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Aaron747
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Flight Controls Check Before Departure

Sun Nov 02, 2003 7:47 am

As we all know, following the checklist is always important. For my flights in the C-172, we always conduct a flight controls check prior to departure in the run-up area. In the Cessna, it's easy because a quick glance back or to the side will verify that your control input is having its desired effect.

For all of you who drive the big iron, how do you verify control input? On most turbine aircraft you're lucky if even the wingtips are visible from the cockpit. Is there verification from the ground or what? I've always assumed that to be the case, but you never know.  Big grin

Also, I've noticed on a couple recent flights (Southwest 737, American 757, jetBlue A320) the pilots cycling the spoilers and ailerons more than once. Is that just a case of 'double check-itis' or does a control check appear on more than one checklist?

Lastly, is there any significant difference between MDD/Boeing/Airbus pre departure checklists? I couldn't imagine why there would be, but curiosity's got me nonetheless.



[Edited 2003-11-01 23:50:24]
If you need someone to blame / throw a rock in the air / you'll hit someone guilty
 
Guest

RE: Flight Controls Check Before Departure

Sun Nov 02, 2003 7:58 am

In the 747 - we have a flight controls position indicator - and secondary indications can be seen on hydraulic pressure gages...
xxx
Occasionally yes, a visual ground check may be required by maintenance...
xxx
Happy contrails  Smile
(s) Skipper
 
chdmcmanus
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RE: Flight Controls Check Before Departure

Sun Nov 02, 2003 8:11 am

Ditto with what B747Skipper said for the DC-10 series. A "Surface Position Indicator" or summation gauge for short, is used to show all primary surfaces (Inbd/outbd Aileron, Elevator, upper/lower rudder,) and some secondary (speedbrake) positions. The Flaps/Slats and trim are separate indices, and the motion can be confirmed with hyd pressure. The control's are checked for full authority and motion in the before takeoff check, unless the summation gauge is mel'ed, then a visual confirmation must be accomplished.

Keep the paint side up and rubber side down!
ChD
"Never trust a clean Crew Chief"
 
air2gxs
Posts: 1443
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RE: Flight Controls Check Before Departure

Sun Nov 02, 2003 8:20 am

The second time the flight controls move it is probably the other pilot checking his. I know the checklists here at UPS call for that on the MD11 and A300.
 
jhooper
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RE: Flight Controls Check Before Departure

Mon Nov 03, 2003 8:14 am

perhaps a dumb question here, but just because you have an indicator in cockpit how does this give you a positive confirmation that the control surfaces are actually moving?
Last year 1,944 New Yorkers saw something and said something.
 
Guest

RE: Flight Controls Check Before Departure

Mon Nov 03, 2003 8:27 am

Dear Jhooper -
xxxx
I said there that the surface position indicator is the primary indication...
Secondary would be the 4 separate hydraulic pressures gages cycling...
If that does not satify... (I mention the 747 here, remember) -
We ask for maintenance to go and have a look as we cycle the controls.
Good question, Jhooper...
xxx
Happy contrails...
(s) Skipper
xxx
P.S. - all of you, learn one thing about airplanes... which is -
"Something is ON (or OFF) - how do you know? - light is ON or OFF (or switch)...
Then there is a secondary indication... a cross check, i.e. ammeter draw increase when ON...
xxx
Everything in airplane should have a primary check, then a secondary check.
Finished with editing...

[Edited 2003-11-03 00:43:09]
 
AJ
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RE: Flight Controls Check Before Departure

Mon Nov 03, 2003 9:07 am

On the glass cockpit 767 and 747-400 the preflight control check is conducted with reference to the EICAS 'STATUS' page. Of all my 767 flightdeck shots I only have one showing the control surface indicators: http://www.jetphotos.net/viewphoto.php?id=133383.

The STATUS page is the screen directly above the thrust levers. At the top are some blurry (sorry!) figures that show hydraulic system pressure and quantity. Once pressurised the pressure reads approximately 3000psi. We pressurise the hydraulics about five minutes before departure and conduct the control check.

