what is flaps 30 followed by 'Green light'

[rascalsailor]

Hi - Unless I'm imagining it - I thought I head the word 'green' or 'green light' sometimes after the Flaps 30 checklist call. Why is this?
Thanks
Russell

[Johnny F@rt Pants]

On B737 it is to verify that the leading edges have deployed correctly. The green light is relating to the leading edge device position.

[rascalsailor]

Thanks for the reply

[RAT 5]

The 2 lights under the flap gauge, IMHO, are mis-named. They say "Leading Edge Flaps". The LED's consist of Flaps & Slats. On selection of TE flaps the LE Flaps go to Ext, which is their Full position, and Slats to EXT (mid position). The Amber transit light illuminates during transit and then the Green light illuminates to show TE & LED agreement.
Depending on model the combination of TE & LE Slats to Full Ext will differ.
When the TE flaps are selected to a higher setting the LE Slats will go to FULL Ext, the LE Flaps will NOT move, yet the Amber transit light, named LE Flaps Transit, will illuminate. It is the LE Slats that are in Transit not the LE Flaps.
The FCOM text says that the transit light is an indication of any LED moving, so why is it not named LED, and which one, slats or flaps, can be monitored on the OVHD panel? (better ask the B707 cockpit panel designer).

The LE Flaps have only 2 positions: Up, or EXT, which is their Full position. LE Slats have 3 positions: UP, EXT, Full Ext. On early B737's, of all models, the LE Flaps move Up - Ext (full) when any TE is selected. The LE Slats would move to EXT until TE Flaps moved beyond F5. Hence the need to check the Green light "LE Flaps EXT" when selecting F1 or F10/15. This indicated the LED's & TE's were in agreement and giving the correct lift for the F speed. On later models, with which I am not familiar, I read that LE Slats move from EXT to Full EXT when TE Flaps are F25 - F30. This newer version will explain why it is necessary to call "F30 - Green light".

I'm curious why this is the case and what effect it has on F speeds during approach. Why? I can only surmise that it is a fuel/noise issue. On older models F10 was often used because the extra drag caused by LED's all to FULL Ext could help slow down, or avoid acceleration on steeper slopes or with tailwind when at idle thrust. (F5 idle thrust was good for 3 degree slopes, with a gentle headwind at normal weights). Selecting F10 (same speed as F5) required a small increase in thrust. F15 + Gear down would obviously need more thrust, but if LE Slats are at EXT setting the thrust increase will be less, hence less noise & fuel.
For those familiar with the newer models will you tell us if F5 & F10 are the same speed. I seem to remember on B732, where there was a fixed speed schedule the flaps UP-1-2-5-10-15 went in 10Kt intervals. On the NG speed tape (variable speed schedule) this was the same expect F5=F10. Then F5/10 – F15 was only 10kts.

[Johnny F@rt Pants]

The Green Light went via Amber to Green again F5 - F10 and will/should not change again when selecting F15/25/30/40.

Not correct on B737-800, our new 800’s with the SFP have a different LE schedule and the full extend doesn’t happen till after flap 15.

[RAT 5]

I thought I mentioned that in the middle part of my comments; it was implied by saying LE go Full EXT at F25.

[Johnny F@rt Pants]

I thought I mentioned that in the middle part of my comments; it was implied by saying LE go Full EXT at F25.

I was referring to your comment in post 4, which you have then contradicted in post 7.

To clarify, B737 Classics had LE devices at full extend with TE devices at 10, on the B737 NGs this is the same unless they are fitted with the short field pack, in which case the LE devices do not fully extend until a flap setting beyond 15 is taken.

[RAT 5]

Ah: I had forgotten about #4. Like TangoA I went to some research afterwards and discovered the change in newer models which I never flown. It was news to me and thus led to #7. I'll delete #4.