flat approach

[ElNull]

"Glide path angle also affects total landing distance. As the approach path becomes flatter, even whiile maintaining proper height over the end of the runway, total landing distance is increased."

when I read the above, by "flatter" I assume this means glide path angle decreases.

but why would this increase the landing distance?

[FatFlyer]

Landing distance is measured from crossing threshold ( normally 50 feet) till aircraft stops, landing run is from touchdown till aircraft stops.
Crossing threshold at 50 feet on 3 degree slope, touchdown ( no flare) at 50/tan3= 954 feet. On a 2.5 degree slope 50/tan2.5 = 1145 feet from threshold.

[BOAC]

but why would this increase the landing distance?- as with all number games, have a look at how accurate your landing spot is with a glidepath angle of 90 deg and what it would be like with an angle of 0. Cross the threshold at the correct TCH with a 0 deg angle (yes, I've seen it!) and tell us how far down the runway you would land:)

[Miserlou]

And a function of how much energy is used in the change of attitude.
A larger change of attitude from a steeper approach will result in a slower touchdown speed and therefore shorter landing distance.

I never understood colleagues saying, "going low on purpose". I always asked "What purpose?"
And anyway, 3 reds to the runways brings you to the same point on the runway as 3 whites.

[BOAC]

Not quite! "3 reds to the VASIs" takes you to the same point as "3 whites" (if you are lucky........)

"3 reds to the runway" could take you into the mud.

[mustafagander]

The problem I see with a flat approach, I mean one significantly below 3 degrees, is that the "numbers" all are wrong.

Landing approaches are standardised as much as possible to help us fallible humans to put the aircraft in the "right place with the right energy state" repeatably. Hence we try to fly 3* as close as possible so that any variations are obvious and able to be seen and corrected. That's what the certification is based on too.

A flat approach is quite dangerous because the aircraft energy state is significantly changed - much more thrust to maintain speed and much less rate of descent - so a float is almost guaranteed, eating up runway at a truly alarming rate.

If Miserlou means PAPI, he is correct - it is a point source and you will end up at the same spot, but your energy state will be all over the place. With a wide body aircraft you may well rip the wire off the fence though because the wheels are so far below the pilots eye height.