At bottom left of the STATUS page are the control surface position indicators.

The horizontal bar at top is the rudder indicator. To check the rudders first the nose wheel steering tiller is held neutral to prevent the nosewheel moving (nasty, especially if a towbar is attached). The rudder pedals are then cycled full left then full right and the white arrow above the horizontal bar is observed to move in the correct sense to full deflection. On the 747-400 there are two rudder position indicators as the aircraft has a split rudder.

The left and right vertical bars are the aileron position indicators. Notice that the bars have two white arrows each, as they indicate the outboard and inboard aileron positions. The control wheel is deflected full left and the indicators are observed to rise up on the left side and go down on the right side. This is then reversed with the wheel deflected to the right. On the 747-400 the spoiler indicators are also observed to rise up on the downgoing wing.

The middle vertical bar is the elevator indicator, with white arrows for the left and right indicator. The control column is moved full aft then full forward to check full movement in the correct sense.

After the check it is ensured that all trim controls are placed in neutral, except the elevator trim ('stab' trim), which is placed in the takeoff position.

There is a more in-depth check conducted if the aircraft flight control surfaces have been disturbed during maintenance. This involves check full movement of the control surfaces as described above, plus fully cycling all trim controls, flaps (if they were disturbed) and spoilers. For the spoilers an engineers must check these visually as we have no indicators on the 767.

I hope this has been of interest!

Cheers.

[Edited 2003-11-03 01:13:22]
 
CX Flyboy
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RE: Flight Controls Check Before Departure

Mon Nov 03, 2003 9:49 am

The 777 automatically detects if the control column position does not match with the control surface position. Also, any fault in the control surface movement itself will be detected. When we do our control checks we do not bring up the Flight Controls page on the EICAS. The 777 will automatically tell us if anything is wrong. It's putting a lot of faith in the systems, but if the system works.....
 
bio15
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RE: Flight Controls Check Before Departure

Tue Nov 04, 2003 5:53 am

AJ, you mentioned that for checking the rudder position the tiller must be held neutral. What is that specifically? I thought that the rudder had authority on nosewheel steering, like 7° or so. Holding the tiller neutral makes me think that when the rudder pedals are depressed to one side, the tilles will move as well, and that therefore it must be held in place with the hand. Is this correct? I always thought that the bypass pin would override hydraulic input to the nosewheel steering system, is this not true?

I don't know if the question is clear, please tell me. Thanks in advance.

-Alfredo
 
w_a_s_p_i_e
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RE: Flight Controls Check Before Departure

Tue Nov 04, 2003 6:07 am

and CX flyboy, what if the system doesnt!!  Smile, or more likely  Sad
 
Guest

RE: Flight Controls Check Before Departure

Tue Nov 04, 2003 6:52 am

Hola Alfredo -
xxx
Rudder inputs and steering tiller...
Most airplanes, the rudder pedals also move the nosewheel for steering, but with limited authority, i.e. sufficient for taxi straight, or steering on runway centerline.
When you would do a rudder check with the pedals, that would also move the nosewheel steering. So to prevent that, the tiller is held neutral...
xxx
Fact is, at PaAm, all the 747s had their nosewheel steering with the rudder pedals disconnected... even for the airplanes they acquired later, from UAL or SIA... Old timers told me that since "they were accustomed to the 707, which had no nosewheel steering with the rudder pedals, they did not need it on the 747"...
xxx
Happy contrails  Smile
(s) Skipper
 
AJ
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RE: Flight Controls Check Before Departure

Tue Nov 04, 2003 7:55 am

What Skipper said Alfredo!

The steering bypass pin allows the towbar more authority over the nosewheel turn radius, however it still moves the tiller and vive versa. As we are pushed back we can watch the tiller move when we are towed/pushed around a corner.

