Auto/Manual Tuning of Nav Beacons

[Guest frankathl]

The navigation radios in the classic 737s have an AUTO/MANUAL function which allows nav beacons to be tuned automatically by the FMC, or manually by the pilot(via the AUTO-MAN switch). While, presumably, this function is also available in the NGs, there is no such switch on the VHF NAV panel. How, then, to distinguish between the two functions in the NG?BR,Frank

[744pilot 0]

Do you realy beleve that???NGs doesn't have auto tuning, but PMDG is making the auto tune on the B744.Check out A-net. and you will see.

[Guest frankathl]

Hi Ramon,I was speaking of the real aircraft.Are you suggesting the NG has no FMC auto tune function? Perhaps you were referring to the PMDG implementation only?BR,Frank

[crvm 0]

>Hi Ramon,>I was speaking of the real aircraft.>Are you suggesting the NG has no FMC auto tune function?>Perhaps you were referring to the PMDG implementation only?>BR,>Frank Yes Ramon is correct, there is no Auto tuning on the real NG aircraft and neither in the PMDG sim. You must manually tune the navs. Best Wishes,[h4]Randy J. Smith[/h4]http://www.rawbw.com/~bdoolin/shinault/southparkcartmad.gif[h3]PMDG 747![/h3]Caution! Not a real pilot, but do play one on TV ;-)ASUS KV8 DLX | AMD 3200 64 | 1 GIG PC 3200 DDR | GIGABYTE 5700 ULTRA | ViewSonic VP192b 19" |

[Guest frankathl]

Thanks, Randy!In that case, how does the NG use VOR and DME stations to update its position(these are not manually tuned)? The flight manual is slightly ambiguous("in AUTO, if applicable"), but I take the following description to cover the NG as well as the Classic:"The navigation radios are automatically tuned by the FMC(s) for the purpose of radio updating (in AUTO, if applicable). The stations to be tuned are selected based upon the best available signals (in terms of geometry and strength) for updating the FMC position, unless a specific station is required by the flight plan. Radio position usually is determined by the intersection of two DME arcs...."BR,Frank

[Guest Lenny Zaman]

This radio updating is in fact the reason. One could ask Boeing to put auto-tuning in the NG, no problem.But for Boeing to keep the NG certified they needed to have some form of position updating and these days most aircraft have built in GPS systems which accurately update the position of the IRS's calculation. SO in fact the GPS replaced the 'auto-tuning' of the nav radios.That's why the old 737 still has this autotuning, to keep that 'RNP' level(required naviation performance) high enough for the aircraft to be certified as at those times GPS was not common(737 EFIS is a pretty old tech plane)Cheers(edited for spelling)

[Mats_J 2]

Frank,The NG do have some radio updating features not available to the crew. See this response to another recent thread from our real world driver Kris:http://forums.avsim.net/dcboard.php?az=sho...mode=full#73190Hope it helps,

[744pilot 0]

I think it's a good future from Boeing, that the NG updates via the GPS pos.

[Guest frankathl]

Thanks, Lenny!"SO in fact the GPS replaced the 'auto-tuning' of the nav radios."The flight manual seems to disagree, Lenny? The description below specifies the priority order by which the aircraft updates its position. Although the GPS is the primary source of position updates, if this fails, radio updating is used. My understanding is that all such updating is automatic, and is not related to the nav beacons manually tuned by the pilots. Maybe I've got it wrong, though???"In flight, the FMC position is continually updated from the GPS (as installed), navigation radios, and IRS. Updating priority is based on the availability of valid data from the supporting systems.FMC position updates from navigation sensor positions are used in thefollowing priority order:

[Guest frankathl]

Hi Ramon,Yes, but what if GPS updating fails?See my response to Lenny above.BR,Frank

[744pilot 0]

Check Mats. post. ;)

[Guest Lenny Zaman]

Hi Frankagreed, the DME's provide updating aswell. I think i might not have explained what i meant correctly, but your explanation is alike mine only explained in a more clear way(english is not my mother tongue)I'll get an update from my instructor as soon as i see him.Cheers

[Guest frankathl]

Hi Mats,Yes, thank you. In fact, I contributed to the thread you mention myself, but will need to re-read everything again to refresh my memory about all that Kris and others wrote.Nevertheless, just to make my main point again(and not to get too obsessive about it :-))- The NG has multiple methods of updating its position, none of which makes the other ones obsolete. What you have is a priority order in which the updates are taken(with some cross-checking, I assume). Should the data from any of the nav systems be deemed unsatisfactory by the FMC, then the next in line method of taking the updates is used. GPS is the preferred method of providing aircraft postion, but radio updating is always available if needed.BR,Frank

[Guest frankathl]

Thanks a lot, Lenny!Yes, I see that we are agreed:-).Appreciate your help.Best wishes,Frank

[Guest frankathl]

Thanks, Ramon!See my response to Mats.Best Regards,Frank