39

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 discharge—lightning. From the FAA's AMT Airframe Handbook, in Chapter 4, page 4-82: Lightening holes are cut in rib sections, fuselage frames, and other ...


18

The F-16 has an all moving tail plane all right. What you are referring to as the 'fixed part' is actually the fuselage portion which houses the air brakes. It can be seen clearly in the following photograph. Belgian AF stabilizer; image from designer.home.xs4all.nl


17

Short answer: Yes Generally you are right. You are trimming the aircraft for a point on its polar, and that point is reached at a specific angle of attack. You say yourself we should neglect secondary effects like the propeller blast, and under this condition you are right. Trimming means to set the distribution of lift between wing and tail surface, and ...


15

(Source: concordesst.com) It does have elevators in the form of elevons at the trailing edge. A delta is effectively a tailless flying wing with a really long chord. Like any flying wing, pitch stability is achieved by down force generated at the local trailing edge by a control surface that does the same job as a regular elevator/stab, by applying down ...


15

This would fall under catastrophic failure and theres not much that can be done. You may as well ask what will happen if a wing falls off. but.. UA232 Sioux City. The #2 engine (in tail) blew up and took out the hydraulic lines rendering all tail control surfaces (horizontal and vertical) inoperative. The crew found they could regain limited control of the ...


14

There are probably many factors in choosing aluminum vs. composites. A big one is bird strikes. The leading edges are at the highest risk for this. Metal tends to absorb the impact better while retaining its strength, while composites would tend to delaminate and become much weaker. Resistance to in-flight hail must also be considered. (Source Left, Right) ...


13

A Boeing 737 has a movable horizontal stabilizer for pitch trim with elevators for pitch control (also known as a THS – Trimmable Horizontal Stabilizer). This is true for all 737 variants, including the MAX. Note: The term stabilator is typically used when the entire tail is rotated for pitch control, like e.g. on a Piper Cherokee. The following image (...


12

Most airliners with low horizontal tail surfaces have dihedral on them, for two reasons: To lift the horizontal surface above the wing wake. To lift the swept tail above the ground, so it will not be damaged in a tail strike. Note that the tail is roughly horizontal at the tail strike attitude to have enough clearance for full down elevator deflection. ...


12

In a general sense, there are multiple reasons for the horizontal stabilizer to have dihedral/anhedral. To clear the tail from the downwash/propwash. A good example is the Cessna 425, which was developed from the Cessna 421. The 421 had a straight horizontal stabilizer. However, with the addition of dihedral, the tail is kept out of the propwash, improving ...


11

The main aerodynamic purpose of the horizontal stab (or certain canards) is to provide longitudinal stability. If the rear wing with the 5th and 6th engine flies "up," like the main wing, then it will counteract the longitudinal stability of the horizontal stabilizer. If the rear wing flies down, like the h-stab, then it is just extraneous, since the h-...


11

Tryin' to cheat the laws of stability, aren't we? In both videos it is evident that the plane is unstable in pitch. Adding a lifting prop will not change this, because changes in the angle of attack will not affect this prop's lift force much. Stability is achieved by shifting the center of gravity forward, so that changes in the angle of attack will ...


11

Here is a screenshot of a B737 Max 8 Runaway Stabilizer Checklist. There might be some small variations in the checklist when comparing each individual airline. Additionally, here is the Boeing "Uncommanded Nose Down Stabilizer Trim" bulletin that was issued to all B737 Max 8 operators after the Lion Air crash.


10

If you look from enough of a distance, the answer is yes. Close up, both will have their own developing wake. The boundary layer leaving wing and tail will leave a speed discontinuity, and the downward moving wing wake will be complemented by a tail wake which will slow down this downward movement directly behind the tail and increase it left and right of ...


8

For the impatient reader: The answer is no. Let me explain it in detail. For this, it is helpful to simplify things as much as possible and then add the complications step by step so I can explain what each changes. The simplest layout uses a symmetric airfoil for both wing and tail and arranges both in the same plane and without a difference in incidence. ...


