What if the guys misread the cross too..........:E

Besides you can see the other crew member stirring his stick out the corner of your eye.........:eek:

Guys....

As so often happens, several of you have gone off at a tangent; getting into a heated argument about a side issue. In the meantime, I've contributed a thoughtful post (see previous page) which directly answers the question originally posed by granard.

granard has since edited his post, and asks:

"Thanks for all the replies.
What are we agreeing to as the correct use of the indication?"

Any comments?

PS
Provided the PF does not rush the flight-control check, it's a cynch for the PNF to monitor both white crosses reaching full deflection, as well as the appropriate control responses on the F/CTL page. The PF simply holds the stick at full deflection until the PNF is satisfied, which he indicates by whatever verbal response is defined in your airline's SOPs. The PF then releases the stick. When it reaches neutral, the PF waits for the PNF to confirm that the flight controls (and both white crosses) have returned to neutral.

What makes you think that the system which displays the GERMAN cross will show a different indication to the control deflection? If there is an error, it will affect both presentations in the same sense.

Should be used, while PM, to confirm side stick neutral at the "100 knots" callout during the take-off roll. Also useful to check if the PF applies back stick at Vr.

Cheers.

OK. Let us suppose the output of the sidestick is sent on a data bus or wires both to the DMC's, which generate the white crosses, AND the flight control computers, which of course move the controls. However, let us suppose that either the DMC or a flight control computer has a fault internal to itself, (for example a dry joint)*, which reverses the sense of the sidestick - hey presto, one system thinks 'stick left' the other thinks 'stick right'. The box appears after engine start (i.e. before taxying), and not on application of take-off power - why would that be if it was not to provide sidestick position info during taxying?

That's my logic for my extra check, (which by the way takes all of half a second to perform). From what I know about electronic circuits and dry joints etc., this is what I will continue to do.


The OP wanted to know what the white cross was used for. I think that myself and others have answered their question.


U


*For those who may not know; a dry joint is a faulty electrical soldered connection in a circuit, which results in an intermittent electrical connection. Sometimes the joint is electrically sound, other times it is open circuit. These joints can and often do look perfect to the naked eye, and when electrically tested can appear sound. However, when the circuit heats up to operating temperature the joint can go intermittent. Dry joint faults are very difficult to trace.

Sidestick position cross
 

quote:
The Maltese cross is only for the PM to monitor what the PF is doing on the ground

unquote.

Not really!!!

U is right on, obviously flying 330.

The sidestick cross indicates the position of the sidestick.
Is used by the Pilot Flying during takeoff.
For example: Half scale Deflection downwards, until 100kts during the takeoff roll when it is placed on the horizon line on the PFD.
Then aids stick position indication when rotating to the appropriate angle at VR.
As mentioned, during crosswind takeoffs the sidestick is deflected to half a cross deflection (into wind) until, as described above, the aircraft rotates and weathercocks into wind, as in a conventional x-wind takeoff. . .
after which the cross disappears.
Some, operators prescribe full cross down in a crosswind takeoff with the into wind input, I don`t like this method, but is the way to do it whether I like it or not.

:added later . . .My point, though perhaps poorly laid out, is, that, the white cross is an indicator of sidestick position as opposed to anythingelse, like, flying controls.

And, the original question is/was: "How do the pilots use the target cross on the PFD ?" And, the answer is what I have written above.

ton pi

You would be welcome to quote your FCTM if and how it states so ?

You have obviously also missed a notorious serious incident report.
Cross is certainly not to be used by the PF for rotation.


You are definitely correct Chris, the initial Q. What are we agreeing to as the correct use of the indication? needs further consideration ...

SSI
 

For info the SSI / maltese / german/ swiss cross etc... Used to disappear after ground to air switch over... Then Emirates had a near hull loss as the crew used (wrong) training info during a takeoff out of
Jo berg some years ago... You can read about that somewhere else i guess.. After that incident AB modified it to disappear at NW extension ... You can verify this in the sim if youload the aircraft really aft in Cog and may note on a rough runway setting that it drops in and out as the aircraft goes light on the NW ...

i think all aircraft should be modded like this now but could be wrong..

Most of the remaining posts are pretty spot on regards limited use/ value to most parts of the operation.

WJA

Nobody seems really to agree on the way to call it after all but is it that surprising when Airbus itself names it Sidestick Order Indicator in the FCOM but Stick Cross Symbol in the FCTM.
On the same order, its function is also ambiguous and has evolved following serious incidents. Was it avail at all airborne in the early days, maybe for a few seconds after take off ... Chris ?
Now its time for being displayed has been reduced to a minimum and the advise not to use it by the PF during take off is clear.
The single note I can see to promote its use is addressed to the PM to validate the PF initial stick input. Interconnected sidesticks would do that nicely and much more.

Salut Confit,

Regret I cannot remember exactly when the "white cross" (as I usually call it) disappeared after take-off. And I don't know if the logic ever changed. I don't remember ever watching the white cross after 100kts, even as PNF.

As you know, the only Airbus FBW I flew was the A320 family, but I'm very interested in woodja51's post. Until now, I have assumed that disappearance of the white cross may be part of the logic of the introduction of Roll Normal, and the gradual introduction of Pitch Normal. My old FCOM says these two processes start when the a/c becomes airborne, which implies the main L/G weight switches. But we know that the nose L/G also has weight switches, and woodja51 says the disappearance of the cross is now on that. I presume this may not apply to the A320 family?

