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53 votes
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Why do military jets sometimes have elevators in a depressed position when parked?

It generally means that the hydraulic actuator (power control unit) driving the surface has an "idle" facility that allows fluid to move internally between the two sides of the actuator piston, or ...
John K's user avatar
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40 votes
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What are these holes in my Cessna 172, just in front of the elevator?

Those are called "Lightening Holes". The name refers to the weight reduction brought about by removing part of the material—lightening—and should not be confused with anything to do with electrical ...
J W's user avatar
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32 votes
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Why there so many pitch control surfaces on the Piaggio P180 Avanti?

Surface 1 is a horizontal stabilizer with elevator, just the same as on any other aircraft with a T tail arrangement. Surface 2 is called a rear strake or a tail fin. There is one on each side of ...
Jpe61's user avatar
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26 votes
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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,...
Zeus's user avatar
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17 votes

Why do military jets sometimes have elevators in a depressed position when parked?

@John K's answer is perfect. However, in other mechanical systems such as elevators, fork-lifts, factory machines, etc and also NON hydraulic systems (and also possibly Jets) it is designed to be so ...
Mr. de Silva's user avatar
14 votes
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Why does the Boeing 737 have a pitot tube on the tail?

There are five sets of pitot tubes on the 737, organized into two groups, the pitot tubes on the nose are used for airspeed measurements, independent for the pilot and copilot and one as a backup. ...
Ron Beyer's user avatar
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11 votes

Why do military jets sometimes have elevators in a depressed position when parked?

This is a safety feature. You don't want the airplane to blow over in a strong wind. With the elevators down (as you see them in the pictures), a gust from the front will push the plane's nose down ...
jgershon's user avatar
  • 111
9 votes
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Elevator or Aileron?

Wikipedia has a useful page on flight control surfaces, which includes this image: (Credit: Wikimedia Commons) The item labeled inboard flap may be the items you are asking about. From that page: ...
Dave Gremlin's user avatar
  • 2,740
8 votes

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

For a small RC plane that travels at slow speeds your design would work great. However these type of designs have structural limitations. For an all movable vertical and horizontal stabilizer setup ...
DLH's user avatar
  • 5,799
8 votes

Why does the MCAS use the horizontal stabiliser rather than the elevators?

MCAS uses stabiliser input to retain full elevator authority in both directions for pilot input. MCAS is set up as an Inner Loop autopilot: it controls behaviour around the CoG of the aeroplane ...
Koyovis's user avatar
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8 votes

Why is the F-35B's elevator not in neutral position when in vertical flight mode?

In this video you can see it better I think: I drew on a screenshot of the video from the side where you can see the air moving under the aircraft. Compare this to ...
Jan's user avatar
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8 votes
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Why do many aircraft have both all-moving tailplanes and elevators?

Moving each part has different effect on drag: Moving just the elevator increases camber, producing large force which is useful for manoeuvring, but it also produces more drag. Moving the whole ...
Jan Hudec's user avatar
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7 votes
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How do aircraft manufacturers determine the elevator size?

There are many factors going into the sizing of elevators, and they are all interconnected with other considerations such as CG envelope, static margin, flight controls, etc. Here are some factors ...
JZYL's user avatar
  • 11.1k
7 votes

Does the yoke move when trimming a THS like it does when using elevator trim?

When I was type rated in the CRJ200 with hydraulic controls and a THS, directly coming from light aircraft, the differences in technique are significant and it was definitely something new to learn. ...
John K's user avatar
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6 votes
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What would happen if a takeoff is not rejected following an elevator malfunction?

There are a number of scenarios that I can see happening, most of which depend on the aerodynamics specific to the aircraft. Scenario 1: Nose Down Force > Up Force I believe this to be exactly what ...
Ron Beyer's user avatar
  • 36.2k
6 votes

Would there be any benefit in placing the aircraft engines on the elevator (end-tips)?

There are some issues with placing engines in the horizontal stabilizer tips (I'm assuming you mean putting the engines in stabilizer- elevators are the control surfaces): The engines are heavy- ...
aeroalias's user avatar
  • 100k
6 votes

What exactly is a variable incidence tailplane?

Incidence is the angle at which an aerodynamic surface is mounted to the remaining structure of an aircraft. Variable means that this angle can be changed in flight. Normally, a control surface is ...
Peter Kämpf's user avatar
6 votes

Is setting elevator to certain angle equal to trimming the horizontal stabilizer?

Yes, both are equal for small angle changes. Exceptions do apply, especially in transsonic flow. Both changing the stabilizer incidence and the elevator deflection will change the lift distribution ...
Peter Kämpf's user avatar
6 votes

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

Well they do to a degree. Large commercial aircraft have considerably larger CG ranges than their smaller counterparts do in order to accommodate a wide range of loadings as well as shifts in the Cp ...
Romeo_4808N's user avatar
  • 73.8k
6 votes

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

The fixed tail surfaces are to provide a passive weathervaning effect for stability. If you have an all-flying tail, it tends to just want to trail into the airflow, so you need one of two things; ...
John K's user avatar
  • 132k
6 votes

Why do many aircraft have both all-moving tailplanes and elevators?

Drag is one main reason, as outlined in @JanHudec's answer; the other one is maneuverability given the fairly wide CG range that exists on modern transport category aircraft. Without horizontal ...
JZYL's user avatar
  • 11.1k
6 votes
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How are flaps and the elevator positioned in cruise?

Wing flaps are used to significantly change the wing (size/shape/aerodynamics) so that it flies better at the slower speeds associated with taking off & landing. With rare exceptions (fly-by-wire ...
Ralph J's user avatar
  • 51.8k
5 votes

Why does the Boeing 737 have a pitot tube on the tail?

The 2 pitot tubes on the dorsal fin provide pitot pressure (raw airspeed data) to the elevator feel and centering unit to provide artificial feel to the control column. The faster the aircraft flys ...
Mr LaRue's user avatar
  • 111
5 votes
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Is it correct to say "the up-elevator position decreases the camber of the elevator"?

You're absolutely correct, camber equals curvature. The camber of the horizontail tail is changed by deflecting the elevator, not the camber of the elevator itself. And yes the local angle of attack ...
Koyovis's user avatar
  • 61.7k
5 votes
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How to trim in level flight when speed increases?

The angle of attack is lower for the faster flying aircraft. More speed means more dynamic pressure, and in order to create the same lift (weight did not change, after all), less angle of attack is ...
Peter Kämpf's user avatar
5 votes
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How do I achieve a lower stall speed, and capture potential CLmax without enough elevator control authority?

It depends, partially on what you precisely mean with "trim". Pilots use a rather narrow definition where trimming means to zero the control forces for a specific control surface deflection and speed....
Peter Kämpf's user avatar
5 votes
Accepted

Does being out of trim affect drag?

Normally not; details depend on the control system and by how much the aircraft is out of trim. The force produced by the empennage will be the same in the trimmed state and when out of trim, only the ...
Peter Kämpf's user avatar
5 votes

What are these holes in my Cessna 172, just in front of the elevator?

That is one of the horizontal stabiliser spars that holds the plating together. It has holes in it so that it would be strong and still lightweight.
SMS von der Tann's user avatar
5 votes

Amazon Atlas nose-down elevator deflection?

"Nose-down elevator deflection" is a long winded way to say the elevators moved in the direction that would push the aircraft into a dive. It's phrased this way because it isn't always clear from ...
Zeiss Ikon's user avatar
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