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Rottenlungs

No Flap Takeoffs

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Hi all, can someone explain to me the purpose of a no flap takeoff? I notice that this is quite common on the Fokker F-100, but Im sure other planes perform a no flap takeoff. I have also notice some pics at Airliners.net showing a 737 taking off with 1 notch of flaps when I think usually they use 5 degrees.Thanks,Bill

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G'day Bill,Flaps are absolutely critical for Take-off off with the B737. (all Boeings in fact.) The small swept wing has very poor lift at low speeds. So much so that if the flaps are not in the 1-15 unit range then a Take-off warning horn will sound if a Take-off is attempted. Even 1 unit of flap makes a huge difference. The leading edge slats are positioned at their mid range and the trailing edge flaps moves rearwards thus increasing wing area.The actual setting used is dependant upon the aircraft weight and available runway length. My GUESS ( I'm not a jockey ) is that using low flap settings is used as a noise abatement proceedure for aircraft on climb out. A reduced flap setting equates to a higher take-off speed which could be utilised to produce an intial higher rate of climb thus leaving a smaller noise footprint on the ground on climb out.Roger

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Good guess Roger! The basic first principle to understand with flap is that any setting other than fully up will reduce your rate of climb (Vy), a small flap setting will reduce your ground roll and increase your climb gradient (you climb higher in less distance - Vx), but the increase in drag of any flap setting, no matter how small, moves the drag curve up and left (more drag at a lower speed) so the best rate of climb speed is reduced but requires commensurately more power to achieve.Therefore, if you only need to a achieve a certain rate of climb after take-off you can do it with less fuel and less noice with zero flap as you can throttle back slightler to account for the better maximum rate of climb.

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As far as i know, flap 1 on a 737 wont even move the trailing edge's at all. They will only put down the leading edge.

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Here another question, does the first notch of flap extend the slats and kruger flaps completey or half way?Thanks,Bill

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G'day Bill,@ 1 unit it's 50/50 Bill :-) The inboard Kruger leading egde FLAPS are fully extended.The leading edge SLATS (outbd of egines) are operated by telescopic actuators and move to their mid range position. To move the leading edge slats to their "full extend" position requires a selection of 10-40 units of flap.Cheers,Roger

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Some aircraft are made to not use flaps on takeoff. The Aztec and the Apache are two examples. Their flaps are what are called "all drag flaps." Don

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G'day Brent,I'm recalling things from over thirty years ago ( and on a -100 series 737 at that ) but as I recall the flap lever in the cockpit only operated the trailing edge flap control valve.The flap control valve ported fluid to a hydraulic motor which through a gearbox drove the flap torque tubes to extend the trailing edge flaps.The follow-up cables going from the gearbox back to the flap control valve also operated the leading edge flap control valve. Thus if the main flaps don't move then the leading edge control valve isn't opearated.Things MAY have changed with the later series 737's. ( I don't know)The 737 flap lever has 9 settings.0-1-2-5-10-15-25-30-40 Obviously 1 unit is not going to be a huge amount of flap but I do believe there is some trailing edge flap movement with 1 unit of flap. If anyone can give a definitive answer I'll stand corrected because it is only memory and was so long ago. You might be correct.Cheers,Roger

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Somewhat like the Grumman AA5. That was a zero flap t/o according to the flight manual. The reality was that 1/3 flap drastically reduced the t/o roll and the climb to 50' was swift, so it was common practice amongst Grummanites to use 1/3.

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A normal takeoff in a Caravan is flaps 20, but a takeoff after type II or type Iv anti-ice fluid has been applied is done flaps 0.John

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Hi GuysI regularly fly on Saab 340B`s in New Zealand. They take off from longer runways with no flap.The first time I rode on the plane, I was wondering what else they had forgotten when rolling! CheersJames

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