ETOPS / EDTO and the 747-400

[Will]

I've put ETOPS, EROPS, EDTO, and other search terms into these forums as well as over on the PFPX support hub, and I looked on Wikipedia and in Google, and read and digested what I could. I'd like to summarize what I understand here, and hopefully get corrections from the community if I've gotten anything wrong.

1. ETOPS used to stand for "Extended Twin Engine Operations" and was a set of criteria that a twin could follow that would allow it to fly farther away from enroute airports than it otherwise could. The acronym was later revised to mean "Extended Operations," and the rules were extended to apply to aircraft with more than two engines. Most recently, the phrase ETOPS has been replaced with EDTO, "Extended Diversion Time Operations," and comes with rules for all aircraft with at least two engines.

2. Aircraft have a "threshold time" beyond which EDTO rules apply. The threshold time is the time away from the nearest airport that is adequate for use as an alternate (called an "adequate airport," sometimes referred to in shorthand just as an "adequate"). For a twin, the threshold time is 60 minutes. For a four-engine aircraft, the threshold time is 180 mins. This means that the 747 is able to fly up to 180 minutes from the nearest adequate airport before EDTO rules would come into effect.

3. EDTO rules allow an aircraft to fly for a certain distance beyond the threshold time, based on the aircraft's installed equipment and its type's proven performance with regard to engine reliability, fire suppression, and the like. This will be different for each operator and each aircraft type. In addition to aircraft factors, the alternate airports used for EDTO operations need to meet more stringent criteria than merely being merely "adequate," they have to be "suitable," which mainly means they need to be open for landing with higher forecast weather minima than a typical destination alternate, at the time the aircraft would arrive on a diversion.

4. Regarding the 747, for American operators anyway, compliance with EDTO criteria was not worth the tradeoff in economics or convenience, since the 180-minute threshold time already allowed them to fly all over the world without being too far from an adequate airport. This included the North Atlantic tracks as well as polar overflights on Asian routes. Therefore, no American 747-400 operator ever pursued permission via EDTO rules to fly farther than 180 minutes from an adequate airport.

5. You can see this graphically on PFPX. Plan a flight (hypothetically, from Hong Kong to Chicago). Make sure the aircraft profile has 180 minutes as the threshold time. Then, before computing the flight, and without entering anything in the EDTO planning pane on the "Advanced" section, go to the world map and toggle the "adequate airports" button. You'll see a series of 180-minute arcs drawn around adequate airports selected by PFPX. The entire route will be contained within these overlapping 180-minute bubbles, showing you that no EDTO rules or EDTO alternates are required for the flight. (To see EDTO requirements, you could look at the same flight-planning data using a twin-engine aircraft with a 60-minute threshold time. In this case, the bubbles are 60-minute bubbles and there may well be gaps between them, which means you would need to enter EDTO alternates in the EDTO pane.)

6. For situational awareness, PFPX puts these "adequate airports" into the written flight plan (the OFP), so you can see which one you are closest to at any given time. You could optionally display these transition points on the ND by entering them as lat/long waypoints after a discontinuity following the final leg in your route; however, in practice this may not add much practical value, because the "adequate airports" may not be the airports you would really divert to. (Perhaps your company has fuel contracts, passenger handling capabilities, and/or landing rights at different airports, for example.) To get PFPX to display the alternates you would really use, just go into the "adequate airports" section under the alternates tab, and replace the auto-generated adequates with your own, new updated choices. This will toggle the 180-minute rings to show your chosen alternates, and these will show up in your OFP with the lat/long crossover points between them. This is a fairly powerful feature of PFPX: you can pick your own diversion airports along your route, and the OFP will tell you which one you are closest to at any given time; using the DISCO trick above, you can also make these changeover points visible as waypoints on your ND. On the printable route map, these points show up as "GO:XXXX" where XXXX is the diversion airport that you are closest to; on the OFP, the points show up as a lat/long waypoint with the name of the alternate. Again, a fairly powerful tool, and good for situational awareness when you get the ND to display these crossover points.

7. When you choose your own adequate airports, as long as the 180-minute rings on the PFPX world map overlap, you know you're always within your threshold time, and EDTO won't apply. If your 180-minute rings don't overlap, PFPX gives you the lat/long of your EDTO entry point and your EDTO exit point for when your route crosses out of the 180-minute rings and passes back into them. When this happens, PFPX automatically prompts you to enter EDTO alternates on the "Advanced" page. But again, this is rare, and would mostly happen over the Pacific or elsewhere far from land.

