I realize that the 737 NGX and the 777 are deferent beasts.  However, has anyone been able to successfully make RNAV approaches in the 777? 

 

In the NGX aircraft, I select the approach in the FMC, then once I pass over an approach fix, I can hit the "APP" button on the MCP, and the aircraft flys the approach. 

 

During a maiden voyage from California to New Zealand, I flew direct to the approach fix, hit the "APP" button, and nothing happened.  I ended up having to manually fly the approach, and ultimately landed way short of the runway in a field.  I realize RNAV approaches are non-precision approaches, so there really isn't a glideslope to follow.  I believe the NGX handles it in a way that it creates a "virtual" glideslope for the AC to follow.

 

Does the 777 do the same thing?  Can I enter a glideslope different than a traditional 3-degree slope path?

 

Thanks,

 

Chris

Aren't RNAV approaches done in VNAV mode, not APP?

You are right, it's not like the traditional ILS where you would use the APP button.  But it seems I still have to hit that button to activate the approach, once it has been selected in the FMC.

As far as I know there's no need to hit APP unless you want to intercept an ILS glideslope. 

Yes RNAV are done in VNAV/LNAV (actually not 5 minutes ago just completed the RNAV Y approach to 04R at PHNL).  The challenge (at least for me) is setting up the FMC properly with regard to speed.  If you leave the default the speed will be high so you need to put in the optimum numbers and then fly it in manually once you are past the final approach fix.  I would be really interested to know how the real crews set up for this type of approach.

I'd like to know the procedure more, as Im doing a VOR/DME approach - and if the Visibility is how it normally is, foggy as expected, I need to trust the RNAV.

The B777 is perfectly capable of RNAV (GPS) and (RNP) approaches, but as mentioned it is not a B737 with the IAN option that provides a glidepath. See FCTM pg 1.27 for discussion on how it works and how to use it. It is a pretty good write-up if you haven't glanced at it before.

The B777 is perfectly capable of RNAV (GPS) and (RNP) approaches, but as mentioned it is not a B737 with the IAN option that provides a glidepath. See FCTM pg 1.27 for discussion on how it works and how to use it. It is a pretty good write-up if you haven't glanced at it before.

 

Thanks for the tip. 

You are right, it's not like the traditional ILS where you would use the APP button.  But it seems I still have to hit that button to activate the approach, once it has been selected in the FMC.

 

 

Good discussion here, so I'm leaving the post alone, but the forum rule here is to sign posts with your real first and last name, otherwise it disappears. Please make the correction for the future. This can be automatically configured by clicking on your user name at the top right, then My Settings, and then Signature.

 

As others have noted, the 777 just uses LNAV/VNAV only.

"See FCTM pg 1.27 for discussion on how it works and how to use it. It is a pretty good write-up if you haven't glanced at it before."

 

There is a very detailed document starting at page 1.27 but it goes well beyond that with diagrams, etc.  Very useful.

 

 

I am still wondering about the speed control.  I think you have to just enter the speeds in the FMC.  As an example in Toronto (CYYZ) the normal instruction from the Arrival Controller is "Air Canada 123, speed 170 to Rexdale (ZDH), contact the tower there"  but you may not know that and get the instruction as you are capturing the inbound track.

 

Chart here

https://www.czyz.ca/files/charts/class-c/CYYZ_Approaches.pdf

 

 

I am still wondering about the speed control.  I think you have to just enter the speeds in the FMC.  As an example in Toronto (CYYZ) the normal instruction from the Arrival Controller is "Air Canada 123, speed 170 to Rexdale (ZDH), contact the tower there"  but you may not know that and get the instruction as you are capturing the inbound track.

 

Why not just use the SPD INTV function, just like what you'd use for an ILS approach? No need to be over-reliant on the box.

I'm not sure of the "proper" 777 procedures for RNAV approaches but I like to fly these approaches as step down descents using SPD INTV to decelerate and bring the flaps down on schedule.  A good rule of thumb for a 3 degree glideslope is to use ground speed x 5.  So for a 180 kt ground speed your vertical speed would be 900 ft/min.  You can step down all the way to your MDA and then visually land as usual.

Why not just use the SPD INTV function, just like what you'd use for an ILS approach? No need to be over-reliant on the box.

 

OK thanks!

for a 3 degree glideslope is to use ground speed x 5.  So for a 180 kt ground speed your vertical speed would be 900 ft/min.  

or you can add a zero and devide by 2.

 

180.....1800.....900....;-)

Why not just use the SPD INTV function, just like what you'd use for an ILS approach? No need to be over-reliant on the box.

Yes, that is what our SOPs make us do.

Yes RNAV are done in VNAV/LNAV (actually not 5 minutes ago just completed the RNAV Y approach to 04R at PHNL).  The challenge (at least for me) is setting up the FMC properly with regard to speed.  If you leave the default the speed will be high so you need to put in the optimum numbers and then fly it in manually once you are past the final approach fix.  I would be really interested to know how the real crews set up for this type of approach.

Just before the final descent point/final approach fix:

- have max flaps 5 and flaps 5 speed.

- in the CDU check to make sure the final approach altitude is entered.....and that after that a 3 degrees (can vary a little bit) is displayed.

- set MDA

- make sure you are in Vnav Path......if in Vnav Alt you can change that to Vnav Pth by clicking the altitude selector once.

- immediately after changing from a non Vnav mode (like altitude hold) to Vnav Pth the speed window will blank and you need to reopen it (click speed switch) to prevent the target speed to jump somewhere you do not want it to go!.....the jump could be unsafe as often Vnav will automatically set the target speed to something well below your current flap speed!!

 

Vnav approaches can be precision as well as non precision by the way.

For the precision approaches the temperature is not allowed to exceed certain minima and maxima.....otherwise you would end up too low or too high while following the Vnav profile (it is after all based on following your barometric altimeter.....not a glide slope signal!)

On 22/12/2014 at 3:21 PM, 777simmer said:

or you can add a zero and devide by 2.

 

180.....1800.....900....;-)

Yes, that is what our SOPs make us do.

Just before the final descent point/final approach fix:

- have max flaps 5 and flaps 5 speed.

- in the CDU check to make sure the final approach altitude is entered.....and that after that a 3 degrees (can vary a little bit) is displayed.

- set MDA

- make sure you are in Vnav Path......if in Vnav Alt you can change that to Vnav Pth by clicking the altitude selector once.

- immediately after changing from a non Vnav mode (like altitude hold) to Vnav Pth the speed window will blank and you need to reopen it (click speed switch) to prevent the target speed to jump somewhere you do not want it to go!.....the jump could be unsafe as often Vnav will automatically set the target speed to something well below your current flap speed!!

 

Vnav approaches can be precision as well as non precision by the way.

For the precision approaches the temperature is not allowed to exceed certain minima and maxima.....otherwise you would end up too low or too high while following the Vnav profile (it is after all based on following your barometric altimeter.....not a glide slope signal!)

And, don't forget to monitor RNP stuff on the FMC prog page 4/4. If I'm correct, for an RNAV approach :

- Lateral RNP = 0.3

- Vertical RNP = 75ft

Regards,