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6 Answers

Brake and flaps in landing

Asked by: 2275 views Aerodynamics, General Aviation, Private Pilot

Hi, I have a question about flaps and landing

 

When landing, I use aerodynamic brakes after touchdown for Cessna 172 before using foot brakes.

However, between settings of no flap and flaps 30, which one is better for making better aerodynamic brake effect?

 

Some CFI says that "no flap setting makes more lift and it decreases landing distance a lot"

Some CFI says that "flaps 30 will make more drag because it has higher AoA and already increased chord line + form drag"

 

How do you think about it?

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6 Answers



  1. KDS on May 07, 2020

    It is best to use the flap setting that is appropriate for landing in the given situation (aircraft type, runway size and condition, wind and weather, traffic, pilot competency and currency). Then land and don’t touch them again until you are off the runway.

    If you find yourself in a situation that warrants a more complex answer, then the first question you need to ask yourself is why am I trying to land here and wouldn’t somewhere else be a better choice.

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  2. dgssss on May 07, 2020

    Ohhh. Probably I didn\’t make it clear enough.

    I mean not the \”final approach\”, but \”after touchdown\”.

    I did many times with flaps and no flap landing, and have a reasonable ways of choosing between them(wind and gust factor etc.) [Unfortunately, my question was not about this.]

    What I mean is about only \”after touchdown\”.
    Pilots pull full back elevator after touchdown for aerodynamic brakes. It is hard to tell without any picture, though.

    I hope you got my point.

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  3. Russ Roslewski on May 08, 2020

    I can’t imagine that having the flaps in or out makes any measurable (or repeatable) difference for aerodynamic braking in a typical aircraft like a 172. Far more important is the actual speed you touch down at, your use of brakes and the wind.

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  4. Richard Eastman on May 08, 2020

    IF (note the big “if”) you are fully stalled on landing … then the drag of the flaps would be marginally more effective in slowing a 172 with or without braking. If you are NOT fully stalled on landing, the flaps will continue to generate lift which will negate the drag caused by the wheels and if you are braking, the brakes. The drag resistance of the wheels is the primary slowing effect, whether braking or note braking.

    A no-flap configuration means that you would be landing faster, which would negate the value of wind drag. Landing with no flaps might add marginally more weight to the wheels, but once below the stall speed, the effect would be minimal.

    As noted in the other answers, (a) the difference in a 172 will be marginal and perceptually not noticeable by any pilot, and (b) if you are in need that kind of braking, you should ask yourself why you are attempting to land at such a location in the first place.

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  5. dgssss on May 08, 2020

    @Russ Roslewski : Yes you got my point, and I understood. So you think “there is no big difference”. Hmm It is actually minor factor regarding landing distance, but I need more scientific reasons for that argument. Your opinion can be correct but there is no evidence or reference of FAA about it. Anyway thank you for your answer.

    @Richard Eastman : I always check possible landing distance and calculate it from PoH according to SOP as a student. I agree that your mention of “approach speed” is critical factor in landing distance.

    But I still get curiosity about what if I have “same approach speed and at 30degree flaps landing.

    It starts from same 30 degree flap landing(same approach speed) – touch down – and then it has 2 options.

    After the touch down,

    option 1 The pilot can leave the flap and clear out of the runway
    option 2 The pilot can make flaps up and clear out of the runway

    Anyway thanks for your comment

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  6. KDS on May 08, 2020

    Do not get in the habit of pulling flaps up while on the runway. It may not seem like a critical issue at this point in life, but it leads to a habit pattern that can result in a gear-up event later in life.

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