shamrocka330
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737 Take Off Question

Tue Jul 18, 2006 5:03 am

On a 737 - 800 flight recently I was closely watching the wing as we rotated and just started to climb... My question is why did the spoilers activate (come up) on the top of the wings as we rotated? I was under the impression that the spoilers were there to disturb (spoil) the airflow over the wing. Why would you want to disturb this airflow at this critical moment when you want every ounce of lift from your wing?
aka thebigjd (member since Sept 2001)
 
2H4
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RE: 737 Take Off Question

Tue Jul 18, 2006 5:11 am



What you saw was almost certainly the roll control spoilers. After the ailerons reach a certain angle of upward deflection, those spoilers are mixed in to assist.




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mighluss
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RE: 737 Take Off Question

Tue Jul 18, 2006 5:14 am

the spoilers are used to aid roll control in the 737. If you have crosswind at take off, you will need ailerons to compensate wind at lift off, and if you need too much ailerons, spoilers will deploy also.
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RE: 737 Take Off Question

Tue Jul 18, 2006 5:17 am

Quoting 2H4 (Reply 1):
What you saw was almost certainly the roll control spoilers. After the ailerons reach a certain angle of upward deflection, those spoilers are mixed in to assist.

Is this done to gain a steeper angle of attack after the rotation? Something that the ailerons can't achieve on their own so the spoilers come in and help out?
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RE: 737 Take Off Question

Tue Jul 18, 2006 5:23 am




Quoting Shamrocka330 (Reply 3):
Is this done to gain a steeper angle of attack after the rotation? Something that the ailerons can't achieve on their own so the spoilers come in and help out?

The 737 drivers will be able to answer much more accurately, but the spoilers simply increase roll authority and response. Without them, roll control would be very sluggish and difficult. The 737 isn't the only aircraft that uses such a system.




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shamrocka330
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RE: 737 Take Off Question

Tue Jul 18, 2006 5:31 am

Thanks for the replies guys!
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RE: 737 Take Off Question

Tue Jul 18, 2006 5:53 am

Quoting 2H4 (Reply 4):

hehe! you are answering at the same time than me... :p

just to add that ailerons (and eventually spoilers) have nothing to do with AoA (angle of attack), they are just for roll control. Elevators makes the plane go nose up.
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RE: 737 Take Off Question

Tue Jul 18, 2006 6:01 am




Quoting Mighluss (Reply 6):
just to add that ailerons (and eventually spoilers) have nothing to do with AoA (angle of attack)

While I agree that AOA isn't the focus in this particular question/discussion, ailerons certainly do effect the AOA. During a stall, for example, commanding left roll input will result in a roll to the right.

Why? Because the aileron on the right is deflected downward, increasing the angle of attack to a point beyond the critical AOA, and causing that wing to stall first.




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bri2k1
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RE: 737 Take Off Question

Tue Jul 18, 2006 6:12 am

Nothing like overcomplicating things. Ailerons also increase drag disproportionately.

But that 737 wasn't in a stall at takeoff, hopefully...
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AirWillie6475
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RE: 737 Take Off Question

Tue Jul 18, 2006 7:49 am

Yes it has something to do with angle of attack but for the wing not the airplane. For example to turn left, the ailerons on the left wing must be up and the ailerons on the right wing must be down. When the aileron is down on the right wing(use your arms) this will increase the angle of attack and create lift. BUT this lift also causes drag on the right wing. This means that even though the plane is established in a left turn the aircraft will still have a tendency to turn to the right or not turn as efficiently to the left because of this induced drag on the right wing. That is where the spoilers come in. The spoilers don't turn the aircraft they just disturb the airflow over the wing on the inside of the turn just enough so the ailerons can better bank the aircraft. They use spoilers because using the rudder as is the case in small aircraft to help bank the plane is not an option for large aircraft such as the 737. Hope you understand.
 
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RE: 737 Take Off Question

Tue Jul 18, 2006 8:02 am




Quoting AirWillie6475 (Reply 9):
Yes it has something to do with angle of attack but for the wing not the airplane.

The airplane doesn't have it's own AOA. AOA, by definition, applies only to things with camber and chord lines (ie: airfoils). AOA in reference to only the fuselage is meaningless in terms of lift production.




