PPRuNe Forums - View Single Post - Why isn't AOA on the panel?
View Single Post
Old 2nd Sep 2006, 18:22
  #18 (permalink)  
Mad (Flt) Scientist
 
Join Date: Sep 2002
Location: La Belle Province
Posts: 2,179
Likes: 0
Received 0 Likes on 0 Posts
For those advocating use of AOA for approach instead of airspeed. If the aircraft weight is correctly known, they amount to the same thing. Consider, though, what happens if the weight is wrong.

Assume the aircraft is 5% heavier than calculated (a pretty gross error, but its just a number...)

For an aircraft flying airspeed, it will be flying at a higher AOA than it should (effectively flying at 1.20 Vsr instead of 1.23Vsr) and it will also have 5% more energy/moment to bring to rest - say 5% more landing roll required (though in fact the brakes will work better, so it'll be less in practice)

If instead the aircraft flies AoA, it'll be at the 'correct' 1.23vsr, and consequently 2.5% faster than the book says for the weight. Therefore it'll now have 10% more enegry/moment to bring to a halt.

Flying AoA protects more in terms of stall speed margins, but puts all the error into the landing distance, unless you recalculate based on the actual speed flown (which would seem a bit of an imposition)
Mad (Flt) Scientist is offline