# Difficult to slow her down during descent !

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2 hours ago, grayal said:

Just found this thread after having the same slippery issues. The math here is messing me up though. I keep seeing a formula that essentially says Altitude to loose X3 = Distance To Decend needed. Ok this is what doesnt make sense. For example im at FL300 and need to get to 0 for simplicity's sake. 30000ft X 3 = 90000ft. Im gonna need a LOT more than 90000 ft from my destination to decend. Can someone please explain this to me. I'm clearly missing something.

(Start FL - End FL) * 3 = dist in NM

(FL320 - 10000) =  66 NM

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Kyle Rodgers

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To expand slightly (the engineer within...., sorry):  The distance * 3 thing works because 1 nm is required to descent 318 ft on a 3 degree flight path angle..... or, 3 nm for about every 1000 feet of descent.  I have also used the altitude/3 thingy when flying our twin or the DC6 but correctly 30,000 ft = 90 nm so the actual rule of thumb here is altitude in hundreds (300/3=90) but when using the rule of thumb it is pretty easy to accept the rough answer is 90 and not 9 or 900. I guess being old enough to have used the E4B circular slide rule helps with the order of magnitude thing.  This will provide a 333 ft/nm descent to sea level, which is about the same as the other rule of thumb.

Edited by downscc

Dan Downs KCRP

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So what CI do you guys use for getting the FMC to calculate the optimal TOD? I normally use 85. Do you guy start your descent right at T/D or before or after?

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7 hours ago, captain420 said:

So what CI do you guys use for getting the FMC to calculate the optimal TOD? I normally use 85. Do you guy start your descent right at T/D or before or after?

A low ci basically results in a climb/decent with a lower speed, a higher ci means a pace down to 10000ft with a higher speed. (And a climb above 10k with a high speed of course)

And I normally use the ci I get from simbrief, pfpx also calculates it afaik.

If I do flights without the calculated performance I typically use 30 to 60 for „normal“ airlines like DLH, KLM and 10-15 for low cost though I normally don‘t fly them anyway. Don‘t like the thought to earn nothing but a warm hand shake...

edit: oups, 777 forum... thought it was for the 737 😋... in the 777 the ci is a bit higher on my flights, around 100.

Edited by Ephedrin

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16 hours ago, captain420 said:

So what CI do you guys use for getting the FMC to calculate the optimal TOD? I normally use 85. Do you guy start your descent right at T/D or before or after?

What is an optimal TOD?  If time is more important than cost then use a higher CI and vice versa.  Optimal?

Why start a descent at any other point than TOD, other than if you are being controlled by an ATC that hasn't given you descent clearance yet.  One might get a smoother transition from cruise to descent if you start a few miles before TOD but I don't see any other reason to do so.

Dan Downs KCRP

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As I learn more and more I find that having accurate descent winds, using the calculated TOD  and careful deployment of flaps and associated speeds gives me accurate descents. Practice makes perfect

The easiest way to get the descent and approach wrong is to not fully concentrate on instruments, not thinking ahead and looking out of the window. Get things wrong at any stage and problems soon mount up.

HTH

Edited by Richard McDonald Woods

Cheers, Richard

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Agree, practice makes perfect. When I first started flying the jet, it took up lots of mental capacity to try to get a "perfect profile", but as time goes on, it is all about approximation and I always believe a theory of "low and slow is better than high and fast".

As one gains more experience, a typical line pilot will understand for a typical STAR or arrival, the descend profile is meaningless due to various vertical restriction on the STAR when you are further away from the airport. It is very common for a star to drag you quite low initially then ATC holds you at 6000ft with 20nm to go and a speed restriction of 250kts which makes you high again. Sydney runway 34L Boree arrival is prime example.

Not so much in FSX, but the in real life, sometimes ATC, especially those in Seoul Approach, believe a 773ER / A333 at MLW can lose 10000ft in 5nm and they can cut you really short. My record is 30nm to go at 12000ft and 280kts on an A330..... which was almost undoable on the Airbus.

Therefore sometimes a little local experience will help. For example, going into LAX coming from IRONMAN arrival, the descend profile before reaching Santa Monica is basically fixed, you only need to watch your speed. Therefore one can enjoy a cup of coffee while going down before reaching SMT (or CLIFY for RNAV STAR) at 7000ft, and get ready for a slam dunk.