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RE: 737 Take Off Question

Tue Jul 18, 2006 8:17 am

Quoting AirWillie6475 (Reply 9):
They use spoilers because using the rudder as is the case in small aircraft to help bank the plane is not an option for large aircraft such as the 737.

Not to get TOO far off-topic, but I thought the rudder was indeed used, just via the Yaw Damper, instead of footpedal inputs (landing phase excepted).

The spoilers are certainly not used on all rolls. They also are typically only extended while the airplane is actively rolling (to decrease lift on the inside wing). I don't think this is really comparable to what the rudder does in a coordinated turn, but maybe I'm wrong.

~Vik
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RE: 737 Take Off Question

Tue Jul 18, 2006 8:33 am




Quoting AirWillie6475 (Reply 9):
They use spoilers because using the rudder as is the case in small aircraft to help bank the plane is not an option for large aircraft such as the 737.

No, I'm with you, Vik....this is a rather confusing statement. If it were accurate, then only large aircraft would utilize roll control spoilers....which doesn't explain their presence on smaller aircraft like the MU-2 and Cessna Caravan.




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AirWillie6475
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RE: 737 Take Off Question

Tue Jul 18, 2006 8:35 am

Quoting 2H4 (Reply 10):
The airplane doesn't have it's own AOA. AOA, by definition, applies only to things with camber and chord lines (ie: airfoils). AOA in reference to only the fuselage is meaningless in terms of lift production.

I know that, I was telling the thread starter that because he said tha angle of attack of the aircraft.
 
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RE: 737 Take Off Question

Tue Jul 18, 2006 8:45 am




Quoting AirWillie6475 (Reply 13):
I know that, I was telling the thread starter that because he said tha angle of attack of the aircraft.

Ah, sorry about that, Willie. I misread what you said.




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RE: 737 Take Off Question

Tue Jul 18, 2006 9:00 am

Quoting Vikkyvik (Reply 11):
Not to get TOO far off-topic, but I thought the rudder was indeed used, just via the Yaw Damper, instead of footpedal inputs (landing phase excepted).

The spoilers are certainly not used on all rolls. They also are typically only extended while the airplane is actively rolling (to decrease lift on the inside wing). I don't think this is really comparable to what the rudder does in a coordinated turn, but maybe I'm wrong.

It's not what the rudder does in a coordinated turn, no, but there's more. The high-speed, swept-wing design of big planes like the 737 mean that rudder inputs do more than just yaw the plane -- they actually bank it, too.

The yaw damper deflects the rudder a very small amount to maintain turn coordination and control yaw during flight -- much smaller corrections than could be made by the pilot's booted feet. Look at the size of the rudder! Only a tiny deflection is a huge control input with the amount of air flowing over that huge control surface.
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RE: 737 Take Off Question

Tue Jul 18, 2006 9:43 am

Quoting Bri2k1 (Reply 15):
It's not what the rudder does in a coordinated turn, no, but there's more. The high-speed, swept-wing design of big planes like the 737 mean that rudder inputs do more than just yaw the plane -- they actually bank it, too.

Rudder input on any plane will eventually cause the plane to bank.
 
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RE: 737 Take Off Question

Tue Jul 18, 2006 9:55 am

heres a video showing the roll control on a 737 during takeoff...

http://www.flightlevel350.com/Aircra..._Airlines_Aviation_Video-2582.html


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shamrocka330
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RE: 737 Take Off Question

Tue Jul 18, 2006 7:22 pm

Quoting HighFlyer9790 (Reply 17):
heres a video showing the roll control on a 737 during takeoff...

cool video HighFlyer9790, that's exactly what I saw the spoilers do on the aircraft I was on!

Sorry to drag this on guys but the term roll control has been used many times in the previous replies but the take off I started this thread talking about had no turns or sideways movement at all during rotation and the beginning of climb. There was no wind either. I'm thinking that roll control manages the aircraft during turns but I'm thinking this maybe isn't the case?  Confused
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RE: 737 Take Off Question

Tue Jul 18, 2006 8:54 pm

Was it on the Side of the Wing going Down.Those are Flight Spoilers.
Operated with Roll control.
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RE: 737 Take Off Question

Tue Jul 18, 2006 9:09 pm

Quoting Shamrocka330 (Reply 18):
There was no wind either.

