How Go Down?

Captain

Captain

Final Approach
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This comes up all the time, especially for me and my 'stay high' flying style.

Situation: you're level at FL350. ATC tells you to descend to FL250 and you roger that and start down. ON THE WAY down ATC gives this transmission:

"BPITW 34, cross DIGGY at FL190"

You roger that and program the box to hit DIGGY at FL190. Presently you are at FL295 and descending.

Now, here's the question;

Do you continue to FL250 (previous clearance) and then descend to cross DIGGY at FL 190? Or do you level where you are and descend later to cross DIGGY at FL190?

The answer is the later. A descent (or climb) clearance cancels all previous clearances. I stop my descent and program the box to hit DIGGY and half the guys I fly with will insist we need to continue to FL250.
 
Even though I do not fly at flight levels, I would say the last command you get from ATC is the one you honor. I would do the same putting around at 5,000 feet.
 
Captain said:
This comes up all the time, especially for me and my 'stay high' flying style.

Situation: you're level at FL350. ATC tells you to descend to FL250 and you roger that and start down. ON THE WAY down ATC gives this transmission:

"BPITW 34, cross DIGGY at FL190"

You roger that and program the box to hit DIGGY at FL190. Presently you are at FL295 and descending.

Now, here's the question;

Do you continue to FL250 (previous clearance) and then descend to cross DIGGY at FL 190? Or do you level where you are and descend later to cross DIGGY at FL190?

The answer is the later. A descent (or climb) clearance cancels all previous clearances. I stop my descent and program the box to hit DIGGY and half the guys I fly with will insist we need to continue to FL250.
Click to expand...
If your rate of decent from FL350 to FL250 will put you over DIGGY at FL190, maintain rate of decent. If not, adjust accordingly to achieve FL190 upon arrival at DIGGY unless otherwise instructed.
*EDIT* looks like I was late to the party with my response.
 
dtuuri said:
No.

No again. You just change your descent angle to cross DIGGY at FL190.

dtuuri
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If I issue those clearances, it's because you're clear of whatever traffic I descended you under. If you leveled off, cut the descent rate to less than 500 ft/min, or dove to FL190, it wouldn't matter to me. Normally pilots would adjust their rate to make the crossing, but any of the aforementioned actions are correct in following the clearances given.
 
MarkZ said:
If I issue those clearances, it's because you're clear of whatever traffic I descended you under. If you leveled off, cut the descent rate to less than 500 ft/min, or dove to FL190, it wouldn't matter to me. Normally pilots would adjust their rate to make the crossing, but any of the aforementioned actions are correct in following the clearances given.
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It may be "correct", but I wouldn't level off after having started a normal descent without saying something first in that case. According to you, Captain could level off at, say, FL290 just as well. I don't think he would have done that after reporting out of FL350 for FL250. My sixth sense is based on previous experience and I can't always cite why I do some things, but in this case I wouldn't make the assumption ATC doesn't care if I level off unexpectedly.

dtuuri
 
If you get "cross a X altitude" or "pilot's discretion to X altitude" you can level off at an intermediate altitude and they don't expect you to say anything.
 
dtuuri said:
It may be "correct", but I wouldn't level off after having started a normal descent without saying something first in that case. According to you, Captain could level off at, say, FL290 just as well. I don't think he would have done that after reporting out of FL350 for FL250. My sixth sense is based on previous experience and I can't always cite why I do some things, but in this case I wouldn't make the assumption ATC doesn't care if I level off unexpectedly.

dtuuri
Click to expand...

Again, most of the time what you're saying is true. In ATC speak, when I issue a crossing, I issue a pilot discretion descent with a condition. You can't go back up, but other than that it's your airplane, just be at a certain altitude by a certain point. I agree with the heads up call, that's always a good thing.

Nowadays, it's a blue moon when a pilot reports leaving an altitude.

:mad2:
 
I thought this was going to be an offshoot of the mile high thread...

Since last clearance is controlling and doesn't mention the former restriction, I would set up to cross DIGGY at 190 and forget the former.
 
Henning said:
I thought this was going to be an offshoot of the mile high thread...

Since last clearance is controlling and doesn't mention the former restriction, I would set up to cross DIGGY at 190 and forget the former.
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Pretty sure "Going Down" in a pilots forum should be about an off field landing. This thread should be titled "Descending". :dunno: :rolleyes:
 
You FMS Diggy/FL190 and set 190 in the window...

I get the same crap sometimes..."descend FL320 pilots discretion FL240..why on earth do people put FL320 in the ALT window:confused:..finally someone did it to a check airman and it was inserted into SOP but I still see people do it once in a while.
 
