Descent tips

[Joers182]

Hi Folks,

Whats the recommended way to descend in this bird? I like to use idle descent in the big jets obviously, however when I select -2000fpm on the vnav profile, i find myself having to keep a bit of power in to hold the speed.

What method are you guys using? idle descent with FLCH or VNAV?

[Jakobb]

Normally I combine both. I set myself a reference waypoint to which I would descend with VNAV and after that use FLCH mostly. I love to fly shortcuts so that is important to take into account, as it means that I have to be lower than if I would fly the whole transition from the STAR to the RWY.

Example LOWS LOWW RTE: NEMAL NEMAL1W 

NEMAL1W has a FL170b restriction at BARUG and after that I would continue with a direct onto any of the transitions. If I get a vector, FLCH is a must. DCT FAF (or close) favours VNAV imo. 

[Vantskruv]

As I always do, if aircraft has a GS indicator, I calcluate TOD and descend manually. 2000 ft/min, and try my best to hold GS speed through whole the descent.  It is easiest in headwind, because you know that GS is low, and you can still keep the same GS below FL100. Tailwind though, GS is quite high, and it will be harder to hold the lower you go. Also, you may come in too fast at FL100, which means you need to slow down, which at that end means you have made a premature TOD. Often I try to do it by feeling, sensing to drop down a little later, depending on winds dow below.

Hence VNAV is so boring.

[sdflyer]

I'm lazy so I use VNAV

[Vantskruv]

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Edited November 28, 2018 by Vantskruv

[Greaser]

VNAV works fine here too. That the whole point it reduces workload on the pilot to focus on other things. To Not use those tools is poor piloting.

[Jakobb]

16 hours ago, Greaser said:

VNAV works fine here too. That the whole point it reduces workload on the pilot to focus on other things. To Not use those tools is poor piloting.

To use other methods shows awareness for the situation! If there is a long RNAV transition and you follow only your VNAV path, you'll end up flying +40nm more than if you gave ATC the possibility of shortening your route with a direct or vector  

[Greaser]

The plane costs over 4 millions dollars partly because of all the advanced avionics and Garmin systems. To Not use those tools is a Huge waste of money and means you are flying the wrong plane!

[CapnDave]

The problem with a VNAV descent is that you can't often use it in the real world.  Controllers can give you descent instructions that may be before or after the VNAV TOD point due to traffic or other considerations, so not using VNAV is what is called for.  By the same token you will sometimes be given clearance to descend via a STAR, so VNAV is a good way to go.  Mixing it up from time to time is what makes it interesting anyway.

LOVE this bird by the way.

[FuelFromButter]

In Descend via STAR, just use VNAV for happy & easy. 

If not, usually controllers will give you descend instruction from based on 30NM for each 10,000ft rule unless he/she forgot you.

I prefer using V/S for 3 degree descent, the calculation is divide GS by 2 then add "0" to the end.

Keep watching GS, then recalculate V/S when GS has changed a lot.

[dcowsill]

I really should figure out how to manually calculate my descents.  I've been too long pampered by commercial jets.  I use the VNV mode for most of my descents.

[RobW05]

As a rule of thumb, this works quite nice:

For a 3° descent path angle, subtract your target altitude from your current altitude, drop the zeros and multiply by 3. 

If you're flying at 27000 ft and need to descent to 3000 ft, this would be

27000 - 3000 = 24000

drop the zeros = 24

24 x 3 = 72

So you start your descent 72 nm before your target waypoint. (you can always add a few miles for safety) 

To figure out what vertical speed you need roughly for the 3° angle:

Multiply your groundspeed in kts by 5.

280 kts would make a 1400 ft vertical speed. 

Quite easy and works for any plane. 

Edited February 7, 2019 by RobW05

[dcowsill]

Thanks RobW05.  I'll try this out once I can fly again!

[leinsters]

On 2/7/2019 at 7:54 AM, RobW05 said:

As a rule of thumb, this works quite nice:

For a 3° descent path angle, subtract your target altitude from your current altitude, drop the zeros and multiply by 3. 

If you're flying at 27000 ft and need to descent to 3000 ft, this would be

27000 - 3000 = 24000

drop the zeros = 24

24 x 3 = 72

So you start your descent 72 nm before your target waypoint. (you can always add a few miles for safety) 

To figure out what vertical speed you need roughly for the 3° angle:

Multiply your groundspeed in kts by 5.

280 kts would make a 1400 ft vertical speed. 

Quite easy and works for any plane. 

Brilliant!

[Joers182]

Thanks for all these tips the are very helpful!

[slicker55]

On 2/7/2019 at 3:54 PM, RobW05 said:

Quite easy and works for any plane. 

Thank you, may be a few years since you posted this info but still very useful to a newcomer like me