Hi, how do I decide flaps 25 or flaps 30 for landing? what is the difference?

I'm pretty sure it has to deal with the weather on the approach i.e. WINDS. There might be other reasons i'm not aware of though. Less flaps in the real world mean less noise but a faster approach. SO take your pick. In PIC either would be fine although I find 25 just right most of the time with little wind. Best Wishes,Randy J. [email protected]" A little learning is a dangerous thing"

30 is normally used ,although some airlines do use 25. flaps 30 gives you 1 foot of extra clearance at the tail during the flare to avoid tailstrike. I believe flaps 25 will also be used in an overweight landing, if flaps 30VREF speed plus additives for wind and gust is within 10 kts of flaps 30 placard speed, the use of VREF25 is desirable.

Modern jet transport aircraft have wings designed to operate efficiently within a wide range of air speeds. Transport aircraft must be able to fly at speeds of from 100 miles per hour to close to the speed of sound. A look at the wing's secondary control surfaces -- flaps and slats -- will explain how the highly adaptable wing accommodates this range of speed. Flaps are located on the aft or "trailing edge" of the wing and increase both lift and drag. Because of the increased drag, flaps are only partially extended on takeoff, and fully extended on landing. The added drag created by full flaps on landing allows the aircraft to approach at a steep angle without excessive air speed. Think of a car as it rolls downhill. If the hill is too steep, the car's speed becomes excessive. By using the drag of the brakes, the speed stays under control. The greater the wing's camber, or curvature, the better the wing will perform at slow air speeds. Flaps extend downward and rearward, thereby increasing both camber and wing area. The flaps extend in several segments, creating gaps, known as slots, in the wing. The slots allow high energy air from below the wing to vent over the top of the wing. This high energy air "tricks the wing into thinking" it is traveling faster than it actually is, enhancing the low speed performance. On the leading edge of the wing are the slats. As the slats extend forward another slot is opened on the leading edge of the wing. The combination of the slats and flaps creates an airfoil of significant camber for low speed operations. The wing is said to be "dirty" when the flaps and slats are extended, referring to the high amount of drag the wing experiences. In the dirty configuration the wing is capable of low speed flight; the high drag would, however, prohibit high speed flight. After takeoff the wing is "cleaned up." After climbing through 400 feet the air speed is allowed to increase, reducing the need for the flaps and slats. After the completion of the flap and slat retraction, the aircraft can accelerate to cruise speed. During the approach for landing, the flaps and slats are again extended. The flaps are set to an initial setting, usually one degree. The leading edge slats are later deployed. When initiating the final descent for landing, the flaps are fully extended. Now that the wing is again in its low speed configuration, the aircraft can be slowed to its final approach speed. Aircraft designers know that no wing is efficient at all speeds. By using flaps, slats and slots, a wing can take on beneficial low speed characteristics for takeoff and landing, and characteristics beneficial for high speed flight while at cruise. If it were not for flaps and slats, the takeoff and landing speeds would have to be much greater and runways would be prohibitively long. On the PIC767, I use a flap setting of 30 for landing in most cases. I find that the aircraft flair and touch down are better controlled in this setting. I hope that this clears up your question about flaps. Bill

Bill,Thanks for a very thoughtful and informative response.

Thanks but I can't take credit for it. It is out of the Continental Airlines' in-flight magazine, Published in the October 1997 issue of, on the Embry- Riddle website.Tons of info there.Billhttp://www.charityflight.com/images/bvcavitar.jpg

SP,For what it is worth, at Air Canada Flap 25 is the preferred flap for landing. This creates less drag and therefore requires less fuel (x 1000s of approaches this small difference adds up) and as a side benefit, less noise. Generally lower flap settings give better handling in gusts/windy conditions as well.Flap 30 can always be used at the Captain's discretion as conditions warrant. Some other factors may be the available runway length and runway condition, ie. where stopping distance is a concern, poor weather (use flap 30 in low vis)and whether autoland is being used (also calls for flap 30).Kevin in CYOW.PS, you really should change your handle!

Speaking with an ACA 767 F/O a couple weeks back on ACA869, he said they almost always use 5 for take off and 25 for landing, with very rare exceptions otherwise. ACA-767 F/O Bill at charity flight also said the same thing (5/25). Seems some of the American airlines prefer 15/30.Rob.edit - now I see CYOW's message above...hehe...duplication of efforts, his answer is better! ;-)

"During the approach for landing, the flaps and slats are again extended. The flaps are set to an initial setting, usually one degree. The leading edge slats are later deployed."Sorry, I can't make any sense of this, Bill? It sounds like the LE slats are being deployed after the TE flaps (?)... which, as far as I know, is not the case. Typo?Thanks.Cheers.Ian.

QANTAS standard procedure is flaps 30 for all landings, unless a different setting is prescribed by a non-normal checklist, or an overweight landing is being made.Something interesting to try (if it is correctly modelled in PIC), at heavy weights, Vref 30 will be higher than Vref 25, if this happens you use flaps 25 for landing (this also ensures that flap limit speeds are not exceeded, but is not the reason for the differnce).

Bill's an FO? Most American airlines seem to like 5/30, although some go to 15/30. The 757 uses 15/30, and I've never heard of any other flap settings, although it would of course be possible.

Actually Bill VC is a captain ;-)The Bill Rob speaks of is Bill Christopulos, the owner of Threshold Aviation in Toronto.

I see. :-lol

Now I see...guess i'll use 5/25 as much as possible!uhm, no offence here, were u tokkin about me when u referred to SP? I guess i've not much time left so i'll stick with it for the remaining time.PS:Im goin for national service(slavery) soon. I'm from an asian country in ASEAN. Guess which isit? :)geez...im such an idioT :)

SI,Yeah, sorry about that, I thought I read "Stupid Pilot" (RTFH!). Still...Anyway, as for flaps, as you see, take your choice, depending on which airline op you want to emulate.Cheers,Kevin in CYOW