RNAV approach help and RAAS problem

[ceranes 0]

That is where the problem has been the whole time...the plane does not behave like the 737 for obvious reasons, but I'm not sure how to fix it.

 

So you're saying I need to select the RNAV approach in the FMC, and then set 1100ft in the Altitude Selector (the MDA in this case).  Will the FMC then calculate a fake "glide slope" for the plane to descend along, or do I need to manually fly the whole approach?

 

This is assuming that both LNAV and VNAV buttons are pressed in and active.

[downscc 1,327]

 

 

Will the FMC then calculate a fake "glide slope" for the plane to descend along, or do I need to manually fly the whole approach?

 

Fly the approach in VNAV/LNAV modes, set your minimums and take over from A/P before mins (Boeing recommends setting mimums about 50 feet above published to ensure you do not descend below).

 

I don't like the term 'fake glide slope' because that is what the IAN option does in the B737.  What you are flying is a VNAV PTH set up by the database. However, I understand what you are trying to say and you're close.

[777simmer 117]

Fly the approach in VNAV/LNAV modes, set your minimums and take over from A/P before mins (Boeing recommends setting mimums about 50 feet above published to ensure you do not descend below).

 

I don't like the term 'fake glide slope' because that is what the IAN option does in the B737. What you are flying is a VNAV PTH set up by the database. However, I understand what you are trying to say and you're close.

We use the term "glide path".

 

 

I have posted this in a similar thread today, so I thought I would copy/paste it here as well.

 

Just to confirm, YES, to fly an Rnav approach you have to choose an Rnav approach from the database.

An Rnav approach is not the same as a VOR approach that is flown with Lnav!

It seems the same but is not.

In have posted that before.....quite a while back.....maybe I can dig it up.

 

In real life you are not allowed to change or add or remove any waypoint from the selected Rnav approach!

(this is FSX so you can do as you please ofcourse, but just saying).

 

 

Just before the final descent point/final approach fix:

- have flaps 5 and flaps 5 speed max.

- 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!)

 

Oh.....and once established on final approach and below the missed approached altitude (at least 300ft below) you can and should set the missed approach altitude!

(you can also wait with that untill the AP levels off at the MDA but that would cause an unstable short final if you dont disengage the AP right away).

So to repeat; you first have the MDA set in the altitude window......then at the FAF, Vnav starts the descend.....and while descending to you minimums you can wind up the altitude selctor and set the missed approach altitude.

While you wind up from MDA to missed approach your AP will NOT level off as you dial it to your current altitude (.......nice real world feature and works perfect......well done PMDG :-)

 

Once you reach the MDA the AP will not level off if you do what I said above because the missed approach altitude is already set.

And since an Rnav approach or an Rnav/Vnav approach is created without a level phase at the end (unlike some VOR or NDB approaches that can have a level segment at the MDA), you have to either:

- rwy insight: disengae the AP once below 200ft AGL (minimum AP enaged altitude unless you do an autoland) and land.

- rwy not in sight at MDA: immediately fly a go around.....hit TOGA, do everything you usually have to do for a go around and watch how the airplane levels off at the already set missed approach altitude :-)

 

I have not done many Rnav (=Lnav) approaches with the P,DG777 but those that I did worked excellent.

 

Great fun.....lots of new things and traps you could fall into, lots of ohhh and ahhhh and what is it doing now?!.... I highly recommend playing with it.

Just keep asking when it did something you did not expect.....it is bound to happen.