MarkZ said:
Again, most of the time what you're saying is true. In ATC speak, when I issue a crossing, I issue a pilot discretion descent with a condition. You can't go back up, but other than that it's your airplane, just be at a certain altitude by a certain point. I agree with the heads up call, that's always a good thing.

Nowadays, it's a blue moon when a pilot reports leaving an altitude.

:mad2:
Click to expand...

I ALWAYS report 'vacating an assigned altitude'. I make it a point. With that said, I only report leaving ASSIGNED altitudes as per the AIM. So...if I self level off because you changed my clearance and gave me DIGGY at some alt.. and I leveled off...that's not an 'assigned' altitude. Ergo, I wouldn't report leaving the altitude that I happened to level off at.

However, every single time I leave an assigned altitude, whether it's pilot discretion or assigned by ATC, I always report 'Leaving FLXXX descending FLXXX'.

That's why i'm awesome.
 
Geico266 said:
Pretty sure "Going Down" in a pilots forum should be about an off field landing. This thread should be titled "Descending". :dunno: :rolleyes:
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Maybe you should petition Congress to formulate a 'Department of Internet Correct Thread Titles'. What we need is a government agency to bounce our thread title suggestions off of to determine if they are good enough. I know how much you like regulation. What do you say?
 
Captain said:
However, every single time I leave an assigned altitude, whether it's pilot discretion or assigned by ATC, I always report 'Leaving FLXXX descending FLXXX'.
Click to expand...

Ditto, even in my little beercan.
 
Captain said:
Maybe you should petition Congress to formulate a 'Department of Internet Correct Thread Titles'. What we need is a government agency to bounce our thread title suggestions off of to determine if they are good enough. I know how much you like regulation. What do you say?
Click to expand...

I would like to say what is on my mind, but this is not the SZ. ;)


:rofl:
 
Curious - What "box" do you program to have the AP fly a smooth decent to hit a specific altitude at a specific point in space?

I've received these clearances many times (albeit at a much lower altitude) and it is a manual mental exercise to comply usually leading to a 1500 fpm decent rate over the last two miles.
 
Baron2PG said:
Curious - What "box" do you program to have the AP fly a smooth decent to hit a specific altitude at a specific point in space?

I've received these clearances many times (albeit at a much lower altitude) and it is a manual mental exercise to comply usually leading to a 1500 fpm decent rate over the last two miles.
Click to expand...


You don't need to program no box, just a better manual mental exercise. Money can't buy everything. If you can't figure it out mentally while scanning for traffic, you're sure to run into somebody while trying to program a "box".

dtuuri
 
Baron2PG said:
Curious - What "box" do you program to have the AP fly a smooth decent to hit a specific altitude at a specific point in space?

I've received these clearances many times (albeit at a much lower altitude) and it is a manual mental exercise to comply usually leading to a 1500 fpm decent rate over the last two miles.
Click to expand...

The FMS must be updated so the automation can hit the fix if a clearance is received to do so (ie. Cross 45 miles west of Gibbs at FL240)

On the "new" style RNAV arrivals that are becoming the norm at most major airports...save yourself an ASAP/NASA report and just let the plane fly it... without autothrottles/VNAV these arrivals are a bigtime workout
http://imageserver.fltplan.com/merge/merge1312/Single/05100GIBBZ.PDF
 

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Baron2PG said:
Curious - What "box" do you program to have the AP fly a smooth decent to hit a specific altitude at a specific point in space?
Click to expand...
I'm sure all systems are different but we can enter an altitude next to the waypoint name on the FMS then hit "direct", push the line select key next to the altitude then hit VNAV and the airplane will decent at constant rate from the current altitude to the one you want, well, provided you have also changed the altitude selector.

BTW, was the snarky response two above this one really necessary?
 
taters said:
You FMS Diggy/FL190 and set 190 in the window...

I get the same crap sometimes..."descend FL320 pilots discretion FL240..why on earth do people put FL320 in the ALT window:confused:..finally someone did it to a check airman and it was inserted into SOP but I still see people do it once in a while.
Click to expand...
Why wouldn't you? If I don't want to descend to FL240 yet, I'll set FL320 in the window, get down to there, then cruise at FL320 until I'm ready to head on down to FL240. What do you do?
 
Sluggo63 said:
Why wouldn't you? If I don't want to descend to FL240 yet, I'll set FL320 in the window, get down to there, then cruise at FL320 until I'm ready to head on down to FL240. What do you do?
Click to expand...



Looking back the example I meant to use was "descend to FL320 cross Benke at 14000" etc.. when the lower altitude is not set guys forget about the crossing restriction until its too late...on a decend/decend discretion clearance.. I just set the bottom altitude and let the AP hit on profile ensuring the first altitude is at least met with 500FPM.
 