That's a bold assertion. How do you know? There's always wind. Always. And it's never, ever straight down the runway...it's at least a few degrees off the nose. Many times, on longer runways, airliners will take off with a slight tailwind component to get a more favorable initial heading or to avoid noise-sensitive areas whenever possible.

Even if there wasn't any wind, the plane still has to be controlled after takeoff. The wind could also shift right after takeoff, especially if buildings or terrain played a part in wind dynamics at the surface. That can play a part in a tower reporting "wind calm" when there's actually some wind, at least light and variable winds, at another part of the field, or just a few feet above the ground.
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RE: 737 Take Off Question

Tue Jul 18, 2006 9:32 pm

Quoting Bri2k1 (Reply 20):
That's a bold assertion. How do you know?

I could see the wind sock at the end of the runway, it was fairly lifeless! I'm sure there was some element of wind but not enough to cause a large amount of roll control (which was mentioned in a number of replies above where I assumed they were talking about strong winds).
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RE: 737 Take Off Question

Tue Jul 18, 2006 9:56 pm

Quoting Bri2k1 (Reply 20):
There's always wind. Always. And it's never, ever straight down the runway...it's at least a few degrees off the nose. Many times, on longer runways, airliners will take off with a slight tailwind component to get a more favorable initial heading or to avoid noise-sensitive areas whenever possible.

With all due respect, this is false. Up at altitude there is always wind, but on a lot of nights, the surface winds are completely calm. And as for direction, mother nature doesn't know or care which magnetic heading the runway is aligned with, so you can't say that the wind is always a few degrees off. Most times it may be, but when planning an airport, designers look at the prevailing winds to determine which way(s) to face the runway(s).

As for taking off with a tailwind, the only reason I'm aware of for airliners doing this is runway slope. Small airplanes may do this to save time, but not airliners. Especially on longer runways, which are usually at bigger airports with lots of traffic. ATC has an active runway for a reason, and won't take special requests for direction just to get on a better initial heading. This would totally screw up their spacing and such unless its VERY late at night. In LYH, sometimes the Dash-8s will take off on 22 instead of 4 because of the runway gradient and required takeoff distance. It's not a huge difference in elevation from end to end, but enough to make the pilots want gravity on their side.

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RE: 737 Take Off Question

Tue Jul 18, 2006 10:09 pm




Quoting Shamrocka330 (Reply 21):
I could see the wind sock at the end of the runway, it was fairly lifeless!

That only tells you what the wind was doing at the end of the runway....




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vikkyvik
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RE: 737 Take Off Question

Tue Jul 18, 2006 10:29 pm

Quoting Shamrocka330 (Reply 21):
I'm sure there was some element of wind but not enough to cause a large amount of roll control (which was mentioned in a number of replies above where I assumed they were talking about strong winds).

I think it's less about how much roll you need as opposed to how fast the roll was commanded. I believe the spoilers will help with roll control when faster rates of roll are commanded (where the ailerons may not be able to meet the commanded roll rate on their own).

Also, there could have been a gust of wind at that time.

Keep in mind, also, that there was probably a good mile or more between the windsock and where you rotated. Airports are big places; as 2H4 stated, the wind may not necessarily be the same all across the field.

Quoting Shamrocka330 (Reply 18):
Sorry to drag this on guys but the term roll control has been used many times in the previous replies but the take off I started this thread talking about had no turns or sideways movement at all during rotation and the beginning of climb.

The roll for crosswind correction would probably be pretty small in the grand scheme of things - small enough that you may not have really noticed it. I'm sure in my life I've been in plenty of crosswind takeoffs and landings. It's only been noticeable once or twice.

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RE: 737 Take Off Question

Tue Jul 18, 2006 10:38 pm

Quoting CptSpeaking (Reply 22):

I have to disagree with all of that. Surface winds result from uneven heating of the Earth. Clearly, the runway surface absorbs a different amount of heat than the surrounding terrain, so right there you have the basis for wind.

Can there be situations where winds are light enough to be negligible for aircraft operations? Yes. But that's not what I said.

