most cases the normal fuel covers the ETOPS requirements as well.

The "Getting to Grips with ETOPS" document is an excellent guide as are all the GTG books - regardless of what aircraft you fly in this case. (never thought I'd compliment an Airbus Manual!!)

[Spooky 2]

The Critical Fuel Scenario is usually a loss of one engine and a descent to 10,000'. But....some airframe engine combinations give less favorable fuel specifics with both engines operating and LRC at 10,000', than with 1EO. A case in point is the B767-200ER with the JT9D. Your actually a little worse off with both engines running at 10,000' than with only 1EO.

[737ngpilot]

I know for our ops, 2 engine divert depress is the worst case scenario

[BOAC]

Jim C - it's a complicated world! I don't think we ever plan for that 'double emergency' you quote. In addition, it is often the case (depending on engine design) that the higher RPM with a single engine may produce a more efficient engine than 2 running at cruise RPM.

It is worth everyone remembering that the whole ETOPS planning thing is just that - a 'thing' used to generate circles on a map you stay inside. What you do when 'it' happens is, as we are all saying, down to that well-worn 'airmanship' thing.

If bucker's regulatory authority have approved Mmo so be it - look on the bright side - at least bucker will be 'up' on fuel if he/she flies at more normal speeds on the divert:)

[FE Hoppy]

The nice thing about planning VMO/MMO is you will have buckets of fuel as BOAC states. Remember that the additional fuel is to ensure you have the correct fuel at the crit point, and that fuel is based on your ETOPS divert speed.

On the down side you may have other systems that are more limiting than the fuel. For example a low rate fire suppresion system in your cargo compartement. It only needs to cover your diversion time. So if you planned to divert at MMO but choose to divert more slowly you could be inflight longer than your suppresion system lasts.

[BOAC]

I reckon I'd be at LEAST Vmo:)

[B737NG_man]

hi all....in my airline, we've got the divert speed at 214kts for dispatch calculations for a 120 min ETOPs flight on a B737 800W. Ofcourse, if you actually divert, it's at your choice of speed depending upon the situation. Isn't that the way it is supposed to be?

[737ngpilot]

Where did the 214 come from....your EAO will not be very large.....Where do you operate

[PappyJ]

From somewhere in the Annex's...


In-flight, where real circumstances vary from the plan, the captain must evaluate the situation and take the most appropriate course of action dictated by the changed circumstances.

This may well include revised speeds or alternate(s) other those used at the planning stage.

[9.G]

OK...here we go again...my flight ops tell me that on 737-800 all our divert scenarios are based on LCR with 1185NM 180 ETOPS. To me this does not seem realistic. Where am I going wrong here. Circles are simply drawn using declared speed usually VMO MMO. It seems you're somewhat confused about usage of LRC which is part of FUEL planning as follows:
-One engine inoperative (1E) based on the following speed like .82/330 for A 330
-Decompression with One engine inoperative (1D) based on Long Range Speed (LRC).
-Decompression with Two engine operative (2D) based on Long Range Speed (LRC).

For dispatching an aircraft for an ETOPS flight, the ETOPS dispatcher must determine, for the considered route, both a standard and an ETOPS fuel planning. The highest of the two fuel requirements shall be considered as being the minimum required block fuel for the flight.
For ETOPS operations, a specific fuel planning (Critical Fuel Reserve) shall be established.
The ETOPS fuel planning is split into two parts :
– A standard fuel scenario from the departure aerodrome to the Critical Point, and
– The critical fuel scenario from the Critical Point to the diversion aerodrome

Once again it's the highest of the two for planing purposes in regards to the fuel calculation.

Once airborne it's the famous '' cancel all after good morning and do whatever is safe and suits your need best'' :ok:

[None]

There have been many good comments on the speed to fly. I would like to offer another for the aircraft I fly.

For the 767-300ER that I fly, I am not able to provide engine anti-ice for the inop engine.

This means if I am flying at Vmo at FL 210 in the clouds, I might be adding a bit of complexity to the event (increasing ice accumulation). If I am able to remain on-top of the clouds at FL270 by flying the FMS engine out speed, then I would certainly take that as an option.

[BOAC]

I am not able to provide engine anti-ice for the inop engine. - why would you want to?