The rudder check can/will move the nosewheel, so some force is required to hold the tiller neutral.
 
bio15
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RE: Flight Controls Check Before Departure

Tue Nov 04, 2003 7:58 am

Thanks Skipper. Just to get it crystal clear, using the rudder pedals will also physically move the tiller a couple of degrees and so it must be held tight so it doesn't move? It seems odd that way, mainly because it's like interfering with the part of an aircraft trying to move. I see it as a pilot moving the yoke to the right, while I hold one aileron so it doesn't move. Do you see my concern?  Smile Thanks again

-Alfredo
 
AJ
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RE: Flight Controls Check Before Departure

Tue Nov 04, 2003 8:33 am

Alfredo, that is just how it is!

The rudder is a primary flight control, so it's movement is more important than NWS, therefore checking it's full and free movement before flight is very important, therefore we do what it takes!

Taxying on long straight stretches of taxiway we use the rudder pedals to steer the aircraft, and as we make small inputs the tiller does move slightly. To take larger turns the tiller is used, but using the tiller does not move the rudder!

On the takeoff run rudder pedals are used for directional control, unlike on earlier aircraft (and aircraft with the NWS disconnected as Skipper described) where the tiller had to be used until the rudder became effective at approximately 80 knots.

BTW, I'd like to see you try to hold that aileron against 3000psi of hydraulic pressure, the aileron will win!
 
CX Flyboy
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RE: Flight Controls Check Before Departure

Tue Nov 04, 2003 11:11 am

Waspie,

The thinking is that the system WILL detect any error. There are many redundancies worked into the system and the theory is that despite being a highly electric aircraft, any error will be sensed and the pilot will be informed. It's the direction that aviation is going, and whether we like it or not, we are putting a lot of faith into the aircraft and the system. So far, it seems to work.
 
bio15
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Joined: Fri Mar 23, 2001 8:10 am

RE: Flight Controls Check Before Departure

Tue Nov 04, 2003 10:56 pm

Thank you AJ now I get it, I didn't mean to be such a pain in the a$$  Smile. I see how the rudder control should be by far more important than NWS. The aileron thing was just to show my point. Since the rudder input is connected in some way to the tiller, by cables probably, holding it still would stretch such cables as pilots do some rudder input, and there was my doubt. But there must be a nice fancy mechanism for that thing to be done. Bye


-Alfredo
 
FDXmech
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RE: Flight Controls Check Before Departure

Wed Nov 05, 2003 12:42 am

Bio15

I see your logic, but depending on aircraft type, there are several methods in which conflicting control inputs do not cause damage or more realistically enable them to be done in the first place.
The NWS system incorporate (again, depending on type) spring rods, spring clappers and other such devices which allow conflicting inputs to be made.

If these soft interfaces weren't put in, holding the tiller while pressing the pedals wouldn't be realistically possible. It would be a fight between your legs pushing and your arms trying to restrain the tiller.

These soft interfaces (as well as shear rivets) are in all the flight control systems to prevent a cable jam, or an actuator jam, or a control column jam, etc, from disabling the entire system. This is what allows, for example one control wheel to be turned while the other is held stationary.
You're only as good as your last departure.
 
bio15
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Joined: Fri Mar 23, 2001 8:10 am

RE: Flight Controls Check Before Departure

Wed Nov 05, 2003 3:15 am

That is great information FDXmech, thank you. It's logical to use spring devices for such purposes.

-Alfredo
 
AJ
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RE: Flight Controls Check Before Departure

Wed Nov 05, 2003 6:49 am

Alfredo, by no means were you being a pain in the proverbial! These kind of questions are what this forum is about!
 
XXXX10
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RE: Flight Controls Check Before Departure

Wed Nov 05, 2003 10:44 pm

I believe there were a couple of incidents when the controls were incorrectly wired an A320 as I recall took off with the sidestick creating wrong way roll inputs.

The aircraft's wing nearly hit the ground when the non flying pilot intervened.

