Airline Flying Management

[loopa]

I thought I would get input from you airline dudes about the following inquiries.


For the descent, do you guys calculate your own T/D or do you just let the FMC/FMGS take care of it and follow the profile it publishes? What if ATC takes you off of the STAR and you have now had significant reduction in track miles. You will end up high, right? Sure you put up spoilers and yati yati yata to get down quick. But is there anyway to anticipate this? How hard will your CP crack down on you if you end up being too LOW because of ATC's vectors and you end up using Thrust for an extra 20 miles in straight and level?

So how do you well-plan a descent taking into consideration all the distractions that can be applied to it?


In the FMC/FMGS, back at the departure gate, do you put in the entire route INCLUDING the star? Or do you put in the STAR when closer to the T/D? If so ? How many miles away from T/D do you put the star in.

How do you know which Arrival Runway to put in the FMC if you're 250 miles out? I assume you can't pick up the ATIS when so far out? Because won't the arrival runway COMPLETELY change your T/D position?

Imagine 26L and 08R at YVR. Coming in from Northeast, you will have an extra 30 track miles for 08R. I assume you would start your descent later, or at least, AFTER VITEV's -FL210 restriction, you would maintain a shallower descent profile?



If somebody could answer those, that would be great ! I've always wondered

[The Hammer]

Most airliners can get the dest. ATIS while still at the gate via ACARS. The flightplsn provided by dispatch determines this as you have to plan for something (usually the longest STAR/runway combo)

[ea306]

Hello Loopa,


Good thread starter question.

When it comes to descent planning there are many ways to "skin a cat" as they say. (Just a figure of speech to any of you PETA followers....Gotta love Pamela). Hopefully we will see lots of good comments to your questions.

Doing a quick mathematical cross check for the reasonableness of the FMC computed T/D point is a good airmanship thing to do.

As for the probability of which approach to plan for, that can be a bit of a crap shoot at times depending on the airport. Baring unexpected runways changes and arrival routing changes, having the latest weather is a big help. Besides the ATIS which as you commented can be out of range, you could make use of FSS or VOLMET if you are not equipped with ACARS. I have found that YVR ACC have been very helpful when reporting at their FIR boundary. Just ask them which approach and runway can you anticipate. It may change by the time you get there...oh well....not the end of the world.

As for the extra miles you fly due to ATC.... not a lot you can do about that. What you can do to be as efficient as possible is delay your flap extension if you have a few more track miles to fly. Your fuel consumption generally increases by 10% with the first selection of flap. Wait until you are approaching your profile distance for the present altitude you are flying and then do as you normally would. No point in being fully configured 15 or 20 miles back at 3000 feet. As you get to know your airplane you will be able to anticipate how many track miles are needed to decelerate from any given speed to a new target speed. Comes with time. Rule of thumb for many airliners is approximately 1NM per 10kts of deceleration in level flight. ie: 250kts to 210kts would be approximately 4NM. There are other factors as well that will affect that such as A/C weight as well as Engine Anti-Ice which as you probably know affects the flight idle N1/EPR. In those cases you might need a little more room.


I cannot imagine any CP giving you grief for flying too low on a profile due to an ATC instruction. Neither can I imagine any CP giving anyone grief for being too low on the profile ever really...not withstanding that we all want to fly as efficiently as possible and in time we develope the skill sets to accomplish that. I would really hope not.

The best remedy is to be situationally aware of the anticipated track miles and also try to visualize what a cleared direct to point along you arrival routing will do to shorten your track miles.

Does your aircraft have the ability to draw a 30NM or 40NM ring on the FIX Page? If so, as a matter of technique...some like to draw a 40NM circle as a reminder of where they may be on the profile. Depending on what you are flying, you may want to be at 250kts at 10000' at 30 miles or 40 miles depending on what type you are flying. That gives you a direct distance heads up...not track miles. Alternately you also have DME at your disposal which you could use off the ILS if it is DME equipped.

If there is anything that will get you a visit for "Tea and Biscuits" with the company CP ...it will be for flying an unstabilized approach to a landing...that is a completely different matter. Many companies want to see you fully configured and meet their criteria for a stabilized approach by 1000' AGL. Staying ahead of the game should help you to avoid that situation. No excuse for an unstablized approach...there is that maneuver called a "GO-AROUND".

As for programing the STAR when doing your initial setup, that is personal preference. If you want to get a good routing distance cross check between your flight plan and your FMC inputs you may wish to omit putting in the STAR...depends...you may want to put in the arrival route you think you will get as opposed to the flight planned arrival route in order to get a fuel prediction that you are comfortable with. But that is up to you.

As I mentioned already, there are many ways to "skin a cat"... I hope we will see lots of suggestions on this thread. You can try what you like and develope your own technique that works for you.

