Flight Control Check

[rondon9898 84]

Hi folks,

 

This isn't a problem but just a query about technique. I have heard and read from several (not totally reliable, in my opinion) sources that the flight control page is not summoned on the systems display whenever pilots in the RW 777 perform the flight control check, which is what I've been doing since I first owned the PMDG 777. Is this true, and if so, why? It seems perverse to have a visual synoptic display of control movement during a control check and not use it.

 

Cheers chaps

[Etturaz 3]

Hey Rondon, it is actually true. The rational behind it being that, unlike in other birds like Air-bus (but not Air-craft) where you have a joystick, and you actually have to pull out the synoptic, the yoke gives you an immediate "feedback" of the actual position of the Flight Controls (if this wouldn't be the case you would end up with a bunch of EICAS messages) and, above all, of what the other guy is doing: therefore, once you have determined that the Yoke returns back to the center position, you can assume that the Surface(s) just tested is properly working. Why  to complicate life? Remember: Boeing builds airplanes for pilots: you pull--->Earth smaller, you push--->Earth bigger, and the rest is philosophy.

 

Pinko Palla

[rondon9898 84]

I suppose it just feels a bit like the part of a Bond movie where the villain has the opportunity to kill Bond but doesn't take it - if the synoptic page is there, why not just get visual assurance that the control surfaces are moving as expected? Sure, there would be EICAS alerts in the event of a detected control system fault but does control column movement completely and absolutely guarantee associated control surface movement in all circumstances?

[kevinh 409]

Hey Rondon, it is actually true. The rational behind it being that, unlike in other birds like Air-bus (but not Air-craft) where you have a joystick, and you actually have to pull out the synoptic, the yoke gives you an immediate "feedback" of the actual position of the Flight Controls (if this wouldn't be the case you would end up with a bunch of EICAS messages) and, above all, of what the other guy is doing: therefore, once you have determined that the Yoke returns back to the center position, you can assume that the Surface(s) just tested is properly working. Why to complicate life? Remember: Boeing builds airplanes for pilots: you pull--->Earth smaller, you push--->Earth bigger, and the rest is philosophy.

 

Pinko Palla

It has nothing to do with it not being an Airbus. You can't feel whether the control surfaces are moving correctly. All you are feeling is the artificial feel. The surfaces might not be moving for all you know. The only way to check is to use EICAS.

[rondon9898 84]

Do you know if that's what's done in the real aircraft, Kevin? It's the only option that makes sense to me but hey-ho.

[Alpha Floor 237]

I would use the synoptic if I have it, as a re-assurance. It's for free anyway, right? It's a FBW aircraft so I think it makes sense to use it.

 

I checked my Continental manual and saw this in the Before Start flow:

 

[xkoote 57]

As a side note. As an MD80 driver I always got in the thought process of thinking how

the flight control check during taxi out was of only part use. The MD80 flies on control

tabs. So when you deflect your control column, only a small tab moves. Same for the

elevator. So you could have a working control tab and a jammed aileron and never know

until you're airborne. Of course the aileron/elevator has now less that can jam it. No

cables or pulleys because those go to the control tab.

As for the original topic, I find it pretty stupid if an airline's book doesn't say you verify with

the synoptic. It's there and it's a FBW aircraft. You have no mechanical feedback of

a jam. You can rely on failure sensors bit then what is the point of testing anything.

 

 

Cheers,

[Alpha Floor 237]

As a side note. As an MD80 driver I always got in the thought process of thinking how

the flight control check during taxi out was of only part use. The MD80 flies on control

tabs. So when you deflect your control column, only a small tab moves. Same for the

elevator. So you could have a working control tab and a jammed aileron and never know

until you're airborne. Of course the aileron/elevator has now less that can jam it. No

cables or pulleys because those go to the control tab.

As for the original topic, I find it pretty stupid if an airline's book doesn't say you verify with

the synoptic. It's there and it's a FBW aircraft. You have no mechanical feedback of

a jam. You can rely on failure sensors bit then what is the point of testing anything.

 

 

Cheers,

 

Very interesting comment Xander, thanks!

