Can't wait until we get to servo/anti-servo tabs! 
MolaKule Q&A on Aircraft Structures VI WIngs
- Thread starter MolaKule
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MolaKule
Staff member
Thanks, I have modified question #18 to reflect that.
My understanding is the F-4 Corsair had that wing shape in order to keep the huge prop clear of the ground. F-4s were not allowed to land on carriers until the end of WWII, but that was not because of the prop issue.
Combination of prop clearance and landing gear strength.
Long spindly gear wouldn’t have been sturdy enough for carrier operations.
The gull wing shortened the gear length by bringing the wing structure closer to the ground, allowing shorter landing gear while still providing prop clearance.
The outboard wing was given dihedral to counter the anhedral of the inner wing.
I’ve talked with a few Corsair pilots.
Visibility over the nose was nonexistent. So, for carrier ops, they landed it in a slip, with substantial right rudder and left aileron, allowing the pilot to see the deck and the LSO.
MolaKule
Staff member
Next Wing question: What is an aileron, and how does it affect or control the movement of the aircraft?
An aileron changes the lift of that wing, causing motion in the roll axis of the airplane. A simpler, more consistent method of roll control than the wing warping first employed by the Wright Brothers.
Roll can also be controlled via spoiler deflection on top of the wing, or differential horizontal tail movement.
Roll can also be controlled via spoiler deflection on top of the wing, or differential horizontal tail movement.
We could go on to Fly By Wire systems, and the associated aileron/roll control, and more.
On the G650ER, there are ailerons and spoilers for roll control. 2 ailerons and 6 spoilers.
8 individually controlled surfaces, the ailerons each have two distinctly different actuators, distinct wiring run in different locations and separate control for each actuator. With a total of 5 different computers
On the G650ER, there are ailerons and spoilers for roll control. 2 ailerons and 6 spoilers.
8 individually controlled surfaces, the ailerons each have two distinctly different actuators, distinct wiring run in different locations and separate control for each actuator. With a total of 5 different computers
MolaKule
Staff member
On the G500/550 series we still had a differential data bus and had not graduated to fiber as yet for fly by wire at the time I was involved in the project. We had developed a Synthetic Vision System option for it.
MolaKule
Staff member
Next wing question:
What is a Flaperon and how does it affect flight?
What is a Flaperon and how does it affect flight?
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MolaKule
Staff member
Well, cool your heels because we will be easing into more control surface details such as trimming devices in the future, but here is a prelude:Can't wait until we get to servo/anti-servo tabs!
https://takeflightsandiego.com/assets/documents/Anti-Servo Tab.pdf
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MolaKule
Staff member
Anyone?
The word is a portmanteau of flap and aileron. It provides both roll control, and when symmetrically deployed with its counterpart on the opposite wing, lift. So, it serves as both flap and aileron.
Technically, the ailerons on the F/A-18 are flaperons, because they control lift, and act as trailing edge flaps when landing flaps are selected.
But the manual for the airplane calls them “ailerons”.
Take a look at this photo. Both ailerons are deflected downward along with the inboard flaps. They are providing lift. They are flaps.
But the right hand aileron is deflected upward ever so slightly. It is providing roll control.
So, both lift and roll, flaperon.
I discovered today that the Boeing 787 has flaperons.
At low speeds, the flaperons are part of the high lift system of trailing edge flaps, while roll control is provided by the outboard ailerons.
At higher speeds, the outboard ailerons are locked out, and roll control is provided by the inboard flaperons.
This is a common Boeing arrangement (true on the 747 and 767) where inboard ailerons were used for high-speed role control and outboard ailerons for low speed roll control.
At high speed, the control surfaces are very effective. So, to balance the control feel and response throughout the envelope, only the inboard ailerons were used at high-speed. Further by using only the inboards, you reduce the torsional load on the wing when those control surfaces were deflected.
At low speeds, the flaperons are part of the high lift system of trailing edge flaps, while roll control is provided by the outboard ailerons.
At higher speeds, the outboard ailerons are locked out, and roll control is provided by the inboard flaperons.
