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Questions tagged [control-surfaces]

Aircraft flight control surfaces allow a pilot to adjust and control the aircraft's flight attitude. Development of an effective set of flight controls was a critical advance in the development of aircraft. Early efforts at fixed-wing aircraft design succeeded in generating sufficient lift to get the aircraft off the ground, but once aloft, the aircraft proved uncontrollable, often with disastrous results.

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Effect of Rudder on Velocity Vector

Suppose we have an aircraft flying in steady, level flight at zero angle of attack. In this configuration, the velocity vector $\vec{V}$ is perfectly aligned with the $x$ axis. At some time $t=t_0$, ...
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Why do aircraft have a crossover airspeed, and why does it increase at higher vertical load factors?

According to the NTSB accident report on the crash of USAir Flight 427, all commercial aircraft have a crossover speed (the speed at which the maximum rolling force from the aircraft’s ailerons and ...
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How long does it take on average for a control surface to deflect by one degree

I know this should vary quite a bit (because of aircraft size / use / build / actuation / control surface weight), but I was wondering if anyone here could ball-park some numbers on how long it would ...
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Why don't commercial aircraft use all-movable tail surfaces like my RC plane? [duplicate]

Many conventional RC planes use control surfaces at the tail just like the image below: You can see there is a part in front of each surface control that never moves and only the surface control ...
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What would happen if the elevators were set to opposite angles?

For example left elevator angle = +30 deg, right elevator angle = -30 deg. Would these settings be able to induce a rolling moment on the aircraft? What would happen with the pitch?
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How to determine maximum loads on control surfaces for supersonic flight

I checked control surface sizing and actuator selection having some estimates, but are largely meant for subsonic flight adhering to FAR regulations which dictate the maximum loads and flight ...
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1answer
138 views

How do you know the maximum load a control surface can withstand?

source This is a separate strength testing (load testing) of the elevator of an airplane, how was the load determined? How did the engineers determine the maximum elevator load?
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1answer
218 views

How can an airplane roll, yaw and pitch up and down without control surfaces?

This is a Sprat 103 ultralight, it has no ailerons, and no ruddervator (on its v-tail). How then does it fly controllably?
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Is aerodynamic flutter speed dependent?

Is it possible for control surface flutter to occur at low Reynolds and low speed? If yes,why don't Ultralights have counter weights or tail sting mass to immune the control surfaces against flutter ...
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186 views

Is the 737NG hydraulically controlled or electronically controlled?

I know that the 737NG is not fly-by-wire, but are the control surfaces controlled with hydraulic systems that transfer the input from the pilot to the control surfaces via fluid (hydraulics), or is ...
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1answer
390 views

Do airliner spoilers really “spoil” lift?

The two illustrations below show the typical spoiler location and the lift distribution of a wing. For comparison a third picture shows the location of spoilers on a glider. It appears the airliner ...
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2answers
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How can larger wingspan decrease the strength of wingtip vortices?

In the last paragraph from the link below, it states that Vortex Strength is inversely proportional to Wingspan. Why is this? http://avstop.com/ac/flighttrainghandbook/wingtipvortices.html EDIT: ...
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2answers
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Is having the tailplane at the wings backwash a design flaw?

Most airliners have their tailplane below or above the backwash of the wings, so is placing the tail control surfaces directly in the backwash of the wing a disadvantage?
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In the early days of flight, were there any cockpit control schemes other than the modern one?

Back in the early days, what kind of control schemes were invented for aircraft, other than the modern one? (pedals to yaw, yoke to pitch and roll). I'm only interested in control schemes that can be ...
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How do I calculate the lift force on an aileron?

How do I calculate the force of lift acting on an aileron with a deflection of 8° and a flight speed of 40km/h?
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2answers
282 views

What is a minimal step angle deflection for flight control surfaces?

If the flight control surfaces (ailerons, elevators, rudder) are controlled digitally by servo motors, yet disregarding the way how the input to the servo motors get generated (manually or autopilot), ...
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How does the propeller position affect the effectiveness of control surfaces?