Personally I think it's poor form to simply VNAV direct to a point from present altitude without giving it some thought. I'd much rather fly a 4.0 degree path for fuel savings by delaying the descent as long as possible.

Many guys just start down and burn the extra gas. There are three possible profiles;

- stay high long and descend steep,
- descend early and keep a marginal descent rate,
- descend early and steep so as to fly level at the lower altitude.

The last is worst for fuel savings and the first is best. My flying style is to, when able, shoot for that first profile. By voluntarily selecting the second or third you're wasting gas and money with no benefit.
 
Last edited:
Captain said:
Personally I think it's poor form to simply VNAV direct to a point from present altitude without giving it some thought. I'd much rather fly a 4.0 degree path for fuel savings by delaying the descent as long as possible.

Many guys just start down and burn the extra gas. There are three possible profiles;

- stay high long and descend steep,
- descend early and keep a marginal descent rate,
- descend early and steep so as to fly level at the lower altitude.

The last is worst for fuel savings and the first is best. My flying style is to, when able, shoot for that first profile. By voluntarily selecting the second or third you're wasting gas and money with no benefit.
Click to expand...

Yep, the program they've been working with the airlines into SFO for a couple years now where ATC uplinks a direct descent to the runway to the FMS and keeps them high for as long as possible has shown some really nice fuel savings benefits.

That said there is limited applicability of that to non pressurized GA aircraft do to potential physiological boundaries. I've had to start descents way out and limit them to 200fpm because people had sinus and ear clearing issues.
 
To answer the question in the title, plug your nose.
 
Everskyward said:
BTW, was the snarky response two above this one really necessary?
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Let's see, one, two... that was MY post you're slandering!

Merely trying to help save some money and point to the real problem. Keeping a ratio between the altitude to lose and the distance remaining, by adjusting the descent rate, is easy to do and isn't heads down. Just because the task is automated doesn't relieve the the PIC from continuing to monitor the automation.

dtuuri
 
dtuuri said:
Let's see, one, two... that was MY post you're slandering!

Merely trying to help save some money and point to the real problem. Keeping a ratio between the altitude to lose and the distance remaining, by adjusting the descent rate, is easy to do and isn't heads down. Just because the task is automated doesn't relieve the the PIC from continuing to monitor the automation.

dtuuri
Click to expand...
The poster was just asking out of curiosity and didn't deserve that response.
 
taters said:
Looking back the example I meant to use was "descend to FL320 cross Benke at 14000" etc.. when the lower altitude is not set guys forget about the crossing restriction until its too late...on a decend/decend discretion clearance.. I just set the bottom altitude and let the AP hit on profile ensuring the first altitude is at least met with 500FPM.
Click to expand...
I get what you're saying, but I still do it the same way.

If you're 200 miles from the field, cruising at FL340, and center gives you "descend to FL320, cross BENKE at 14,000," I'm going to set 320 in the window and use V/S at -500 fpm to get to FL320. That takes 4 minutes, at 420 GS, that's 28 miles. Now you're about 170 nm from the field. Rough wag (depending on winds, direction of landing, anti-ice usage, etc.), I want to start down at 105 miles from the airport. I would rather cruise at FL320 for the next 65 miles, then start down on profile instead of just a continuous descent to 14,000.

Granted, I agree with you on the HF issue of forgetting to set 14,000 in the window. It's been known to happen...

I don't think either way is wrong. More of a technique thing. I've seen guys do both.
 
taters said:
I get the same crap sometimes..."descend FL320 pilots discretion FL240..why on earth do people put FL320 in the ALT window:confused:..finally someone did it to a check airman and it was inserted into SOP but I still see people do it once in a while.
Click to expand...

Couldn't there be a good reason to stay at the higher altitude for a while? :dunno: I got discretion from 10,000 to 4,000 125nm from my destination a couple weeks ago. Whaaa? Uh, OK. Read it back, stayed at 10.
 
Captain said:
Personally I think it's poor form to simply VNAV direct to a point from present altitude without giving it some thought. I'd much rather fly a 4.0 degree path for fuel savings by delaying the descent as long as possible.

Many guys just start down and burn the extra gas. There are three possible profiles;

- stay high long and descend steep,
- descend early and keep a marginal descent rate,
- descend early and steep so as to fly level at the lower altitude.

The last is worst for fuel savings and the first is best. My flying style is to, when able, shoot for that first profile. By voluntarily selecting the second or third you're wasting gas and money with no benefit.
Click to expand...

Pax comfort? ("Hey, why's my pilot keep going up and down?" :goofy:)
 
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