Questions tagged [horizontal-stabilizer]

Questions about the surfaces that typically extend out from the left and right sides of an aircraft's tail, providing longitudinal stability and a place to mount the elevators.

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Control surface deflection during takeoff

What is a reasonable (or typical) control surface deflections required for takeoff? I would like to know two ball park values if possible elevator deflection for conventional transport aircraft ...
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Why are C17's horizontal stabilizer mounted so high? [duplicate]

The C17 has its horizontal stabilizer mounted at the top of the vertical stabilizer, way above the plane of the wing but most aircraft, including other large aircraft made by the same manufacturer (...
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Why is there this open gap (?) above the root of this DC-10's horizontal stabilizer?

Aircraft with trimmable horizontal stabilizers need some way of sealing the area around the root of the stabilizer, so it can move up and down for pitch trim without opening up gaps in the fuselage ...
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What impact had the removal of the horizontal stabilizer end plate on the H135?

In the last update of the H135 helicopter line (EC135 T2 -> EC135 T3) Airbus removed the end plate at the horizontal stabilizer on the tail. I heard from some some people that they had aerodynamic ...
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Can I assume that aoa on horizontal stabilizers correspond to aoa of the main wing?

I am in the process of designing a small wing (Re ~ 50-100k) and am wondering if given (a) the Cm on the main wing is relatively small at low aoas, (b) the horizontal stabilizer will produce lift as ...
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Why do big modern airplanes not use a T-tail configuration for the horizontal stabilizer?

I'm wondering why modern widebody aircraft (such as B787/777, A330/350 etc.) don't use horizontal stabilizers with T-tail configuration. What's the difference between placement of this element? There ...
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Charger vs Bronco horizontal stabilizer volume?

While watching this video on the Convair Model 48 Charger, I was surprised by the dimensions of the horizontal stabilizer. Compared to the North American OV-10 Bronco, which is relatively similar in ...
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What are the degree markers on the tail of this MD-10 for? [duplicate]

I took this picture of of Orbis's McDonnell Douglas MD-10-30. Tail: N330AU. What purpose do the 0 and 2 degree markers serve?
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What are these things on the horizontal stabilizer on a Diamond DA40?

What are these things encircled on the horizontal stabilizer on the Diamond DA40? And why are they used from an aerodynamic point of view? Source: grupooneair.com
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In this MD-11 stall test video, are we seeing the tail stalling first?

Watching this short stall test video for the MD-11, one can notice obvious buffeting (starting at about 0:04) of the tail section, while at the same time – at least apparently – there doesn't seem to ...
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Have an airliner's vertical or horizontal stabilizers or rudders ever broken off?

For a commercial airliner, how strong and reliable are the vertical and horizontal stabilizers and rudders? Can they just break off?
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What are the advantages and disadvantages of the MiG-29's horizontal stabilizers (not what do they do)?

The MiG-29's tail axes are located fairly close to the leading edge, and rotate along an axis oblique to the chord. What are the possible consequences to this arrangement (e.g. actuator torque, ...
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Why do most aircraft with variable incidence tailplane have the possibility to trim much more degrees for nose up than for nose down?

Probably the question will be a little bit confusing but I'll try my best to make it clear. Due the position of the CP with respect of the AC, symmetrical airfoils don't produce pitching moments, but ...
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Why are the Antonov An-124 horizontal stabilisers directly behind the wings?

With the wings being on the same plane as the horizontal stabilisers, turbulent air from the wings would interfere with the airflow over the elevators making them flutter. Surely putting the ...
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For a coaxial rotorcraft, Do horizontal and vertical stabilizers in the tail really make much of a difference?

Can we design a coaxial rotorcraft without tail and tail boom completely? What might be the consequences?
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How to calculate the the variation of Cl wrt the angle of defection of the elevator?

I've checked the lift requirements of the aircraft and selected an optimal airfoil and designed a wing with dimensions of MAC 47cm and semi-span of 163.2 cm and a airfoil S1223. The horizontal ...
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Why do many aircraft have both all-moving tailplanes and elevators?