I've found several questions about differences between pusher and puller aircraft, but the effectiveness of control surfaces was not discussed in any of them. Consider the following three scenarios: ...
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833 views

How strong would a servo motor need to be to power the control surfaces of a fixed wing ultralight aircraft?

I'm looking to build an ultralight aircraft. The video above shows a good example of how one is controlled with wires or with metal fulcrums/levers, but I am ...
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3answers
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How do elevons work to roll a flying wing?

I have a RC Flying Wing that uses elevons for control. To go up both elevons pitch upwards and the wing climbs. Both go down and the wing falls. I’m OK with this. However, if I want to roll right, ...
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3answers
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Do fighter jets use elevators as ailerons?

I saw jets in game using elevators to roll right and left, but I never saw them doing in real life. I was wondering if fighter jets actually use elevator to roll like they do in game.
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1answer
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How are the dimensions of the empennage determined for jetliners?

How is the height of the vertical and span of the horizontal stabilizers determined for different turbofan aircraft like the Airbus A380 and the Boeing 747-8? What are the maximum forces (in ...
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What is the relation between missile fin deflection limit and altitude?

What's the relation between limit of deflection for aerodynamic control surfaces (tail control) and altitude for surface to air missiles? Also how can the fin deflection range (Max/Min) be determined ...
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2answers
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How does hydraulic actuator servo valve feedback work?

The book Aircraft Systems uses the following diagram for a mechanically controlled hydraulic linear actuator (for moving a control surface e.g. an aileron): The following explanation is given about ...
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5answers
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Can an aircraft be turned without rudder input?

Is it possible for pilots to make a right or left turn, using just the ailerons and without rudder input in all airliners? If not why so, for what reason?
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2answers
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What kind of flaps are used in gliders?

I'm estimating some wing parameters for an imaginary airplane (simple college project). We are allowed to use coefficients for any basic types of flaps (plain/split/slotted/Fowler etc), but since I'm ...
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1answer
345 views

Does it make sense to use a canard in combination with a conventional aft elevator control surface?

I am designing a UAV and have settled on a canard design. However, I’m curious whether it would be helpful to have a typical horizontal stabilizer behind the wing as well as a canard wing in front of ...
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Can an airplane fly with on-off control surfaces?

I understand that, at least for remote-controlled model planes, the control surfaces can point to a range of angles, say, from $-30^\circ$ degrees to $30^\circ$. My questions are: Would the same ...
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1answer
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How does rudder size influence its ability to produce lateral lift?

Does anyone know how the area, height and width of a rudder affect how well it provides lateral lift? I've heard that the most effective rudders are around 35% of the vertical stabiliser MAC but is ...
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2answers
261 views

What is the purpose of the extra horizontal and vertical surfaces on the tail of the Beechcraft 1900? [duplicate]

I am building a very large(11ft span) twin engine RC airplane that is loosely based on the Beechcraft 1900D design. I can't help but notice the extra horizontal surfaces sticking out of the aft ...
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3answers
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Is it correct to say “the up-elevator position decreases the camber of the elevator”?

Aft movement of the control column deflects the trailing edge of the elevator surface up. This is usually referred to as the up-elevator position. The up-elevator position decreases the camber ...
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1answer
317 views

What does “redatum” means?

I was doing a question about a fully hydraulic elevator and it's position in relation to the trimmable horizontal stabiliser and the explanation of the answer contained the word "redatum". What does ...
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1answer
230 views

What does runaway failure mean (position difference between APPU and FPPU) on A320?

I've been reading the description and operation of Flap systems. WTBs will stop and hold the transmission whenever SFCCs receive some failures.
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2answers
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How are flaps controlled?

I can understand what function(s) the flaps serve, but how are they controlled from an internal perspective? Does flipping the switch send signals to an electrical servo? Or is it hydraulics? How are ...
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2answers
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Do modern airplane controls provide force feedback of external forces on the control surfaces?

