AJ Goes Airbus

[Evan]

Originally Posted by brianw999

I think I've posted this before but what the hell....here it is again.....Try surviving this in a Boeing !!!

http://www.youtube.com/watch?v=IKBAB...e_gdata_player

AFAIK, in manual flight if you hold the stick to the stop if will bank to 67°; if you then release it, it will roll back to 33°, not wings level. So what is going on here? Reverting to A/P?

(sidestick input is a roll rate command with neutral spiral stability under 33°, so center stick maintains current attitude)

[Gabriel]

Originally Posted by Evan

- If you lose Normal Law protections, you also lose static longitudinal stability.

I beg you pardon?

Except at low speed, as part of the slow speed / high AoA protections, and in very high speed as part of the overspeed protection, in the bulk of the envelope the Airbus in normal law is one to two degrees less longitudinally stable than the standard planes (from the J3 to the 777).

In the low-speed range (but not too low) the plane is stable in pitch, and at higher speeds it's stable in load factor / vertical speed, which are respctivelly one and two degrees BELOW what could be called a quasi AoA / speed stability of the "normal" planes. (pitch demand and load factor demand vs AoA demand).

With direct law you'd get the AoA / speed stability back, but not the AoA demand becuase you still have a spring loaded joystic.

In alternate law you get the worse of both worlds: No AoA / speed stability and no low speed / stall protections.

[Evan]

Originally Posted by Gabriel

In alternate law you get the worse of both worlds: No AoA / speed stability and no low speed / stall protections.

Specifically, in Alternate Law:

At the flight envelope limit, the aircraft is not protected, i.e.:
- In high speed, natural aircraft static stability is restored with an overspeed warning
- In low speed (at a speed threshold that is below VLS), the automatic pitch trim stops and natural longitudinal static stability is restored, with a stall warning at 1.03 VS1G.
- In certain failure cases, such as the loss of VS1G computation or the loss of two ADRs, the longitudinal static stability cannot be restored at low speed. In the case of a loss of three ADRs, it cannot be restored at high speed.

[AJ]

The course is very thorough.

It also teaches us to lock out hijackers, and seeing Evan wants to hijack this thread.......