Alternate airport display

[rservice 4]

Does the PMDG 747-400 FMC show alternate airports, or is this a feature not implemented? I notice that the LDS 767 does use this feature.Ron

[G-CIVA 62]

Ron,The ALT ARPT feature was designed for the 'big twin' Boeings (762/3 & 772/3 & now the 737NG & 752/3) operating under ETOPS rules which routinely place them over 60 mins away from a suitable alternate airfield.My PPL instructor was a 763 SFO & she once told me that the engine failure on a twin was not as serious an event as an onboard fire or a depressurisation scenario...you can always drift down slowly on one engine whilst an onboard fire needs no explanation. A cabin pressurisation problem would require a rapid decent to safe level before a diversion at that level...just try it & check out the new fuel burn figures - they can be frightening!!!...not to mention the possibility of a less than direct route if high terrain is an issue.Obviously the loss of an engine on a twin engine aircraft is rather more of an event than on the four-engine 744, so the original 744 FMC did not have this function enabled - as we see in the PMDG 744/F. The alternative is to use the FIX PAGE to enter the ICAO codes of your preferred alternates...then draw arcs within that page to get an idea of distance...this obviously does not take into account your speed over the ground...some maths maybe required to calculate your alternate handover point...unlike the ALT ARPT page which gives your ETA to alternates with FOB figures, remember that these are calculated as direct routings though.I am not sure whether this feature has been retrofitted - perhaps as a customer option...I am sure I have read somewhere that it may be available as such on the 744 ER model...but as with everything I may well be wrong on that point!!Enjoy your flying.Steve B

[rservice 4]

Thanks for the info Steve. I guess the 747 emergencies can be handled with more options, and again the 747 would probably require longer runways than a 767, depending on current gross weight.Ron

[G-CIVA 62]

Ron,Absolutely, the 744 driver has more options in a single engine failure scenario...thats why the ALT ARPT function is more crucial to the 'big twin' driver.The runway length issue is important...but if you look at the declared alternates on any given tranatlantic crossing you will see that most have at least one long runway...I'm sure every pilot (in any type of plane) in this scenario would wish for a nice long runway!!!EnjoySteve B