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Old 22nd Mar 2019, 05:20
  #2301 (permalink)  
SteinarN
 
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Originally Posted by BrandonSoMD
Well, for most pilots in a commercial setting, AOA by itself means nothing.

For a military or airshow pilot who maneuvers to rather excessive AOAs regularly, or uses AOA as a primary reference for carrier landing, it makes a lot of sense to show some flavor of AOA. For example, nearly all Navy carrier aircraft are standardized to show something like15 units AOA in a properly configured approach, and something around 30 units AOA at stall. But there is no consistent units-to-degrees mapping, because the pilot doesn't care about absolutes; he just wants to know how close he is to some practical limit.

But for commercial pilots, AOA is relatively meaningless. In fact, it generally introduces needless concerns. What AOA is correct in a given setting: that's hugely dependent on a ton of factors. Which one (left or right) are you showing? How soon during takeoff roll should they come alive; with zero airspeed they can be at crazy values without any concern. They can be slightly different for various valid aerodynamic reasons (sideslip or roll rate). The only time you really care about AOA is when the two (or three or whatever) sensors dramatically disagree, or when they remain at excessive (very low or very high) values when they should not. That's all fairly easy to automatically check, if the FMC is programmed to do so.

WHY the FMC wasn't programmed to do so is a useful discussion. But showing the AOA to most pilots won't make things any better or safer. Principle #1 of human interface: only show what is important.
Well, for most pilots, and in a normal flying mode you are correct. But we are talking about when somethings going haywire.When you are not sure what the aircraft is doing, you might not be sure if you actually are stalling, you might not be sure about your airspeed. And we could go one step further for the more competent pilots, you wonder why just ONE stick shaker has activated, you wonder what the heck is the reason for the stabilizer trimming like crazy all the time, you wonder what is the reason for the IA showing different values on the left vs right display, and possibly reasons for other fault messages/warnings.

In such a scenario a displayed value of the AoA would in my opinion be VERY helpfull for the pilots in order to figure out what is really going on with the aircraft and what it's performance is.

Last edited by SteinarN; 22nd Mar 2019 at 05:41.
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