Also, at any big airport, with enough runways and controllers, there are multiple simultaneous departure runways and multiple simultaneous approach runways, too, winds permitting. That means if the tailwind component is acceptable, all the Westbound ships out of DEN will gladly take Runway 25. It also means less vectoring by the TRACON to get into the flow at altitude.
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RE: 737 Take Off Question

Tue Jul 18, 2006 11:22 pm

Quoting AirWillie6475 (Reply 16):
Quoting Bri2k1 (Reply 15):
It's not what the rudder does in a coordinated turn, no, but there's more. The high-speed, swept-wing design of big planes like the 737 mean that rudder inputs do more than just yaw the plane -- they actually bank it, too.

Rudder input on any plane will eventually cause the plane to bank.

My old remote control motor glider didn't even have ailerons. Rudder and elevator. The turns weren't perfectly coordinated and I couldn't do a snap roll but otherwise it worked just fine.
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DH106
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RE: 737 Take Off Question

Tue Jul 18, 2006 11:48 pm

Quoting Starlionblue (Reply 26):
Quoting AirWillie6475 (Reply 16):
Quoting Bri2k1 (Reply 15):
It's not what the rudder does in a coordinated turn, no, but there's more. The high-speed, swept-wing design of big planes like the 737 mean that rudder inputs do more than just yaw the plane -- they actually bank it, too.

Rudder input on any plane will eventually cause the plane to bank.

My old remote control motor glider didn't even have ailerons. Rudder and elevator. The turns weren't perfectly coordinated and I couldn't do a snap roll but otherwise it worked just fine.

Yep - but your rc glider would have more dihedral than otherwise with ailerons to help the rudder bank the aircraft.
On a simple plane with no dihedral or sweep, rudder input would pretty much only cause a yaw. Dihedral and sweep both tend to make the 'into wind' wing want to rise and roll the aircraft.
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RE: 737 Take Off Question

Wed Jul 19, 2006 1:03 am

Quoting DH106 (Reply 27):

Yep - but your rc glider would have more dihedral than otherwise with ailerons to help the rudder bank the aircraft.
On a simple plane with no dihedral or sweep, rudder input would pretty much only cause a yaw. Dihedral and sweep both tend to make the 'into wind' wing want to rise and roll the aircraft.

Quite right. Lots of dihedral. This is a smaller version of my old model. Same planform except mine had a conventional tail.

http://www.kyosho.co.jp/web/products...ers/stratus1600/stratus1600-e.html



[Edited 2006-07-18 18:04:02]

[Edited 2006-07-18 18:07:56]
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AirWillie6475
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RE: 737 Take Off Question

Wed Jul 19, 2006 1:37 am

Quoting Shamrocka330 (Reply 18):
he take off I started this thread talking about had no turns or sideways movement at all during rotation and the beginning of climb. There was no wind either. I'm thinking that roll control manages the aircraft during turns but I'm thinking this maybe isn't the case?

Every time the pilot moves the yoke past a certain degree the ailreons will deploy much like that video that was posted on this thread. That plane wasn't banking was it?
 
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RE: 737 Take Off Question

Wed Jul 19, 2006 2:04 am

Quoting Starlionblue (Reply 28):
Quite right. Lots of dihedral. This is a smaller version of my old model. Same planform except mine had a conventional tail.

http://www.kyosho.co.jp/web/products....html

Great looking model Starlionblue!
I fly gas power stuff myself, but am getting more and more into electric  Smile
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RE: 737 Take Off Question

Wed Jul 19, 2006 2:08 am

Quoting DH106 (Reply 30):
I fly gas power stuff myself, but am getting more and more into electric Smile

Haven't flown anything in years  Sad

The advantage of electric is silence. I used to fly in a large city park in Stockholm (no car at the time). Endurance is only 20-25 minuts but if you buy extra batteries it isn't a problem.
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RE: 737 Take Off Question

Wed Jul 19, 2006 4:51 am

Quoting Bri2k1 (Reply 25):
Surface winds result from uneven heating of the Earth. Clearly, the runway surface absorbs a different amount of heat than the surrounding terrain, so right there you have the basis for wind.

I agree with you there, there is the basis for wind due to uneven surface heating, but this isn't always enough to cause measurable surface winds. I'm not from the DEN area, so I don't know whether you guys always have winds or not, but where I'm from, you can go outside almost any night (especially in the winter, when surface heating and cooling isn't as significant) and there is absolutely NO surface wind. Not negligible to aircraft ops, NONE. Period. Dot.

