Just a minor observation on that Tarom incident, referring to the tendency of pilots to pull back the stick when confronted by a stall. The A310 has a yoke control. Where does that leave the "sidestick feedback" argument?

more C*(A330) ...
 

@HN39
Thank you for your graph and edit.;)
Do you know from where the airspeed information is coming in case of ADRs failures ?

Roulis,

The C-star law does not depend on airspeed information. From Favre, C.(1994) 'Fly-by-wire for commercial aircraft: the Airbus experience', International Journal of Control, 59: 1, 139 — 157 :
http://i.imgur.com/osVOR.jpg?1

The load factor comes from an accelerometer and the pitch rate from a gyro. I don't know where these are located, but my guess is in the ADIRU's under the cockpit floor.

@Jazz Hands,
Doesn't disqualify the SS issue from consideration at all. Other yokes have been pulled back to stall as well. Not logical, sorry, BZZZZT!

Regarding the occurrence of UAS at cruise and what information may have been available on June 1, 2009 refer to the BEA IR3, pages 63 and 64. It would appear to me that Air France provided (distributed) information to their crews regarding the ongoing investigation of six UAS incidents and made some recommendations. The 4th recommendation pointed out that corrections made should be "fabiles" or feeble in nature, meaning delicate or gentle. I assume this recommendation would apply to both roll and pitch corrections.

I'm beginning to think that those pilots (447) never read anything, much less advisories from AB or AF. Ignorance is not, in this case, any kind of bliss.

Should it be mandatory for F/Os to take a quiz on everything that's handed out? Yes it should.

Very much alive.
The PF did not insist as he then fully pushed it forward.

Hi HazelNuts39,

Sorry to come back to C*, :{ the speeds which keep my interest are V and Vco, as I readed these two documents, in post #1 Thread8 AF447
Thank you for your help... Perhaps I misunderstand something, but were ? what ? why? ...

.

jcjeant, re: your #1339

I'm happy we agreed on the existence of the procedure. :)
Indeed, we can safely assume that all speed indications were false on AF447.
On the other hand, the condition for "doing nothing" is :
Si les informations erronées de vitesse ou d'altitude n'affectent pas la sécurité du vol (trajectoire stabilisée)
If the incorrect informations of speed or altitude do not affect the safe conduct of the flight (stabilized flight path)

One can argue that, coming from an A/P ON (in cruise) situation, the path was stable enough to skip the memory items. Apparently, that's the position of Mr Rosay (perhaps with his employer's interests in mind, too). ;)

My position remains unchanged:
1/ I read the condition as "if you don't know what to set, then memory items for the time needed to pull the QRH"
2/ but even a crew which won't have the same understanding as Mr Rosay won't put its aircraft at risk by following the 5°/CLB memory items (re: excellent HN39's graphs :ok:)
3/ given all the previous discussions, for a safer world, the "if" condition in the procedure should be clarified (perhaps it's already done, I hope so)
4/ all of this is barely related to AF447, as this crew didn't follow one (do nothing) or the other (5° and CLB) possibility.

roulishollandais,

If Knz is not set equal to 1, equation (6) reads:
Kq/Knz=Vco/g

V in equation (4) and Vco in equation (6) are not airspeeds but are kinematic speeds. Equation (4) applies equally in space without air, usually written as an=ω*V, for any body moving along a curved path and maintaining its orientation relative to the direction of movement.

thank you HN39
it means that kinetic speed information comes from inertial data after integration '?

No, speed information does not appear in the C-star law as such. Airspeed affects the response of the airplane (in terms of pitch rate and normal acceleration) to changes of elevator and THS positions, and therefore may enter in the 'gains' used to calculate elevator and THS commands:
If you are referring to my post #1310, I didn't use airspeed either, just vertical speed and integrated SS angle to calculate pitch from:
Pitch = Pitch(0) + Ks/Kq * ∫ Sdt - Kn/Kq*(Vz - Vz(0))/g,
where S=side stick angle, Vz is vertical speed, and Pitch(0) and Vz(0) are the initial values of pitch and vertical speed.

P.S. About the cross-over velocity Vco.

The 'steady state' relationship between nz and q:
qSS = nz*g/V (4) may be written as:
Kn*nz = V/Vco * (Kq*q) and shown as:

http://i.imgur.com/dsJZT.gif?1

Based on the data posted in #1310, the A330 control law uses a cross-over velocity of ...(EDIT).

Some basics of the control laws
 

Thanks to 'nuts and Rouli for bring up one aspect of the control laws that is independent of all the "autopilot" functions.