Many aircraft - particularly large commercial airliners - have both an all-moving tailplane (horizontal stabiliser) and elevators. (They also have a small third moving element on the trailing edge of ...
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Does the yoke move when trimming a THS like it does when using elevator trim?

I would like a clarification from the operational point of view: Both the THS and elevator trim tab is used to remove pilot pressure on the yoke / stick. On the elevator trim similar to the C-172 the ...
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2 answers
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Do horizontal stabiliser force direction change with CG variation for a given aircraft? [duplicate]

I am wondering about the direction in which horizontal stabilizer provide force. I know that it can provide either upforce or downforce. But I am wondering whether is it determined for a particular ...
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When was the first THS (Trimmable horizontal stabilizer) used and on what aircraft?

When was the first THS (Trimmable horizontal stabilizer) used and on what aircraft? Has any UL or GA trimmable stabilizer?
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2 votes
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Do horizontal stabilizers on airliners have varying angle of incidence in the span-wise direction (washout or negative twist)?

Reading this question and answers, I was wondering if modern airliners with cruciform tail have some noticalbe washout or negative twist along the horizontal stabilizer's span. During cruise, if wing'...
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11 votes
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Why is the angle of the horizontal stabilizer marked on the fuselage?

Why are the angles displayed on the fuselage? I understand having markings with depth on the hull of boats, but I don't understand the use case on a plane. Photo of the root of the trimmable ...
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Do aircraft fitted with both a trimmable horizontal stabilizer and a trim tab exist?

This question is restricted to trim on the pitch axis. Both trim tab and THS (trimmable horizontal stabiliser, a whole moving horizontal stabilizer whose movements are used as trim) are used to trim ...
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14 votes
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Why is a blunt trailing edge a better stabilizer at hypersonic speeds?

Here is what I read about the X-15 spaceplane: The X-15 had a thick wedge tail to enable it to fly in a steady manner at hypersonic speeds.[14] This produced a significant amount of drag at lower ...
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Why does the MCAS use the horizontal stabiliser rather than the elevators?

The Maneuvering Characteristics Augmentation System (MCAS), found, in two slightly-different variants, on the 737 MAX and KC-46, provides nose-down pitch inputs in certain very-high-angle-of-attack ...
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How much does the horizontal stabilizer on a 737 move for one unit of trim?

Inspired by this question, what exactly is the meaning of a stab trim unit? Is it exactly one degree of stabilizer movement? The 737 NG FCOMv2 (9.20.9 Flight Controls - System Description) only lists ...
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Did the First Officer of Ethiopian Flight 302 trim in the wrong direction? [closed]

Looking at the accident report of Ethiopian Airlines Flight 302, it says the cut out switches were used. But the manual trim moved from 2.3-2.1? My reasoning for asking this is because the timeframe ...
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1 vote
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Why is the horizontal stabilizer of the Lazair swept back? [duplicate]

Why is the horizontal stabilizer of the Lazair swept back? I understand the hinged elevators are perpendicular to the fuselage, but the horizontal stabilizer is actually swept back.
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What are the maximum possible stabilizer and elevator deflections for the A320?

For research purposes I would like to know the maximum deflection angles (in both positive and negative direction) of the A320-200's stabilizer and elevator. I am trying to analyse what flight ...
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What kind of horizontal stabilizer does a Boeing 737 have?

Does this plane have fixed horizontal stabilizers and elevators or has it been fixed with stabilators instead?
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Does the canard config have radically different controls than classic config?

Classic configuration is something like the A320: wings in the middle, horizontal stabilizers at the tail. Canard configuration is something like the Beechcraft Starship: wings at the back and ...
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How the stabilizer cutout switch functionality has changed from Boeing 737 NG to 737 MAX?

The Boeing 737 NG has stabilizer trim cutout switches marked as MAIN ELECT (left) and AUTOPILOT (right). Turning off the right switch disables automatic stabilizer trim in autopilot mode and automatic ...
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4 votes
2 answers
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Why can't the 737 MAX's horizontal stabilizer autotrim be cut out by control yoke inputs?

According to this article, a horizontal stabilizer runaway on the 737 MAX, unlike with all other 737s, cannot be countered with yoke inputs: Older 737s had another way of addressing certain problems ...
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Why do the stabiliser trim wheels not move exactly in sync?