Safe Flying!

[loopa]

Awesome reply, it definitely gives me a bit of an insight now.

A question popped up !

What you can do to be as efficient as possible is delay your flap extension if you have a few more track miles to fly.

Do any airlines have a limit for straight and level pitch attitude with respect to PAX comfortableness ? Because what if the STAR requires you to fly at a speed that is equivalent to a very nose high attitude. Say, a H/B744/W doing 200 kts on downwind for 08L. That's going to need one hell of a nose high attitude with 0 flaps.

Would you sacrifice pax comfortableness over fuel? Because by this point you could lower flaps and have a more comfortable attitude.

Doing a quick mathematical cross check for the reasonableness of the FMC computed T/D point is a good airmanship thing to do.

Is this mathematical cross check correct?

ALTITUDE - ALTITUDE RESTRICTION = X

X / 3 for a 3 degree descent profile = Track miles to the altitude restriction where you have to start your descent.

Ex

Altitude = 350000 feet
Restriction = VITEV -FL210

14000 / 3 = T/D = 46nm to VITEV

And if you want a 4 degree descent profile you change the denominator to 4 ?

So the same example would be

140000 / 4 = 35nm to VITEV

The goal of the descent planning is to retard the throttles to idle and have a as little fuel as possible being burned in the descent. Wouldn't the 3 degree descent profile perhaps change to a 2.5 degree descent profile if you're a heavy 747 simply because you have more momentum (Mass x Velocity)? So in order to maintain your speed at throttles idle, you would have to come in at a shallower rate of descent... On the other hand, if you're an A320, you could come in on a 4 degree descent profile because of less momentum ?

How do you know what the descent profile calculation will be? Is that something that you learn in the type rating course for the aircraft or is it something you learn through experience? What if your calculation of T/D is 15nm before the computers calculation. Which one do you use? The computer or yours?

Also, wouldn't there also be a certain speed that would allow you to fly idle all the way down? Because if you fly too slow on the descent, you can only maintain a certain rate of descent before it starts accelerating. And on the other hand, if you fly too fast, you would need to add thrust in order to maintain your rate of descent on the descent profile. So how do you calculate that critical speed that allows you to idle all the way ?




Your insights?

[Rotten Apple #1]

What if ATC takes you off of the STAR and you have now had significant reduction in track miles. You will end up high, right? Sure you put up spoilers and yati yati yata to get down quick. But is there anyway to anticipate this?

If the controller quickely clears you to a series of progressively lower altitudes, one would assume he's planning on turning the airplane onto base leg soon. Depending on the airplane type, you would use a combination of airspeed, speedbrakes, gear, and flaps to expedite your descent.

Toronto and Vancouver are great places to try to guess your base leg turn, but it's a very speculative venture at times. Doesn't matter your experience, sometimes you think one way, but the controller decides to go with his/her plan and voila!, you're levelled off for ten miles with power up.

And if you want a 4 degree descent profile you change the denominator to 4 ?

No one I know ever bothered to calculate a 4 degree descent profile.

[tripleseven]

Going into Vancouver, there is a waypoint with a 10000-14000 restriction, if landing on the 26's. I always put make it a hard 10000, because you never fly the entire star, and it knocks off at least 20 track miles. That way, you have a decent chance of making it straight in on 26R when they give you direct to GOREG.

In Toronto, in my little bit of experience, if you are doing the YOUTH arrival and they vector you to the east of the track, cutting the corner when landing SW bound, I start getting the power off and boards out, because they always seem to slam dunk us when that happens.

I guess my point is, just make it happen the best you can.

[Flying Nutcracker]

Your transition speed from Mach to KIAS is a big key in this as well. If you are planning a High/High descend speed, you will have a relatively steep descend profile in the first place. This will give you some problems if ATC cuts you short on track miles as you wont have the ability to steepen up your profile because of Vmo issues. High/Medium transition speed will give you flexibility once you reach the altitude where you transition to a Medium KIAS from the High Mach. Now if you get cut short you CAN steepen the profile by increasing your KIAS. Energy management.

The worst is getting cut short, being left high AND having to meet a speed restriction. Usually one will have to give.

I think the key is to plan for economy and a normal profile, and if the plan changes because of ATC... well there's not much you can do about it and we take the penalty of burning more gas OR try to get down fast enough. Try not to overcomplicate the planning, but have an understanding of your options if needed based on the speeds that you are using and how much play they give to facilitate a change in plans. A random piece of information, if you plan a high transition speed and ATC gives you a speed restriction during descend, you may have an issue trying to meet any altitude restrictions on the arrival.

