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outlaw2001it

Flaps

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Hello,Alright, I know that this has been discussed before, but I've been reading different posts, and I can't find the answer anywhere (unless I missed it). I understand Flaps at 20 degrees (depending on your plane) for Takeoff, Flaps at full for landing. So when or why would you use Flaps at 10 degrees? Is it to slow the Plane down instead of using the Spoilers (to save fuel)? Thanks J.R. Duda

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It depends on the aircraft. Some reasons for using reduced flap settings include improved controllability in strong/gusty crosswinds, improved missed-approach climb performance, improved second-segment engine-out departure climb performance, and improved stall margin at approach maneuvering speeds, among others.RegardsBob ScottATP IMEL Gulfstream II-III-IV-V L-300Santiago de Chile

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And often in the Allegro trainer I had been flying, my CFI and I would take off with no flaps--actually in all my flight lessons I can think of only one instance where I took off with the flaps. The Allegro has pretty much the same flight envelope as a 172 but with a slower stall. I usually rotate at 48 kts and do the initial climbout at 60kts or so. -John

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J.R.Remember that the purpose of flaps is to change the camber and surface area of the wing to allow lower speeds for a given flight regime.SO, with that said, Flaps 20 is overkill for most takeoffs. For instance, if a Cessna 172, for takeoff all you need is one "notch" of flaps in most cases.In a 737 for example: For a long runway and light loads at standard temperature at sea level, Flaps 5 is fine. As the runway gets shorter, your load increases, high SAT, high elevations, etc you will want to add flaps (10 or 15). The more flaps you give, the lower your Vr speed will be. Likewise, in a 737, Flaps 30 is SOP and NOT flaps 40. As a matter of fact the Airbus A300 and some other aircraft are certified for a ZERO FLAP takeoff! The first time I flew on an A300 jumpset (before COA got rid of em) and we lined up on the runway, I noticed that we had ZERO FLAPS! I almost had a heart attack especially leaving from KEWR which had a shorter runway back in 1992. I couldn't say anything because we were in "sterile cockpit" and only the PF and PNF can talk so I said a prayer and prepared to go sailing into the factories at the end of the ruway. When we go to 10,000 feet an the PF turned off the sterile cockpit light, I shakingly told him about the flaps and he and the FO had a great laugh as they told me about the zero flap takeoff. :-lolBottom line: You want to use just the amount of flaps for your given aircraft and circumstances. Also be mindful that using more flaps than you need causes more wear and tear on the wing and flap assembly so in the real world, flap use is considered carefully. But Flaps 20 for takeoff is too much.

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John:I think we were seperated at birth...check out my post on the zero flap takeoff. LOL! BROTHER!!!!!

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Actually in a Cessna 172 normal takeoff is done with flaps up unless you're executing a short-field takeoff.

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I was also taught in a 172 to use one notch for soft field take off....

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Ahhh, my favorite takeoff of all. Stay in ground effect,raise the flaps, accelerate to 110K and pull up sharply and climb out like an F-18 Hornet.....well, at least for the first 100' or so. Hope the FAA isn't monitoring this:D John M

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The amount of flaps one should use for landing has always been a great debate among flight instructors when it comes to light aircraft, like the 172, especially in adverse weather conditions. Some will say always land with full flaps no matter what the wind/turbulence is doing because it allows for a lower airspeed, therefor very little,if any, float in ground effect. Which gets the airplane on the ground faster. Others will say to use 10*,or no flaps in high crosswinds conditions because it's easier to control the aircraft on short final approach and will not fly like a kite when near the ground. There are, of course, many other techniques used for landing besides the proper use of flaps. And it's the PIC's decision as to what flap settings are appropriate for the situation. The bottom line, as told by my instructors and I passed on to my students is, any landing you walk away from is a good landing. Since I'm still walking, I guess I've been making some good ones:-) John M

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Since it has not been mentioned yet. An airplane such as the Marchetti SF260, requires 20 degrees of flap for takeoff. It has a much smaller wing area than a Cessna 172, but is quite a bit heavier.For this specific aircraft, 20 degrees is what's required.L.Adamson

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Yep, you are right and I got my PP ticket at Boulder Municipal where at 5,280 ft at 90 degrees and a lake at the end of the runway, SOP was 1 notch of flaps! LOL!!!!!

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Gulfstream jets use 20 flaps as the normal takeoff setting...10 flaps is used if needed to meet a climb gradient. Not sure if the original post referred to light or transport category acft...although since he referenced spoilers I tend to think he was asking about transport acft. The discussion here for light acft doesn't apply very well to their heavy big brothers.RegardsBob ScottATP IMEL Gulfstream II-III-IV-VSantiago de Chile

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Hi I regularly ride Air NZ`s SF340a/b`s from Wellington. They always takeoff with zero flap, even on the shorter runways in their route structure. Like the earlier poster, I was fretting the first time experienced it, thinking of the 727 that failed to remain airborne having taken off inadvertantly with no flap set! CheersJames

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J.R.,With an aircraft whose operating manual specifies 20deg for t/o and 30deg for landing, the 10deg setting would be typically used during deceleration during late downwind or on the base leg (basically as you prepare for final approach). In most cases, if you went from 0deg to 20deg you would either have to fly with high nose up attitude for a short while or handle are rather difficult to manage balloon (a climb) due to the increased wing camber and perhaps surface area.Other considersations are that flap will reduce the ground roll on take-off but also reduces your rate of climb - considerably in some cases. So if you have a short field takeoff then flap is usually recommended to provide a steeper climb gradient (best anngle - Vx) because you will have close in obstacles. But if the potentially limiting obstacles are further away from the airfield a flaps up takeoff maybe recommended because you'll get to a safe altitude sooner (best rate - Vy).Different types have different requirements. The Grumman AA5A light single specifies flaps up takeoffs in all conditions.

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One of the most famous takeoff accident cases of slats & flaps was here in Detroit, I think in the mid 80's, Northwest Flt 255, an MD 80. The CVR recorded the callout for the flaps, I even think the co-pilot acknowledged the setting. Because of other cockpit distractions they weren't set for the V speeds. Runway 9L at Detroit Metro seems to stick in my mind. When the plane was rotated it rocked back and forth as the pilots tried to keep the wings level with rudder as it was on the very edge of stalling but still in ground effect. The direct cause of the crash was a parking lot light pole just a little too high in a car rental agency at the end of the runway. If it wasn't for the light pole the Feds speculated that the plane could have made it.Clearing any obstacles at the end of the runway should dictate the use of flaps/slats or no flaps/slats at a given weight and runway length. As a general rule anything over 25 degrees becomes more drag than lift. Flaps allow for a higher angle for the glide slope without an increase of the airspeed during landing. A steep approach is necessary sometimes because of obstacles at the end of the runway or terrain. Daryll

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