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FX915
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Couple questions about the B737

Mon Jan 30, 2017 8:10 am

Hi there! I have a couple questions about this plane

About the yaw damper, does it work as a full automated rudder, or pilots still need to operate it when taking a turn?

The second one is about the slats, in other aircraft I've seen crew extending them manually, but never in the 737, are they linked to the flaps or something?

That is, thanks in advance.
 
AA737-823
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Re: Couple questions about the B737

Mon Jan 30, 2017 8:41 am

Regarding the leading edges (of which, the 737 employs both slats AND Kruger flaps), they're automatic.
The flight crew selects a trailing edge position--I think the detents are 1, 2, 5, 10, 15, 25, 30, and 40--and the leading edge devices position automatically.
The Kruger flaps are two position- either RETRACT or EXTEND.
The slats are all three position- RETRACT, EXTEND, FULL EXTEND.
Everything moves to the extend position with the flap lever in the 1 detent.
Slats move further into the FULL EXTEND position later, and it varies by aircraft series. I know the -700's slats drop at the FLAPS 10 detent. But the short field performance package on the -900ER delayed that to a greater flap setting.

Regarding the yaw damper, I'm not a pilot, so I can't tell you how they handle a turn.
But I know that, with limited exception, the 737 is equipped with only a two-axis autopilot. The autopilot cannot move the rudder.
 
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7BOEING7
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Re: Couple questions about the B737

Mon Jan 30, 2017 7:11 pm

FX915 wrote:
Hi there! I have a couple questions about this plane

About the yaw damper, does it work as a full automated rudder, or pilots still need to operate it when taking a turn?


The yaw damper provides turn coordination and prevents Dutch roll -- no pilot input required.
 
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7BOEING7
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Re: Couple questions about the B737

Mon Jan 30, 2017 7:31 pm

AA737-823 wrote:

Regarding the yaw damper, I'm not a pilot, so I can't tell you how they handle a turn.
But I know that, with limited exception, the 737 is equipped with only a two-axis autopilot. The autopilot cannot move the rudder.


The limited exceptions are those airplanes equipped with a "Fail Operational Autoland" which was not available initially on the NG, provided rollout capability during an autoland and was one of he reasons BA purchased the A320 instead of the NG.
 
hivue
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Re: Couple questions about the B737

Mon Jan 30, 2017 11:14 pm

7BOEING7 wrote:
...and prevents Dutch roll...


Am I correct in thinking this can be a real issue on the 737 with an inoperative yaw damper? I seem to recall in another thread a 737 pilot say something along the lines of, "The yaw damper better not fail because I don't want to listen to the complaints from the passenger cabin."
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
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7BOEING7
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Re: Couple questions about the B737

Tue Jan 31, 2017 5:38 am

hivue wrote:
7BOEING7 wrote:
...and prevents Dutch roll...


Am I correct in thinking this can be a real issue on the 737 with an inoperative yaw damper? I seem to recall in another thread a 737 pilot say something along the lines of, "The yaw damper better not fail because I don't want to listen to the complaints from the passenger cabin."


First, the airplane can be dispatched with the yaw damper INOP -- second, if it goes INOP during flight you just want to "avoid areas of moderate to severe turbulence" but if you can't and the passengers start having issues, you slow down and/or go down. The system is fairly robust and if the air is smooth it shouldn't be a big deal. You have to know what you're doing to get it into a Dutch roll situation and it won't stay there if you don't help it. Having done several thousand yaw damper checks in the 737 through 777 to get the airplane to Dutch roll takes some coordination with the rudders and several practice attempts to get it right.


Links below relate to a Boeing/Braniff acceptance/training flight in a 707 that crashed in 1959 while demonstrating recovery from a Dutch roll that was outside the limits.

http://specialcollection.dotlibrary.dot.gov/Contents Go to 1959 then Boeing

https://aviation-safety.net/database/re ... 19591019-0

http://www.failure-interactions.com/boe ... -1959.html
 
FX915
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Re: Couple questions about the B737

Tue Jan 31, 2017 6:27 am

7BOEING7 wrote:
FX915 wrote:
Hi there! I have a couple questions about this plane

About the yaw damper, does it work as a full automated rudder, or pilots still need to operate it when taking a turn?