Please let me know if I've misrepresented anything, and I hope someone finds this summary helpful.

[Roddez]

Hi Will,

I was always under the impression that ETOPS stood for:
Extended-range Twin-engine Operational Performance Standards.

Cheers,

Rod.

[Jeroen Hoppenbrouwers]

Do we need to mention the Other One?

[Roddez]

Do we need to mention the Other One?

Engines Turn Or Passengers Swim?

[Jeroen Hoppenbrouwers]

I guess we did need to mention it   :-P

[John H Watson]

This is a fairly powerful feature of PFPX: you can pick your own diversion airports along your route, and the OFP will tell you which one you are closest to at any given time;

Just wondering how close to the limits the Sydney/Johannesburg and Sydney/Santiago flights come to the 180 minute rule. Perth, Western Australia will be a diversion for the first. Perhaps Durban, South Africa. Madagascar? Not sure what islands there are in the South Pacific between New Zealand and South America. There are limits on how far south these flights can go (without the appropriate survival gear).  EDTO might put limits on this, too.

Of course, winds would be a factor, too.

[Will]

The following routes take today's winds into consideration... things might be a bit different tomorrow. That said, for Sydney-Johannesburg, you would need EDTO-240, but you'd easily make it with 240 minutes between stations. You're well-covered with the normal 180-minute threshold time from Australia into the polar regions, where Wilkins Runway (YWKS) on Antarctica becomes your adequate airport. As you depart past the YWKS critical point, you pass into EDTO territory for about an hour before flying in range of Tôlanaro (FMSD) on Madagascar. Once within 180 minutes of FMSD, you're back within the 747's threshold time for the rest of the flight. In sum, the EDTO portion lasts about an hour when out of 180-minute range of Wilkins but before coming into 180-minute range of Tôlanaro.

For Sydney-Santiago, you'd need EDTO-330 if you're going to stick to a great circle route (and not go island hopping for your alternates). You'd enter your EDTO space as you pass out of range of Dunedin (NZDN), Otago, South Island, New Zealand, until you fly within 180 minutes of Santiago. Along the way, you'll always be within 330 minutes of either Dunedin to the west or Teniente Julio Gallardo (SCNT), Chile, to the east.

I can't speak to special polar regulations or equipment requirements.

[John H Watson]

Thanks, Will. I was assuming the Antarctic was only an emergency stop, rather than a suitable airport.

Strange... I don't recall Qantas 744ER's having any >180min certification for these runs.

[Will]

Hi John,

PFPX flags YWKX as an adequate airport, but I don't know if that's really accurate in real life ops. Maybe YWKS isn't usable at all, maybe it's only usable part of the year, I don't know. One thing that does come to mind is that the requirements for an "adequate" airport are fairly lax; operators merely need to show that there are facilities and services that are "adequate for the proposed operation" and then later, if used as an EDTO alternate, that the weather is forecast to be decent. So the airports don't have to actually have any regular commercial operations happening. But would YWKX qualify in real life? I really don't know.

One other thing that comes to mind is that for the Santiago route, I picked a route close to the great circle distance. If the airline had extra fuel to burn, they could stay within the 180-minute threshold time by bending the flight path here and there to stay within 180 minutes of runways along the way. So I do think it was possible for QANTAS to fly YSSY-SCEL without needing to use ETOPS rules; it just wouldn't be doing so using the shortest possible route.

[Will]

For example, bending the Sydney-Santiago route just a little bit to the north, you could avoid EDTO airspace by staying within 180 minutes of Christchurch, Rarotonga, Hao (Tahiti), and Mataveri. This would add 8% to the fuel burn (with this morning's winds) compared to the more direct EDTO-330 route, says PFPX.

[John H Watson]

Thanks for your efforts/computations, Will. Much appreciated.

[DougSnow]

I've looked at a few of those routes for a 777F at work. For SYD-JNB, I can do it with 240 minutes on a restricted routing. I'd have to cross 38S080E as that is the point where the YPPH and FIMP 240 circles overlap, before and after that fix I don't really care how I get there.  We'd use YPAD YPPH FIMP FALE as the primary alternates. YPAD as in some cases the best winds route goes south overhead YMML or YPPH.  With 330, there are no routing restrictions (if we want to pay Boeing for the STC to add additional cargo fire suppression in the cargo hold), then use YPPH and FIMP (primarily).  We'd be the only operator in the world with 330 minute 777s (ANZ has 290 on their 773s). 