 

The MD-80 Flight Control System is a study case on its own. The 737 can be flown in Manual Reversion, yeah, but the MD-80 is designed to ALWAYS fly in Manual Reversion, hahaha

[kevinh 409]

Do you know if that's what's done in the real aircraft, Kevin? It's the only option that makes sense to me but hey-ho.

I wasn't responding to your question but an answer made to it which made some comments I thought needed to be questioned.

 

The check is for full and free control movement. It doesn't ask the pilot to check surface position, so strictly speaking there is no need to display the EICAS page. But why not verify surface position at the same time?

[pcubine 143]

At 4:15 of this video - https://www.youtube.com/watch?v=s30vpsVtt3I - the Captain begins to check the flight controls but I can't tell what is on the lower EICAS or whatever you call it.

[kevinh 409]

As a side note. As an MD80 driver I always got in the thought process of thinking how

the flight control check during taxi out was of only part use. The MD80 flies on control

tabs. So when you deflect your control column, only a small tab moves. Same for the

elevator. So you could have a working control tab and a jammed aileron and never know

until you're airborne. Of course the aileron/elevator has now less that can jam it. No

cables or pulleys because those go to the control tab.

As for the original topic, I find it pretty stupid if an airline's book doesn't say you verify with

the synoptic. It's there and it's a FBW aircraft. You have no mechanical feedback of

a jam. You can rely on failure sensors bit then what is the point of testing anything.

 

 

Cheers,

It's slightly more complicated than the control only moving the tab. When the tab reaches its end stop, further control movement will move the surface until the control hits it's end stop. In flight the tab will never get anywhere near its end stops so you never physically move the surface, but on the ground with low airspeed it will happen.

[Alpha Floor 237]

At 4:15 of this video - https://www.youtube.com/watch?v=s30vpsVtt3I - the Captain begins to check the flight controls but I can't tell what is on the lower EICAS or whatever you call it.

 

Yeah, he was checking the STATUS page on the lower EICAS.

 

See here, page 30: http://www.affirm001.com/wp-content/uploads/2011/05/B744-and-748F-Differances-Handouts-rev23.pdf

[Etturaz 3]

@rondon

I'm sorry, but I understand that my answer to your question got a little convoluted and hid my point: On the line you don't check the Synoptic, because this step is not provided for by the Normal Procedures (cf. "Alpha Floor"'s post above, #6). If, as a technique, you want to have a look at it, do it; still it is an unnecessary---for the reason I gave you, and which is something I just inferred; i.e., it is not clearly stated in any pub---manipulation of the system. A better one could be to open the window, lean out, and visually check the movement of the surfaces, just like in the old days, flying a Cessna.:-D

@pcubine

The Display showing the Airspeed, Altitude, Attitude Indication is called PFD--Primary Flight Display; the one showing Navigation information is called ND--Navigation Display; the one showing EICAS indications is the EICAS Display, and the lower one MFD--MultiFunction Display.

       Pinko Palla

[rondon9898 84]

Pinko are you a RW 777 pilot? I ask because I'm genuinely interested about this and don't understand the logic behind it. Using the synoptic display is the exact equivalent of looking out of the window and doing a visual check as I do in my Cessna in real life, surely? As a FBW aircraft, surely the control column movement does not absolutely guarantee that the control surfaces are moving as desired?

Ultimately, in my Cessna or in any other aircraft, I'm not interested in the control column movement per se but rather I am interested in the fact that it's producing the correct control surface movement. In that regard, I don't really see the difference between the 777 and the Airbus aircraft, which as far as I know, automatically summon the flight control page on the ECAM when the sidestick is moved for a control check.

[xkoote 57]

It's slightly more complicated than the control only moving the tab. When the tab reaches its end stop, further control movement will move the surface until the control hits it's end stop. In flight the tab will never get anywhere near its end stops so you never physically move the surface, but on the ground with low airspeed it will happen.

Not on the MD-80 it won't. The control surface will move the control tabs. For lateral control it will move the roll spoilers when you rotate past a certain control wheel angle. For the elevators, you will get hydraulically assisted full down elevator power when the difference between control tab and elevator passes 10 degrees. Both these have annunciators.