Quoting Bri2k1 (Reply 25):
Also, at any big airport, with enough runways and controllers, there are multiple simultaneous departure runways and multiple simultaneous approach runways, too, winds permitting. That means if the tailwind component is acceptable, all the Westbound ships out of DEN will gladly take Runway 25. It also means less vectoring by the TRACON to get into the flow at altitude.

Ahh, but thats not what you said...this is what you said:

Quoting Bri2k1 (Reply 20):
Many times, on longer runways, airliners will take off with a slight tailwind component to get a more favorable initial heading or to avoid noise-sensitive areas whenever possible.

You said nothing about multiple departure and arrival runways. 9 times out of 10, the multiple runways are going to be *L and *R. If the crosswind component on the crosswind runway isn't too big, they may use one of those as well, but there would be no point in wasting a runway perfectly aligned with the wind, or maybe at least a few degrees off.  Wink Late at night, when traffic volume is no factor and winds are calm, or as you say, negligible, ATC will grant requests for leaving or arriving on runways other than the active...I see that all the time with the FX A306s out of RDU around 10:15 at night. It may be an airline policy, but I have never seen a pax airliner leave or arrive on any runway other than the one favored by the wind.

As for less vectoring, thats complete crap. Thats what departure procedures are for. The controllers have no extra work to do when planes takeoff with a tailwind, and in fact they may have more. Think how much easier it would be for spacing if every airplane followed the same route coming out of the airport. Not only would the controllers not have to worry about traffic conflicts trying to fit them into the system, the pilots already know what they're going to do at what time.

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AirWillie6475
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RE: 737 Take Off Question

Wed Jul 19, 2006 6:39 am

Quoting CptSpeaking (Reply 32):
Many times, on longer runways, airliners will take off with a slight tailwind component to get a more favorable initial heading or to avoid noise-sensitive areas whenever possible.

I really doubt it. Most pilots have a monkey-see, monkey-do mentality. They just follow what other pilots do. Plus I don't think anybody cares if they are flying over noise sensitive areas, unless it's part of the departure procedure.
 
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RE: 737 Take Off Question

Wed Jul 19, 2006 6:51 am

Quoting CptSpeaking (Reply 32):
You said nothing about multiple departure and arrival runways. 9 times out of 10, the multiple runways are going to be *L and *R.

Ahh, I'm sorry that confused you. My use of "many times" here could have implied large airports since they see more operations. Even if it's not a large airport, as when I fly in or out of KAPA, I can always request runway 10 for departure or 28 for arrival, even if the ATIS indicates that only 17L is in operation as the crosswind runway is much closer to my hangar. The only times it's denied is when there are already too many people waiting to arrive or depart on it.

Quoting AirWillie6475 (Reply 33):
I really doubt it. Most pilots have a monkey-see, monkey-do mentality. They just follow what other pilots do. Plus I don't think anybody cares if they are flying over noise sensitive areas, unless it's part of the departure procedure.

That's a pretty bold statement about pilots. I know it's not true. Maybe some fellow pilots will back me up on this one.

Also, be more careful with your quotes...those were my words, not the 16-20 year old's.
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RE: 737 Take Off Question

Wed Jul 19, 2006 7:02 am




Quoting Bri2k1 (Reply 34):
That's a pretty bold statement about pilots. I know it's not true. Maybe some fellow pilots will back me up on this one.

While I don't fly for an airline, I'm with you, Bri2k1. That particular statement doesn't contain a shred of accuracy.




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meister808
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RE: 737 Take Off Question

Wed Jul 19, 2006 7:33 am

Quoting DH106 (Reply 27):
On a simple plane with no dihedral or sweep, rudder input would pretty much only cause a yaw.

Nope... you have that backwards. With no dihedral or sweep, the roll moment is actually stronger in that case. As the aircraft yaws, the outside wing travels faster, thus it generates relatively more lift than the inside wing, and a roll is induced to the inside of the turn. This is a manifestation of Dutch Roll, something that dihedral, by definition, dampens. If you want an explanation on that one, I'm game, but you'd probably be better just looking at the Airplane Flying Handbook. Go to http://www.faa.gov and do a search.

