Positive Stability in Fly by Wire Aircraft

[gums]

Salute!

Thanks, "Detent", you have it right.

From what we saw in all the 447 data traces, the 'bus is aerodynamically solid as a rock. In fact, if it was less aerodynamically "stable" on its own, without a lotta help from Hal, maybe the crew would have associated the descent rate with a stall. Some designs would have been shaking and shuddering and possibly have wing rock and other indications that you were stalling or approaching a stall.

@Airmann! Fly by wire has nothing to do with static or dynamic stability or stall characteristics. Zip, nada, nyet, no-way dot com. Attitude hold is not a stability thing, but the 'bus appears to have neutral speed/longitudinal stability as a function of its control laws, not its aerodynamic characteristics. In Direct Law, I bet it slows up with increasing AoA and speeds up with lower AoA. Just like Tiger Moth or Aeronica!!

What FBW allows for fighters as I flew is less stability in order to have better mission performance like nose rates, roll rates, stall protection ( to some extent). smoother tracking of your target and so forth. For the heavies, it reduces workload and likely makes checking out in a new plane a lot smoother, quicker.

Hal is quicker than we carbon-based lifeforms, so you see a very quick and smooth recovery after hitting a thermal or maybe bumping the stick/rudder. As pointed out above, the plane usually will not try to go back to the exact attitude that existed before the upset. You can see this when the Thunderbird solo planes do a snappy roll, because there's no wing rock when the pilot releases presure on the side stick. No roll command? So Hal stops immediately. As light as the Viper was, it felt like a much bigger, more solid plane down low going thru thermals and gusts.

Hope that clears up questions.

Gums sends...