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3 hours ago, Driverab330 said:

Agree, practice makes perfect. When I first started flying the jet, it took up lots of mental capacity to try to get a "perfect profile", but as time goes on, it is all about approximation and I always believe a theory of "low and slow is better than high and fast".

As one gains more experience, a typical line pilot will understand for a typical STAR or arrival, the descend profile is meaningless due to various vertical restriction on the STAR when you are further away from the airport. It is very common for a star to drag you quite low initially then ATC holds you at 6000ft with 20nm to go and a speed restriction of 250kts which makes you high again. Sydney runway 34L Boree arrival is prime example.

Not so much in FSX, but the in real life, sometimes ATC, especially those in Seoul Approach, believe a 773ER / A333 at MLW can lose 10000ft in 5nm and they can cut you really short. My record is 30nm to go at 12000ft and 280kts on an A330..... which was almost undoable on the Airbus.

Therefore sometimes a little local experience will help. For example, going into LAX coming from IRONMAN arrival, the descend profile before reaching Santa Monica is basically fixed, you only need to watch your speed. Therefore one can enjoy a cup of coffee while going down before reaching SMT (or CLIFY for RNAV STAR) at 7000ft, and get ready for a slam dunk.

just to mention, I really like when you tell about your experiences. It's always spot on and somehow a bit sarcastic to read.. thanks for that! very instructional AND entertaining 😃

Edited by Ephedrin

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7 hours ago, Driverab330 said:

Agree, practice makes perfect. When I first started flying the jet, it took up lots of mental capacity to try to get a "perfect profile", but as time goes on, it is all about approximation and I always believe a theory of "low and slow is better than high and fast".

As one gains more experience, a typical line pilot will understand for a typical STAR or arrival, the descend profile is meaningless due to various vertical restriction on the STAR when you are further away from the airport. It is very common for a star to drag you quite low initially then ATC holds you at 6000ft with 20nm to go and a speed restriction of 250kts which makes you high again. Sydney runway 34L Boree arrival is prime example.

Not so much in FSX, but the in real life, sometimes ATC, especially those in Seoul Approach, believe a 773ER / A333 at MLW can lose 10000ft in 5nm and they can cut you really short. My record is 30nm to go at 12000ft and 280kts on an A330..... which was almost undoable on the Airbus.

Therefore sometimes a little local experience will help. For example, going into LAX coming from IRONMAN arrival, the descend profile before reaching Santa Monica is basically fixed, you only need to watch your speed. Therefore one can enjoy a cup of coffee while going down before reaching SMT (or CLIFY for RNAV STAR) at 7000ft, and get ready for a slam dunk.

Hi Wing,

Can you elaborate on the LAX-style slam-dunk?

Cheers,
Rudy

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I have been amazed at how my descents/approaches have improved into many airports with practice.

All of the above posts are most valuable, but in the end, you must just keep practising😉

Cheers, Richard

Intel Core i7-7700K @ 4.2 GHz, 16 GB memory, 1 TB SSD, GTX 1080 Ti, 28" 4K display

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11 hours ago, VHOJT said:

Hi Wing,

Can you elaborate on the LAX-style slam-dunk?

Cheers,
Rudy

before reaching SMT (in the old day for non-RNAV STAR) / CLIFY, we always get a something like "maintain 7000ft over Santa Monica, after Santa Monica fly HDG 250 speed 250kts.

Shortly after crossing abeam the runway threshold of RWY 24R, we get descend clearance of 4000ft initially, then ~1800ft and expect a visual approach to RWY 24R. The next action ATC will do is to turn you in for on base, thereafter expect a 5nm final to RWY 24R with a speed control of 180kts till the FAF which is about 4-5nm to touch down.

The shortest I have ever had was around 15-18nm to run when it all happens at once. Therefore, it can catch people out when they are not ready for it and lead to an unstable approach.

But like everything else in aviation, when you are ready for it, you get a 20nm cruising at 3000ft on downwind flying over Staples Center. 😂

The other typical Slam Dunk arrival in the US is, of course, the SFO arrival coming in from the north over Golden Gate Bridge overflying the SFO at 11,000ft, track south-west after SFO and later make a left tear-drop turn and landing onto runway 28s.

