A few days ago I had a T.E.M class and the FOQA guys gave us some nice numbers to remember (data collected using a huge number of monitored flights) and help managing the energy during approaches that are going south...

1) If you're 1000ft high on the VNAV profile you'll need (using speed brakes):
- 6nm at 280kts
- 10nm at 250kts
- 12nm at VREF40 + 70

2) For every mile on a 3deg glide path you will lose, roughly, 10kts (SPEED DECREASING WITH GEAR DOWN)

3) For every dot high on the glide slope (<10nm from threshold), you will need 1 extra mile to get back to the profile (SPEED DECREASING WITH GEAR DOWN).

4) You'll need 3nm for every 1000ft high on the VNAV profile (GEAR DOWN / DECREASING SPEED)

5) You'll need one extra mile to dissipate the energy generated by 20kts of tailwind on a 3deg glide path (GEAR DOWN).

So... For example: Let's say you aim for 150kt at the FAF (5nm from RWY) and you're with 190kts, 1 dot high with 20kts of tailwind. When should you ask for the gear down ?

19 - 15 = 4 + 1 (high on the glide) + 1 ( 20kts of tailwind) = 6nm from the OM. According to what they observed on all those flights (900+ daily ops), you should ask for the gear around 11nm from the runway in this case.

It was a pretty nice class... Some great recordings of messed approaches !

On the other hand, I still prefer using V/B & V/S indications on the DES page. Much more straight forward with far less thinking !

Hope it helps :)

Wow. That's a lot to remember! It is interesting looking at the FOQA data in ground school for approaches that guys really botched; but I think it is good to keep in mind that it's easy to Monday-morning quarterback. And usually the FOQA guy, who is shaking his head in amazement at how badly it was botched, spends little time as the Man in the Arena, flying the line.

B737SFP: That would have been mind-exploding for most of the cadets I've had through TR's in the past 15 years. Ask them questions like that and the first thing that is brought out is their Japanese brain. Simple mental arithmetic skills seem to have disappeared.
What I found missing on the line was the appreciation of quick 'gross error' checks. This could be load sheets, flight profile, sector fuel required, etc. Perhaps, one is they were never taught, and two is they require mental sums.

I'll start down early if cruising above FL350 with 4nm/1000' before TOD. I find the NG tends to overspeed in the descent above FL350.

But that's 4nm early for FL360, not 40mn!

Decel segments are at -1.3° which can be about -500fpm.

I find the NG tends to overspeed in the descent above FL350.


Do you mean if TOD is >FL350, or for the 1000's when above FL350? But given that you are still >100nm from touchdown does a little overspeed matter; and that depends on your CI anyway.

I mean if the cruise is above FL350, as we initiate descent, the plane often pushes close to MMO. We use .78/280 in the descent usually. Even with automated descent winds, the plane will still get close to the clacker.

I'd prefer not to have to write up an overspeed 100nm, 50nm or 2500nm from touchdown.

Well my point was that if you start down early but leave the jet to do what it is programmed to do you will end up back on the idle path anyway. If you want down early and to "stay" ahead of the path then the thrust levers need to be closed when the servos release i.e. THR HOLD. This applies to the Boeing crates I have flown anyway that does not include the 73NG btw.

After you have programmed your legs page for a descent,connecting the arrival/approach without any discontinuities, you must have a bold speed, and altitude on your legs page, at a point, at the commencement of your initial approach segment,preferably in level flight.This has now instructed the FMC that you intend to arrive at that geographical position, at a specific speed and altitude. The next step is to program the variables into the FMC. Go to the descent page and select forecast. On the forecast page, enter your cruise altitude with the wind direction and speed (just before descent). Do the same for a medium altitude( during descent) and your destination altitude. e.g.If cruise was at FL350, enter the altitude,wind direction and speed.
Flight level. Wind SPD. Direction
FL350 260. 30
Fl160. 220 40
00300. 180 15
If you are unable to get winds at the desired altitudes, you can enter another altitude. It doesn't matter if it is an even or odd altitude. Neither does it matter if the altitude ends in 0 or any other numeral.
This allows the computer to calculate a descent path, considering the winds(Headwind or Tailwind). The final part is this.The computer calculates the descent path to arrive at the position mentioned earlier on, with the "hard" speed and altitude.The only thing is that it assumes that altitude is with a standard QNH(Altimeter setting) of 29.92 or 1013 mb.You now have to apply the variation from the standard setting, on the same descent forecast page, i.e. temperature variation from i.s.a. and the actual altimeter setting at the destination. You will see some green circles on your legs page.They indicate where the Aircraft has to change it's pitch/descent path, for a change in speed.The first two closely spaced dots represent when the Aircraft starts to slow down to 250kts, just before 10,000 ft.The second on represents when the Aircraft is slowed down to 250kts,the resumes the descent path.
The next dot represents when the Aircraft starts to slow down, in order to achieve the hard speed,and altitude programmed earlier. As the Aircraft is approaching the clean maneuvering speed + 10kts, or as shown in the FCTM/FCOM, the flaps are lowered to the initial setting. Once the initial flap setting is achieved, the speed bug automatically moves to the maneuvering speed for the initial flap setting.This process is continued for each stage of flaps, with speed or glide slope as the trigger for the next flap setting, as shown in the FCTM/FCOM.
If the FMC is programmed properly with the previous data(accurate wind direction/speed etc) it will give you the required performance. Remember "garbage in, garbage out"
​​​​​​If you do have any questions,feel free to ask.

Shinobi, thank you, very useful info.
Just a question.

The ND will show a DECEL point. Is this the point where the aircraft begins reducing speed to UP speed or is this the speed it wants FLAP 1?

90% of the time VNAV will work and can be trusted to bring you at the intercept at the right speed and altitude.
However there are times when it gets you there a bit too fast or with ATC shortcuts, a bit too high.
Of course people always forget to "update" the active waypoint from time to time as this also updates the wind info in the FMC and alas updates your path.
The same goes for updating the FORECAST page (especially the use of TAI).
But the FORECAST page is not of too great importance - it's a FORECAST after all.

On the ND(Navigation display), that open green circle (deceleration point), shows where the aircraft will start decelerating to the speed which is shown in bold on the legs to page.If you also refer to the descent page,you will also see the position referred to, with a display showing the "hard" speed and the flap setting required.
The more accurate the wind direction, speed forecasts, and ISA deviations input on the descent page, the more precise the FMS will maintain the desired flight paths, and speeds.
LIke I mentioned earlier, for the computer, it's "garbage in,garbage out".

Not sure what type you're on, but on the 767 when it comes to slowing down to clean speed you can use the speed restriction option on the descent page to slow it down at a particular altitude, or a hard speed on the legs page to slow it down at a particular point. Both options assume idle thrust and rely on the correct winds so you may find yourself needing to add power or speedbrake.

If you're really lazy and want to make VNAV do it all for you, build a geometric path: Pick a prior point and look at the predicted alt - if it says 14100 then type /13000. That will force a geometric path between that and the next point that is slightly shallower requiring more thrust than idle. The FMAs will change to SPD / PATH and the autothrottle will adjust the speed without the need for speedbrake. Just don't confuse it for approach logic!

I'm almost certain that the deviation indicator actually shows feet and only feet, in relation to the different segments your flying, whether they're flat or almost flat deceleration segments or regular ones.

What we accomplished maybe was to befriend the engines and not to go non stop from CRZ power to idle.

I think the blank stare is "Is this guy for real?"

Don't want to shock cool those cylinders.

Yeah, specially those big cylinders mounted under the T7 wing 🤣