I've watched a few videos about the Boeing 737, and in particular because it's a bit of a current topic, about the stabiliser wheels in the cockpit. On some of these videos, which are often in ...
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3 votes
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Is there a general approach for designing a Trimmable Horizontal Stabilizer?

What is the general design flow when designing a Trimmable Horizontal Stabilizer (THS) and the attached elevator? I assume you would dimension the max. positive/negative deflections of the THS to ...
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What are the checklist items for a runaway stab trim on a B737 MAX 8 and MAX 9?

This is a follow up question to this question. This question is not directly related to the MCAS system in the new B737 MAX aircraft, instead, my question is about the checklist for a runaway stab ...
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Do horizontal stabilisers provide any lift?

Do jumbo and smaller airliners' horizontal stabilizers provide any lift? Apart from maintaining the aircraft's angle of attack, can they perform the dual function that includes adding some lift as ...
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3 answers
440 views

Why don’t airliners use stabilizer movement to assist with large pitch control inputs?

Most large airliners not only have elevators for pitch control, but also moveable horizontal stabilizers. The elevators are used for primary pitch control, with the stabilizers being used to trim the ...
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Why does the Comet's horizontal stabilizer have so much dihedral?

The Comet's horizontal tail has a noticeably extreme amount of dihedral compared to that of, say, a 707: (Image by MilborneOne at Wikimedia Commons.) Note how the Comet's tail has about twice as ...
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Why the Antonov AN-225 has negative dihedral wings combined with a positive dihedral horizontal stabilizer?

I know the reason why it has negative dihedral wings, but I do not really know why it is combined with a positive dihedral horizontal stabilzer, which are the benefits this configuration provides?
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Why aren't there any jets with horizontal-stabilizer-mounted engines? [duplicate]

Looking at the spectrum of where jet aircraft put their engines, there are examples of almost every place that could conceivably used to carry a jet engine: slung under the wings buried inside the ...
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How do the vortices affect the flow of the horizontal stabilizer upon leaving the wing?

Other than the downwash effect, what other factors that affect the flow to the horizontal stabilizer? such as Dynamic Pressure? Air Flow Disturbance?
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Why are cambered airfoils used for horizontal stabilizers in some designs?

From what I know, usually NACA9/12 or similar symmetrical airfoils are used for the tail. Still some aircrafts use highly cambered airfoils for elevators. What are some advantages and disadvantages ...
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Is there a difference in stability between a tail downforce (cg ahead of ac) and a tail upforce (cg behind)?

So from what I understand, having a - 1.cg ahead of the neutral point(ac) with a tail downforce and 2.cg behind ac with a tail upforce are both stable configurations.(Please correct me if I'm ...
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Does the A320 Trimmable Horizontal Stabilizer automatically reset after landing?

Does the A320's Trimmable Horizontal Stabilizer (THS) automatically reset after landing? If so, is there any condition where it doesn't? And what about the rudder trim? I'm asking because I'm ...
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7 votes
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What is the horizontal stabilizer failure procedure?

During the final flight of Alaska Airlines Flight 261: The CVR transcript reveals the pilots' continuous attempts for the duration of the dive to regain control of the aircraft. At one point, ...
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Why did Concorde not have horizontal stabilizers?

The Concorde did not have horizontal stabilizers or elevators. As a result, the pilots have to move fuel around the aircraft to trim it up or down, as sluggish and hazardous move. Why did the design ...
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Why would a stretch variant need a larger horizontal stabilizer?

With the 787-10 stretch, Vedad Mahmulyin (a Boeing engineer) saved the company millions by implementing a software solution that negated the need to enlarge the horizontal stabilizer. Software again ...
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1 answer
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What is the sweep angle of the Boeing 787's horizontal stabilizers?

What is the sweep angle of the horizontal stabilizers on a Boeing 787 Dreamliner? Does it have to be equal to that of the wings, and how is it determined?
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3 answers
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Why do tailplanes provide down force, if not for longitudinal static stability?

We can see that most conventional aircraft have their horizontal tail surfaces arranged to provide a down force. This question asks if that is required for static longitudinal stability, and the ...
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