So, woodja51, what about the control laws switching? Presumably, that still uses the main weight switches?

Returning to the original question, I think the white cross is useful for the PF at the very start of the take-off run (partly down, and not too much left or right). At 100 kts, when the PF has finished releasing the down-input, he/she may want to glance briefly to check that the desired aileron (if any) has been maintained. After that, forget it.

Control law change
 

Chris ,

Not able to answer your flight control changover regarding WOW switches.

Have I missed something but does the FCOM not say half stick forward on take off to ease to zero at 100 kts except when xwind > 20 kts or any downwind then to use full forward stick ?

This is a 330 of course so could be diff on other types....

Hlaf stick is where the stick spring pressure increases or half a cross down by my reckoning. The same spring pressure increase in aft stick provides a good tactile input to correct rotation input to commence with from what I was told and do ... Before the cross disappears it will get to about 10degress NU before the jet starts to react and NW comes off... Assuming a 2.3-3 deg pitch rate or so...

Is that of any assistance ? Oh and the small left / right input should be eased out too and allow roll normal to control the drift effect as the rotate proceeds from what I was lead to believe.... Seems to work to me in 6000 hours in the LHS on it.

Pitch and lateral control switching (ground - flight) is not related to weight on wheels. The trigger is when the pitch attitude is greater than 8 degrees. At this attitude, the timing starts for a gradual transition from ground to flight mode. That's how I read my (A320) FCOM anyway!

I don't think the side stick indicator logic on the fleet I fly has been updated on all variants and cannot find the memo we were sent a while back about this. The newer aircraft have a new DMC standard (green VDEV scale on PFD in DES) and I think the new logic could co-incide with this standard.

Thanks Natstrackalpha. :ok:

Having recently flown, (A330), I agree that the white sidestick position indicator does now disappear soon after rotation.

So: Yep; Confit; you're right.

However, I'm sure that some old A320's I used to fly kept the indication to 50 or 100', because I remember using it to watch what PF did with the controls during take-off and rotation when I was learning to fly the thing.

Another reason for the white sidestick position indicator being displayed on the take-off roll is of course to monitor a sidestick fault. If a sudden control hard over was seen, PM could shout stop! (below V1).

U

Hi woodja51,

I can't be of much more use in this discussion, because the last time I was in an Airbus FBW cockpit was the end of 2001! Prior to that, I was a line capt and line checker for 14 years, but only on the A320/A319. So even my A320 FCOM and Training manual are way out of date. I think we used to use half down-elevator, judged by placing the white cross half way down, until 80 kts (as per my post #14, above). Can't remember if we ever modified our policy to use extra for strong crosswind or downwind, but obviously see the argument; particularly on a wet runway, where nosewheel adhesion is important while the rudder-fine steering is available. Even at zero IAS, the down elevator is of some effect for take-off on the A320, due to the slipstream effect.

Quote:
"Half stick is where the stick spring pressure increases or half a cross down by my reckoning."
Which is it? Half stick or half a cross? Half stick puts the whole cross well below the black box, IIRC.

Quote (my highlighting):
"Oh and the small left / right input should be eased out too and allow roll normal to control the drift effect as the rotate proceeds from what I was lead to believe.... Seems to work to me in 6000 hours in the LHS on it."
Yes. One of the commonest handling mistakes I saw - often from the P3 seat on line-checks - was the upwind wing rising during rotation. The theory in the early days on the A320 was that Roll Normal would prevent that happening, but it quickly became apparent to me that this was not the case. The wing would rise immediately rotation was started, before main L/G lift-off (as you would expect). However, many of our trainers clung on to their assumption in the face of all the evidence... :{

Very simple for me.

Until airborne I can ensure as Captain that the f/o is not putting too much lateral control - see Air2000 Bristol tail strike, and then I can monitor amount of backstick in rotation.

What is your opinion then on the Ziegler's concept on which Airbus is built that the other pilot don't need to know how the PF is soliciting the flight control commands ?

Hi CONF iture

I think over the years it can be seen that there have been certain flaws with the concept of the Airbus design. My job is to use best resources to safeguard the aircraft. That includes on day 1 of line training a 200 hour cadet, keeping an eye on his/her initial control inputs. Would not be the first time I have had to takeover during rotate as the f/o has full back stick. If I waited till airborne (ie not monitor the cross) it would be too late.

So with all the comments that have being made, what is the final use of the white cross?

Is it to allow the PF to observe during takeoff the amount and direction of the side stick and at the same time to allow the PNF to observe the PF inputs.

But Roll Normal is not fully active before 2 sec after attitude is over 8 deg. Until that time the roll is still under Ground Mode when aileron deflection is proportional to Sidestick deflection. As you state, pilot's action is necessary to prevent the upwind wing to rise during rotation.

The rule seems to be now that the white cross disappears when the Nose Landing Gear is fully extended. Are your aircrafts still displaying the white cross up to the Main Landing Gear extension ?

Good question....not sure as once wheels off ground I am more interested in the change of flightpath. My gut feeling is that it disappears during the transition to flight mode.