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Old 26th Apr 2019, 18:31
  #4380 (permalink)  
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Join Date: Jun 2009
Location: florida
Age: 78
Posts: 1,433
Inherent stability and "help

Salute!

@ 100% We went thru a lot of the issue concerning stability and such on the 447 thread.

The more we saw of the AB330, and the FDR traces, the more it was apparent that the thing was and is a good design. So smooth an entry to the stall that the crew did not understand why the sucker wasn't reponding to stick commands.

Many of the bent wing designs have obvious clues when you are gettiing to high AoA. Buffet, wing rock, maybe aileron reversal and so forth. Others are smooth and stick shakers or pushers can save the day.

The AB330 does not appear to be statically neutral from what we saw, but the control laws make it appear so. If you use a gee command for pitch, then you will not have speed stability WRT AoA or Q. Duhhhh? Then I see the 737 with the STS kludge and I cannot find enuf early 737 data to indicate a need for the STS when the dinosaur model was certified.

One and not the only reason that a good FBW implementtion helps the $$$, is you can fly with less trim drag by using the stab to keep the tail up than forcing the nose down. My trusty Viper was and is the classic case. However, I do not think that Airbus developed the 320 and subsequent FBW models to be inherently speed neutral or have much longitudinal stability issues. Sure, you could get away with some aft cee gee, but could always fly the plane as you would any other. I"m not even sure if the USAF F-22 and F-35 have the same longitudinal stability properties as the F-16. Their demo routines show stuff that we Viper drivers couldn't dream of, primarily the really high AoA stuff.

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