10 degree flaps increase our lift, reduce stall speed, reduce ground roll. Seems like all advantages with no disadvantages. So why does the Cessna 172 POH say normal take off is 0-10 degree flaps? Why not always use 10 degree?

  • $\begingroup$ Welcome to aviation.SE! This question might be helpful. $\endgroup$ – Pondlife Jul 29 at 1:15
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    $\begingroup$ In some headwinds you might take off backwards. $\endgroup$ – J... Jul 29 at 14:20
  • $\begingroup$ 10 degrees flaps is standard in a 177. There are wind situations where less flaps make the plane mor controllable. I don't think I've ever had to. If the elevator trim is set correctly, basically where it was for the prior landing, the plane will lift off with very littl back pressure. I've only flown a 172 once, for a BFR so I could move my plane on a ferry permit, and I think I took off the same way. May not have used flaps, I don't recall what that plane's check list said. I do remember that awkward sitting up in a high-back chair feeling to see out the front; the Cardinal is much nicer. $\endgroup$ – CrossRoads Aug 1 at 0:08

Flaps out will reduce the ground run, but you're forgetting that they also increase drag. This is why you don't climb all the way to cruise altitude with flap extended. A 172 will climb better without flaps.

With a take-off, you have to consider both the ground run and initial climb. After all, the take-off distance required is defined as the distance required to climb to screen height (50ft in Australia, sorry if the US is different). The aircraft also has to meet a legal minimum climb gradient to that height.

Without looking at the data, it is possible that in certain conditions, taking off with flaps 10 will get you off the ground quicker, but will actually take longer to reach 50ft compared to a takeoff with no flaps. In any case, retracting flaps in a busy time after takeoff is a potential hazard, and in a training aircraft like the 172 simple procedures are best.

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    $\begingroup$ Also, in many places the runway is just way longer than a 172 needs, and it doesn't really matter if you take of at 1/4 of the runway or at 1/3 -- but the faster takeoff takes you out of the airport control zone faster. $\endgroup$ – Simon Richter Jul 29 at 10:39
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    $\begingroup$ Using flaps creates drag. If you have a nice, smooth paved runway, it's more efficient to take off with no flaps. On a rougher surface like grass or dirt, you have more drag from the wheels, so it's better to get them off the ground sooner. $\endgroup$ – jamesqf Jul 29 at 14:36
  • $\begingroup$ Also, in gusty crosswinds, the increased flaps & drag make it harder to control the aircraft. $\endgroup$ – Suncat2000 Jul 29 at 19:41
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    $\begingroup$ And screen height is 35 ft in the US. $\endgroup$ – Kolom Jul 31 at 18:03

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