What is your preferred profile???

[ONESINGLESKY]

Dear all,

I am "deviating a bit" from the possible topics of this forum but anyway here goes.

I am working on a project regarding CDA (Continuous Descent Approach). Although I have a strong ATC (TWR, APP and) ACC and a good Flight Operations background, some things is better to ask the guru's around here and also get different perspectives.

Although most of the crews visiting this forum are Biz Jets professionals, most or at least many of you have airline flight experience. That is why I raise the following couple of questions:

a) do you prefer a continuous descent/approach? or step descent/approach?

b) a late descent with steeper RODescent or earlier descent with "soft" RODescent

I know that different airlines have different procedures, for what they consider to be the most optimum profile.

This program I am involved with, concerns the SESAR (single european sky program) concept and flight development.

Any comments are appreciated and thank you all in advance for your cooperation and time.

Wish you all safe flights.

OSS

[redsnail]

CDA's. Much easier.

[Paradise Lost]

Preferred approach

OSS, I guess everyone would prefer a continuous descent approach if only to give the pax a smoother, quieter end to their flight. It is definitely more environmentally sensitive too, from both the noise and fuel burn perspectives.
Most a/c like to start out (particularly from > FL 430, with a more modest rate of descent (say 1,500-2,000 fpm) until they reach < FL390 where a rate of 2,500-3,000 fpm is quite reasonable until approaching FL 100, where with the requirement to reduce speed to > 250 kts and ground closure require an r.o.d. of about 1,500 fpm again.
That doesn't really sound like a continuous DA but is in fact achieved with virtually no power change from top of drop to selection of full flaps.
That profile is achieved by starting descent at a distance of 3 X Altitude (in 000's) correcting for head/tailwinds.
Keep up the good work!

[CaptainProp]

OSS - I believe it depends very much on the size (weight) of the aircraft. If you are in a 320/737 size aircraft or bigger you NEED track miles/high speed to get the height off. So if pushing it with a late descend, to save fuel and/or get more direct routing, and suddenly something changes in the grand plan and track miles are cut off - Toast. Now you (we) need vectors to loose that height and we have lost, and potentially increased, the very same time and fuel we were originally trying to save.....

CDAs with reasonable margins for unplanned changes seems to be the best way.

CP

[Flintstone]

Well personally I like to start out with a reasonable rate of descent, say 2000fpm, then suddenly point the nose down until all I can see through the front window are fields before hanging everything out to prevent overspeeding causing the cabin contents to end up in the cockpit then level off at 2000' and drag my @rse around the countryside at low level burning buckets of fuel before being vectored onto a 25 mile final for..........................no, wait. That's Paris ATC for Le Bourget.


DCA of course.

[transilvana]

ONESIBGLESKY, you spend too much time at hotels/home doing nothing, every descent is different, thatīs all

[ONESINGLESKY]

transilvana,

I really appreciate your reply, not only as a very constructive opinion but also very inteligent.

All descents are different? Really? Damn, and I've been thinking all my career that they were all identical. After all, what goes up, must come down...

As example, when I controlled KLM flights, they ALL (seldom exceptions) wanted an as late as possible descent. Other companies wanted earlier descents, for same city pair, and it wasn't only for a day, but everyday like that...

What I meant by my question is clear: to receive as much inputs as possible, concerning a subject that affects you all. I thought that by writting a post here, would allow to have a different perspective from the "end-user" (you) who is actually flying the plane.

I know they are all different, with many constraints, but what I meant to understand was what you crews prefer, just to have an idea of your views.

The study I am making is aiming at developing new procedures to help you ALL, and your passengers and companies.

Anyway, I respect your reply and wish you safe flights

PS - My best regards to you Flinstone! and a big thanks to all that participated so far. All comments are appreciated.

[Belgium Legacy]

The most preferred one would be an idle decent to FL 120 and then reducing to roughly 1500 fpm to achieve 250 kts or less at FL 100. This does depend on passenger (and overall cabin ) comfort and a/c limitations.
A 4000 fpm or more then 5 degrees nose down attitude would be uncomfortable. (somebody should tell Paris about that).

So my vote would go for a CDA.

This would mean not only a change in procedures in ATC but also in the training of pilots to follow those procedures.
Some ( my experience ) know the talk but don't walk the walk.

good luck with the study

[2604]

Approximately a 3 degre CDA.

[Retire2015]

"Descend via" with published alt and speed constraints. Each A/C can calculate its own optimum profile.

An arrival like the Kooly1 into KPHX is an example that works well with a minimum of radio communications.

Now part of the deal needs to be, don't monkey with the speeds while arrival is underway. KLAX is notorious for requiring "slow to 250 knots" while doing an optimun descent at 310 knots with a hard crossing altitude coming up.

R

[Brie]

I prefer a CDA as well.

We descent with 3000'/min unless we are low on fuel. In that case we take 4000'/min.

Nice thread by the way