The yaw damper provides turn coordination and prevents Dutch roll -- no pilot input required.


Even whit A/P OFF they don't need to push rudder pedals?
 
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7BOEING7
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Re: Couple questions about the B737

Tue Jan 31, 2017 7:23 am

FX915 wrote:
7BOEING7 wrote:
FX915 wrote:
Hi there! I have a couple questions about this plane

About the yaw damper, does it work as a full automated rudder, or pilots still need to operate it when taking a turn?


The yaw damper provides turn coordination and prevents Dutch roll -- no pilot input required.


Even whit A/P OFF they don't need to push rudder pedals?


Yes
 
benbeny
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Re: Couple questions about the B737

Sat Feb 04, 2017 4:39 pm

So if we able to make the rudder to kick in automatically during crosswind or during engine failure, then we are able to get rid of the rudder pedal?
 
pikachu
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Re: Couple questions about the B737

Thu Feb 09, 2017 3:08 pm

Not really... B777 has Thrust Asymmetry Compensation and still has rudder pedals.
 
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richcam427
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Re: Couple questions about the B737

Thu Feb 09, 2017 3:35 pm

FX915 wrote:
7BOEING7 wrote:
FX915 wrote:
Hi there! I have a couple questions about this plane

About the yaw damper, does it work as a full automated rudder, or pilots still need to operate it when taking a turn?


The yaw damper provides turn coordination and prevents Dutch roll -- no pilot input required.


Even whit A/P OFF they don't need to push rudder pedals?


Correct. Most commercial aircraft from at lest the 707 onward have had turn coordination as part of the yaw damping system.
 
OldAeroGuy
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Re: Couple questions about the B737

Thu Feb 09, 2017 4:18 pm

FX915 wrote:
The second one is about the slats, in other aircraft I've seen crew extending them manually, but never in the 737, are they linked to the flaps or something?


What airplanes have you seen a separate/manual slat extension on?

After the Trident crash where the flight crew neglected to extend the leading devices, all subsequent Part 25 certified airplanes have had leading edge extension tied to a single high lift system (leading edge & trailing edge) control lever.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
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Starlionblue
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Re: Couple questions about the B737

Fri Feb 10, 2017 1:01 am

benbeny wrote:
So if we able to make the rudder to kick in automatically during crosswind or during engine failure, then we are able to get rid of the rudder pedal?


Interesting question. On the 350 and 380 the rudder automatically compensates during an engine failure. The flight control system actually adds bias forcing the pilot to put in some rudder. That way the piltos actually notice. :D

Made for an interesting engine failure just before V1 in the 330 sim after I'd done my 350 course. I put in way too little rudder and it felt like we would run off the side of the runway.

You still need the pedals to decrab on landing and and to control the nose wheel. Yes, the tiller also controls the nosewheel but I only have two hands.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
BoeingGuy
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Re: Couple questions about the B737

Fri Feb 10, 2017 3:44 am

Starlionblue wrote:
benbeny wrote:
So if we able to make the rudder to kick in automatically during crosswind or during engine failure, then we are able to get rid of the rudder pedal?


Interesting question. On the 350 and 380 the rudder automatically compensates during an engine failure. The flight control system actually adds bias forcing the pilot to put in some rudder. That way the piltos actually notice. :D

Made for an interesting engine failure just before V1 in the 330 sim after I'd done my 350 course. I put in way too little rudder and it felt like we would run off the side of the runway.

You still need the pedals to decrab on landing and and to control the nose wheel. Yes, the tiller also controls the nosewheel but I only have two hands.


The 777 and 787 do the same thing. The 777 Thrust Assymetry Compensation is based on a difference in thrust between the two engines. The 787 TAC uses inertial inputs to sense the yaw and add rudder.

They are also intentionally designed to not take out all the yaw so as not to completely mask the tacticle feel of an engine failure on takeoff. As such, the 777 and 787 also have ENG FAIL time critical warnings (annunciated like the Windshear, Pull Up, and Speedbrake time critical warnings) if an engine fails during the later part of takeoff roll. It's 65 knots to V1-3, IIRC.

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