Originally Posted by
formulaben
I guess it depends on where your priorities lie. Given worst-case scenarios, would you rather stall on final, or overrun the runway? I'm pretty certain of my answer.
The problem being, that the existing certification margins for both apparoach speed and landing distance are designed, however empirically, around the CURRENT design assumptions i.e. that the consequences of a weight error are equally distributed between risk of stall and risk of overrun. (If anything, service experience would seem to indicate that risk of overrun is actually far greater, but it is as you note generally (but not always) more survivable).
Changing to a system where all the risk is loaded onto the overrun side of the equation would represent a net REDUCTION in safety unless the conservatism in the current landing distance calculations were increased to account for the increased risk.
Also, give the 'worst case scenario' of being grossly overweight, there are warning systems or characteristics which will alert the crew to a too-slow approach; there's nothing to warn you that your calculated landing distance is too short (that I know of) except indirect clues. So to stall on approach requires the weight error and failure to respond to warnings. With an AoA approach, what's going to protect against overrun?
Is it not significant that many of the military types which use AoA for approach are CARRIER aircraft - a case where landing distance considerations DONT have much significance.
Perhaps. But perhaps not. But pray tell, if it's not a simple function of AoA, then just what exactly else do you suppose is figured into a climb calculation when you're already at max power?! Last time I checked, there's only 2 things can determine climb performance: pitch and power.
Scheduled speeds can also be affected by, amongst others, VMC (a, l or g), VMU or variations in stall AoA with conditions; none of which will be captured by a simple AoA target.