VX for descents?

[InTransit]

Slow and dirty is the best method for getting out of a bind, but a descent at high speed can work great if you're not too heavy. The most important thing is to avoid the middle ground of these two options - that's where you'll lose efficiency to get down.

 

[sinkrate]

I've been having an ongoing discussion with several other pilots, and many seem to be on both sides of the question. The problem is if you are close to an airport and ATC left you too high, what do you do first? I tend to slow down and perhaps stop the descent, put out my gear and flaps, and then drop like a rock. Other pilots believe it's better to keep descending, slowly slow down and put gear and flaps down while still going down. As far as the best angle of descent, or losing the most altitude for a given distance, which is better? I know that you can get a much higher descent rate at a higher speed, but you are also moving over the ground much faster. Even the ground you use up slowing down couldn't possibly make up for putting all of your drag out and going down much faster, could it? Is there a way to resolve this question?

I could just try it in the sim, but I was hoping there was a way to figure it out mathematically. Thanks for the help.

PS, I'm talking about large turbojets in this question.

If safety is no concern, as everyone else has said, slow down then extend the flaps and gear. If safety is any concern at all decline the clearance and request an extended down wind or vector for descent. Don't let ATC push you. These kinds of descents can lead to a number of bad things. If for any reason you must level off unexpectedly (VFR nordo traffic, other side traffic enters your final path, etc) you will be very close to stall speed before you get the engines spooled up. Your AC is in a very vulnerable state. The gear take forever to retract and the first thing that happens if you try to retract them is the doors open and the rate of deceleration increases. Some AC have flaps that may retract quickly but if the gear is out the flaps won't be enough. These descents also precede the majority of unstable approaches.

For safety sake some 'old school' gouge still works very well

Below 10, 3000 fpm max to 3000 AGL
Then the max sinkrate is your altitude AGL until stabilized at 1000'
If you are at idle minimum speed is VREF plus 30
The gear never get extended prior to the FAF on profile or if visual when descending through the pattern altitude - 1500 agl

Most AC can live with this gouge. If you must use some drag for the descent approach flaps and spoilers should be enough for 3000 fpm. Just remember to add 30 knots or so to the published minimum speed for the configuration.

I have seen both regional and 'mainline' crews fully configure at 10, then start an idle descent at the slowest speed possible. It makes the hair stand up on the back of my neck, my skin crawl, stomach get queasy, and body and mind generally revolt. If any little external, unforeseen factor requires a flight path change you will be between a rock and a hard spot with few choices.

Don't let ATC push you. You don't have to accept the clearance. Too many of our brethren do. And ATC knows better. They are just seeing if you will do it to cover their mistake.

 

[CRJ puppy]

It sounds like you didn't understand the question. What I'm asking is, what gives you a better angle of descent, stopping the descent to put out flaps and gear, or continuing the descent and adding flaps and gear as your speed bleeds off. Thanks for the assistance.

It sounds like you didn't understand what he wrote.

A professional pilot stays aware and doesn't permit himself to perform heroics. Talk to atc. Don't allow them to push you. We aren't fighter pilots, these aren't roller coasters.

 

[Dumb Pilot]

I Seriously hope you folks do get a life....!

 

[vetrider]

How close to the airport? How high? Twenty miles and a few thousand high? It might be possible to use speed brakes and/or gear at 250 until leveling to slow. Ten to fifteen miles and a thousand or two high? Completely dirtying up and then descending might br your only chance. Sometimes the gear out a liitle higher and faster than normal is enough.

Of course the 1,000 and 500 feet windows will be controlling as to whether it works or not. The 2500 foot/2000fpm window also.

 

[Blue Dude]

The problem is if you are close to an airport and ATC left you too high, what do you do first?

Tell ATC to bring you around for a better vector so you don't need heroics at the marker.

 

[Nindiri]

Deploy the reversers.

