Flap gates

[Laina Reeves]

What are the flap gates at 1 unit and 15 units for? I read that the one at 15 is for G/A. Is the one at 1 unit also for G/A?

Also, how does the flight crew determine the takeoff flap setting? In other words, what are all of the considerations that dictate flap setting?

Sorry to be so ignorant! I don't fly the airplane, just maintain it.
Thanks for your help!

[Genghis the Engineer]

On what type?

G

[Laina Reeves]

Oops; thought you could read my mind! How about on the 737 NG?

[qwertyuiop]

Are they where the leading edge flaps (slats) go from in/mid/full?

[Laina Reeves]

OK; that makes sense.

Thanks!

[Z-526F]

"I read that the one at 15 is for G/A"

And the gate at 1 is for single engine G/A :)

[Laina Reeves]

Thank you! That sounds consistent with the other forum I read here, regarding losing an engine during G/A, etc. That helps a lot.

[Intruder]

On the 744 the gates are at 1 and 20. The 20 gate is to prevent inadvertent retraction beyond 20 on G/A. The 1 gate is to prevent premature retraction beyond 1, since airplane controllability will be marginal at heavy weights (above approx 310 T).

Since T/O flaps are 10 or 20, the 'gates show the T/O range' theory is not valid for the 744.

[Laina Reeves]

744? Is that a derivative of the 737-700? I looked up the list of effective airplanes in the Boeing Structural Repair Manual, and there was no such animal listed. Please, enlighten me!

[ZFT]

One of the earliest examples of 'preventative' flap gates was the retrofit on the B707 B model and later C models at 14 Flap following the accident at Windhoek in the mid 60s when the flaps were inadvertently retracted after take off (possibly snagged by F/Os shirt cuff when retracting gear?).
411A can probably expand on this incident

[Vee One...Rotate]

744 = 747-400.

V1R

[Flight Detent]

Hi all,

Z-526F is correct !!

Cheers:ok:

[Notso Fantastic]

On the 737, the 15 gate is so when heavily preoccupied doing a go around in the normal landing configuration with 25 or 30 flap, you can simply retract the lever to the gate to get into the correct configuration whilst you then get on with raising gear, ensuring power and attitude are correct etc, and climbing away safely.

If you are on a single engine approach, you only use flap 15 for drag reasons. The procedure on a go around is to immediately retract to 1, then get on with all the other stuff.

The gates stop you over retracting flap at a time when you are very busy.

[mbcxharm]

757: gate at flap 1 is to prevent 'inadvertant retraction' of the slats past the intermediate position they are at with flaps 1 to 20.
(nb. flap 5 is used for a single engine GA)

The gate at flap 20 is for the two engine go-around.