There must be some aircraft with no surface position indicators were the pilots cannot see all of the surfaces, I'm guessing but what about early 737's or 1-11's
 
Guest

RE: Flight Controls Check Before Departure

Wed Nov 05, 2003 11:01 pm

Actually, there have been more than a few accidents caused by reversed flight controls. It typically happens during maintenance when the flight controls are rerigged. I know that the military has lost several aircraft due to reversed ailerons, the same in the civilian world. What a way to die, think about it. You're just taking off, the wing drops slightly, you add a bit of aileron to pick it up, the wing drops more, you add more, it drops more, you add a lot more, you cartwheel into the ground and die. How nice.

My aviation mentor, a military transport pilot and retired airline chief pilot told me to never ever get in any airplane fresh out of maintenance where the flight controls had been removed or rerigged without personally conducting a visual flight control check. I consider anything that man ever told me to be good advise.

Jetguy
 
XXXX10
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RE: Flight Controls Check Before Departure

Wed Nov 05, 2003 11:15 pm

I agree,

Shouldn't the engineers check that when the flying controls are re-rigged that everything functions correctly.

I mean it is fairly important.
 
broke
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RE: Flight Controls Check Before Departure

Thu Nov 06, 2003 2:31 am

As usual, there is always an exception to the standard. In this case, it is the DC-8 elevators. There is no direct connection between the yoke and the elevators. The yoke moves a small tab called a control tab, that is on the elevator trailing edge and that moves the elevators. The control tab (which is also known as the geared tab) should not be confused with the trim tab, which is used to trim the airplane once it is in flight. The control tab cannot move the elevator until there is an airload on it, so the check on elevator movement is done on the take-off run at about 80 knots by moving the yoke back and forth.
If elevator motion is not detected at this time, the take-off is aborted.
 
bio15
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Joined: Fri Mar 23, 2001 8:10 am

RE: Flight Controls Check Before Departure

Fri Nov 07, 2003 12:11 pm

It is the same case for the MD-80's with the control tabs.

-Alfredo
 
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Bruce
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RE: Flight Controls Check Before Departure

Fri Nov 07, 2003 4:57 pm

Pre flight checks are probably much easier on the A340 as they have the camera monitor on the instrument panel so you can actually see what the flaps are doing, viewed from the top of the tail.

bruce
Bruce Leibowitz - Jackson, MS (KJAN) - Canon 50D/100-400L IS lens
 
Guest

RE: Flight Controls Check Before Departure

Fri Nov 07, 2003 6:22 pm

Talking about the flight controls... lets make a "POP QUIZ" here...
Looks like a few of our friends like to do these, so I will make one...
xxx
Why are the "outboard ailerons" locked when the flaps are UP, i.e. 747...?
Those of you who know, leave our younger "future ailine pilots" figure that one first.
xxx
Happy contrails - scratch your heads now...  Smile
(s) Skipper
 
VH-KCT*
Posts: 435
Joined: Fri May 04, 2001 4:01 pm

RE: Flight Controls Check Before Departure

Fri Nov 07, 2003 6:36 pm

OK, let me preface this with I haven't quite got my PPL yet, so no laughing at me!!

Is it because the inboard ailerons are effective enough above Vfe?

Nothing like making a fool of yourself  Smile
I am The Stig
 
Guest

RE: Flight Controls Check Before Departure

Sat Nov 08, 2003 6:12 am

Well, Mate... nooooooooo...
xxx
Why having inboard ailerons... why dont they use one set instead...
Just the outboards, and save weight...
xxx
Who else has any idea...?  Big grin
(s) Skipper
 
goboeing
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RE: Flight Controls Check Before Departure

Sat Nov 08, 2003 6:37 am

My idea:
At the higher speeds the jet normally operates at once the flaps are all cleaned up (210k or more, whatever the speed happens to be), the large vertical moment the outboard ailerons produce is more than enough to have adequate roll control. The inboard ones are smaller and closer to the longitudinal axis, and so the up or down moment they have is automatically smaller. I think they would be a lot more precise for this reason.

