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Airplanes in real life

#1
I was wondering how fighter jets control their ailerons, elevators, and rudders. At first I was wondering if they controlled them with servos and cables, but I cant find anything pointing towards that. How do fighter jets control all those flight controls? What kind of mechanism do they use? Actuator? Servo? Can someone please post a link or video that would help me understand all this. Thanks.

Ps: (I once saw a f22 raptor move up and down its elevators. It seemed like the elevators were connected directly to servos on the side of the aircraft that moved back and forth. Im very confused about of they move that)

Also, this isnt really on topic but what job deals with all this stuff. I would say aeronautical engineer but wouldnt there be a more specific job title. Thanks again :)
 
#2
The most modern aircraft use electro-hydrostatic actuators. Older aircraft use electrically controlled hydraulic actuators.

The EHAs use electric power applied to a mini self contained hydraulic actuator to move the control surfaces. The motive power comes from the electrical system and the EHA is controlled electrically.

The older systems use hydraulic power generated by an engine driven pump, sending fluid pressure via tubes to power the hydraulic actuator at the control surface. The actuator position is controlled electrically, but the motive power comes from the fluid.

The F-22 and all military aircraft using a full flying horizontal tail have a beefy torque tube that goes inside the side of the aircraft, where it is connected to an arm and an actuator.

This is basically more of a mechanical engineering thing, but crosses over into aerospace and electrical engineering.
 

dap35

Active member
#4
The most modern aircraft use electro-hydrostatic actuators. Older aircraft use electrically controlled hydraulic actuators.

The EHAs use electric power applied to a mini self contained hydraulic actuator to move the control surfaces. The motive power comes from the electrical system and the EHA is controlled electrically.

The older systems use hydraulic power generated by an engine driven pump, sending fluid pressure via tubes to power the hydraulic actuator at the control surface. The actuator position is controlled electrically, but the motive power comes from the fluid.

The F-22 and all military aircraft using a full flying horizontal tail have a beefy torque tube that goes inside the side of the aircraft, where it is connected to an arm and an actuator.

This is basically more of a mechanical engineering thing, but crosses over into aerospace and electrical engineering.
The F22 Horizontal actuator is pretty beefy - enough to lift a box car. The sizing is actually driven by the need to maintain the Horizontal under the flight loads.
 
#5
I understand how to get the ailerons to move with a actuator, but what about the rudder and elevator. (Also, just to make sure the actuators act as linear actuaors, correct?)
 

dap35

Active member
#6
I don't remember the setup for the rudders and ailerons, but yes the horizontal (ie elevator) is a linear actuator (think hydraulic piston). They are all buried in the structure, but some there are always compromises so you see bumpouts in the OML to accomidate things like the actuators, etc. Prob not the best picture, and its been a long time, so there might be a couple of errors.
f_22_aft_view_by_spcefrk-d2xk9ef.jpg
 
#9
I don't remember the setup for the rudders and ailerons, but yes the horizontal (ie elevator) is a linear actuator (think hydraulic piston). They are all buried in the structure, but some there are always compromises so you see bumpouts in the OML to accomidate things like the actuators, etc. Prob not the best picture, and its been a long time, so there might be a couple of errors. View attachment 172254
I understand how to get the ailerons to move with a actuator, but what about the rudder and elevator. (Also, just to make sure the actuators act as linear actuaors, correct?)
This cutaway F-22 drawing linked below gives some more details. Shows actuator locations and the shape of the actuators and it’s integral pushrod. If you look closely, you can see a hint of the big conttol horn attached to the torque tube of the horizontal tail, inside the tail boom.

The actuators are orange in this cutaway.

https://conceptbunny.com/lockheed-martin-f-22-raptor/

It basically boils down to an actuator, a pushrod and some sort of small control horn, just like a model.

The leading edge flap actuators are a little different. They use a rotary geared actuator that also serves as the hinges, using torque to move the surfaces, instead of a pushrod.

https://www.moog.com/products/actua...al-actuators/rotary-mechanical-actuators.html

About to retire after 34 years at General Dynamics and Lockheed Martin in Fort Worth. One of my first jobs was wind tunnel and water tunnel work with models of various ATF concepts, which evolved into the YF-22 and then the production F-22.
 
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#10
Thank you Thomas. My dream job is to work at Lockheed Martin as a mechanical engineer or aeronautical engineer. If I wanted to design planes and maybe build them which one of those jobs would involve me doing that?
 

dap35

Active member
#11
Thank you Thomas. My dream job is to work at Lockheed Martin as a mechanical engineer or aeronautical engineer. If I wanted to design planes and maybe build them which one of those jobs would involve me doing that?
When I was in the business, most of the team working on the airframe were Mechanical Engineers, but there were also some Civil Engineers.
 
#12
So the actuator replace the servo that moves the pushrod back and forth, correct?

Sorry I'm responding so late. Also, thank you for all those people who answered and worked on planes in real life. :)
 

quorneng

Well-known member
#14
The term actuator is used to describe a device that converts power into some form of motion. An RC servo is an actuator. It converts electrical energy into mechanical motion. Many actuators, as in an RC servo, have a feed back loop so they can provide proportional motion.
Full size aircraft are no different except they may use hydraulic and/or electrical power to achieve the motion. Hydraulic has the capability to provide a high force from a compact unit but has the risks associated with hydraulic leakage. Electric tends to be heavier but the power is more easily distributed around the structure.
 
#15
Thank you I now understand about hydrolic vs electric. Howver, I really dont understand how the linear actuator moves the aileron and the rudder back and forth and the elevator up and down. I now understand what causes he movement, but not how it makes it. I couldnt find an videos of an rc plane using an linear actuator for flight control or even an animation.
 
#16
This animation of a single and double action hydraulic actuator might help. The double action version is a simplified version of how an aircraft hydraulic actuator functions.


Are you having trouble seeing how the full scale actuator types move the surface without a big control horn sticking out?
This might help.
 

Attachments

#18
That is not a rotary vane actuator. That is a piston attached to a rod inside a hydraulic cylinder. When fluid under high pressure enters the left chamber, the piston moves to the right, causing the pushrod to pull whatever it is attached to the right as well. . The fluid in the right chamber is no longer under pressure and leaves that side.

When fluid under high pressure enters the right chamber, the piston moves to the left and pushes the rod in the other direction. The fluid on the left side is allowed to leave the left chamber.
 
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#20
Aha. A rotary vane actuator like that is usually driven by hydraulic forces and are a variation on a piston actuator. If you google rotary vane actuators, it will show how they work.

Some rotary actuators are electric or hydraulic motors turning gearboxs built into the assembly. It is both actuator and hinges. The control surfaces are bolted to the moving/rotating parts of the actuator while the sections that do not move are bolted to the hinge line area of the aircraft structure. The operation of this creates a rotary force that deflects the surface.

Most commonly used on wing leading edge flaps.

if you refer back to the F-22 cutaway drawing, you can see this type of actuator on the wing leading edge hinge line.
 
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