Slow down
Hi.
Question about slow down while descent.
When i descent with VNAV sometimes even with throttle idle I'm not able to keep good speed.sometimes will go near overspeed.
If I use VS to get a good speed i lose VNAV for RNAV .
i observed if i use propeller to max and i stay in VNAV I'm able to get my good speed to descent.
Is it a good idea or normally you don't put propeller to max before final approach ?
Comments
Hi hélico,
If your path angle is around 3° you should not go overspeed. I assume your path angle is too steep.
There is a rough rule: divide your GS/2 and you'll get the coreect VS for 3°.
i.e.: GS 320 Kts = VS 1600 F/mn
The prop to MAX during descent is normally used in an emergency descent like rapid depressurisation.
JP
Yes, if you want a 3° path angle.
This is ideal for the PAX and performances but ATC could ask you to descend later than you want and then you'll have to increase your path angle.
In RL ATC knows the performances of the different aircrafts and they would give you clearances accordingly.
From SOP:
If ATC require you to descend before the calculated TOD, use -500 fpm in all UK and
foreign airspace until top of descent is reached, unless ATC request otherwise. Crews
should use the FMS VNAV to set-up the descent to any level restrictions on a STAR or
if there are no level restrictions, to achieve 5000 ft AAL with 15 track miles remaining.
All descents should be planned to achieve as near to possible a continuous descent.
Once the descent has commenced, the aim is to achieve a continuous descent at, or
close to Flight Idle. Monitor the FMS V/S target speed, adjusting the rate of descent
accordingly; consideration should be given to the air traffic environment.
JP
You can descend in VS and follow the VNAV glide path and adjust your VS accordingly if you find yourself above or below the path.