Certain places we go we have a reasonable assumption about what to expect based on what we have experienced in the past, and we make an educated guess based on runway in use and the STAR we are flying as to whether or not we would alter the profile. I.e. Cross XXXXX BTWN 12000-16000, if we know that chances are good for a short cut, we will put in as a hard altitude at 12000. If we know there is usually never a short cut, like CYYJ, we let the FMS figure put the best profile.

As for the close in stuff, TCAS and a good listening ear on the radio can give you a good indication of where you fit in the sequence and how you should plan your speeds and configuration. A tailwind on final is a pain in the butt especially if they ask you to keep the speed up, because a 3 degree slope makes it tough to slow down and get configured. It doesn't help when the tailwind swings around to a headwind either.

[Flying Nutcracker]

Here's another tid bit for any one who might be smart out there... So you plan a profile of lets say M0.78/267knots. Somewhere in the descend ATC asks you to transition at 300 knots or greater. You comply and reprogram the FMC.

What happens with your profile?

After a little bit, lets say 5 minutes, ATC cancels the speed and clears you to resume normal speed. WHAT DO YOU DO???

[quietwing]

Hi Flying Nutcracker

In your scenario I would do nothing. If you have programmed the fmc for a 300 kt descent, that is your new normal speed. If atc says slow to 267 again well obviously you would need the boards to meet the speed restriction.

[Four1oh]

I'd like to meet an Airline CP who has time to hound guys on decent profiles!

[groundtoflightdeck]

Not to confuse the matter too much... we have to do our profile manually because we are flying an older machine without the A/T etc. The airplane has a fairly stubby wing so it can be very forgiving if you are a bit high. I always make a descent plan based on a 3:1. The airplane descends faster than 3:1 above 10,000 and about 3:1 under 10,000. So depending on weight, A/I planning and winds I will usually start a descent at 3:1 - 8NM (ie. 33,000 =99-8= 91NM) by the time I hit 11,500 reduce the rate of descent to a little less than 3:1 and slow to 250kias for 10,000, then fly at the 3:1 vertical (gs*5) to the IAF then dirty up in that area... at any point driving the speed up in the descent will get you back onto the profile- but if you get low its going to be an expensive correction. I think some of these "new" airplanes with the high tech wings aren't as forgiving if you are up too high- the A330 sound particularly difficult. The manual decent adds a little bit of mental math on the descent, but very strait forward

[ettw]

I take my altitude to lose x 3 and stick the nose down. When I hit my 2:1 I pull the throttles back to 100psi and if I'm high I hold off on trimming back up from cruise "flap, gear, flap, flap, flare".

Oh sorry....this is a GLASS JET thread....

Cheers,

ETTW

[loopa]

I would like to thank everybody who have commented. I m definitely painting a much better picture of how it's done and how to anticipate changes in your descent.

I particularly like the one about energy management and giving yourself room to move within the momentum scale allowing you to change your descent profile with an easier tone.

[ettw]

loopa,

I'm curious about your back ground. Are you just making the first steps into the fast, slippery jet world, or are you just starting out in aviation? Why did you ask this question?

Cheers,

ETTW

[loopa]

I'm an instructor


I was just curious how they do it up at the flight levels

[Rotten Apple #1]

Flying Nutcracker:

So you plan a profile of lets say M0.78/267knots. Somewhere in the descend ATC asks you to transition at 300 knots or greater. You comply and reprogram the FMC.

Depending on circumstances, it's possible to skip the reporgram the FMC part and just use the Mode Control Panel to increase speed. On occasion I might select V/S (subject to the usual limitations of this mode) and dial 300 kts and an appropriate descent rate to level off at a desired waypoint. At this point when ATC is asking to speed up slow down, getting too bogged down in "heads down" programming has its hazards.

But whatever. As others stated, many ways to skin a cat. (Though many a Captain will probably have the reasons at hand why his/her method is "superior/safer/more efficient/what the Trg dept wants" etc)

[ettw]

I'm an instructor


I was just curious how they do it up at the flight levels

Right on. I was just wondering if the answers were relevent to your flying but on this forum curiosity never killed the cat.

Cheers,

ETTW

[loopa]

Not yet relevant no

How about your self?

[loopa]

Flying Nutcracker:

So you plan a profile of lets say M0.78/267knots. Somewhere in the descend ATC asks you to transition at 300 knots or greater. You comply and reprogram the FMC.

Depending on circumstances, it's possible to skip the reporgram the FMC part and just use the Mode Control Panel to increase speed. On occasion I might select V/S (subject to the usual limitations of this mode) and dial 300 kts and an appropriate descent rate to level off at a desired waypoint. At this point when ATC is asking to speed up slow down, getting too bogged down in "heads down" programming has its hazards.

