"We will start our descent in the next 5 minutes…"

[champ driver]

Or when the FA come on the PA and says that "we'll be making our final approach soon..."
What,.. did we make an approach earlier that I don't know about and this one will be our last one?
What an overused term.

 

[petrolero]

Ever heard the captain say that when you fly commercial? I have, about a million times. And I always wonder - how does he know that? ATC might keep him high, or descend him early - there's no way of knowing.

How do they know? Just experience on that route?

"Descend to x,000 feet, pilot's discretion" would be one way.

He has some leeway as to exactly when to start the descent and he gives people a little notice before doing so probably so the more nervous fliers know that what they feel in their breeches is planned and normal. And maybe to give the flight attendants a cue to start doing whatever they do upon initial descent.

PILOT'S DISCRETION- When used in conjunction with altitude assignments, means that ATC has offered the pilot the option of starting climb or descent whenever he/she wishes and conducting the climb or descent at any rate he/she wishes. He/she may temporarily level off at any intermediate altitude. However, once he/she has vacated an altitude, he/she may not return to that altitude.

 

[coma24]

petrolero, not to nitpick but if if you're going put quotes around it, you have to know people are going to take it literally

The phraseology would be "descend at pilot's discretion, maintain 5000," or, "cross [fix] at and maintain 5000." Both would constitute PD descents.

 

[petrolero]

petrolero, not to nitpick but if if you're going put quotes around it, you have to know people are going to take it literally

The phraseology would be "descend at pilot's discretion, maintain 5000," or, "cross [fix] at and maintain 5000." Both would constitute PD descents.

Right. Thanks.

 

[Gucci Pilot]

It's surprising how different ATC is in other parts of the world. In the middle east and many parts of Europe, ATC will keep you at altitude until you ask for a decent. Sometimes they won't let you decent and you end up doing an idle+speed brakes decent at 4000-6000 feet per minute.

 

[Hank S]

My pet peeve is when we're passing through 10,000ft, there's the "chime" from the front, then the FAs make a PA saying "Ladies and gentlemen, we've been cleared to land at Los...."

There's NO WAY we've been cleared to land from 10,000' and way out. Cleared for the approach, perhaps. Cleared to land, doubtful. It just grates me to hear "cleared to land" and we're nowhere near the airport, and many minutes away from actually landing.

I've been cleared to land Runway 30, while still 11 nm NW of the airport. To do so, I had to fly SE until past the airport then turn and come back. My passenger started laughing we were still so far out. Oh, yeah, it was my initial call to the Class D . . .

 

[Captain]

Simple math version --> (Alt to lose x 2) + 10

In the post above (10K x 2)+10 = 30 miles.

If you've got a sporty tail wind, maybe you add an extra 10. Nice headwind, maybe you don't add 10 at all...

Generally if given a PD to the terminal area I'll use the total distance to the airfield...so from 35K you need to start your descent around 80 miles.

That's not a good rule of thumb.

If I'm at 40K your formula would have me start down at 90 miles while a three to one would be at 120.

The ROT that I use is 30 miles for every 10K feet to lose. While on the descent you add a zero to your ground speed and divide by 2 (same as multiplying by 5 but easier for my brain).

So, if I'm at FL400 doing 420kts ground speed I'd start down 120 nm out and descend at 2100fpm. As I descend I'll adjust the vertical speed as the ground speed changes.

I haven't missed an airport yet and I generally do a constant descent to the runway ATC permitting.

 

[Gucci Pilot]

Simple math version --> (Alt to lose x 2) + 10

In the post above (10K x 2)+10 = 30 miles.

If you've got a sporty tail wind, maybe you add an extra 10. Nice headwind, maybe you don't add 10 at all...

Generally if given a PD to the terminal area I'll use the total distance to the airfield...so from 35K you need to start your descent around 80 miles.

Agree with Capt. This is all dependent on your groundspeed. That can all change depending on your airspeed and vertical speed. In the 10, if I used that, I would need a pretty large vertical speed to get down and probably have to use speed brakes(which I try to avoid using in descents)

The ROT that I use is 30 miles for every 10K feet to lose. While on the descent you add a zero to your ground speed and divide by 2 (same as multiplying by 5 but easier for my brain).

