ETOPS divert speed
Per Ardua ad Astraeus
Joined: Mar 2000
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From: UK
I'm not sure how up-to-date this is, but Smartcockpit has the Airbus ETOPS pdf (18.8MB) and also has a bit on ETOPS/LROPS changes
Thread Starter
Joined: Aug 2007
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From: USA
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.
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.
Joined: Dec 2001
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From: Somewhere over the rainbow
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.
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.
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From: madrid
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!!
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!!
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From: south pacific vagrant
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.
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.
Joined: Jan 2007
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From: Vermont
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.
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.
Joined: Jun 2009
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From: U.K.
ETOPS
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!!)
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!!)
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From: USofA
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.
Per Ardua ad Astraeus
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From: UK
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
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
Joined: Sep 1998
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From: wherever
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.
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.
Joined: Jan 2010
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From: Earth
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?
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From: South of N90º00'.0
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.
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From: paradise
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.
-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''
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From: West
Why different speeds?
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.
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.