AF447 Thread No. 3

[gums]

some positive feelings courtesy of Henra

Thanks, Henra. Good points about overall static stability and such for the 'bus.

Note: Would still interest this old FBW dinosaur to see the pitch moment coefficient graphic for the 'bus, especially in the configuration BEA has determined.

For all: I only present the older FBW system and aero to demonstrate that it is possible to enter a stall that goes and goes and goes unless the crew DOES SOMETHING that the plane allows.

Henra is correct about the c.g. difference and the all-moving tail control surfaces. In our case, we simply did not have enough pitch authority and our cosmic control laws did not allow us to move the stabilators directly. Further, above 29 - 30 deg AoA the rudder was "taken away" from us as the engineers didn't want us to enter a spin ( inverted, we still had control of the rudder as the 'bus does in most laws and same for positive AoA below 29 - 30 degree). Hence, initial recognition of the "dreaded" deep stall was a problem until we all got "educated".

Henra is correct about static stability comparisons. Ours was no-kidding negative until above 0.9 M. Later models, with the big tail, had more pitch authority at slower speeds, but the static stability was almost the same. You could still get into a deep stall with the big tail. I doubt the 'bus has any flight condition with negative static stability. Might have less than other types, but still positive.

So what's your point, Gums?

My point is that the 'bus has more reversion sequences than the jet I flew. I guess to be certified to fly it, one must be able to recite all the sequences and "protections" lost versus actually describing the laws as we had to do. And then appropriate crew actions that won't make things worse.

It has more A/P commands for stuff I find more of a crew function.

It has nothing like our MPO switch to get us to a less complicated set of control laws, but still have more "protection" than a basic "direct" mode for all control surfaces. Fact of life with FBW, and this old dino would not want a plane like the Viper to have such a mode because we had a very expanded envelope and could DESTROY THE JET, as well as ourselves, if we yanked too hard or mis-applied the controls.

gotta go fishing now, later.

Gums sends...