AoA vs ASI
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I think that is commonly accepted that most stall/spin/crash events happen when the aircraft is near to the ground, slow and turning and when the pilot has been distracted. The commonly practiced scenario both in PPL, CPL and FI exams is the turn onto Final with 2 stages of flap on a PA28 or Cessna.
How would an AofA indicator allow for the fact that stalling AofA is less with flap than clean?
How would an AofA indicator allow for the fact that stalling AofA is less with flap than clean?
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Join Date: Jun 2002
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How would an AofA indicator allow for the fact that stalling AofA is less with flap than clean?
If AoA was commonly used on the approach instead of airspeed, every pilot would know that stalling AoA is higher with flap than without, a fairly critical piece of flight information.
I rest my case.
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QDM
Flaps come in a variety of shapes and sizes but consider the Fowler flaps on a Cessna. They increase wing area and camber, thus increasing coefficient of lift. From the lift formula it can be seen that with an increase in S (wing area) and Cl, the same amount of lift can be generated at a lower V (very useful for approach to land). It also means that more lift will be generated for any given angle of attack than for a clean wing, hence a better view of the runway.
Another side effect of flap deployment is that the wing will stall at a lower AofA than clean due to the increase in induced drag as speed reduces. This is partially countered on transport aircraft with the use of leading edge devices to re-energise the boundary layer over the upper surface of the wing but these are not found on most typical training aircraft.
If you still don't believe me, next time you go flying try some stalls (at a safe height, of course!) with and without flap and note the result.
Flaps come in a variety of shapes and sizes but consider the Fowler flaps on a Cessna. They increase wing area and camber, thus increasing coefficient of lift. From the lift formula it can be seen that with an increase in S (wing area) and Cl, the same amount of lift can be generated at a lower V (very useful for approach to land). It also means that more lift will be generated for any given angle of attack than for a clean wing, hence a better view of the runway.
Another side effect of flap deployment is that the wing will stall at a lower AofA than clean due to the increase in induced drag as speed reduces. This is partially countered on transport aircraft with the use of leading edge devices to re-energise the boundary layer over the upper surface of the wing but these are not found on most typical training aircraft.
If you still don't believe me, next time you go flying try some stalls (at a safe height, of course!) with and without flap and note the result.
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QDM
No, I'm wrong! The AofA is measured as that angle between the relative airflow and the chord line of the wing. The chord is a straight line joining the leading and trailing edges of the wing and as such will clearly give a higher AofA for a given NOSE ATTITUDE with flap deployed. Although the wing shape is now different it should stall at roughly the same AofA but at a lower nose attitude.
Who's digging a hole now!
No, I'm wrong! The AofA is measured as that angle between the relative airflow and the chord line of the wing. The chord is a straight line joining the leading and trailing edges of the wing and as such will clearly give a higher AofA for a given NOSE ATTITUDE with flap deployed. Although the wing shape is now different it should stall at roughly the same AofA but at a lower nose attitude.
Who's digging a hole now!
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AoA remains AoA even under different g conditions which is one of the benefits thus Vx and Vy remain the same.
Re. flap settings. An inner scale, or colour codes for the flap fixed settings.
"I can never remember is the cyan scale 20 or 45 degrees?"
Re. flap settings. An inner scale, or colour codes for the flap fixed settings.
"I can never remember is the cyan scale 20 or 45 degrees?"
