chuckk2

From experience with the "old" Cessna's that had a manual flap lever.
It was possible to carefully control the flaps when just above the runway, and control the "float" that many of the Cessna's had over a hot runway on a sunny summer day. Flaps change things in different ways.  Increased drag is obvious as the plane slows down when they are extended.
increased lift at the same air speed can also be true, if the attitude is controlled properly.
The usual primary purpose of flap usage is to obtain a slower airspeed and landing speed, or a shorter takeoff ground run, followed by a steep climb for noise control (on large aircraft).

A really heavily loaded aircraft might need flaps to maintain acceptable flight until some fuel is burned.  In wartime, (WWII) it was commonplace to find out exactly what load a strike aircraft could stagger into the air with, and, as needed, ignore the usual gross weight limit specs.

I can remember a stretch DC-8 at full passenger, baggage, and fuel load taking off from Shannon in the 70's. Winds were not very favorable for the transatlantic crossing, so the maximum amount of fuel was loaded.  The pilot checked the flaps more completely than usual prior to the take off run, then gradually extended them when the plane picked up speed.  The plane came off the ground late, and just as the co-pilot was ready to call for abort.

Flight behavior with flaps is interesting on a DHC 2 Beaver R/C model.  I have one that is somewhat over powered with an E-Flite 32 motor.
Half flaps result in a much slower landing speed (no power). Full flaps require either added power or a rapid decent rate.  Landing with full flaps
can be a bit tricky, due to minor wind changes close to the ground.  Full flaps result in an extremely low forward speed, which naturally, decreases the difference between airspeed and wind speed.
 

Ed

Quote:

ORIGINAL: chuckk2



Flight behavior with flaps is interesting on a DHC 2 Beaver R/C model. I have one that is somewhat over powered with an E-Flite 32 motor.
Half flaps result in a much slower landing speed (no power). Full flaps require either added power or a rapid decent rate. Landing with full flaps
can be a bit tricky, due to minor wind changes close to the ground. Full flaps result in an extremely low forward speed, which naturally, decreases the difference between airspeed and wind speed.

Chuck, your comments on the Beaver are very interesting, as they are known for their STOL capabilities. How many degrees are you seeing when you extend to Half, and then for Full on your Beaver ?

s3nfo

My Feedback: (14)

Used to rent a Cherokee 140 once in a while, loved to land that plane, flaps were controlled with a lever on the floor between the front seats like a parking brake on most cars today. On final carrying a bit of extra speed and just when the VASI goes red over red, pull in full flaps and the little Cherokee would pop up to red over white and on speed. Only 2 possibilities, flaps create lift or I was actually pulling the plane up with the handle.......

invertmast

My Feedback: (23)

Yep.. i've got allot of time in Piper Arrow's (100+hrs) with those, we would do power off 180's. For those who don't know what this is. It simulates a power failure abeam the touch-down point on the down-wing leg of the traffic pattern. The test standards for this maneuver for a commercial pilot is +50/ -0 feet from the touchdown point you pick. With the arrow's, you could be just a weee bit low and going to end up short of your touchdown point, but if you pulled up on the handle the last little bit past the LAST notch of full flaps (roughly another 3-4* of deflection), you could get about a 5-10' rise in altitude that would extend your glide about 50-100'. This proved useful many times.

Top_Gunn

My Feedback: (6)

Exactly. The way I like to think of it is that flaps change the airfoil so that the plane can fly at a slower airspeed without stalling, while also adding some drag. Thinking of flaps as "creating lift" isn't wrong, but it can be misleading, as in the earlier example of the Cessnas unable to clime well with 40 degrees of flaps.

NickC5FE

My Feedback: (31)

Wow, seems as though someone is very sure of his theories on lift generation so that is it...he is right. All of the aeronautical engineering and research over the last 100+ years is a sham.

It also seems as though the very sure person has no clue about aerodynamics so i will continue to follow the theories that were bestowed upon us since the beginning of flight.

Yes, flaps do increase drag and lift. Depending on the type of flap arrangement (split, fowler, slotted fowler or plain) is what determines the total ratio of lift to drag that will be produced.

C-5 Flight Engineer (3100 flight hours) with a degree in aeronautics specializing in aerodynamics

Top_Gunn

My Feedback: (6)

[quote]ORIGINAL: NickC5FE

Wow, seems as though someone is very sure of his theories on lift generation so that is it...he is right. All of the aeronautical engineering and research over the last 100+ years is a sham.



Uh, who are you disagreeing with here? The person you replied to agrees with you, as does just about everybody else who has chimed in. Yes, flaps increase lift and drag.

invertmast

My Feedback: (23)

[quote]ORIGINAL: Top_Gunn


Don't pay any attention to that "in reply to" in the bottom right corner.. it just pops up whoever's name was the last one to post when someone clicks on the "post reply" button..