Quoting CptSpeaking (Reply 32):
As for less vectoring, thats complete crap. Thats what departure procedures are for. The controllers have no extra work to do when planes takeoff with a tailwind, and in fact they may have more. Think how much easier it would be for spacing if every airplane followed the same route coming out of the airport. Not only would the controllers not have to worry about traffic conflicts trying to fit them into the system, the pilots already know what they're going to do at what time.

You have a point about making life easier for pilots and controllers if everyone is doing the same thing. However, saying that it is complete crap that taking off downwind might make less work for a controller is making a pretty bold statement. I guarantee if the runway/airport is clear enough to allow a departure against the flow of traffic, the airspace is most likely clear enough to allow for some play in the system. And who's to say that downwind isn't with the flow of traffic? Sometimes a minor shift in the wind favors switching directions, but it simply isn't worth telling the 15 airplanes getting lined up on the approach and the 20 airplanes heading to departure runways on the ground that they need to go to the other side of the airport. If a pilot specifically has a problem with the downwind departure or landing and voices it, things will probably get changed, but if all 35 of those airplanes are CRJs and the runways are 10,000' long (trust me, this happens at CVG  Wink), then there's not going to be a problem.

Quoting AirWillie6475 (Reply 33):
I really doubt it. Most pilots have a monkey-see, monkey-do mentality. They just follow what other pilots do. Plus I don't think anybody cares if they are flying over noise sensitive areas, unless it's part of the departure procedure.

Thanks man, I appreciate that. Hopefully that was meant as the joke that I'm taking it as, because thats about the rudest blanket statement I've heard said about a group that, worldwide, encompasses several million people. What might be the proper interpretation of your observations about pilots is that pilots tend to think about the large-scale picture, so if 20 other people are doing it and I see no reason not to, I'm probably going to do it as well for efficiency's sake. That's not monkey-see, monkey-do, that's critically analyzing a situation and taking what I see and have been trained to recognize as the proper action.

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cptspeaking
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RE: 737 Take Off Question

Wed Jul 19, 2006 7:37 am

Quoting Bri2k1 (Reply 34):
not the 16-20 year old's.

wow...in the future, keep the discussion on the topic. Age has nothing to do with what we're talking about, but even so, this 20 year old has much more experience than a lot of people in this forum. I respect those that know more than me and strive to learn more about aviation from anybody that has accurate information. My experience has shown me that some of your statements just weren't true. Maybe it was a clarity issue, but the way they were stated they just weren't true.

BTW...if you read a little further in my profile, you'll find that I hold a CPL with an instrument rating, and my CFI checkride is a couple weeks away. I'm not a bored high school kid who plays flight simulator and thinks he knows everything from that alone. In my first reply, notice this:

Quoting CptSpeaking (Reply 22):
With all due respect,

I'm not here to bash anybody, don't do it to me.

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RE: 737 Take Off Question

Wed Jul 19, 2006 7:46 am

When I flew the BAe146, we often had full into wind aileron at the start of the take-off roll to counter-act wing lift. There was a greatly reduced risk of pod strikes due to the high wing
When on the B737 though only a little aileron could be applied (about 1 unit I think??) before the roll spoilers would kick in. There is so litlle clearance on the engine pods that it was quite possible to strike one due to excessive crosswind correction.
 
AirWillie6475
Posts: 2372
Joined: Thu Jan 27, 2005 1:45 pm

RE: 737 Take Off Question

Wed Jul 19, 2006 7:51 am

Ok I guess I should back-up what I said. I agree Meister808, it's not exactly monkey see monkey do but you know what I mean. I tend to have this too, I just go with the flow but I guess it's because I don't have that much experience flying and don't want to piss people off. I used that phrase because I was reading an article somewhere, I think fligh training magazine about a United Captain. She was a DEN based captain and in DEN as you can imagine there is a lot of aircraft traffic and multiple runways. Anyways in this article she explained that a lot of guys tend to be monkey see monkey do and instead of doing the extra work of askig controlers and checking the airport info, they just go with the active runway and stay in line with 20 other aircraft. She prided herself that she tries to avoid these situations by being a little more aware and not being afraid of not going with the flow. So a lot of times whe would endup using runways that were open and she would be airborne while other were still waiting in long lines to take off.
 
