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74 votes
Accepted

Why are the F/A-18 rudders deflected in opposing directions during takeoff?

Living Wing The Super Hornet has a living wing, that is to say, the shape of the wing is constantly in motion throughout every regime of flight. Trailing edge flaps, leading edge flaps, stabs, ...
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45 votes

When does an airliner switch from using the tiller to the rudder?

I flew for two 747 carriers that never bought new aircraft, and thus this answer applies to 747-100/200 aircraft as originally manufactured for a number of different airlines. The tiller is active ...
  • 38.7k
39 votes
Accepted

What is the advantage of the two-part rudder and how does it work?

This is called Split Rudder and it provides redundancy. They run on different systems so if one fails, the other one can be used. Here is a picture of a split rudder: Split rudders also provide a ...
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39 votes
Accepted

What's the purpose of yawing?

From a totally practical standpoint, let's say you're in a small tricycle gear aircraft with a freely castoring nose wheel (or a tail dragger) and you're starting your takeoff roll in a calm wind. ...
  • 38.7k
39 votes
Accepted

Why are airplanes parked at the gate with max rudder deflection?

The control surfaces of airliners are not connected to the pilots' control via cables; they are operated by a hydraulic pump. When the engines are shut down, there is no hydraulic pressure in the ...
  • 39.3k
33 votes
Accepted

Does an F/A-18 require a lot of rudder in turns?

I used to be an avionics instructor teaching maintenance type courses for the F/A-18. I have plenty of hours flying in the simulator where I would get the students to conduct navigation flights to ...
  • 890
30 votes

Why are the F/A-18 rudders deflected in opposing directions during takeoff?

The rudders are deflected inwards during takeoff of the F/A-18E to help in raising the nose of the aircraft as it leaves the ship. As the vertical fins are canted outwards, deflecting both the rudders ...
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30 votes
Accepted

Are the functions of ailerons and rudder similar?

Short answer: Rudder and ailerons have different purposes and control rotation about two different axis. However a rotation about one axis induces a usually unwanted rotation on the other one. In ...
  • 68k
25 votes

Why are the F/A-18 rudders deflected in opposing directions during takeoff?

The real reason: Ground effect was not considered during development. Ground effect reduces the lift curve slope of lifting surfaces, and the low tail position of the F-18 makes this effect very ...
25 votes
Accepted

Why don't commercial aircraft use all-movable tail surfaces like my RC plane?

What is better and easier for small-scale models is not necessarily better for larger aircraft. First, you can't say that the fixed part "does nothing". The tail is primarily a stabiliser; without it,...
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23 votes
Accepted

Why does rudder cause roll?

There are many higher-order effects. For example, yaw causes a slight increase in airspeed over the outer wing of the turn and a decrease in airspeed over the inner wing. As a result, the outer wing ...
23 votes
Accepted

Do modern aircraft require rudder input in order to perform a coordinated turn?

Most transport aircraft use yaw damper systems to take care of minor rudder inputs. Most autopilot systems are actually only 2-axis - pitch and roll since the rudder's job is only to keep the tail ...
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21 votes
Accepted

What are the disadvantages of using just rudder to roll an airplane?

It works in a half-assed way but the key word is half-assed. You'll always be skidding around the sky since sideslip is required to obtain and maintain any rolling moment. Control response can be ...
  • 110k
18 votes

What happens after a rudder hardover?

With a fully deflected rudder the airplane will fly with substantial sideslip, and by dropping the windward wing it can be held on a straight course. This is usually done intentionally with gliders ...
18 votes

What happens if only rudder is applied in a turn without ailerons? Do the two have to be applied together all the time?

To turn – any vehicle, not just an airplane – you need to generate corresponding centripetal force. When you only apply rudder, the plane will turn a bit, but because unlike boat it has no keel, it ...
  • 54.5k
18 votes

Why increase or decrease rudder when using elevator in turns?

Instructors that teach that to students are fools. You should be using rudder only as required to keep the ball centered - period. If you are applying rudder to influence the pitch attitude, to "...
  • 110k
18 votes
Accepted

Do pilots use the pedals in flight on planes with a sidestick (Airbus)?

The rudder pedals are not usually used in flight, even with the autopilot off. The rudder on the Airbus A320 can be controlled via a mechanical connection to the rudder pedals in the flight deck, but ...
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18 votes
Accepted

Why are there double hinge lines on the rudders of the Grumman C-2?

The double hinged rudder is also a Dehavilland Canada feature on most of its larger designs like the Caribou/Buffalo/Dash 7/Dash 8, where maximum yaw power for a given surface area was a design ...
  • 110k
16 votes

What's the purpose of yawing?

The purpose of yawing is, as you note, to provide a way to rotate the airplane around a vertical axis. Ailerons can roll the airplane around a longitudinal axis and produce a slipping turn, and ...
  • 34.9k
16 votes
Accepted

Did any aircraft ever use stick twist for rudder control?

Yes, the RAH-66 Comanche FBW system used a twist control for the yaw channel. The RAH-66 Comanche used a twist in the pilot's stick to control the rudder/yaw inputs. It had no rudder pedals. (Yes, a ...
14 votes

Why are airplanes parked at the gate with max rudder deflection?

I have no experience on Boeing or Airbus airplanes but the most likely cause would be gust locks installed on the aircraft. Some aircraft, like a C-172, have a pin that locks the aileron and ...
  • 11k
14 votes
Accepted

What is the difference between a vertical stabilizer and a rudder?

The vertical stabilizer is immobile (if it starts to move, you're in deep shit), and provides stability in yaw (it keeps the aircraft pointed more or less in the direction that it's moving). The ...
  • 26.3k
14 votes

Why are there double hinge lines on the rudders of the Grumman C-2?

2 hinge lines will give the rudder more authority because it will direct the air more aggressively. We can think of rudders as vertical and two way extending flaps. It's like the difference between a ...
  • 457
13 votes

Why does rudder cause roll?

After stopping by at our physics friends, it's probably because of the swept wings (causing a lift differential) of the B737: [...] if you introduce a yaw to the aircraft, one wing will extend out ...
  • 255
13 votes

Why does rudder cause roll?

The reasons can be split in two categories: Direct and indirect. Direct reasons are rolling moments which are created directly due to the rudder deflection and the side force on the vertical tail: ...
13 votes
Accepted

How do pilots make rudder inputs during negative G flight?

The short answer is that at negative 2 G, the airframe limit for the A7-E, it took little effort to keep your feet on the rudder pedals. In controlled flight there are aircraft limitations on both ...
  • 4,248
13 votes
Accepted

What is the reasoning behind Kamov twin-rudder design?

It's kind of a hard one. It looks like in this helicopter directional stability is a challenge because: the tail arm is quite short; there is no tail rotor, which provides directional stability just ...
  • 58.9k
13 votes

Can all airliners be turned without rudder input?

It depends on the aspect ratio of the wing and the lift coefficient. Short, stubby wings at low angle of attack will not create much adverse yaw with aileron input, especially when the ailerons have ...
13 votes

When does an airliner switch from using the tiller to the rudder?

Depending on the manufacture of the aircraft (Boeing or Douglas) the use of the tiller or nose wheel steering is different. Douglas aircraft, like the DC-8 and DC-9, had limited nose wheel steering (...
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13 votes

Do pilots use the pedals in flight on planes with a sidestick (Airbus)?

Side stick or no, once airborne, you never touch the rudder pedals in any airliner when flying except during landing where independent rudder inputs are used to keep the airplane lined up during the ...
  • 110k

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