A B747-400 question

[Cklasse]

I am building the B744 in the in progress post now. A quick question on the take off configuration of this aircraft. 
I want to depict the aircraft taking off with the  main wheels still on ground but the nose wheel in the air. 
What is the position of the horizontal stabilizer? Does it move up slightly, which logically should be to point the nose up. However, pictures of plane take off doesn’t show much deflection. 

[skippiebg]

Hi -- The stance you are describing is technically know as "rotation."

 

The tailplane does not move -- it is set ("trimmed") in the takeoff position during the set of procedures known as the "before takeoff checklist."

 

The elevator (the movable aerodynamic control surface at the trailing or rear end of the tailplane) would not necessarily be deflected at precisely this moment for a complex set of reasons. All control surfaces move for very brief periods: observe the ailerons if you are sitting in an opportune position when you fly next -- you will see them perhaps deflecting for a quarter second or so.

 

Moreover, the elevators might actually be deflected in the opposite direction: once a control surface moves in one direction, the handling pilot immediately moves it in the opposite direction -- otherwise, the aeroplane would continue the manoeuvre until it is inverted and performing a loop or else a tonneau (one or more full rolls or corkscrew manoeuvres). Bicycle riders perform the self-same to/fro movement with their bicycle handlebars -- otherwise, they would end up riding in a circle.

 

Finally, the elevators deflect very little -- again, observe how minute the aileron deflections are.

 

So -- the tailplane would be deflected a few degrees nose-down but the elevators are best left undeflected.

 

Funnily enough, a different set of control surfaces (all four of them on a 747-400) might be deflected quite visibly.  These four surfaces together form the aeroplane's rudder and are positioned at the rear end ("trailing edge") of the fin or (vertical stabilizer in US parlance). The rudder sees very limited use in any flight -- only during the takeoff run and immediate climbout, and again only during the final stages of the final approach and during the landing roll. It induces a sideways slip which helps in those stages of flight by keeping the bank angle neutral. Pilots use the rudder quite energetically during departures in high wind.

 

Hope of help Happy modelling!

[Cklasse]

I get what you mean on the control surfaces moving slightly and briefly. This is what I do when flying radio control helicopter. The transmitter sticks are moved slightly and quickly return to neutral or opposite direction. Failing which, the heli will continue the direction change and may worst case, crash.

 

Good that I do not need to modify the tail planes. The flaps are already slowly torturing me.

[Tbolt]

1 hour ago, Cklasse said:

I get what you mean on the control surfaces moving slightly and briefly. This is what I do when flying radio control helicopter. The transmitter sticks are moved slightly and quickly return to neutral or opposite direction. Failing which, the heli will continue the direction change and may worst case, crash.

 

Good that I do not need to modify the tail planes. The flaps are already slowly torturing me.

 

I'm assuming you are modifying the main gear, but are you having all the main wheels on the ground? If so I would have thought the nose is still going to be fairly low and the aircraft will still be rotating.

 

Also I don't know how accurate your kit is but the inboard elevators are actually rigged slightly more nose up than the outboard ones.

[AV O]

1 hour ago, Cklasse said:

I get what you mean on the control surfaces moving slightly and briefly.

 

These will give you an idea of the position of the stabs on landing and the effects of the stabs movements.

 

https://www.youtube.com/watch?v=XHPv0qt03aA

 

https://www.youtube.com/watch?v=lveluhORNQo

 

Then trying to spot this very instant when the airliner takes off or lands when the stab is almost parrallel to the ground:

https://www.youtube.com/watch?v=Uoq-YsdlkaE

 

Enjoy watching...

 

Edited July 5, 2022 by AV O

[Cklasse]

This is the position of the plane that I will attempt to build. Will likely have to fabricate the main landing gear with metal rods. Still sitting on the fence on whether to do the tilting wheels. 

[Tbolt]

15 minutes ago, Cklasse said:

This is the position of the plane that I will attempt to build. Will likely have to fabricate the main landing gear with metal rods. Still sitting on the fence on whether to do the tilting wheels. 

 

Well you are going to have to tilt the gear because of the angle the aircraft is sitting but you could keep all the body gear wheels on the ground but it would look really strange if the wing gear wasn't close to full tilt.