EDTO Calculation seems wrong?

SimBrief Feature Requests
1

Hi guys,

First of all thank you for all your work, SimBrief and Charts are simply fantastic.

I just wanted to report (I don’t know if it can be a feature request actually) that EDTO calculation seems wrong for me. I will explain:

  1. First of all SimBrief reports the EDTO section as ETOPS, I know it still exists the name but due to the new ICAO Annex would you change the name to EDTO for more realism as it is already widely known as EDTO? If possible, otherwise no problem.

  2. I want to explain according to our manual how the EDTO dispatch is done basing my words on SimBrief Tools:

So SimBrief has a section for ETOPS, and it can calculate entry, exit airports and different alternates. All good with that. Where is the problem?

It does not consider that:

Entry aerodrome = Departure aerodrome
Exit Aerodrome = Destination Aerodrome
Alternate 1 = Departure Aerodrome
Alternate 2 = Suitable Aerodrome in range
Alternate 3 = Suitable Aerodrome in range
Alternate 4…. And so on and…
Alternate X (last one) = Destination Aerodrome

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This is in our manual

And this is how the real rule is applied to Simbrief

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You can see all the ETPs.

But if I let Simbrief do it:

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Sometimes it calculates EDTO only for a part of the route, where it thinks you are away from a suitable aerodrome and you need them. Example

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Just the part from Alaska to Japan is considered with a mess of range rings and only one ETP. Consider it is a Toronto - Taipei.

Strangely ETOPS Fuel is 0.

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This is the Critical Fuel (0032 min) with the EDTO Rule I explained above:

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32 min more or less realistic.

Again, I am talking about what I could see in our OFPs and EDTO manual in real life. In the manual it’s stated how it should be dispatched (according to the list above).

Of course due to this “glitch” in SimBrief, the critical fuel (SimBrief calls it ETOPS Fuel, can you change this?) it’s always around 1 or 2 hours, that is huge amount of fuel.

CF is normally around 18/30 min maximum as far as I could see.

Also due to this wrong calculations (in my opinion) SimBrief generates always ONE ETP very close to the entry sometimes with range rings really close together and unrealistic.

Of course I can override manually and I normally do and so 3 ETP and sometimes 4 are generated and the CF gets to normal values of 15 to 35 min.

I am wandering if you can have a look to this and you can maybe change that. I don’t know if anyone agrees with this, I just report that with the knowledge of our operations IRL amd our manuals of EDTO OPS.

Let me know,

Best Regards!

2

While yes the ICAO term of art is EDTO, US FAR 121 operators and other operators worldwide may still refer to it as ETOPS as that is how their manuals are written, and we arent going to go through the expense to change just one word in the manual system absent a directive from our regulator.

You can always change your entry/exit airports and airport scenarios to more of what you would be expecting. But I don’t think your ETOPS speeds are adjustable however which can absolutely drive the total fuel required. For example, almost all US 121 operators will plan their ETOPS speeds between the US Mainland and Hawaii at a slower planning speed than say across the NAT to either reduce or eliminate ETOPS buildup fuel; those flights off the US West Coast are almost always less than 6 hours long where an alternate isn’t required 24/7/365, and how often do you require an alternate in Hawaii due to weather - very rarely.

Consider these two ETOPS analyses for a 763 OAK-HNL. At the faster ETOPS speed (1EO350, 350 KIAS), the required fuel at brake release is 72.4 with 6.9 ETOPS ADD fuel. We have 67.3 required fuel at the slower ETOPS speed (with the most critical scenario being AE LRC down at 10K) with 2.9 ETOPS ADD fuel, both with Hawaii alternate none. We’re keeping 5.1 off the airplane by planning the ETOPS scenarios at a slower speed, solely between the US West Coast and Hawaii.

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1 Like
3

Thanks dougsnow,

So you are saying that the ETOPS section of Simbrief is based only on US FAR 121?

As regards the speed for the B777-300ER we have:

0.84M / 320 KIAS

Distances based on this:

60 minutes / 439 nm

120 minutes / 865 nm

180 minutes / 1291 nm

207 minutes / 1483 nm

4

No, but each operator uses different speeds, and different radii, even for the same airplane make and model. And other worldwide operators still refer to it as ETOPS, not just us in the 121 world.

5

And which speeds is Simbriefing using by default?

6

SimBrief uses the speeds and distances you posted above for the B777-300ER: 320 IAS.

Perhaps in a little more time. EDTO is not yet widely known in the simulator community, ETOPS is still a much more recognizable term.

Regarding your whole ETOPS/EDTO scenario example, I think you are making some assumptions that are not correct:

Nowhere is this formula required by regulation. It might make sense for your operator if you only fly certain ETOPS routes, but they are not obligated to plan it this way:

  1. There is no requirement for the departure/arrival airports to be the ETOPS entry/exit. In fact, this makes no sense for a route from KDEN to EGLL for example, where you do not reach the Atlantic ocean until many hours after departure.
  2. There is no requirement for the entry/exit airports to also be designated as ETOPS suitable/alternate airports, in fact this is normally suboptimal from a fuel planning perspective (see below).
  3. ETOPS/critical fuel is only required if the fuel needed to divert from the most critical point to a suitable airport exceeds the amount of fuel you would normally have on board at that point. By always considering the arrival airport as both the ETOPS exit and last ETOPS alternate, you are basically guaranteeing that you will need additional ETOPS fuel, since a depressurization/failure from the last ETP to the arrival airport will certainly require more fuel than a normal flight profile would. This is very inefficient, and most dispatchers will instead try to choose a different scenario to minimize/reduce the amount of ETOPS/critical fuel required.

Of course, if the airline you are simulating always plans their ETOPS flights this way, then you are free to manually set SimBrief’s ETOPS options to match. But I do not agree that SimBrief should plan it this way by default, in fact the vast majority of airlines I have seen do not plan ETOPS this way.

Best regards,

1 Like
7

All clear, thank you!

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