Rule of thumb to calculate " distance to descent "
 

Hi,

This is my first post.

I would like to know what kind of "rule of thumb" you use to compute the distance to start a descent from a flight level at +- M.78, deceleration included. E.g. : FL330 M.78 , you want to descent to the ground : 0foot.

I would be pleased if you can explain me how you crosscheck you distance/altitude during the descent.

Thanks,

Chfeudpail

3 x height + 10nm(for decelleration) adjusted for wind.
ie FL330 => 33x3 = 99 + 10 = 109nm from present position to touchdown. It's pretty much a ballpark figure, but it works well.

Make that tailwind. :ok:

Desc Calc
 

Yep,
All good.

3nm per 1000' ie FL330 = 99nm
add 2nm per 10kt of TWC or subtract 1nm per 10kt of HWC
add 1nm per 10kt above min clean speed.

EAI on adds around 5-10% to above total.
Use of speed brake will cancel out that added by EAI.

Above based on B757.

CY&B