It should look something like this:

https://www.youtube.com/watch?v=fYkaMQIFopA&feature=player_detailpage

 

[labbats]

Stop the descent and dirty it up. Then hold the fastest safe/allowed speed for parasite drag to maximize your descent.

It doesn't have to be gear down. Sometimes if you're just a little high using this method with lesser flaps/spoilers will get you back on profile too.

I hope that answers the question.

 

[pianoman]

I agree with the level off and dirty it up answer. If you recognize the need far enough out, you can perform it very smoothly without violating any stabilized approach procedures. Gear down, landing flaps setting and speed comfortably between target and placard limit with idle thrust. Gradually add power to join the glide path and it's fine. (Obviously the air show needs to be over by 1000 AGL or so)

Yes it's not ideal but there are times due to fuel, weather, traffic or f'd up third world ATC that it's the best option.

 

[flythere]

If you are talking 737NG, either method seems to work! Gear and speed brake are a popular method, dive down, level off keeping the speed brake out until you slow to flap speed, stow and dump the flaps. The wing is so clean on the NG's, she doesn't like to slow down and come down, especially a heavy -800/900. Now the old classics are a different story, that wing is so thick and dirty, it will slow down and come down a little easier.

Now, the MD-80 was a whole different animal, from 15,000 feet, use speed brake to 280 knots, then throw the slats out, and I think SPD mode, 737 equivalent would be level change and she would drop like a rock! That MADDOG was great!!!

 

[scoreboardII]

If your abeam and knowingly hi, better be slow, if slow, dirty up and drop. While there is caution for the "nose over scare the pax" issue, you get paid to get it on the ground, not take a five minute tour to 15Nm final.

 

[waveflyer]

If safety is no concern, as everyone else has said, slow down then extend the flaps and gear. If safety is any concern at all decline the clearance and request an extended down wind or vector for descent. Don't let ATC push you. These kinds of descents can lead to a number of bad things. If for any reason you must level off unexpectedly (VFR nordo traffic, other side traffic enters your final path, etc) you will be very close to stall speed before you get the engines spooled up. Your AC is in a very vulnerable state. The gear take forever to retract and the first thing that happens if you try to retract them is the doors open and the rate of deceleration increases. Some AC have flaps that may retract quickly but if the gear is out the flaps won't be enough. These descents also precede the majority of unstable approaches.

For safety sake some 'old school' gouge still works very well

Below 10, 3000 fpm max to 3000 AGL
Then the max sinkrate is your altitude AGL until stabilized at 1000'
If you are at idle minimum speed is VREF plus 30
The gear never get extended prior to the FAF on profile or if visual when descending through the pattern altitude - 1500 agl

Most AC can live with this gouge. If you must use some drag for the descent approach flaps and spoilers should be enough for 3000 fpm. Just remember to add 30 knots or so to the published minimum speed for the configuration.

I have seen both regional and 'mainline' crews fully configure at 10, then start an idle descent at the slowest speed possible. It makes the hair stand up on the back of my neck, my skin crawl, stomach get queasy, and body and mind generally revolt. If any little external, unforeseen factor requires a flight path change you will be between a rock and a hard spot with few choices.

Don't let ATC push you. You don't have to accept the clearance. Too many of our brethren do. And ATC knows better. They are just seeing if you will do it to cover their mistake.

Wtf is this??^^^^

Are you serious?
Or even a pilot?

 

[scoreboardII]

Wtf is this??^^^^

Are you serious?
Or even a pilot?

Double ditto.

 

[Dodge4SRT]

I don't post much but General Lee actually had good advice. He also is right with the plane telling on you to the company. The aircraft I fly does if you are outside of certain parameters set by the company.

 

[Blue Dude]

you get paid to get it on the ground, not take a five minute tour to 15Nm final.

No, you're paid to make good decisions and not let ATC push you into a bad position. Who's in charge, anyway? If you're even close to requiring max angle of descent to fix the problem ATC put you in, you're making the wrong choice of how to fix the problem.