This is all dependent on aircraft as well. You have an Optimized profile, a Crossing profit, and then there is a normal or comfortable profile (I made all of those up). I think most of anything other than RJ's use an ODP for an Idle descent. In the CRJ for example it's not really practical to do this when you have step down fixes and other things like tail winds. Idle decent in a CRJ holding a anything over 300KIAS is pretty aggressive and not comfortable for passengers. At least that has been my experience. Seems like rule of thumb is to descend at 3 degrees and it works well. Except for those short stepdowns and such.

 

Correct, MFD data shows decent rate to meet the next altitude. Following that can result in missing an altitude or speed restriction. Best example is MEM Tammy arrival landing north transition. There is a fix that has a soft window of 16000B/10000A. 2 miles later is a hard restriction of 10000 and 210 knts. If you follow the MFD data you will be 2 miles away from the 10,000/210kt restriction at 16,000ft. Following the snowflake will allow you to meet the altitude. Speed is on you. Flight spoilers likely required.

No need for any of the DIR/INTC info. Just will add to confusion. Level off til TOD, divide your ground speed by 2, and add a zero for your descent rate, then follow snowflake

 

Please don't take my previous post as saying you were doing it wrong. Technique is individual to each pilot. Some guys set the hard alt in the FMS and preselect each step down and use the banana bar, some don't set the hard alt in the fms (leaving between and above/below), and use the snowflake, some set the hard alt in the preselect and use the banana bar and DIR/INTC page on the FMS to meet the restrictions. If your carrier doesn't "specify" it to be done a certain way and you don't bust an altitude, it's simply your technique. If you don't bust anything, your way works just as well as anyone's. The OP asked about the way of DIR/INTC, and I think he understands it. Obviously, with 2 folks up front, both "should" be very vigilant of where you are and where you are going on the "descend via" rnav arrivals. There are many "gotcha's" on some of those that require extra attention. The one that comes to mind is the eldee in DCA that throws a 10000 to 9000 step down.... The speed reduction and short distance between fixes can "bite" when trying to slow and get down if you get a little behind.

The beauty of the DIR/INTC is you see the speed as well as the VS required for all the fixes, much like the legs page and MFD display, yet you also see the planned VS, which can be very handy if you have a "between" altitude followed by a speed restriction and continued descent. Obviously, if you are familiar with the arrival, you may already know the speeds by memory/familiarity and not necessarily need the extra info. So in the end, it's up to you.

 

There are a few CRJs out there that have a VNAV button on the flight guidance panel and when that is selected the flight director will give guidance to follow that snowflake. The FMS also expects you to enter the destination OAT and will present a CHK APT OAT caution if you don't provide an OAT prior to the FMS entering TERM.

 

I have to agree with you on the DIR/INTERCEPT page..... In a place like DCA with a strong west tailwind it will get you violated quickly..... If not it will leave you diving for the next fix on the ones in which are only very few miles apart.....

I guess with us I rather just put down the USA today and have the chart at and hit the lowest altitude for the specific fix we are crossing.... Then when there's the strong tailwind from the west we don't to worry about the ones with a good amount of altitude to lose and very few miles to do such..... Who knows we all have our different approaches. Unfortunately the software in the CRJ doesn't offer a great solution in which one is better then another..... To each their own....

 

What is taught at XJET is you have to set up the VNAV snowflake by going to the VNAV Decent menu and making sure that the Mach/indicated speed is set up correctly and the 3.0 degree is indicating as well for the descent.

Example: on some arrivals you have to read the STAR where it might tell you to maintain mach until transition to 280 maintaining that until reaching 10000 feet where you slow to 250. etc. then go to the PERF menue select Vnav, scroll throught the pages, where it is titled Vnav Descent, and plug in the numbers.

should look something like this:
.80/280

10000
250/10000 VPA
3.0 degree

once that is set up the snow flake will guide you through all the at above and at below along with in between until reaching your hard alt. you need to make sure you take your ground speed/2 add 0. example: 200 GS/2 add o. 1000 fpm should keep you in line with the snow flake with a little adjustments.....

 

Can I claim target fixation? ODPs are burned into my head from my days as a II because nobody and I mean NOBODY had a clue how to depart an airpart IFR unless it was a published SID. So teaching ODPs was a crusade of sorts for me. Consider MY cajones busted and I will be TOTD.

 

FYI, the snowflake and the DIR/INTC vertical speeds do correlate. The most restrictive vertical speed is what the snowflake is giving you. My personal technique is to start a descent using the snowflake, then check the DIR/INTC page to see what vertical speed I need to hold the snowflake. Works like a charm.

 

Here's a little video to help you remember all the FARs relating to "getting down with ODPs"...

Naughty By Nature - O.P.P. - YouTube

 

Ha!! Funny!

Edit; I think I am still "old school" in thinking of CDA vs thinking ODP (continuous descent approaches). I believe the preferred terminology is ODP now. (??) Tried doing a ctrl F of the AIM, Instrument Flying, and Instrument Procedures Handbooks and couldn't find anything on CDA or ODP.