Nick
 
Guest

RE: Flight Controls Check Before Departure

Sat Nov 08, 2003 7:14 am

Dear Goboeing -
xxx
Well, fact is the outboard ailerons are probably "more effective" yes...
Their surface is larger...
But why not use them in cruise at high speed is the question...
Why making 2 sets, outboards, inboards, and lock outboards...
Sounds like a lot of complication to me...
xxx
Keep on thinking, friends...
Tonight, if no progress, I will give you a cue...  Big grin
(s) Skipper
 
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Bruce
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RE: Flight Controls Check Before Departure

Sat Nov 08, 2003 7:20 am

I have a feeling that it has something to do with roll control and stability at high speed - the wing surface is smaller way out there near the end and it might disrupt the stability during the manoeuver if the aileron panel moved and changed the air flow on that smaller part of the wing.....

how's that?


bruce
Bruce Leibowitz - Jackson, MS (KJAN) - Canon 50D/100-400L IS lens
 
Guest

RE: Flight Controls Check Before Departure

Sat Nov 08, 2003 7:56 am

Not yet Bruce...
xxx
Your are getiing a few inches closer. You said a few words...
They are not directly involved, but think along the lines of stability/roll control.
A clue, an aerodynamic, and a structural reason...
Another clue later if need be.
Keep on working your brains, Gentlemen...
xxx
Happy contrails  Smile
(s) Skipper
 
liamksa
Posts: 301
Joined: Mon Oct 29, 2001 1:13 pm

RE: Flight Controls Check Before Departure

Sat Nov 08, 2003 8:02 am

Due to the danger of aileron reversal?

The ailerons are so effective at high speeds that they twist the wing around the lateral axis, reducing the angle of attack (on the wing with the downgoing aileron) and therefore reducing lift. Result - you roll the opposite way you were hoping!  Smile

Rob.
 
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Bruce
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RE: Flight Controls Check Before Departure

Sat Nov 08, 2003 8:14 am

hmmmmmmmmm..........

well obviously the wing is structurally stronger inboard. I have actually walked on a Dc10 wing and as you go further out you can definitely feel the movement up and down. you dont want to overstress the end of the wing...

As for aerodynamically, let me try this. If you use the larger outboard aileron at cruise you will be changing the airflow pattern, and near the end of the wing you dont want to do this because it will effect the high speed airflow (disrupt) around the wingtip which would cause more drag. so when you bank into a turn it may cause you to lose control & stability if you have more drag. It is not going to generate the extra lift that would normally lift that wing (while the other one drops..)

bruce
Bruce Leibowitz - Jackson, MS (KJAN) - Canon 50D/100-400L IS lens
 
Guest

RE: Flight Controls Check Before Departure

Sat Nov 08, 2003 8:25 am

Bruce, you are getting a little closer...
Reread the first paragraph of what you said about stepping on the wing...
Another clue - have you ever heard of "control reversal" (early supersonic planes)...?
xxx
(s) Skipper
 
DL727-200adv
Posts: 146
Joined: Sun Sep 03, 2000 10:23 am

RE: Flight Controls Check Before Departure

Sat Nov 08, 2003 8:32 am

I believe that the outboard ailerons are locked out on aircraft such as the B727 & B767 because at higher speeds the outboard ailerons might produce aileron reversal. These aircraft have flexible wings and if the outboard ailerons were enabled at high speed their movement would likely flex the wings enough to produce roll in the opposite direction.

DL727-200adv
 
Guest

RE: Flight Controls Check Before Departure

Sat Nov 08, 2003 12:01 pm

Well, our friends Liamksa and DI727-200adv get the palm...
And Bruce, you were getting close as well...
xxx
Expressed in other words, the wing flexes, up/down and in pitch (lateral axis)...
If you know what a "balance tab" does... now think about this -
The "whole aileron" becomes a "balance tab" for the portion of the wing it is attached to.
Bad news - a "down aileron" forces that portion of the wing to a negative angle of attack as it flexes
Result, loss of lift > result, control reversal...
Q.E.D.
xxx
Congratulations to you ... Hope some of you did learn something...
That was the problem of some WW-2 fighters in high speed dives - P-47, P-51 etc...
All the Boeings - 707 to 777 have outboard ailerons locked when flaps are up.
xxx
Happy contrails -  Smile
(s) Skipper

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