ETOPS calculations.
 

Hello there,

I have a question regarding the critical fuel scenarios with the etops calculations.

When the single engine speed has been determined for example TAS of 340 kts. Do the critical fuel scenarios have to be calculated with this speed or is this speed only of use to determine the range? For example 120 min so the range rings will be 680nm.

Any help on the subject is very much appreciated.
Or any directions on where to find it.

Thanks:confused::confused:

Not sure, but this is something I use at work for rough planning...

Great Circle Mapper


The blue hyperlinks off the ETOPs rule/time section should give you some guidance.

Hope its of some help.

If you plan your range circles at a certain TAS, you must also carry the fuel to achieve that TAS, with minimum reserves at landing.

Whether or not the crew elect to fly at that speed is another matter.

If this amount of fuel is not carried then they must fly slower and then by definition could be outside the 120min (or whatever) approval. Remember, an ETOPS requirement is to be within a certain time of an adequate airport, not a certain distance.

......in still air..........

There are two conditions:
1) ETOPS Route validation. It means the route must be within the circles with centers on adequate airports and calculated according to the single engine approved speed per time (still air).

2) Fuel critical scenario. It must include the engine out fuel calculation plus decompression, emergency descent fl100 etc... and consider the higher fuel.
Normally the planning system would use a IAS (costant value), to be then converted in TAS at 10.000ft (then you would see a critical fuel scenario showing different TAS).

Just to ezxpand on vipero's post - the critical fuel calculation DOES have to allow for wind effect - as in normal route/div fuel planning, whereas as stated, the route planning does not (as long, of course, as the actual limiting critical fuel requirement can be achieved on the planned route)..