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Old 14th Aug 2022, 15:52
  #173 (permalink)  
FlightDetent

Only half a speed-brake
 
Join Date: Apr 2003
Location: Commuting not home
Age: 46
Posts: 4,319
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Another observation:

The 330 mtrs aiming point as marked with the blue line would result in MLG touch at 400-450 m distance as per AFM, leaving 1120 m of braking pavement ahead.


Touchdown geometry (not on the FCOM graphics above - numbers for A320):

No-flare brings the MLG to ground 130 m ("B") short of the aiming point point whereas 'typical' landing touches about 100 m past the aiming point (430m let's say). A cropped half-flare of 130 meters instead of optimal 230 will land the plane exactly at the aiming point.


Going for the MARKERS with such short flare, which seems to be the most frequent result from the good videos, yields an additional 280 m for braking =>> 1400 v.s. 1120. A marked difference, also giving you the chance utilize the uphill slope.

What about the wheel clearance? (significantly corrected from own post above).

Aiming at markers (150 m) gives around 8 feet.
Threshold is displaced by 60 m providing additional 10.
Ground loop for turning has another 50 mtrs for +8 more.
= 27 ft compared to theoretical 31, not bad.

If the pilot eye ignores the painted lines, crossing the pavement edge while aiming at the makrers (+ invisible PAPI) is not critical and will feel somewhat normal. From a 3 deg profile, that is. Of course, the big squares are 260 m from the grass.




Last edited by FlightDetent; 15th Aug 2022 at 04:39.
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