Actually, ATC is very relevant to this discussion.

 

Why, though?

 

The "expect to cross DRUZZ at 10,000 and 250 knots" is on the chart because it is part of that air traffic control facility's SOP, which means that 9 times out of 10, you're going to hear:

"United 962, cross DRUZZ at 10,000, 250 knots. Dulles altimeter 29.87."

That being said, dump that into the CDU so the aircraft expects it way ahead of time. With this arrival in particular, it ends on a long downwind, which the computer will assume can be used as extra mileage to burn altitude, which is isn't.

 

You can get into a chicken/egg argument on the whole deal, because controllers refine procedures developed by the TERPS team, and they work hand in hand. So it isn't necessarily that the developer of the chart (in most peoples' minds the FAA) sat down and said "this plane should be at 10,000' right here," it's more that the cartographer came up with the general flow, alongside controllers, and they figured out that for the airport and the surrounding airports 10,000' is a good altitude to cross that fix (a great graphic of how intricate these things are is shown above for the NorCal area).

 

In any case, a lot of the arrivals in the States are still for older school nav, and don't have hard altitudes set in like most RNAV arrivals. Because of this, if you don't hand enter them, you're going to be high or low compared to where ATC wants you, I can guarantee it.

 

So no, the controller isn't affecting this one flight versus all of the other flights given the same instruction, but ATC helped develop that crossing restriction, so it is valid to say that ATC is affecting your descent profile.

 

 

 

In any case, regardless of the nitpicking in here, Dan has offered sound advice and should be commended. The FORECAST page isn't going to know crossing restrictions, and in many cases, altitudes are not set in on any STARs unless they're RNAV STARs. So, if you don't set them in yourself, you're going to be off.

 

Computers are great at crunching numbers and optimizing things. They are very poor, however, at reading minds, or analyzing information that was never provided.

 

Always remember: trash in -> trash out.

Hi Guys,

 

I thought I would chime in with some imputs here.

 

First of all the altitudes printed on the charts must be followed! if it say cross at FLxxx then you should aim to do so as precisly as possibly. This is to ensure vertical seperation from terrain and also airspace seperation. A STAR may keep you above minor airports airspace below or it may keep you above terrain. Many times it's also for noise.

 

Only "expect to cross xxx" can be obmitted, but I would see how they fit in with the predictions and also experience. Like if the chart says "expect to cross at 12000feet or below" and the fmgs gives me 11800feet as a prediction you just have to monitor it. Ask ATC if you are unsure.

 

If you are cleared via a STAR ATC expects you to follow the route and altitude restrictions. Also to keep above minimum altitudes. IE. if you are cleared to 6000feet, but the minimum untill next waypoint is 9000feet then you should only decend to 9000feet untill crossing. Then continue decend. This is especially important in a mountainous area with no radar!

 

There are only 3 times you may decend below MSA. 1: when VMC 2: When under radar vectors 3: when established on a STAR/IAL

 

With regards to slowing down. The 737-800 maybe a little slippery, but it's nothing compared to the A321!! However it is very possible. First of all if you blindly start the decend at T/D then you are already mentally behind. Also to be noted is the speed you're decending at and have programmed. I can fly past the T/D and be 4000feet above profile and still make it down without the use of speedbrakes. Just dail M.80 and LVL CH and watch the VS drop like a piano. If you are decending at a slow speed and you are high, you can, to recapture, just select a VS of -4000feet. Decend a few hundred feet below the Vnav path and re-engage Vnav. THAT is very efficient!

 

It's not that hard. you guys should try hand fly it in a non-fmc aircraft in a stromy night in a non-radar place.

 

Know thy aircraft!

 

Kind regards,

I apologize a little for the nitpicking, but I feel it's important that the regs/books are properly explained here, as there are a few minor oversights.

 

Only "expect to cross xxx" can be obmitted, but I would see how they fit in with the predictions and also experience. Like if the chart says "expect to cross at 12000feet or below" and the fmgs gives me 11800feet as a prediction you just have to monitor it. Ask ATC if you are unsure.

 

As I mentioned earlier, the reason the "expect to cross at XXX" is there is that 90% of the time you're going to hear ATC say "Cross DRUZZ at 10,000 and 250 knots." That being said, it's not mandatory until ATC says it. The chart says expect it because 90% of the time ATC is going to tell you to do it, which then makes it mandatory, so you might as well throw it in there, especially in slippery planes like the 738 and the 'buses. This gets the system expecting to cross it ahead of time, which only works in your favor. If ATC then doesn't say anything about it, or cancels the restriction, delete it and shallow the descent. It's a lot easier to shallow a descent than it is to try and dive bomb a crossing altitude, especially those you have to reduce speed as well.