DH106
Posts: 595
Joined: Wed Jun 15, 2005 5:32 pm

RE: 737 Take Off Question

Wed Jul 19, 2006 2:54 pm

Quoting Meister808 (Reply 36):
Nope... you have that backwards. With no dihedral or sweep, the roll moment is actually stronger in that case. As the aircraft yaws, the outside wing travels faster, thus it generates relatively more lift than the inside wing, and a roll is induced to the inside of the turn. This is a manifestation of Dutch Roll, something that dihedral, by definition, dampens. If you want an explanation on that one, I'm game, but you'd probably be better just looking at the Airplane Flying Handbook. Go to http://www.faa.gov and do a search.

I agree with your statement about the roll moment caused by wing speed differential (I was actually considering a steady, damped yaw with no wing speed differential), but this can't mean that this roll is 'actually stronger' with no dihedral or sweep as these add more roll forces to the Dutch Roll equation.
...I watched c-beams glitter in the dark near the Tanhauser Gate....
 
twal1011727
Posts: 449
Joined: Thu Mar 23, 2006 5:36 am

RE: 737 Take Off Question

Thu Jul 20, 2006 6:19 am

Quoting 2H4 (Reply 10):
AOA in reference to only the fuselage is meaningless in terms of lift production.

AOA is the relation between the wing chord line and the relative wind.
The wing chord line changes with extension/retraction of flaps/slats or with any other change of the wing shape.

The video (real good one) looks like a departure from rwy08 at ABQ. If so...the winds that come off the Sandia mountains just love to put out eddy currents between gnd level and 400-600' (also that explains the right turn out.) The flt spoiler input starts after rotation thru liftoff and climbout. This is due to climb airspeed needing more control wheel input to keep the wings level. Once above 210 knots(average flaps up speed),the ailerons do a good job in roll control

KD MLB
 
meister808
Posts: 924
Joined: Sat Jan 01, 2000 11:45 am

RE: 737 Take Off Question

Thu Jul 20, 2006 7:29 am

Quoting DH106 (Reply 40):
I was actually considering a steady, damped yaw with no wing speed differential

Fair enough

Quoting AirWillie6475 (Reply 39):
Anyways in this article she explained that a lot of guys tend to be monkey see monkey do and instead of doing the extra work of askig controlers and checking the airport info, they just go with the active runway and stay in line with 20 other aircraft.

Gotcha, I see what you're getting at now and, yes, it happens all the time.

Quoting DH106 (Reply 40):
but this can't mean that this roll is 'actually stronger' with no dihedral or sweep as these add more roll forces to the Dutch Roll equation.

Hm.. I think you've got me on the sweepback. I swear I recall being taught that dihedral counters dutch roll, but for the life of me I can't make the aerodynamics of it work out in my mind right now.

-Meister
Twin Cessna 812 Victor, Minneapolis Center, we observe your operation in the immediate vicinity of extreme precipitation
 
highflyer9790
Posts: 1189
Joined: Thu Jul 07, 2005 1:21 am

RE: 737 Take Off Question

Thu Jul 20, 2006 9:25 am

Quoting Shamrocka330 (Reply 18):
Sorry to drag this on guys but the term roll control has been used many times in the previous replies but the take off I started this thread talking about had no turns or sideways movement at all during rotation and the beginning of climb. There was no wind either. I'm thinking that roll control manages the aircraft during turns but I'm thinking this maybe isn't the case?

Whenever a gust of wind requires a correction input from the yoke, you are essentially doing the same motion on the yoke that you would do to enter a bank. but because all you are trying to do is keep the wings level, the input is only a little, very quick one. the bigger the gust, the more input is required. the more input required will start raise the flight spoilers on the wing with aileron up. near the ground, unexpected currents may be encountered, therefore a wind sock may fall short to show what above the tree line, so to speak. the slower the speed of an aircraft, the lfight spoilers will activate with less control input, where as while at 250kts, the flight spoilers will activate with a large control input.

here are some photos with roll control spoilers activated with "up aileron":


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Photo © Alessandro Savarese - SpotIT



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Photo © Ben Hewitt



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Photo © Jason Nicholls



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Photo © Gordon Ho



hope it helps!

highflyer  wave 
121
 
bri2k1
Posts: 952
Joined: Sun Dec 19, 2004 4:13 am

RE: 737 Take Off Question

Thu Jul 20, 2006 11:03 am

Quoting CptSpeaking (Reply 37):
Age has nothing to do with what we're talking about, but even so, this 20 year old has much more experience than a lot of people in this forum.