8

Of course it creates a pitching moment! Now we need to define around which reference point this moment should be measured. If the reference point is the center of gravity, it is even equally strong as the pitching moment of the elevator, it only has the opposite direction. If you use the aerodynamic center as the reference point, the moment will be less ...


8

No, static longitudinal stability does not necessarily imply a download on the tail. Static longitudinal stability requires that the Centre of Gravity is in front of the Centre of Lift, indicated as n.p.$_{fixed}$ in the drawing. Only then will an increase in Angle of Attack d$\alpha$ result in an opposing pitching moment: if d$\alpha$ > 0 then $dC_N$ > 0, ...


8

A converging shape at hypersonic speed in a low-pressure medium will produce close to vacuum pressure on its surfaces (hypersonic shielding). A small sideslip angle will only result in a very small pressure difference between both sides. Contrast this with a diverging shape which produces higher than ambient pressure on both sides. In hypersonic flow this ...


7

When the fuselage is stretched, the arm of the horizontal stabiliser is increased, and hence it's effectiveness increases linearly with the fuselage length. However, because the mass is distributed further away from the centre of gravity, the pitch moment of inertia increases too. If the fuselage would be modelled as a uniform rod, the moment of inertia ...


7

Yes it is done regularly on recurrent sim training, but not to full travel because it is normally treated as a control system fault that can be stopped before it becomes totally uncontrollable, and the Alaska Airlines incident was a mechanical failure of the acme threads on the screw jack where the stab was free to tilt up as far as it could go and they were ...


7

The horizontal stabilizer provides lift, but usually in the negative direction. Could one provide positive lift? The answer depends on cg location. Forward CG, the answer is no. Aft CG, the answer is yes but only if the CG was aft of the center of lift. In other words, the more forward the CG is compared to the center of lift, the more downforce the tail ...


7

As per the A320 flight manual (§127.20 p3), the maximum permitted total pitch alteration in normal law depends upon speed, aircraft mass, CoG, and other factors: Pitch Attitude Limitation: Pitch attitude is limited to: 30º nose up in conf 0 to 3 (progressively reduced to 25º at low speed) 25º nose up in conf FULL (progressively reduced ...


7

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 without displacing the cockpit flying controls. For aeroplane pitch control there are indeed two options: the stabiliser and the elevator. If the elevator is chosen ...


6

Is the aircraft also equipped with trim tabs? From the images available online (this is a youtube screenshot, click it to see the larger version), no. And see point 3 on why I was not expecting any different. If an aircraft has both trim tabs and movable stabilizer I do not see the need of such a solution, a trimmable stabilizer is already ...


6

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 between wing and tail surfaces and will trim the aircraft for a different angle of attack. Changing the incidence gives the empennage a new angle of attack while ...


6

Because the safe situation is: a gravitational moment nose down, trimmed with an aerodynamic moment nose up. In all flight conditions. The critical situation is not cruise, but the conditions at low speed. At TO and landing the Angle of Attack is high: a nose up attitude, commanded by a downward tail force. Velocity is low, so the large force is achieved ...


6

The primary reason is probably because a larger tail increases the CG range. It does not make sense to stretch an aircraft without increasing the CG range. calculating tail volume Often the horz stab is used for the extra fuel capacity needed for stretch models (i.e MD11 and B747). "...the tail fuel tank will provide added range and improve the aircraft’s ...


6

The rear wing (horizontal stabilizer) of a 737 is effectively one piece. There is no separate left and right trim control. Both sides during assembly are attached as one. This is just a visual illusion because the white marks are not aligned. If you manually move one wheel, both wheels will move. It's worth noting that the white marks do not represent the ...


5

Forward sweep is chosen when the designers value resistance against tip stall and a rear location of the wing spar higher than low mass. None of those advantages of a forward swept wing has any weight in the design of a horizontal tail, so a forward swept tail has never been selected.


5

There is some confusion on the different types of tabs that can be found on aircraft: servo tabs, geared tabs, trim tabs. The servo tab is an aerodynamic lever. It is connected directly to the pilot flying controls. When he moves the controls, he deflects the servo tab only, and feels aeroforces acting upon the servo tab only. When the servo tab deflects, ...


5

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.


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