Part of the quote mentioned by Rouli strikes home, as it was inplemented operationally years before the shuttle entered drop tests and so forth:

The biggest thing we did not have was the airspeed feedback loop. The Nz and body rates ruled! Only thing dynamic pressure did was provide values for the "gains" that determined how much the control surfaces moved to produce the commanded Nz or roll rate ( gear up). AoA was much more important than speed, and it limited us from about 15 deg to 27 degrees with respect to gee. Figure about 15 degrees at 9 gees and 27 degrees at 1 gee ( draw the line yourself). Gear down blended AoA with the gee command and body rates. Gains were still a function of dynamic pressure. So we had the "feeling" that we were trimming for speed or AoA and not Nz as with gear up. Wasn't a real strong "feel" compared to conventional control systems, but better than a pure body rate or gee command.

Interestingly, if dynamic pressure was lost or deemed unreliable, the system used "standby gains". So gear up was 300 knots or so, and gear down was 180 knots. Simple deal, and landing gear handle switch provided the changeover. The biggest thing was the system used AoA intil the bitter end. The one example I provided was the guy who lost most of the radome due to a bird strike. This included the AoA probes. So he flew for 7 or 8 minutes using nothing but Nz and body rates and standby gains.

I am glad to see that some of our primitive control laws were improved for the Shuttle and later FBW planes.

Thank you Gums and Hazelnuts39 : ;) PPrune has the best specialists !

Reading you, Gums, i understand that it is airspeed (or an equivalent information as dynamic pressure) who determine the gains and not kinetic speed . It seems to me very logic.

Reading Hazzelnuts39 i don't understand that A330 (edit : add "does not use", del "used") does not use standby gains in case of loss of dynamic pressure, unlike the F-16. And that VCO=1200 KT.

but on the F-16 HUD (this of Gilbert Klopfstein) you have the speed vektor himself.

You are right to say and repeat that airspeed is not very important, much more is the Angle of Attack with adequate training.
But AF447 lost the PF (and the headdown Pilot managing !) without speed nor AoA. (Sure they still had pitch and power who were enough to save their lifes : but i let to other the Rosay discussion about the pitch, despite having had an ice-clogged pitot tube I guess for the "do-nothing" not written in the procedure).

It seems easy for engineers to explicite and display anywhere the inertial speed information in UAS case. K/s is not very expensive...

I will try to find the Favre's book and understand better why this C*,seems so unusefull and inadapted to transport aircraft.
Still a question, gums : why had the Pelican F-16 finally a PIO/APC

This is baffling to me.

HazelNuts39Is that a typo? Was it meant to be 210 kt?

Thanks for all your good work on C*, and am slowly working my way through the references. I note that Boeings patent was dated 1989, which is a clear indication that "change" happens very slowly in the aviation industry.:cool:

Not a typo, but the value of Kq/Kn is in error.
Vco = Kq/Kn * g = Kq/Kn * 32.17 ft/sec

Apologies for the confusion.

Now it makes sense!!:ouch:

Thanks.

Did a similar exercise on QF72, which stayed in normal law, and Vco=400 ft/s seems to give a reasonable fit:

http://i.imgur.com/hJU7D.gif?1

Good curve fit, 'nuts.

A year or more ago I raised the issue of "standby gains" to use a given value for dynamic pressure should the normal sensors go off to wonderland or the system deems the values FUBAR. Unfortunately, the 'bus laws are not designed to provide the AoA/speed "feeling"most pilots are used to. Only time we had that in the Viper was gear down, and even that mechanization was a kludge.

The 'bus laws are primarily a Nz command ( just as ours were, and best I can tell) and looks to me that AoA and other inputs only come into play when approaching a stall AoA. And then the system appears to ignore AoA if the dynamic/static pressure inputs are deemed to be unreliable ( and the infamous 60 knot deal), or we are in sub-mode "c", of mode "b", and the beat goes on.

As 'doze has pointed out over and over, and on end, our FLCS was designed for a different mission, but I can tell you that we would like to have had an airspeed/dynamic pressure feedback when gear up to "feel" more like a normal jet. Our feel was strickly biased according to the commanded Nz we had set using a roller wheel or the hat switch on the stick. let go of the stick and the jet assumed the "trimmed" gee, and rather aggressively, heh heh.

@ rouli

Probably the best flight instrument ever invented for us was that flight path marker in the HUD. Ooooops, the 'bus didn't have one. We had it back as far as 1968 - 1969 in the A-7D. No air data required. The sucker used inertial data only, and showed where the jet was gonna impact the ground or climb above the ridge or.... Invaluable for an instrument approach. And with AF447, it would have shown that the aircraft velocity vector was approaching zero pitch well before they flew into the stall. My lef failure video shows the ILS "cross bars" which I used to help in the dubious WX I had to deal with. You can also see where I mistakenly had my vector slightly short of the runway, as I expectd it to move down the runway when I got close and "flared". Hell, was 30 knots above approach speed, but happy I still had roll control.

http://www.sluf.org/warbirds/lef-landing.m4v

For now, I can still see a procedure change and maybe a tweak to the 'bus flight control laws and reversion sequence.