I was flying  KMIA to MKJP. More than 100 NM before arrival at FL 37 P2ATC started vectoring me to the approach (no STAR assigned).   A first question at this point: When/Why P2ATC provides vector as opposed to continuing as per the flight plan while assigning a STAR?

At some point later (around 50 NM before arrival) while providing vectors to the approach  P2ATC instructed me to descend and maintain five thousand feet. Unfortunately the descent profile (although reasonable) does not clear the terrain obstacles (mountains) around the island/airport that can as high as 9000 feet. This would not have occurred if a STAR were assigned and the associated altitude restrictions were met.  Is this situation an issue/bug on P2ATC side or did I miss something?

Sam

Please email the log file for this flight to [email protected] so I can see the details of what caused the vectors to be given.

Thanks,
Dave

Thank you Dave. I guess the log is for the last flight, then I'll have to redo the flight to get the log. I will do this. In the meantime if you can explain in general what are the cases when vector is provided instead of a STAR this would be helpful.

Sam

If the STAR has a manual termination defined or if the angle to final approach is too steep, you will get vectors to final at some point.  

Dave

Here is another flight from SACO to SCEL when I was vectored very early (without STAR) to the final ILS approach. I have several problems with this:

1) I am not sure of the benefit of this (vector vs STAR) since the vector follows roughly the direct route (no optimization) however with several turns few degrees right and left. Basically it is more load without any benefit that I can perceive;

2) The major problem with early long vectoring (as opposed to a STAR) is the lack of vertical guidance (where a STAR provides such guidance). During this flight I have been cleared from FL44 to FL16 in very high mountains area. I could avoid the crash only thanks to the high visibility (a beautiful sunny along with magnifiant mountains views) and to the fact that I had already done this route (using a STAR with very precise altitude restriction so the terrain can be cleared) 

3) The final vector was  given too high and in a way that i could not catch the ILS

Again the major issue here is to clear high mountains area which is not possible with the vectors provided by P2ATC because of the lack of precise altitude guidance. 

Is there anyway (specific request to ATC for exemple) to avoid vectoring in such high mountains routes?

 

Sam

Adding a STAR to your flight plan should give you what you want.

Dave

 

I understand (but I may be well wrong) that having ATC assign STAR and Approaches during the flight is closer to reality than forcing them (via the Config button), therefore this what I do in general. The question is if there is any way during the flight to request to ATC (P2ATC) to change the assigned STAR and/or approach (such as requesting another STAR/Approach call).

On the other hand I am still not sure why  P2ATC decided to select vectoring instead of STAR, did I do or configure something that caused this? (I am talking here about early vectoring and not the one typical in many cases that provides transition from a STAR to a final approach).

Any clarification will be very helpful. Many thanks.

Sam

This has happened to me from time to time. Usually it occurs when during the cruise I decide to ask for runway change. At that point, it goes to a vector approach and I get unreasonable descent instructions. Most times I just shut p2atc down. 

P2A selects the STAR when you file, and recalculates it when setting up the arrival.  If the STAR (or route without a STAR) ends with a severe angle to the Approach final, then you will get vectors.  This is more likely to happen when you don't have an Approach Transition, but can happen any time.

When you ask for a runway change, it is highly likely that you will get vectors to the approach for that runway.  Depending on where you are when you ask, you may not have enough distance left for a "reasonable" descent.  For example, approaching from the north with a planned landing on runway 35, if you request landing on runway 17, you may have cut 50+ NM off the route, so the descent will need to be done with speed brake, gear and flaps extended, at approach speeds, instead of cruise speeds.  Not good on an airliner, but a fighter jet can handle it.

Dave

Dave, here's the thing. Using your example of coming from the north and the flight plan was setup for a STAR and Approach to land on 17. So far great, P2atc will flow perfectly. But prior to TOD (greater than 100nm away) the winds change for a 35 landing. I request a runway change. P2ATC will instantly put me on vectors (no more STAR) and give me a descent instruction to 3000ft (seems unreasonable). Maybe I'm not doing something procedurally in the software when requesting... Not sure. 

 

Thanks for helping, 

Scott 

If you're cruising at 450 kts GS and about 100 NM out, at FL370, and if your planned descent rate is 1800 FPM, then it's going to take almost 19 minutes to descend and you will cover 141 + NM in the process, so P2A does the math and if the terrain allows, gives immediate instructions to start down.

If you were a couple of hundred NM out, then you would get a more normal descent, likely with stepped altitudes.

Dave

Edited April 21, 20215 yr by Dave-Pilot2ATC

Ok. It makes sense what your saying, maybe I'm missing a detail. I'll try again and check it out. Thanks for your time. 

Thank you Dave for the clarification.

However I am still confused, in case of a vector assigned by ATC (P2ATC) who is responsible of managing the descent profile (clear the terrain), me (pilot) or ATC (P2ATC) ?  The couple of times when vector was assigned instead of STAR I did not receive precise instructions for managing the descent profile and have missed barely (thanks to nice weather) crashing into the mountains!

Sam

ATC tries not to vector you into mountains.  Assuming you stay on course, P2A will try and keep you above the terrain.  In very mountainous terrain, you may have problems, especially if you are not following the headings correctly.

The descent from altitude assumes you are descending at the Planned descent rate and ground speed.  If you go faster than the planned GS, then you will not get down in time.  If you descend faster than the planned descent  rate, you may get down too soon and encounter terrain that you should have cleared.  This is known as "dive and drive" and has killed pilots in the real world too.

Dave

 

Thank you again Dave, this is very helpful.

 

Now how to get The Planned descent rate/ground speed from the point where the initial vector is provide to the IAF?