 

If you are cleared via a STAR ATC expects you to follow the route and altitude restrictions. Also to keep above minimum altitudes. IE. if you are cleared to 6000feet, but the minimum untill next waypoint is 9000feet then you should only decend to 9000feet untill crossing. Then continue decend. This is especially important in a mountainous area with no radar!

 

Here's where you have to be careful with the phraseology:

If ATC says "descend and maintain," it's actually an immediate instruction that supersedes any crossing restrictions. If ATC wants to give you a minimum altitude to hit, but still comply with restrictions, they will specifically state "descend and maintain 6000, comply with restrictions." Most of the time, however, ATC minimizes confusion with "descend via the [xxx] arrival," and you just cross at all of the proper altitudes for the fixes.

 

Moral of the story:

"Cross DRUZZ at 10,000 and 250 knots," is a pilot discretion descent.

"Descend and maintain 9,000," is mandatory, even if it's the same arrival and there are crossing restrictions in between.

 

There are only 3 times you may decend below MSA. 1: when VMC 2: When under radar vectors 3: when established on a STAR/IAL

 

This is not true. MSA as a charted altitude is an advisory altitude only (you'll find references to it being specifically for emergency purposes as well). There is no regulatory requirement to remain above this altitude on either side. Granted, the regulatory agency will likely point that out if you're below it and end up crashing, but if you're below it and not established, you can't be violated for it.

 

That being said, the items you listed are the only cases in which it is smart to descend via the MSA.

 

Minimum Safe Altitudes, as defined by 91.119 (not the IFR MSA on the approach plates) are mandatory, however. For those of you who don't want to look it up, it's the whole bit about congested (1000abv/2000horiz) versus other than congested areas (500abv), and so on.

Kyle&all just a reminder we are not all in the FAA world.

For starters there is no "descend and maintain" at all this side of the pond... and I dont think I have seen "expect to cross at" anywhere but the UK lately...

I think you guys are over complicating it. If you look at the FAA charts, it will say:

 

TURBOJET VERTICAL NAVIGARTION PLANNING

EXPECT TO CROSS SCOTT AT 10,000ft & 250kt

 

It's just that simple. The FAA knows that crossing restrictions take some planning, so to make our lives easier they give you the information ahead of time. It would be unwise not to put that information in your FMC, unless you want to do a lot of mental math.

 

Sometimes you do end up high and fast, but with a bit of planning, it's very rare, and usually quite managable.

 

Paul

Kyle&all just a reminder we are not all in the FAA world.

For starters there is no "descend and maintain" at all this side of the pond... and I dont think I have seen "expect to cross at" anywhere but the UK lately...

 

Fair enough, but UK Phraseology isn't too far off with "descend to."

 

Here's an example of "expect to cross at" from the States. They're actually everywhere:

http://155.178.201.160/d-tpp/1205/05100SHNON.PDF

Yep I should have specified - I dont fly stateside... so my "apart from UK" really meant within Europe exc. UK

 

I dont disagree with you, I just wanted to point out that "you are wrong not you are wrong" style argument is out of place.

Wow! Why is this such an argumentative topic? Kinda childish isn't it? All I've suggested is to take a look at real world charts when flying cause it makes things easier. Take into consideration the Approach star I used. Lets say I was expecting a landing to the south at KMCO on Runway 17L. If I let the FMC calculate EVERYTHING and DO NOT take into account the vertical planning on my chart, I am going to run into BAIRN at about 13,000 ft. instead of 11,000. Its not an unmanageable task and quite a nice approach. However lets say on my descent, runways switch to North landings. I now have to land on 35R. According to the chart it says for North landings I should Expect 8000 at BAIRN. Because I am already descending, I am now going to cross BAIRN at roughly 5,000 ft higher than I would if I had just entered in my crossing restrictions to begin with as BAIRN 250/8000 11000B. It just makes the ENTIRE APPROACH more manageable. Just because it says to expect doesn't mean its set in stone or required, but its nice to set anyways as a way to be sure I don't have to rush to make adjustments. I didn't mention anything about ATC as I don't even fly with ATC, but I doubt any controller would scold you for being on top of your plans. Pre-planning is just another way to have a more efficient and enjoyable flight. Just opening options to those who haven't thought about it before.

 

Thanks,

~DAN~

It's not that complicated as some on here make it sound.. One thing I've learned for over 20 years is that FAR's, books, and all the studying is more difficult than the actual act of piloting an aircraft.. SIDS and STARS mostly take the workload off the pilots and ATC.. ATC assigns speeds, altitudes, headings, etc and they know your type of aircraft and it's nuances.. The -800 being too slippery is a not true, just takes a little longer to slow so you plan accordingly.

FL CH and speed management. Problem solved.

 

I use the FMC to draw a pretty map, and not for much else.

 

Best regards,

Robin.

Hear, hear. I used to fly the Tu-154 a lot. No fancy VNAV...

 

"We will descend... about now". And down I went. Landed safely every time, too. Overreliance on automation is not a good thing.