So, if I'm at FL400 doing 420kts ground speed I'd start down 120 nm out and descend at 2100fpm. As I descend I'll adjust the vertical speed as the ground speed changes.

That's the rule of thumb I use and it is money.

 

[narchee]

I thought you folks in the big iron didn't need to do much thinking. Just plug in the crossing altitude into the flight plan then push a button and the AP does the rest Why do you even need a rule of thumb?

 

[jordane93]

I thought you folks in the big iron didn't need to do much thinking. Just plug in the crossing altitude into the flight plan then push a button and the AP does the rest Why do you even need a rule of thumb?

You need brains to back up the computer.

 

[Gucci Pilot]

I thought you folks in the big iron didn't need to do much thinking. Just plug in the crossing altitude into the flight plan then push a button and the AP does the rest Why do you even need a rule of thumb?

I can plug in an altitude to reach a point on the flight plan and it will give me a vertical speed I need to fly. But if I get "cross 60 miles east of XYZ at 14,000", I would have to first figure out the reciprocal of the course I am flying(not hard), plug in the waypoint, reciprocal course, distance they wanted me to cross at, and input that as a waypoint in the flight plan. Then I need to plug in the altitude they wanted me to cross at. All of that has just wasted time and created a larger vertical speed I now need to descend at. If I screw up the reciprocal course, the airplane will immediately start a turn off course which I do not want it to do. By the time I notice it and turn it back without scaring everyone on board, we are already a half mile off course. To prevent all of that, I just do the math in my head.

Not all big iron planes have the latest and greatest.

 

[kayoh190]

I thought you folks in the big iron didn't need to do much thinking. Just plug in the crossing altitude into the flight plan then push a button and the AP does the rest Why do you even need a rule of thumb?

Sometimes the computer gets itself confused, and there are also a number of ways to incorrectly set up the VNAV to give you the wrong result. Point is - you'll do a quick 3 to 1 check anyway to make sure the automation is in the ballpark.

Another scenario is when you get a last minute restriction from ATC that was completely unexpected. It takes some time to get the VNAV set up, and if it's a late call from ATC that's starting you high to begin with, I'll do a quick 3 to 1 to see if I need to get the plane headed downhill while I dick with the FMS and get VNAV all sorted out.

 

[Captain]

I thought you folks in the big iron didn't need to do much thinking. Just plug in the crossing altitude into the flight plan then push a button and the AP does the rest Why do you even need a rule of thumb?

It's true I can enter an altitude for a fix, arm the VNAV and the plane will start a descent at the point on the desired angle to cross it. My simple plane requires me to pull the power back to avoid the overspeed so it's not quite 100% automatic.

But that's not the point. That only happens if I'm given a crossing or I choose to enter a ref altitude. Many times ATC is late or early with the descent a pilot should know where they are, either above or below the desired descent angle.

It's sad but I've flown with many a professional pilot who are unaware if they are high or low. Twice I've flown with pilots who missed the airport because they mismanaged their descent and one even answered my question of what they use for descent planing with, "ya know...I just wait for ATC".

So, even with all the automation a pilot needs to know what's going on. Otherwise they're just a pax with access to the cockpit.

 

[narchee]

I'm still not getting why you need such a complicated rule of thumb that you described. Can't you see on your FMS what time you're going to be at the airport and do the same kind of mental calculation we do in smaller planes? So like "I need to lose 40,000 at 2,000 fpm so I better start down 20 minutes before the destination. Oh look I've got 30 minutes to go, I'm good right now". If I'm ignorant my excuse is the closest I've ever got to a big iron cockpit is taking a dump in the first class lavatory.

 

[Gucci Pilot]

I'm still not getting why you need such a complicated rule of thumb that you described. Can't you see on your FMS what time you're going to be at the airport and do the same kind of mental calculation we do in smaller planes? So like "I need to lose 40,000 at 2,000 fpm so I better start down 20 minutes before the destination. Oh look I've got 30 minutes to go, I'm good right now". If I'm ignorant my excuse is the closest I've ever got to a big iron cockpit is taking a dump in the first class lavatory.

I don't aim to fly direct to the airport, cross over it at 1000 AGL and enter a downwind leg. I'm getting vectored and sequenced behind other heavy airplanes. I'm also not doing a constant decent to the airport, I'm getting stepped down by ATC.