PD and help + tips on Alt Rest when descending

[Driver170 42]

Hi this is a short message! Basically i'm looking for tips or even advice on how to use that Alt rest / speed when you're descending. Only once i didn't make it and got vectored of course.

 

Can anyone give advice on how to do this? I prob could work it out but its good to see other peoples plans and thoughts.

 

Also about PD when descending, do i have to uncheck pilot auto reply during setup or just hand over comms to myself not otto before TD?

 

Thanks RC users and looking for a good answer from ron here

[ronzie 21]

If you are using an FMC type aircraft (I see you have the B737NGX in your profile) you can put a range ring or two around your arrival aircraft to show on your navigation display. For the Boeing Smiths type FMC go to the FIX page and enter the ICAO code of the airport. Now enter in the bearing/distance line /40 and EXE it. On the nav display you should now have a dashed circle around your destination airport. You also might want a range ring of 30 nm out to define the airport traffic area. Set this up pre-flight or far enough out once you are assured of no destination change.

 

The 40 ring represents your crossing restriction boundary from destination. As you start your descent the Boeing FMC can show altitude trend arcs. If necessary adjust V/S and aircraft speed so the descent arcs stop short of the 40 nm range ring (the crossing restriction area).

 

To valculate TOD, RC uses the aviation 3 in 1 descent glide path rule (three degrees) but not to the surface but from your cruising altitude to crossing restriction altitude to determine the anticipated change in altitude. Some other devices like flight planners calculate your estimated altitude to the destination surface altitude as a constant descent approach.

 

As I recall, PD can not be requested by Otto. However, if it is still on the RC menu you can still use the keyboard to request it and ack it. Pilot auto reply will get it off the menu first I believe before you have the chance to request it.

[Driver170 42]

Ron thanks man got it !!!

 

But to get PD you need to un-check pilot autoreply but i like this feature?

[ronzie 21]

It is similar to copilot coms. From the manual:

 

"At any time, while the copilot has the comms it is possible for you to override him. If you want to ask clearance for a higher flight level, it is perfectly possible to do so. Likewise for requesting a weather report, declaring an emergency, or any other type of communication you would like to have. The copilot will restrict himself to acknowledging all comms from the different controllers to your aircraft, including setting the transponder."

 

 

[Driver170 42]

Yes thats understood but PD isn't in the option list when you get your first descend clearance?

[Ray Proudfoot 8,954]

Yes thats understood but PD isn't in the option list when you get your first descend clearance?

 

Just to confirm Ron's post. You - as the pilot - must have comms to make the PD option available. Otto will just ack the instruction if he has the comms. if you want the option just temporarily take comms back around 100nm from ToD.

 

You can hand comms straight back to him after you have requested a PD.

 

If Otto acks the descent instruction and you want to remain as high as possible just initiate a descent of around 200fpm until you reach your calculated ToD. That will satisfy the controller.

[Driver170 42]

Right but does that mean i still can have pilot auto reply on for PD? And 100nm before my TD just hand comms back over to myself?

[Ray Proudfoot 8,954]

 

 

Right but does that mean i still can have pilot auto reply on for PD?

 

NO! Did you read what I said in my post? YOU must have comms for PD to become available.

 

 

 

And 100nm before my TD just hand comms back over to myself?

 

That's what I said.

[Driver170 42]

Well i like that feature - pilot auto reply and need it checked when setting up RC. Per the FCOM PM will do comms not PF

[Driver170 42]

Ok i created that 40nm ring and placed 250/FL110 at the created waypoint at the border ring but RC still descended me 40 nm early from my TD its getting annoying now i didn't even reach my cruise alt.

 

i thought created this PBD at 40nm from the dest airport would match my TOD with RC 3 in 1 rule or whatever it is.

 

any help will be appreciated thanks guys.

[David Vega 348]

Vernon,

 

Perhaps it helps if you think that RC is simulating real world ATC where typically there is more traffic than just you at your arrival airport.  The RC center controller needs you to be at either 11000 or 12000, and max 250kts, about 40nm from your destination airport before it hands you to the approach controller.  That speed and altitude is ideal for the approach controller to handle you and the other traffic in that 40nm circle of airspace around the airport.  

 

Your FMC should be computing TOD to meet any altitude restriction in points between the TOD and the arrival airport.  If you have a point (either user defined, or one that's already there) at 40nm from the airport, with altitude and speed restrictions set, the FMC should take that into consideration when computing the TOD.  

 

You mentioned that you couldn't reach your cruise altitude before RC asked you to begin the descent.  Could, in this case, your cruising altitude be too high for that route?  

[ronzie 21]

Just to be clear, RC does not look at what is set at your FMC. The restriction RC imposes at 40 nm out as SAX stated is a vertical altitude where handoff from center to approach controllers exists. It is average for many airports in the real world. If you do not meet that restriction RC will give you delay vectors until you meet that restriction before passing you on.

 

What I recommended if you have an FMC that supports range rings as a guide which I prefer since the flight path that close in may vary from an established route after runway assignment. Using that range ring if you spot a waypoint in your plan near that range ring and before it you can hard code on your LEGS page the altitude restriction and your FMC will adjust its TOD to meet it as SAX stated. As he stated you can create your own FIX as well to meet those requirements.

 

On the FMC the altitudes after the restriction are based on a constant descent to the destination surface.

 

In the real world some but not all airports support a constant descent from cruise to surface. Airport ATC operations managers in the FAA realm have the option to support CDA or not. Center controllers communicate with approach controllers to see what they request and assist accordingly. Most approach controllers especially in dense traffic times prefer a constant handoff altitude to assist in their situational awareness site picture and get their "ducks in a row". I found by flying recommended aircraft descent schedules after the restriction I frequently get a CDA often cleared to a lower level before reaching the last commanded altitude using near idle descent and rare use of spoilers where terrain does not interfere with a CDA approximation.

[Driver170 42]

So even though i make this fix at 40nm out my FMC TOD will still not match RC des instructions?

 

Thanks for the help

[ronzie 21]

If you create a hard fix as a LEG waypoint with a hard altitude of 11,000 or 12,000 feet you'll meet RC requirements. Your FMC should create approximate altitudes to that fix and adjust as you pass each one to meet that criteria. The adjustments should dynamically be based on time and ground speed with the FMC handling engine criteria. If pilot intervention is needed you may see alerts such as Drag Required if overshooting will occur.

 

As the RC manual states that a crossing restriction is a pilot's discretion procedure. ATC does not care how you accomplish it, just get it done.

[Driver170 42]

But what i'm asking is, if i enter these alt rest 11000 and 12000 will RC des not match up with my TOD?