But whatever. As others stated, many ways to skin a cat. (Though many a Captain will probably have the reasons at hand why his/her method is "superior/safer/more efficient/what the Trg dept wants" etc)

Could you also use the FLCH mode or LVLCHG if your goal is to fly a rate of descent that gives you your selected KIAS on the MCP ? Or in the case of the Airbus, pull on the altitude knob?

[Rotten Apple #1]

Could you also use the FLCH mode or LVLCHG if your goal is to fly a rate of descent that gives you your selected KIAS on the MCP ? Or in the case of the Airbus, pull on the altitude knob?

Bingo!

For example, you're on an arrival that has you flying X track miles. ATC clears you direct to some waypoint that shortens the number of miles to be flown.

You as flying pilot are going to request that the PNF sets direct to that waypoint in the FMC. Before that even takes place, you can select VNAV SPD/LVL CHG/FLCH/Open Des/Selected Speed to start descending now if you're going to be appreciably high on the newly computed profile (and either increase speed to increase descent angle, and/or add speedbrakes to increase descent angle and/or decrease speed and deploy leading/trailing edge flaps). This way you can devote the required mental energy to confirming any inputs into the FMC, knowing all the while that the airplane is in a thrust idle descent. That's handy because it's simple. "Boards Out, Thrust Idle...not much more I can do before I'm throwing out flaps and gear". Ideally you will converge on the lower vertical path and engage VNAV PATH or Managed/Profile Descent or the like.

But many examples of how and what to do are context based (How much altitude to lose? Is there a tailwind or headwind to consider when slowing down? Etc.). I have a few tricks in my book, but I don't use them all, all the time. Some I don't use much anymore. Biggest thing that makes sense to me as I age as a pilot of these gizmo machines is probably simpler is better, (but then complacency's a killer) and don't rush.

[Flying Nutcracker]

One thing about Level Change is that it will pitch for selected KIAS/Mach on the MCP. Be it idle or full thrust it will pitch for the speed. With idle thrust descend and in Level Change, the way to change your descend rate is to adjust your KIAS/Mach up or down for increased or decreased (respectively) vertical speed.

Like Johnny D said, don't rush. There are times when we get caught up a little bit trying to make the most of an impossible situation and end up sewering a perfectly normal descend and approach by accepting a short cut because sometimes time is very high on our priority list for some reason, when infact the short cut in the end cost us more time because we couldn't configure in time. How is that for a long sentence...

As for the 300 knots ATC speed restriction thing I mentioned... The key the way I see it is when you get told to keep a higher speed, you will end up burning more gas because your profile will be steeper. You will have to speed up and shallow the descend to get up to your idle thrust profile for the higher speed. So when you get cleared for "normal speed" again, if you reprogram the FMC back to the normal speed, you will be high on profile. My point being that once you are on a 300 knot profile it would be more beneficial to stay on that profile until you level off at an altitude and then go back to your normal descend speed. Otherwise you have just wasted the extra energy of getting up to the new profile that already cost you gas in the first place.

Then again, like many says... several ways to skin a cat!

[loopa]

One thing about Level Change is that it will pitch for selected KIAS/Mach on the MCP. Be it idle or full thrust it will pitch for the speed. With idle thrust descend and in Level Change, the way to change your descend rate is to adjust your KIAS/Mach up or down for increased or decreased (respectively) vertical speed.

Like Johnny D said, don't rush. There are times when we get caught up a little bit trying to make the most of an impossible situation and end up sewering a perfectly normal descend and approach by accepting a short cut because sometimes time is very high on our priority list for some reason, when infact the short cut in the end cost us more time because we couldn't configure in time. How is that for a long sentence...

As for the 300 knots ATC speed restriction thing I mentioned... The key the way I see it is when you get told to keep a higher speed, you will end up burning more gas because your profile will be steeper. You will have to speed up and shallow the descend to get up to your idle thrust profile for the higher speed. So when you get cleared for "normal speed" again, if you reprogram the FMC back to the normal speed, you will be high on profile. My point being that once you are on a 300 knot profile it would be more beneficial to stay on that profile until you level off at an altitude and then go back to your normal descend speed. Otherwise you have just wasted the extra energy of getting up to the new profile that already cost you gas in the first place.

Then again, like many says... several ways to skin a cat!

Wait,

Wouldn't it make sense for you to make the descent rate shallower if you are to maintain a slower speed? Because if you're at idle thrust, and 280kts. If you pitch down for a steeper descent profile, you will have a greater speed, as well as a greater descent rate. On the other hand, if you are at 280, and pitch up for 260, you will maintain a shallower rate of descent hence a shallower profile.

I agree about maintaining that 300 kt and leveling off earlier to allow a few miles for the slow down to the previous speed.

But if you could clarify the above paragraph that would be great !


Cheers