Not chronologically possible. But since you brought it up (and I did not -- read more below)

Quoting CptSpeaking (Reply 37):
if you read a little further in my profile, you'll find that I hold a CPL with an instrument rating, and my CFI checkride is a couple weeks away

I'm a pilot, too. I'm reminded of the joke...How do you know when a pilot enters a room? He tells everyone!

Quoting CptSpeaking (Reply 37):

I'm not here to bash anybody, don't do it to me.

I didn't. I quoted what I believe to be a factual statement from your profile without judging it. You should be proud to be able to speak with more initial accuracy and respect than your fellow poster (to whom my comment was addressed).

It was only you who insinuated that there was anything "wrong" with being 20. Do you think there is anything wrong with it? I don't. The FAA establishes the age minima and maxima for various categories of pilots, and I continue to abide by their rules.
Position and hold
 
DH106
Posts: 595
Joined: Wed Jun 15, 2005 5:32 pm

RE: 737 Take Off Question

Thu Jul 20, 2006 4:46 pm

Quoting Bri2k1 (Reply 44):
Quoting CptSpeaking (Reply 37):
Age has nothing to do with what we're talking about, but even so, this 20 year old has much more experience than a lot of people in this forum.

Not chronologically possible. But since you brought it up (and I did not -- read more below)

Why isn't is chronologically possible ?
Are ALL the forum posters commercial pilots with many years service? No.
Bri2k1 holds a CPL which makes him considerably more experienced than me for a start.
...I watched c-beams glitter in the dark near the Tanhauser Gate....
 
chrisMUC
Posts: 54
Joined: Sat Jul 22, 2006 7:47 pm

RE: 737 Take Off Question

Sat Jul 22, 2006 8:11 pm

The activation of flight spoilers on a B737 depends on control wheel displacement, if it's larger than appr. 10� the flight spoilers will be mixed in.
To avoid additional drag during take-off roll (and of course situation permitting) you try not to displace the control wheel more than these 10� on ground.

Reasons for significant control wheel input after lift off in a no wind condition can be turbulance caused by different thermal warming or, very likely, encountering wakes from a preceeding aircraft.

Reasons for tailwind T/O can be noise abatement (LHR), terrain situation (NCE, STR), traffic flow (FRA). The limit for most aircraft and airlines is about 10kts on dry RWYs).

hope this helps,

chris
 
cptspeaking
Posts: 567
Joined: Mon Apr 24, 2006 2:49 pm

RE: 737 Take Off Question

Sat Jul 22, 2006 11:24 pm

Quoting Bri2k1 (Reply 44):
Not chronologically possible.

Are you serious? Even if I had just one flight hour in my logbook, that would give me more experience than some in here. Thats cool that they're here, i'm glad more people are interested in aviation and want to learn about it, but number of years doesn't necessarily vary directly with experience. To the other comments, I don't think there is anything wrong with being 20 either, my point was that that information has nothing to do with the discussion. You could have left that out of your reply, or just said "CptSpeaking", but chose not to, implying that you were disappointed your words were attributed to somebody younger. Take them, I disagree anyways!!  Wink Aight, I'm done with this, whats the point?!

Chris, thanks for the info...welcome to A.net! Smile

Your CptSpeaking
...and don't call me Shirley!!
 
Eddie757
Posts: 21
Joined: Sun Jul 23, 2006 7:07 pm

RE: 737 Take Off Question

Mon Jul 24, 2006 12:57 am

An important fact concerning the aid of spoilers in the act of roll at low speeds is that in the case of an engine failure after t/o it is extremelly important not to use the ailerons at all (if possible) to avoid the deployment of the spoilers on the "low" wing and the consecuent decrease of lift and increase of drag.
Some planes have this mix (ailerons-spoilers) activated by speed and others by flap configuration.
 
bri2k1
Posts: 952
Joined: Sun Dec 19, 2004 4:13 am

RE: 737 Take Off Question

Mon Jul 24, 2006 3:11 am

Quoting CptSpeaking (Reply 47):
Even if I had just one flight hour in my logbook, that would give me more experience than some in here.

I disagree. You would have more logged flight time than many here. But this is the kind of thing that no one can tell you, you just have to experience it. So I will let it go.
Position and hold

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