November 28, 20169 yr Hi, what's the 1 engine out speed of the 777? I know that in the tutorial it is stated that we should draw 420nm rings around the nearest suitable airport (not our ETOPS-alternates, I know) to mark the borderline where we are entering into the ETOPS-zone on the ND. The problem arose when I saw that the ETOPS-borders of PFPX don't match a 420kts line. In fact, they match a 480kts line. I know that this depends on the wind as well, but I'd like to know what 1EO speed I can assume. Can I take 480nm rings or do I have to teach PFPX the 420kts? Regards Lars Regards Lars Wüst
November 28, 20169 yr Hey Lars. It's always the still air distance you use, On our NGs we use 388/394 nm (without winglets/with winglets) and our 767 it's 430. So the 420 doesn't seem right for the 777 and 480 seems a bit too high but then again I'm not typed on the 777 so I would just be taking a stab at it. Jack Colwill
November 28, 20169 yr IIRC you should be able to change the size of the rings by adjusting the diversion speed. Bryan Richards "People depend so much on automation that they forget how to get the automation to work." B.W.
November 28, 20169 yr At my company, we indeed use 420 nm Cheers, Xander Koote All round aviation geek 1st Officer Boeing 777
November 28, 20169 yr If you are using SimBrief for flight planning,they use for the 777-200LR 60 mins = 453 miles 120 mins = 886 miles 180 mins = 1320 miles Tony Simpson FLYING FROM EGKK, The worlds busiest single runway Airport.
November 29, 20169 yr Author Hi and thank you for your answers so far. I have bothered to take a look at the FCOM that's provided by PMDG. There is an awful lot of conversion tables that repeat themselves to my understanding. If I interpret them correctly, the 77L and 77F have a diversion speed of M.70, approximately and according to their weight, which in turn affects diversion altitude, and the 77W has a diversion speed of M.68 roughly. There exists a website that converts Mach to knots, but the problem is that M.84 gives 555kts. When I fly, M.84 never gives 555kts TAS, but rather 490kts (perhaps this changes with altitude as well? Frankly I don't know). So I converted Mach into knots and substracted 12% each, and these are the results: B77L: M.70 463kts 407kts TAS B77F: M.70 463kts 407kts TAS B77W: M.68 450kts 396kts TAS These numbers don't seem right to me. On the other hand, the Great Circle Mapper uses 410kts as 777 diversion speed. Regards Lars Wüst
November 29, 20169 yr But when you are talking ETOPS, a diversion is considered to be a loss of one engine therefore you won't be doing M.84 anyway and you will be descending to a lower altitude which will end up giving you a lower Mach number anyway.
November 29, 20169 yr Author But when you are talking ETOPS, a diversion is considered to be a loss of one engine therefore you won't be doing M.84 anyway and you will be descending to a lower altitude which will end up giving you a lower Mach number anyway. You are right on that I think. Does anyone know a formula to convert Mach to knots TAS depending on Altitude? Regards Lars Wüst
November 29, 20169 yr Hi, You may search for it on internet: type "Convert mach number to TAS". An exemple of the result returned: http://www.hochwarth.com/misc/AviationCalculator.html Romain Roux Avec l'avion, nous avons inventé la ligne droite. St Exupéry, Terre des hommes.
November 29, 20169 yr I have bothered to take a look at the FCOM that's provided by PMDG. There is an awful lot of conversion tables that repeat themselves to my understanding. Just in case if you aren't aware, those tables assume max continuous thrust from the point where failure occurs to engine out cruising altitude. So you are calculating the average TAS of diversion, which can be slightly different than the TAS at final cruising altitude. The speed of sound is proportional to the square root of temperature, so it varies with altitude. The website Roman posted above is pretty accurate in my experience. David Chen
November 30, 20169 yr Author Hi, You may search for it on internet: type "Convert mach number to TAS". An exemple of the result returned: http://www.hochwarth.com/misc/AviationCalculator.html Thank you for this useful link. With that calculator I get 419-430kts TAS @ FL200-260 for M.70 and 407-417kts TAS for M.68. So 420kts is about right. Just in case if you aren't aware, those tables assume max continuous thrust from the point where failure occurs to engine out cruising altitude. So you are calculating the average TAS of diversion, which can be slightly different than the TAS at final cruising altitude. The speed of sound is proportional to the square root of temperature, so it varies with altitude. The website Roman posted above is pretty accurate in my experience. Thanks for the clarification. Regards Lars Wüst
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