pilots....when do you extend the flaps when landing....wheather its the leading edge or anything?

Question

i usually do it at the last moment just because its harder to descend

Answer 1

MIke and Chris are pretty much right. I'd just like to add that in flying light planes -- all my experience so far -- in the standard traffic pattern, I was taught to throttle back a bit on downwind, and to start extending flaps as I got abreast of the approach end of the runway. My plane, a Beech Musketeer, had three notches, and the usual thing to do was first notch at that point and throttle back more, second notch after turning base, and third and final notch as soon as I roll out on final.

Answer 2

Flaps are high lift devices. When you create lift by extending the flaps you also create lift induced drag. That's what causes you to descend faster. The lift that is created also allows you to land at slower speeds.

Notice how, with flaps extended, you need to add power to maintain a glideslope? That's how you overcome the drag on approach.

But, when you want to descend faster, the induced drag, idle power, and nose over to maintain airspeed is how you can increase your rate of descent.

In a traffic pattern, say in DTW, ATC may slow you to a speed below your VFE. Therefore, you may have to go to flaps 1 as far as 25 miles out to comply with ATC assigned speed.

To make a smooth transition on glideslope, when you are at 170 kts, flaps 15, and 1 dot below the glideslope (level flight) start getting the gear out. By the time the gear extends, the GS will capture and there won't be much change in power making a really smooth intercept. Now, as you approach the FAF, slow to your final approach speed and flap setting and land.

The leading edge (slats) come out with the first flap setting. In a DC9, you can extend the slats without extending the flaps.

Answer 3

I'm sure you're talking about simulators but...

The purpose of flaps are to change the shape of the airfoil and increase the critical angle of attack so that you can fly at slower approach speeds while maintaining a safe margin above stall.

Plain flaps on a supercub don't really belong in the same in the same category as double-slotted flaps on a BBJ. They serve different purposes and have much different characteristics.

Back to the question... most pilots operating in a structured environment like to make sure the aircraft is fully configured prior to crossing the final approach fix. That means landing flaps and everything. Late configuration changes, in practice, are not advised simply because it de-stabilizes the entire approach.

Answer 4

For airliners, it depends on speed control that ATC gives you. With any slat/flap setting, there is an associated minimum controllable airspeed you have to fly, otherwise the airplane will stall. So when on approach ATC gives you a lower speed than you can sustain without any slat/flap, you extend the flap until you're comfortable with. Usually airliners start extending their flaps approx. 10 miles outside the field (if no ATC restrictions apply).

Airlines will have specific operating procedure as in when the flaps will be extended, i.e. downwind, base leg, downwind.

Answer 5

On simulators? You wouldn't be asking if you'd been taught and were doing this in the real world... would you?

Cessna 172 Man!: "Flaps are used to increase the rate of descent without decreasing speed"? Erm, no, those are spoilers. Flaps let you maintain the same rate of descent despite having reduced speed and maintained the same pitch. Mike is right, though he was a little careless in how he stated, flaps do allow you to slow down; he didn't says cause.

You extend the flaps as your speed decays towards the minimum for that speed. There is a window for each flap setting bordered by the highest speed at which it can be deployed and the stall speed for the current load. But you achieve the speed reduction by reducing throttle, or your rate of descent, or by using spoilers and increasing the AOA whilst maintaining your rate of descent. If it is too hard to descend then you are going too fast! In commercial aircraft you need to start getting the flaps down somewhere in the low 200s, in puddle jumpers you need to be going a heck of a lot slower.

If you wait until the last moment you risk stalling and ploughing in to the scenery, or you are going to float on down the runway with too much lift because your speed is still bleeding off.

In any case you should have landing flaps selected and down before you cross the threshold.

(What did I get marked down for? The low 200s? 170 might work for a small jet, but if you try that in a heavy with a few hundred passangers and a final approach speed in the 135-145 area you are going to become a big smoking hole.)

Answer 6

For small aircraft at least, it is generally easier to descend with the flaps.

It allows you to make a steeper descent, which increases your forward view of the runway (easier), and reduce your speed - allowing more precise control of the descent.

In the piper aircraft I was used to flying in, flaps were deployed in stages, starting on the base leg - or 2 miles away for a straight-in descent - with all three stages out once comfortably on final depending on any adjustments required for height. But I'm sure it depends on the aircraft, and obviously conditions e.g. crosswind.

Answer 7

You want to extend the flaps gradually so you can slow to a slower speed thus creating more lift and more drag you should start increasing them about 15 miles out but depending on the plane maybe as close as 6 miles out

Answer 8

Sorry but Mike is wrong. Flaps are not used to slow you down or control airspeed True they can be used for this but are not meant for this. Flaps are used to increase decent rate with out decresing airspeed or pitch. Flaps are deployed gradually while the aircraft is receving final approach vectors any where from 10 to 5 miles from the airport.