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Boeing 747 Roll-Control

Sun Nov 04, 2001 6:25 am

Okay, I know already that the 747 has 2 pairs of ailerons, one inboard, high-speed set, and one outboard, low-speed set.

I'm not exactly certain here, but in pictures, at low speeds with the flaps extended, both low and high-speed ailerons are working at the same time, in conjunction with the flight spoilers in roll-control mode.
Once the flaps go up, the low-speed ailerons are centrally locked in position. The inboards remain online.

Question 1: Is the outboard Aileron's locked-out partially as the flaps go up? With the 727's when you're at Flaps 40, the outboard aileron's are unlimited, but as the flaps pass through 35-degrees of deflection on their way to the 30-detent, a micro-switch restricts aileron motion to 80%, and 50% to flaps 2, and totally locked out at Flaps Up detent or something along those lines. Does it work similarly on the 747? If so, how does this work?

Question 2: Is the inboard aileron's movement always allow 100% of possible travel?

Question 3: Now how exactly do the spoilers work in conjunction with roll-control? At low speeds it appears that the outboard pair of 4-spoilers pop out, and one of the inboard two. Which ones pop up first? In all the pictures all 5 are popped out, but in others only a few are popped out if you know what I mean.

Question 4: Do the spoilers work for roll-control at high-speed?

Question 5: Do they work the same way as they work at low speed, or do they work in a different fashion? If so, which one's pop up, like how many?

Question 6: Does the 747-100 or 200 have flaperons? Or are they just ordinary ailerons? Does the -400 have flaperons?

Can anyone answer this?

I remember there being a person by the name of Aria who was a 747-200/300 pilot, probably a Captain, wonder if there are any other 747-pilots here.

That's all.

-Andrea Kamarov
Posts: 327
Joined: Thu Jul 20, 2000 2:28 pm

RE: Boeing 747 Roll-Control

Mon Nov 05, 2001 5:06 am

The 747 has no flaperons...the massive triple-slotted flaps appear to be sufficient.
Posts: 3552
Joined: Tue Oct 26, 1999 11:34 am

RE: Boeing 747 Roll-Control

Mon Nov 05, 2001 6:52 am

Can a humble 747 ground Engineer answer ?

1. No, The Otbd Ailerons either full range or locked out. Lockm out occurs at 1 unit of flap.

2. Yes

3.The 747 has 6 spoilers per side. #1 Otbd - #6 inbd. .

Lateral Control (Roll)
Spoiler #1 thru 4 have an opearting range of 45 degrees.
Spoiler 5 operates to a maximum of 20 degrees in flight.
Spoiler 6 locked out

In Flt Speed Brakes
Spoilers 1 & 2 do not operate.
Spoillers 3 & 4 max deflection of 45 Degs.
Spoiler 5 & 6 20 degs max.

Ground Spoilers
Spoiler 1 thru 6 45 degs deflection.

Spoiler operation is controlled by two Spoiler Differential mechanisms located on the Fwd b/hd of the wing gear bay. The LH one controls spoilers 3, 4 & 5 while the RH one controls 1 & 2.

They both work on a geometric principle as they consist of bellcranks & levers. Each mechanism can recieve inputs from two sources, the Central Control Actuator (2 off) that controls roll inputs & a Grnd Spoiler Control Valve that controls the operation of Spoiler 6

The amount of deflection is just linearly controlled by the mechanism.

Within the cable run to the #5 Spoiler actuator there is a ratio changer that geometrically modifys the input mechanism movement to limit the spoiler panel range of movement to 20 degs in flight.

4. Yes.

5. Yes.

6. No & No.

I hope that answers your question

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