Hence, for those who cross the pacific very often going to the US they all have the following "speed brake is your friend and just get the XXXX down" 😂

To be honest, there aren't that many places in the world now where ATC will let you do a perfect profile - i.e. no speed brake descend from Cruise to touch down with the thrust lever only come up at 1000ft and fully configured. The sky is getting too busy nowadays.

My colleagues always joked about how people failed their instrument rating in the old days because they forgot how to insert a HOLD in the FMC. It is surely not the case now, we use the HOLD button 8 out 10 flights.

Edited by Driverab330
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1 hour ago, Driverab330 said:

The other typical Slam Dunk arrival in the US is, of course, the SFO arrival coming in from the north over Golden Gate Bridge overflying the SFO at 11,000ft, track south-west after SFO and later make a left tear-drop turn and landing onto runway 28s.

This is the one I think of when I think of a Slam Dunk.  ATC is keeping you high because abeam KSFO is also abeam KOAK and those departures are climbing below you, while a long downwind is not practical because ahead of you is Moffett and KSJC.  I believe this procedure has been replaced in practice by the BDEGA RNAV arrival where you make a left pattern towards Palo Alto which gives us a little more room for the descent.

That LAX arrival over SMO is one of my favorites, originally known as the SADDE but now mostly flown on one of a couple of RNAV arrivals such as the IRNMN.  I grew up in LA in the 50's and still enjoy seeing old landmarks and new.... back then what is now the Goodyear Blimp base was a landfill and I used to chase rabbits with my dog and a BB gun, being careful to avoid "the word not allowed" range.  It was a different place back then. EDIT:  Hahaha word not allowed, well whatever you call a place where you shoot clay pigeons with shotguns.... ahaha

Edited by downscc

Dan Downs KCRP

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50 minutes ago, downscc said:

This is the one I think of when I think of a Slam Dunk.  ATC is keeping you high because abeam KSFO is also abeam KOAK and those departures are climbing below you, while a long downwind is not practical because ahead of you is Moffett and KSJC.  I believe this procedure has been replaced in practice by the BDEGA RNAV arrival where you make a left pattern towards Palo Alto which gives us a little more room for the descent.

That LAX arrival over SMO is one of my favorites, originally known as the SADDE but now mostly flown on one of a couple of RNAV arrivals such as the IRNMN.  I grew up in LA in the 50's and still enjoy seeing old landmarks and new.... back then what is now the Goodyear Blimp base was a landfill and I used to chase rabbits with my dog and a BB gun, being careful to avoid "the word not allowed" range.  It was a different place back then. EDIT:  Hahaha word not allowed, well whatever you call a place where you shoot clay pigeons with shotguns.... ahaha

Yes the “old” SADDE ARRIVAL 🤣 I have been using the Ironman one for a while and completely forgot what it was before.

The new taylored arrival ( Pacific 1 / Pacific 2) works quite nicely in my opinion. However we only use it when flying a more southerly route across the Pacific.

The worst “Slam Dunk” arrival I have ever done was going into Bahrain from Dubai on an A330. Managed to land from 16,000ft to touch down in 35nm. I knew it was gonna happen so I slowed down quite a bit early before I had to go down. (Unlike the 777, the A330 can never slow down and go down)

Thanks for sharing, it is nice to know what LA used to be like. It’s one of my favourite City.

I always love to go to LA on holiday, but I rarely request to operate there till to the almost unbarable 15 hours time zone change.

With a 24-30 hours layover, its better for me to stay in Asia time zone and stay  up in the middle of the night and sleep during the days. 😔

fortunately restaurants in LA opens till late especially those in little Tokyo and China town, I can always catch a short uber ride to grab a decent “brekkie” when I wake up at around later dinner time.

Thats why I don’t like long haul flying that much unless the layover is long enough (which is hardly the case now with airlines trying to squeeze rest to maximise productivity). Love flying the 777 at 250 Tons or below for a short 1 hr - 4 hr flights and have a bit of fun.    😁

sorry guys, a bit off topics

Edited by Driverab330

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On ‎6‎/‎6‎/‎2018 at 10:53 AM, downscc said:

old enough to have used the E4B﻿ circular slide rule

I still have the small medal one (with the case) I was issued in flight school.  I also have the small  sectional plotter that would fit inside. ROFL

As for descents I always used altitude/3 plus 10.  These things go with double checking flight plan fuel (B707) with 12,000/hr * flight time.

I Earned My Spurs in Vietnam

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