This is a common Boeing arrangement (true on the 747 and 767) where inboard ailerons were used for high-speed role control and outboard ailerons for low speed roll control.
At high speed, the control surfaces are very effective. So, to balance the control feel and response throughout the envelope, only the inboard ailerons were used at high-speed. Further by using only the inboards, you reduce the torsional load on the wing when those control surfaces were deflected.
I suppose at higher speeds less input is wanted for a nice customer friendly ride?
Higher velocity air over the control surfaces = more authority. More leverage. And, being at the end of the wing (a longer moment arm), it has more leverage and more control authority.
At 500+ MPH cruising speeds, you don't need a lot of control authority from the ailerons in an airliner to do the gentle rolls they normally do (Tex Johnston and the Boeing Model 367-80 aside
)Engineers/pilots, feel free to elaborate or correct anything I'm wrong about here.
Less input is warranted because the controls become much more responsive, because of increased airspeed, but that is managed through the fly by wire system.
I believe the reason that Boeing does that outboard aileron lockout (and they have done that on lots of wide bodies) has to do with torsional loads in the wing structure - moving the roll loads closer to the fuselage puts less “twist” on the wing. The load is generated where the wing is thicker/stronger.
I can see the logic and or science in that. That is what I was understanding from the subtopic, without the proper words to convey it.
I was not sure if the necessary "directional control" was commensurate with airspeed or if less input would be needed at higher speeds. I assumed in my thought experiment that less input would be needed.....or maybe more specifically "wanted" in such an application. I imagine the rules are slightly different in a fighter as opposed to a commercial airliner.
Flaperon, new one on me. What a name....I reckon they run out of names at some point.
@Astro14
Just sort of a general question:
What speed do you like to fly at in the 757 when in a “holding pattern” for some reason, such as, to wait for T’storms to pass out of the area of the airport?
Is there a certain range specified by your company or in the flight manual?
Or is it directed by ATC?
What determines your speeds in certain flight regimes like this?
Thank you.
Just sort of a general question:
What speed do you like to fly at in the 757 when in a “holding pattern” for some reason, such as, to wait for T’storms to pass out of the area of the airport?
Is there a certain range specified by your company or in the flight manual?
Or is it directed by ATC?
What determines your speeds in certain flight regimes like this?
Thank you.
In general, you are constrained by ATC holding speed limits, which have to do with protecting airspace and traffic deconfliction.
In the US, they are max 200 up to 6,0000, 230 from above 6,000 up to 14,000, and 265 above 14,000. Different countries have different limits, but in general, it’s 200 up to 6, 210 from 6 to 14 and 220 above.
The FMC will calculate a clean maneuver speed, and a recommended holding speed, which is a bit faster. That depends on things like gross weight and OAT.
If you’re able to, you would prefer to hold clean, flaps up, because that gives you the best endurance due to the lowest drag, but depending on weight, altitude assigned, and the country in which you’re flying, you may not be able to.
So, often, going into LHR, for example, we will have to hold at flaps 1 (because we are below flaps up maneuver) and sometimes at flaps 5. Increased flaps increases the drag a bit, by roughly 5-10%, but over a 20 minute hold, it’s not significant.
In the US, they are max 200 up to 6,0000, 230 from above 6,000 up to 14,000, and 265 above 14,000. Different countries have different limits, but in general, it’s 200 up to 6, 210 from 6 to 14 and 220 above.
The FMC will calculate a clean maneuver speed, and a recommended holding speed, which is a bit faster. That depends on things like gross weight and OAT.
If you’re able to, you would prefer to hold clean, flaps up, because that gives you the best endurance due to the lowest drag, but depending on weight, altitude assigned, and the country in which you’re flying, you may not be able to.
So, often, going into LHR, for example, we will have to hold at flaps 1 (because we are below flaps up maneuver) and sometimes at flaps 5. Increased flaps increases the drag a bit, by roughly 5-10%, but over a 20 minute hold, it’s not significant.
So their required max speed is lower?
