Flaps question

[nwafan20]

Well, looking at some photos (mainly the B747), I noticed that some airplanes have quite a bit of spaces between the flap layers, why is that? Wouldn't they be much more efficient if the flap was full without spacing (vertical spacing..)

Example:
http://i125.photobucket.com/albums/p75/nwafan20/Undercarriage_b747_arp.jpg

[Mateo]

Fowler flaps, the kind that are pictured above, generate lift themselves, allowing for the production of lift at a higher angle of attack and lower speeds. This lets the aircraft more efficiently shed the kinetic energy of flight by increasing the AOA and lowering the stall, and thus landing, speed.

[nwafan20]

Yeah, I understand the Fowler flaps concept, but couldn't they make it without spaces in between? Wouldn't that increase the amount of lift without affecting the chord?

[PhilDernerJr]

I think th gap is what lets the flaps get that extra lift. With the gap, air is passing along each individual one and they all act as an extra wing.

[nwafan20]

Alright, I guess that makes sense. Thanks both!

[HPNPilot1200]

Alright, I guess that makes sense. Thanks both!

Phil nailed it. The whole concept behind a slotted flap system is that there are slots between the flap panels themselves which act as additional lift producers. The two basic concepts behind lift (Newton's 3rd Law of Motion & Bernoulli's principle) still apply to those panels since air molecules still travel above/beneath them, though Newton's 3rd is much more prevalent because of the downward deflection of air molecules causing an increase in lift, thus delaying the stall.

With such a large aircraft, it takes a lot of lift to accomplish the task of a flap (high AoA/low stalling speed) which is likely why the fowler flap system was used.

[nwafan20]

Ok, thanks alot!

But here is another question, how come the 777 doesn't use Fowler flaps?

[Idlewild]

Aren't the flaps on the outer edge of a 777 slotted? I know the inner edges and the aerilons (when they act as flaps) are not.

[DHG750R]

older types like the DC8/707 used single or double slotted trailing edge flaps. the next generation transports :727/737(classics) and 747 used triple slotted ones which provided better field performance at the time.

Notice now how aircraft like the 737NG and A320 series have reverted back to double slotted flaps. The wing designs of the newer aircraft has improved to the point where the heavier, more complex and more maintenance intensive triple slotted ones of the 70's and 80's are no longer needed.

[USAF Pilot 07]

It's actually to allow the birds flying near the planes a hole to fly through when the planes go by them... :wink:

[Derf]

ahahahahah!!!! ****, now I need to clean up the coffee that I spit all over my LCD! It was still worth it!

[USAF Pilot 07]

LOL :lol: