Convert TAS cruise speed to Mach number for the FMC?

[scandinavian13 5,192]

 

 

Thanks. I added my name to my post before did not know you had to do it every time. Ok.

 

Yep - every post. You can configure an auto-signature, like the one I use, by going into your user settings.

 

 

 

So if I am flying NATs or other segments requiring set speeds I have to do this manually once I cross over the waypoint, I go to CRZ and select the assigned speed? Thought the FMC would have an option like the 777 with setting desired cruise speed at each waypoint. Guess not!

 

As I mentioned in my last post, the frequency that the 737 traverses constant speed segments is pretty limited, when compared to the 777. The 777 and NG, though both made by Boeing, are vastly different aircraft, made for entirely different purposes.

 

 

 

If any NGX update is planned it would be great to have auto tuning VOR's like the 777 has I believe the 737 has this in real life

 

Have a specific reference for this? I know there is some autotuning (which ours already has), but only on a DME level for crosschecking and updating the computed IRU position, supplementing the GPS. You can see this on the NAV STATUS page.

[kevinh 409]

 

 

If any NGX update is planned it would be great to have auto tuning VOR's like the 777 has I believe the 737 has this in real life

The 737 Classic had VOR auto-tuning. The 737 NG does not.

[JRBarrett 3,070]

The 737 Classic had VOR auto-tuning. The 737 NG does not.

The NG has dual-channel DMEs, which are each capable of tuning two DME ground stations (on separate frequencies) simultaneously, and calculating distance to each.

 

The primary channel of the DME transceiver is linked to the VOR or ILS frequency of the onside NAV control head, and provides the cockpit display of distance to the facility. The primary channel remains fixed on whatever VOR or ILS has been manually tuned by the flight crew.

 

The secondary channels of the DMEs are auto-tuned by the FMS to provide DME-DME distance updates for updating the IRU position (in addition to GPS updating).

 

The auto tuning of the DME secondary channels takes place in the background and is not normally visible in the cockpit, though the crew can see which secondary DME channels are currently in use by selecting the appropriate page on the FMS CDU.

[Boeing or not going 578]

So if I activate VOR1 and VOR2 switches the stations do not get auto-tuned to closest stations in your flight plan like they do in the 777 and 747? Obviously my 737 systems knowledge is pretty basic I figure it would be like other Boeings.

 

David Lee

[scandinavian13 5,192]

 

 

So if I activate VOR1 and VOR2 switches the stations do not get auto-tuned to closest stations in your flight plan like they do in the 777 and 747?

 

Not sure what you mean by "activate VOR1 and VOR2 switches." I'm guessing you're talking about the display switches for the ND. These only toggle the display of the currently selected VOR, and do not prompt the aircraft to automatically tune them (or not tune them). The 777 and 747 are always doing this by default, but you may not see it if the VOR/ADF switches are not switched to VOR to display this.

 

The 737 is doing this as well, but it just doesn't show you on the ND, because it is only tuning the appropriate DME frequency, without affecting the basic VOR tuning.

 

 

 

Obviously my 737 systems knowledge is pretty basic I figure it would be like other Boeings.

 

Define "other Boeings," though. The 744 and 777 are both on the same 'generation' so to speak. The 737 has been lagging behind mostly for reasons of commonality. It's somewhat the "odd man out" when it comes to aircraft offerings, as it's a design from 1964, with roots back to 1958. The 737MAX is where I think you'll see it get up to the 744/777 'standard' of things. The 744, by comparison, was an extensive update of a design from the same time period, but the elimination of the FE meant that the increase in automation, and extensive re-design were easier to justify to the industry. Interestingly enough, the original 767s delivered to UAL had an FE position because of pressure from the operator/union to not eliminate the position - aircraft development is a tricky business, which is partially why the 737's changes have been piecemeal. The 777, coming post 744 updates, of course, reaped these benefits, and entered into the product line without the roots holding it back from the "new Boeing" if you will.

[JRBarrett 3,070]

So if I activate VOR1 and VOR2 switches the stations do not get auto-tuned to closest stations in your flight plan like they do in the 777 and 747? Obviously my 737 systems knowledge is pretty basic I figure it would be like other Boeings.

 

David Lee

Although the 737 is an older design than the 747/777, the avionics in the 737 NG are actually of a newer generation than what is found in either the 747-400, 757/767 or earlier 777s. DME transceivers capable of tuning and tracking two simultaneous DME ground stations (one for the cockpit display, one for the IRU updating) only became readily available in the mid 1990s when the NG was introduced.

 

The 747/757/767 use older, single channel DME's which is why the primary NAV receivers have to be auto tuned, which is visible to the flight crews on the RMI and Nav displays. This does not happen on the NG because there is no need for it. It happens in the background.

[kevinh 409]

The NG has dual-channel DMEs, which are each capable of tuning two DME ground stations (on separate frequencies) simultaneously, and calculating distance to each.

 

The primary channel of the DME transceiver is linked to the VOR or ILS frequency of the onside NAV control head, and provides the cockpit display of distance to the facility. The primary channel remains fixed on whatever VOR or ILS has been manually tuned by the flight crew.

 

The secondary channels of the DMEs are auto-tuned by the FMS to provide DME-DME distance updates for updating the IRU position (in addition to GPS updating).

 

The auto tuning of the DME secondary channels takes place in the background and is not normally visible in the cockpit, though the crew can see which secondary DME channels are currently in use by selecting the appropriate page on the FMS CDU.

I didn't mention DME auto-tuning and I don't disagree with any of what you said. I referred to VOR auto-tuning as per the OP's question.

[Olympic260 415]

19 minutes ago, rsneha said:

nice info thanks

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[MarkJHarris 128]

You do need to remember that the 737 has always been a parts bin special. It may use the same GATES or various tuning units on the pedestal, and have similar screens to other more modern Boeings but there is a fundamental difference that even the MAX shares. 

It is not a digitally integrated data bus design. Thus all the systems are discretes and owe more to the 707 and 727 than the 787!

A lot of stuff in there has no idea what other bits are doing. You select VORs from the tuning head, and the boxes under the floor do as they are told. 

Yes, we have dual channel DMEs, and the FMCs do talk to the NAV boxes as a result. but without the integration you will never get EICAS and other system information on screen.

Never overestimate the simplicity of the 737! It's not big and it's not clever...

[Spin737 102]

Probably no need to run a converter. Just look at the TAS and if it's off, change your MACH speed in the MCP or CRZ page until it matches your desired TAS. Or you could change your CI to increase or decrease your TAS. That's not a constant, however.