As I was sitting inside the cockpit of an old AN-26 at the aviation museum, long grounded and no longer flightworthy, sudden gusts of wind outside would sometimes move the control surfaces and make ...
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4answers
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Is a monobloc variable incidence wing viable (updated)?

Could this be a viable way to control roll on an aerobatic airplane, using some sort of tab to control a monobloc variable incidence wing? Both wings are mechanically linked together in order to only ...
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3answers
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Has anyone researched or built an aircraft that controls pitch and roll by pumping liquid within the airframe?

I am confident I have seen an article couple years ago about a "static surface aircraft" (or at least a concept of it) with no control surfaces, which uses a "wet mass" to adjust its roll and pitch. ...
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2answers
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What is the difference between “x” and “+” configuration in missiles?

What is the difference between "x" and "+" configuration tail fins, and what are the advantages of each in free flight? (for example JDAM missiles)
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How do the actuator loads (e.g. for the ailerons) vary between different flight phases?

Assume the hinge moment is given as $HM = 0.5\rho v^2*C_{h\delta} \delta*S*c$ $\rho$ = air density $v$ = air speed $C_{h\delta}$ = Hinge moment coefficient $S$ = Control surface area $c$ = ...
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How to find runway direction classification, code number and code letter?

I am creating a solution that generated the limitation surfaces for runways according to ICAO Annex 14. One of the parameters that I need is the runway directions classification, code number and code ...
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1answer
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May someone please suggest EHA design procedures for AFS?

Are usual electro-hydraulic actuator designs for aileron control employable for aeroelastic flutter suppression? If not, where can I find design procedures for this specific case?
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1answer
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What aircraft had the first pilot-assisted controls?

This question about regulations regarding hydraulic flight controls got me thinking about the history of hydraulic or pilot-assisted controls. As aircraft get larger the control surfaces must grow ...
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3answers
4k views

How do pilots adjust trim on the B777, where the control forces are simulated?

I know that pilots of small airplanes (e.g. Cessna 172) use force to trim, i.e. they hold the required attitude using the yoke, then trim the aircraft until no force is required to hold the yoke in ...
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1answer
830 views

777 small wing panel moving all the time during landing [duplicate]

What is the small wing panel called that moves up and down all the time during landing? See the following video: What purpose does it serve?
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1answer
221 views

What would the “wings level” button most likely do if activated in the event of a flat spin?

If an aircraft equipped with a wings level button (such as the TBM 930) entered a flat spin, would pressing it accomplish anything productive? I am aware that the purpose of the button is to return ...
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1answer
1k views

What is the purpose of this aileron trailing edge strip?

See the following photos of the LH aileron of a Beechcraft King Air B200: Source: own work Source: own work As seen in the above photos, the Beechcraft King Air B200 has what I would describe as a ...
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3answers
598 views

Can large airliners such as a 747 maneuver without electricity?

Small aircraft have the flight controls physically linked to control surfaces by some kind of cable and pulley system. For a large aircraft such as a 747, are the control systems mechanically aided ...
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1answer
153 views

Does the size of control surfaces affect maneuverability, and if they are smaller, is it easier to stall?

Does the size of control surfaces effect maneuverability and make it easier to stall?
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2answers
694 views

How to calculate aileron deflection for achieving similar roll dynamics at thin and dense air?

my question is inspired by projects like Perlan etc when one is trying to fly in thin air with a glider. It is well known that at high altitude (say 10-20km) aircraft control becomes 'sluggish'. ...
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Why aren't tilting propellers used as an alternative for ailerons or elevators?

I was wondering what are the reasons for not using tilted propellers fixed to ailerons/elevators/elevons? Or even on wings with no control surfaces at all? Wouldn't the 2nd way of thrust vectoring ...
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2answers
391 views

Why are trailing-edge control surfaces usually split?

I've noticed on many military and commercial jets, the trailing edge control surfaces (ailerons and flaps) are separate from each other. Why is this? Can't both serve the same function? It would save ...