How many NM out from any runway, do you put flaps down? The other day i landed my A-6 intruder @ KSJC, i put 10 degree of flap down @ one mile out. The next thing i know I'm on the ground, but way before i reach the runway. I had to roll the rest of the way to the runway..lol

My Boeing 737 checklist:

Approach Checklist:
(excluding the pretty stuff)
Speed: Establish  210 KIAS
Flaps                 5-10 degrees
Speed: Establish  180 KIAS
Flaps                 15-20 degrees
Speed: Establish  160 KIAS
Landing Gear       DOWN
Turning toward runway: set flaps 30 or FULL


So I lower my flaps systematically as I'm on approach.  And I begin slowing down and what not when I get ILS vectors, (I consider this officially entering 'approach' mode). Though it's different for small aircraft you probably get the idea.

The purpose of flaps (for landings) is to allow a steeper descent angle without increasing airspeed. They also allow you to fly at a low airspeed with good control, which may help shorten the landing rollout.

Obviously the use of flaps varies with aircraft type, airport, etc... but in any case, distance from the threshold really doesn't figure into it.


But there's a limit to how slow you can go, flaps or no flaps, and still have a workable descent rate, particularly in jets. In all planes, thrust also figures into it... for example, to fly level with full flaps on the verge of a stall, in any airplane, you will need lots of power.

The only reason I can think of that you landed short with the A6 is that you were too slow to begin with, or you failed to apply a little more power to control the descent rate as the aircraft slowed down (remember, in a continuous descent, the throttle is your preferred up/down control, not the stick).

If you have any info on recommended approach speeds/power settings at various flap settings for that aircraft, that might help.

C wrote on Mar 27^th, 2010 at 5:33am:


I disagree- I've never seen a specific distance shown for flap deployment in the POH even for a heavy jet.

I wasn't suggesting that you can deploy flaps whenever, or at the last minute or something... but in a heavy, or a fighter, or any airplane, flaps are simply used as needed to maintain the glide angle, descent rate and airspeed that is appropriate.

Generally, it begins about the same time the gear is lowered, although maybe one notch just before that.
How far from the runway you are at that time can depend on a number of factors.

It's quite possible to fly the same sort of descent profile in a light single as in a heavy, albeit at a lower airspeed. 500 fpm works very nicely most of the time. Us "little guys" don't want to scare our pax, or controllers, any more than the heavy iron drivers. 

And under some circumstances, the big boys have to come in quite steeply... pax comfort gets sacrificed then, in the name of safety.

beaky wrote on Mar 27^th, 2010 at 11:34am:


It just generally will always end up in the same place. Most of the time will be aiming to put you on the localiser about 10 miles out, so you'll have take off flap out a few miles before that to decrease to the approach speed by the time you hit the glipepath. Gear will also come before that to allow the checks to ideally be done before you commence the final approach. In the VC10 we generally aim for 15 track miles for the initial flap selection, and 12 for the gear, allowing the crew to devote their attention to the approach. Further flap is take once the aircraft reaches the glidepath, unless ATC dictate otherwise. I caveat that as type specific, but generally in my experience its been similar on civilian airliners


Quote:


It certainly is, but the heavy has a lot of energy to dispose of. I'd certainly never expect anything light to take any of the distances I've thrown in to the discussion - not without upsetting all the other flyers in the pattern!


Quote:


Tell me about it. Those days are called fun (apart from when the weathers rubbish! They normally induce a bit of sweating too), particularly when you still doing 300kts as you start the procedure turn!