Landings with Flaps vs Flapless landings and effect on glide slope?
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Landings with Flaps vs Flapless landings and effect on glide slope?
We know all textbooks say that flaps are supposed to increase drag and cause a steeper approach angle (w/out increase in airspeed) during a landing, while in a flapless landings, the a/c must fly a shallower approach and slightly higher speed to maintain the same amount of lift but also not to pick up excessive airspeed. But when my instructor showed me a flapless landing, the "picture" did look shallower, but we still maintained a 2 reds 2 whites glideslope? He said in a flapless landing, just like in a flap extended landing, it is still possible to maintain a VASI glideslope. This totally confused me: if the approach is shallower with a flapless, why didn't I see 3 reds and one white or maybe all reds, as this would have been consistent with a shallower approach? Please unconfuse me 
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The 'textbooks' you describe refer to light aircraft, such as (for example) a single engine Cessna.
In reality, of course, whether the approach is flown with full, partial or without landing flaps selected in a jet aeroplane, the desired approach glidepath angle is more or less the same.
In reality, of course, whether the approach is flown with full, partial or without landing flaps selected in a jet aeroplane, the desired approach glidepath angle is more or less the same.
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The reason that it looks shallower is because the nose attitude is higher (there's a higher AOA for a flapless approach relative to that with flaps extended). The higher nose attitude reduces the visual segment (how much you can see over the nose) and it is the visual segment that determines whether it looks steep/shallow to the pilot. To maintain the PAPIs the aircraft is still descending on a 3 degree glideslope and for a flapless approach with a higher approach speed, the rate of descent to maintain that glideslope will be a little higher than that for a flaps extended approach.
This visual picture (in terms of visual segment) applies equally from a 152 to a 737 (where variable flap landings are the norm and the effect can be seen quite clearly).
This visual picture (in terms of visual segment) applies equally from a 152 to a 737 (where variable flap landings are the norm and the effect can be seen quite clearly).
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"The books" are also describing a power-off approach -- a flapless landing will then be shallower and faster.
However, especially in IFR conditions, we strive to maintain a constant glide slope, so we adjust power to compensate. We "always" fly the 3 degree glide slope, but may be faster or slower depending on weight and flap configuration. As the others pointed out, the sight picture may vary with the airplane and flap setting.
However, especially in IFR conditions, we strive to maintain a constant glide slope, so we adjust power to compensate. We "always" fly the 3 degree glide slope, but may be faster or slower depending on weight and flap configuration. As the others pointed out, the sight picture may vary with the airplane and flap setting.
