Question about elevator movement in a real 737 NG

[Maurice]

In a real 737, do you need to pull the yoke all the way back to lift the nose wheel off the ground during initial rotation or will the nose wheel lift off with only partial yoke/elevator movement, assuming of course you rotate at the correct rotation speed?

Thanks,
Maurice

[Flying_Fox]

Agreed with your question, Maurice and adding mine:

From the other thread we figured out that the real 737 yoke turn is +- 90 degrees.
What are the situations (if any) in the normal real flight (not emergency situations) when the full 90 degrees yoke turn is used?

[Garys]

No, you wouldn't pull all the way with correct trim setting during takeoff.

During manual reversion the yoke force and rotation would be greater in order to turn the aircraft.

Gary

[Maurice]

No, you wouldn't pull all the way with correct trim setting during takeoff

Gary

The trim setting only affects how much manual force is required to move the yoke/elevator and not how far back you need to pull on the yoke to get the nose gear off the ground. So my question still stands.

At the relatively low rotate speed, I imagine you would need a rather large elevator deflection to be able to raise the nose wheel. Hopefully Mike L. will answer this post 

Thanks,
Maurice

[Garys]

Watch this video  747 takeoff cockpit view

Fast fwd to 3.25 and watch the full yoke deflections and then continue watching the takeoff.  The NG is no different.

[Maurice]

Very interesting! It looks like he barely moved the yoke to raise the nose. If I had not seen this, I would not have believed that you could lift such a massive 747 nose with so little elevator movement

Here is a short video that shows the same thing on a 737. It makes you wonder why the yoke can allow such big movements and yet, at relatively low speeds, you only need to barely move it to raise the nose. When would you ever need full deflection then?

http://youtu.be/tEv_MlGLesQ

Thanks,
Maurice

[Nat Crea]

The trim setting only affects how much manual force is required to move the yoke/elevator and not how far back you need to pull on the yoke to get the nose gear off the ground.

Mau,

Trimming the horizontal stabilizer moves the whole stabilizer up and down about a fixed point on the fuselage, so it indeed effects how much elevator movement required to lift off...hence the small amount of yoke movement in reality if trimmed correctly.

Nat

[Maurice]

Mau,

Trimming the horizontal stabilizer moves the whole stabilizer up and down about a fixed point on the fuselage, so it indeed effects how much elevator movement required to lift off...hence the small amount of yoke movement in reality if trimmed correctly.

Nat

Ok, now I partly understand. I thought the elevator had a trim tab in the elevator surface like it does on a Cessna for instance. But if the trim moves the whole elevator surface, would it not move the yoke as well and yet, in the videos, it looks like the yoke is in the neutral poison until rotation?

Maurice

[Nat Crea]

Mau,

Its opposite to what you were used to in the Cessna.
Here's a cool video which shows it in action! (737-200)

Aircraft trim system, 737-200

Nat

[Maurice]

Mau,

Its opposite to what you were used to in the Cessna.
Here's a cool video which shows it in action! (737-200)

Nat

That is a GREAT video! It all makes sense now. The trim switch moves the entire elevator surface but does not move the yoke at all. I can now rest in peace 

Thanks Nat,

Maurice

[sagrada737]

Great thread!  Watching these videos has helped me as well to understand some of these systems, as I try to sort things out flying my own Sim.  It was interesting to see in both the 747 and 737 the need to "relax" the Yoke (elevator) upon Gear UP - looks like they maintain about 15 degrees climb rate, while manually flying the aircraft.  I assume that Autopilot comes ON sometime above 1,000 ft., or depending on the nature of the Departure.

Thanks for sharing.  By the way...   It's a good thing that the Trim Wheels don't have any sharp edges on them! 

Mike

[Garys]

"When would you ever need full deflection then?"

In normal flight, Never. However there is a breaking point in both the elevator and aileron movements in that if one control column becomes jammed, you can overcome the jam  by extreme movement on the free control column. Only the free moving column would now control the aircraft.

Its all Magic Mau.   

AIR PLANES ARE MAGIC!

[jameas]

The question of how trim works on these aircraft has always confused me, having been more used to light aircraft myself.

A further question to add to this would be - when changing configuration for instance pitching to climb you would pull on the stick and then remove the back pressure using the trim, the stick then remaining in the new position in a light aircraft.
If I have understood the information correctly then how would you know how much trim to apply on the 737 in this case as surely you would have to apply back pressure, add some trim, return stick to neutral and check pitch, then maybe add more trim if the nose didn't stay where expected.
Or am I missing something else here.

thanks
James

[Garys]

Hopefully Mike or Rhys can jump in here but I think when changing configuration such as a climb its more engine thrust that initates the climb an then you would adjust trim accordingly to maintain desired airspeed and angle

Gary

[Maurice]

"When would you ever need full deflection then?"


Its all Magic Mau.   

AIR PLANES ARE MAGIC!

LOL! Loved the video

Maurice

[Joe Lavery]

Brilliant Video, I've sent it all around the world. All received with howls of laughter.

Without hijacking this thread to much, does anyone (seriously), know why we have to turn off these devices? I've heard all sorts of weird and wonderful explanations, none of them really make much sense.

Perhaps Mike Leavy can finally put these myths to bed. 

Joe.

[Maurice]

Without hijacking this thread to much, does anyone (seriously), know why we have to turn off these devices?

Joe.

Here is my theory: probably because as is, very few people ever listen to the safety briefings from the flight attendants. If they were allowed to use their electronic devices, then nobody would listen and nobody would know how to fasten & unfasten their seatbelts. So the flight attendants would have to go through the whole airplane to show people how to buckle up before take off.

That's my theory and I'm sticking to it. 

Maurice

[sagrada737]

The reason of course is Government Regulations - made up by people in a vacuum against "what if" understandings about how things are designed and how they work in the real world.  Literally, it's all about control, with very little practical sensitivity applied to the situation. 

Have you ever tried to argue with a Flight Attendant about such things?  These days, it will get you thrown off the airplane.  Fact is... Most people on a flight leave most of their electronic stuff ON and don't give a hoot about safety briefings.  I think this is why Soutewest Airlines allow some humor (subjective) to be injected into their safety briefings.  They understand the reality of human nature.   

There is something absurd in why an iPad would be harmful to an aircraft and its electrical systems, yet these same planes are designed to fly through intense lightning environments, where EMI influence is massive - despite the Faraday Cage effect.  Go figure...

Me... I just read the Sky Mall magazine - as instructed 

Mike

[Sam Franklin]

http://www.bbc.co.uk/news/technology-24369188

[jackpilot]

My 2¢
It  cant harm any nav/com systems but...

..for God sake this is one of the last environment where you do not have to be subject to a dozen  private conversations on mundane or business topics, which are just noise!
Just imagine what it would sound or look like if  half of the 200 to 400 passengers were talking (yelling) on their cell and the other half were texting like mad, all of them squeezed within 2 feet from each other!!
Cell phones are not allowed in European High speed trains, not for any tech reason but as a courtesy to fellow travelers.