itsjase

Best descent rates

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Is there a recommended way of setting descent rates? As for example on Airliners the descent rate will change quite a bit due to the big changes in speed throughout the descent.

For example on an A320 or 737 if I set the descent rate to 1500fpm the top of descent matches quite closely with the FMC's calculated TOD but the "pass WAYPOINT at " altitude for the STAR will be quite high. If I set the descent rate to 1200fpm I get called to descend much earlier, but the STAR waypoint passing altitude is much nicer.

With 1200fpm I also tend to sometimes get vectored off the STAR, is this cause 1200fpm isn't enough to follow the STAR altitude restrictions?

Thanks,

Jason

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Jason

The "core" chartered descent profile on STARS & APPROACH is a 3o fpa ..... 320fpnm / 500fpm per 100ktsGS.

Review each time to check the required profile at different stages.

So, at TOD say FL360, GS (still wind) about 460kt / M0.78 in ISA, descent 2300fpm for 3o fpa

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I might've worded my question badly. I understand how descent rates work, but I'm wondering what it's best to set it at in Pilot2ATC because like you mentioned it changes considerably throughout the descent.

460Kts at 3fpa is 2300fpm like you said

but then when you get down lower and are travelling slower

250kts at 3fpa is 1250fpm.

Putting the descent rate in Pilot2ATC at 1500fpm seems to average it out and give the correct TOD but then the "pass at" altitude for the STAR entry waypoint is a bit high.

Edited by itsjase

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Getting the TOD to be at about the right place is key.  Usually 1500-1700 FPM will do this.  Once you get the descent instruction, you can let the FMS determine the passing altitudes and you won't get called for being off any of the planned altitudes, unless they are actually restricted altitudes (next to last column in the flight plan), and the FMS should be complying with these.

Getting vectors should have nothing to do with the descent rates or TOD.  You might get vectored off the STAR when the transition from the STAR to the Approach is too acute the STAR ends in a Manual transition.  

Dave

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Thanks for that Dave, will disregard the passing altitude and just follow restrictions if it won't call me.

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Timely discussion, I've been struggling a little with TOD today on two flights from KFLL to KMCO.  Descent rate set at 1800fpm. First flight there was no recommended STAR so I flew the THNDR4 SID out of KFLL to the TRAMP transition to ILS 36R.  I waited to see what would happen and finally called for an en route descent but was already 7,000 ft above profile.  Second flight, no SID, flew the BAIRN4 arrival with vectors to HAMMY for the ILS 18R. ATC advised me to expect the BAIRN4 but I didn't get a descend via the STAR instruction until BAIRN, which according to the chart you should expect to cross at 11,000.  I was still at cruise FL230.  I'll try adjusting descent rate to 1500 - 1700.  

Edited by BobKinSTL
Changed SID to STAR

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