For a VCP-AKL, due to field length at VCP I cant takeoff at MTOW which limits the economics, and at 240, I have to cross 40S140W, we'd use SCIE, SCIP, NCRG and NZAA. SCIP has timing restrictions to be used for ETOPS and specific remarks to be added to the FPL when using it as an ETOPS alternate. With 330 again, there would be no routing restrictions, and no mid Pacific alternate, just South America and NZ.  Using today's winds, 330 is around one hour shorter (14+49 vs 15+42), and I'd only need SCCI and NZCH.  Today's ETP would be over the coast of Antartica.

----------------------------------------------------------------------
    ETOPS/ETP CRITICAL POINT INFORMATION (ETOPS RULE TIME:330MIN)
    -------------------------------------------------------------

ETOPS ALTNS WX/NOTAM SUITABILITY PERIOD - UTC
SCCI   (23:40-08:14)
NZCH   (06:45-08:14)

ETOPS INFORMATION
----------------------------------------------------------------------
ETOPS   SAP       ELTME TIME   DIST      SPD     ICE  CFUEL  FOB  COND
                                ALT     WCMP

ENTRY   SAWH       0531
S6139.2 W06252.8

ETP1    SCCI/NZCH  0921 0600 2171/2210 1EO320    1.2  105.5 110.5  DX
S7619.1 W14754.8                100   P004/P008               

EXIT    NZCH       1257
S4952.1 E17755.3


TIME LIMITED SYSTEM COMPLIANCE SUMMARY
LONGEST ALL-ENG DIVERSION IS 269 MINUTES FROM ETP-1
CARGO FIRE SUPPRESSION CAPACITY MINUS 15 MINUTES IS 315 MINUTES
LONGEST ONE-ENG-INOP-DRFTDN IS 306 MINUTES FROM ETP-1
OTHER THAN CARGO FIRE SUPPRESSION MINUS 15 MINUTES IS 330 MINUTES

TIME LIMITED DIVERSION SUMMARIES - ETP-1
DIVERSION AIRPORTS                      SCCI              NZCH
CONFIG                             ALL E    1EO      ALL E      1EO
FL                                 350      222      350        222
SPEED                              M0.85    320      M0.85      320
AVG W/C                            P020     P004     P011       P008
AVG OAT                            M54      M25      M57        M27
SYSTEM CAPABILITY MINUS 15 MIN     315      330      315        330
TIME TO ALTERNATE (MINS)           269      306      269        306

[Will]

Here is a bit of additional information, for the sake of completing my mini-tutorial above. You might be wondering: Why not just pick one of the adequate airports as my EDTO airport? Let's say you are flying the 747 with a typical 4-engine threshold time of 180 mins, and a distance-to-EDTO airport of 330 mins. Let's say also that your adequate airports are along the route, and your ETOPS entry and exit points are about an hour apart as you fly 180 mins from airport XXXX, over the ocean, until you get to YYYY.

An example of this would be Brisbane to Desierto de Atacama, Chile, with adequate airports of YBBN, NZHN, NZCI, SCIP, SCIE, and SCAT. Note that YBBN and SCAT are the departure and destination airports, respectively. The whole route is covered by 180-minute circles except for an hour-long stretch due south of Tahiti (NTTO).

Option #1 might be to list NTTO as your ETOPS airport, since it's less than 330 mins from every point from ETOPS entry to exit. But Option #2 would be to just pick SCIP, which is on the flight plan already as an adequate airport. If you "upgrade" SCIP from a merely adequate airport into an EDTO destination, then the 330-min circle around SCIP covers the ETOPS stretch. This seems simple, so why not always do it?

The answer comes down to the requirements at the airport itself, in terms of weather and accommodations. For use as an adequate airport, SCIP just has to exist, and it has to hypothetically take a 747 for landing, but maybe in real life we wouldn't want to divert there because the weather is bad, fuel is outrageously expensive, and the station chief absolutely hates your airline based on that one truly regrettable experience back in '97. For that reason, we choose NTTO, even though it is much farther away, because it's an operationally better airfield with a weather forecast that is suitable, plus cheap gas and white sandy beaches.

This illustration is to make the point that the route can look simpler if you concentrate exclusively on adequate airports, but the EDTO airport that you choose has to be suitable, which means good for real world ops, given today's weather and your airline's operational requirements and preferences.

I'm adding this partly to make my mini-tutorial more complete, and partly because I tend to forget things like this from time to time, and so I'm happy to have a reference somewhere that I can look at later...

[peb]

That is really interesting, thank you Will