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Driver170

Help again. STAR RWY 03 CDO (RNAV) IMBOM5K

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I'm look for some tips and techniques on how to manage a CDO at LPPT arrival STAR.

 

Once i select RWY 03 and the IMBOM5K STAR from the FMS DB. Is there anything i should do on my part, for this type of approach at the start of the CDO or is it basically all managed from the FMS in VNAV and LNAV? I'm using the 737 NGX and always looking at new ways to improve myself on this piece of kit.

 

 

I appreciate any help from pilots or NGX users, thanks alot.

 

 



Vernon Howells

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As long as it's not interrupted by MCP altitude restraints, the FMC should handle the whole

descent LNAV/VNAV.  Which means you are going to have to reset the MCP alt before the 

TOD, same as most any other VNAV descent. Hope this is what you are asking..  ??


Mark Keith

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Hi, so i'll keep on resetting the MCP alt to each constraint and just before each alt constraint i'll reset it to the next hard alt constraint. That way i should have a continous descent at idle thrust?

 

If you check out my link from drop box you'll see on the STAR each waypoint has a min and max alt, i just set each minimum alt.


Vernon Howells

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Hi, so i'll keep on resetting the MCP alt to each constraint and just before each alt constraint i'll reset it to the next hard alt constraint. That way i should have a continous descent at idle thrust?

 

If you check out my link from drop box you'll see on the STAR each waypoint has a min and max alt, i just set each minimum alt.

 

Ehhhhh...yes and no.

 

The FAA offers specific guidance on the use of the AP when in an area with closely spaced constraints. It essentially boils down to "don't overreach, but choose the last constraint in a group of closely spaced constraints, unless the instructed altitude is higher.* " That guidance was written specifically for OPD (OPD is another name for CDO - optimized profile descent) STARs, actually.

 

*In the United States, this instruction would be in the form of:

"United 132, descend via the GIBBZ2, except maintain 1-1, 000."

 

In the above case, while the GIBBZ has altitudes that are closely spaced enough that I might roll it all the way down to 6000 (the last altitude on the chart), I would roll my altitude wheel down from cruise to 11,000 because the instructed altitude is higher.


Kyle Rodgers

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I have to say the FMS handled it well but i needed a few level segments or speed brakes to get my speed down for these additional speed restrictions....

 

MAX 220 at or below FL70

MAX 200 at or below 4000

 

I found speed brakes were slightly un-helpfull at speeds below 250kts.

 

I did however roll my MCP ALT down to the FAF alt 3000 and closely watched and made sure each alt constraint was being made....

 

In the FCTM - Alternate MCP Altitude Setting Technique using VNAV

 

When using the alternate technique, the FMC generated path should be checked against each altitude constraint to ensure that the path complies with all constraints.

I did however, get a VNAV DISCONNECT. CHECK ALT TARGET.

 

After the flight i re-run the descent and everything worked well. Not sure what i done there! I'll try it again tomorrow.


Vernon Howells

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I found speed brakes were slightly un-helpfull at speeds below 250kts.

Vernon

There pretty much useless at any speed when compared to the MD-11 or the 77LR and 777F.

 

Where does that STAR end and what kind of final approach did you use for that runway?


Michael Cubine
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