Mach: Sure, Mach and TAS display with all three pitot channels blocked had been a simulator imperfection.
Phugoid: I would expect that the airframe would manifest phugoids, Dutch roll, etc. in a way comparable to other conventional designs. In direct law that is [to non AB world: movement on the stick commands movement of the control surfaces]. Once in normal or alternate [stick commands the trajectory and flight control computers calculate what kind of control movement is required to achieve so] I would guess that you would not get any of these natural behaviours as FCCs filter the unwanted effects out.
1g This is a can of worms. I would again, hazard a guess, that AB does not want to explain all the true details behind FWB logic in FCOM as it is a) too complex for pilot to understand b) in turn might freak you out and lose your trust in the system c) reveal too much know-how.
Doc 7488 Manual of the Standard Atmosphere:
It is known that gravity is a vectorial summation of the gravitational attraction and the centrifugal force induced by the earth's rotation; it is therefore a complex function of a latitude and a radial distance from the earth's centre and the expression for acceleration due to gravity is generally awkward and unpractical for use. However, the acceleration g may be obtained with sufficient accuracy for the purpose of this standard atmosphere by formally neglecting centrifugal acceleration and using only Newton's gravitational law. NOTE FD: For standard g the centrifugal force cannot be neglected (effect of 0,0337 m*s-2 at equator). However, this paragraph further develops the principle of geopotential altitude and changes of g with increasing height. Because the difference in centrifugal force and associated acc is miniscule with height (see my calculation 1 below), to determine the total change of g with height the delta(Fcentripetal) is being ignored.
....
Doc 7488
h=0 m ---- g = 9,8067 m*s-2
h=11000 m ---- g = 9,7728 m*s-2
See, delta g between surface and 36000 ft is 0,0339 ms-2.
conclusion A The altitude plays a role.
On the other hand, I've done some calculations and this is what I got:
-1) the difference of centripetal acc of a stationary object (still subject to earth's rotation) on surface compared to tethered object 11000 m above = 0,000058 m*s-2:
conclusion B The effect of change in centripetal acceleration due increased height has only 0,17% effect on total g change with altitude; negligible.
-2) the difference in centripetal acc of a tethered object (still subject to earth's rotation) 11000 m above surface compared to moving object at same height travelling 500 kt in a direction
identical to earth's rotation = 0,000000037 m*s-2:
conclusion C1 The effect of increased tangential velocity (calculated at altitude) on g compared to total g change with altitude, would only be +0,00011%; negligible.
-3) the difference in centripetal acc of a tethered object (still subject to earth's rotation) 11000 m above surface compared to moving object at same height travelling 500 kt in a direction
opposite to earth's rotation = -0,000000037 m*s-2:
conclusion C2 The effect of increased tangential velocity (calculated at altitude) on g compared to total g change with altitude, would only be -0,00011%; negligible.
To summarize:
(i) Normal g changes with altitude due to increased distance from earth's centre.
(ii) Normal g changes with altitude due to difference in orbiting speed; compared to (i) above, this delta g is inconsequential for aircraft.
Based on (ii), while eastbound trajectory provides the theoretical maximum delta g, the speed and direction of flight has no relevant impact.
My points:
If FWB had a hard-wired "g" value, at altitude it would naturally seek a pitch up to increase load to the hard-wired value.
The designers surely must have been aware of this. In order to provide compensation algorithm, you would need altitude information thus linking F/CTL system to altimetry and make it vulnerable to possibly incorrect data. I do not know squat about aircraft design and system engineering, yet this does not seem like a clever thing to do.
Contrary to what I had written in previous post, the FCOM1 clearly states [1.27.20 p2 A320] that manual trim will disengage automatic p.t.
Questions:
Is it true that FBW will attempt to pitch up in altitude due to different normal g?
If so, does your simulator replicate this phenomenon?
Yours,
FD (the un-real)
Microburst2002:
I was told on my instrument class that the curved path is compensated using the Shuler's pendulum principle
Pendulum - Wikipedia, the free encyclopedia, or algorithm providing the same in strap-down, laser ring gyro systems. Also I fell that NAV (IRU) and F/CTL (FAC, ELAC, SEC) could be independent. True, however, that loss of all 3 IRs puts you to Direct Law. There's one line on FCOM1.27.20 p2 saying
... the system maintains 1 g in pitch (corrected for pitch attitude)... With no pitch, no g correction, no normal law.