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The physics of maintaining a specific state in the dynamic system of aircraft flight.

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0answers
27 views

How would a sudden change in weight affect a plane? [duplicate]

If I have a plane trimmed for perfect straight and level flight and then suddenly I removed some mass from the airplane (let’s ignore any momentums introduced by mass release) – how would the aircraft ...
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2answers
176 views

What would happen if the elevators were set to opposite angles?

For example left elevator angle = +30 deg, right elevator angle = -30 deg. Would these settings be able to induce a rolling moment on the aircraft? What would happen with the pitch?
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1answer
175 views

What is the source for the “rule” forbidding configuration changes below 200ft AGL?

I keep hearing from countless instructors, and even some DPE's, that in single engine aircraft, no configuration changes are allowed below 200AGL (i.e. flaps). Some have also stated that this is ...
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0answers
44 views

What are stick position stability and stick force stability?

What are stick position stability and stick force stability? What are the difference between them? How will changing trim of an aircraft affect them?
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5answers
164 views

Is the aircraft neutral point a function of the tail incidence angle?

While using XFLR v5 for a basic analysis I am facing this issue. For a fixed configuration I varied the tail incidence angle and XFLR is displaying a change in the Neutral point location. But as per ...
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1answer
96 views

Why is the delta wing naturally stable in pitch?

Any thoughts on why the delta wings are naturally more stable in pitch, so they don't require any tail surface? What's the physics behind this?
4
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2answers
258 views

What happens aerodynamically when we trim an aircraft?

I'm trying to understand stability & control. Please correct me if I'm mistaken. An aircraft will have longitudinal stability if the aerodynamic center (AC) is behind the center of gravity (CG). ...
2
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1answer
97 views

What is the location of AC for typical modern airplanes?

Some sources state that AC must be located behind CG, so that AC is stable. There is a source, which throughout the study of stability and control consider AC located ahead of CG and positive cambered ...
5
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1answer
140 views

Why do some Mach trimmers move the elevator?

A pop-up rod on a the FO's control column on a DC-9 that shows the Mach trim position. (YouTube) Regarding the title, I'm not sure if it's just some or all jetliners (I tried to research it). On the ...
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3answers
213 views

Do high-wingers have dihedral?

I know that high wingers have an inherent dihedral effect. Are there any examples of high wing aircrafts with a dihedral? If so, what is the reason behind it?
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1answer
93 views

Is aerodynamic flutter speed dependent?

Is it possible for control surface flutter to occur at low Reynolds and low speed? If yes,why don't Ultralights have counter weights or tail sting mass to immune the control surfaces against flutter ...
1
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0answers
36 views

What happens to the neutral point of a fighter jet during supersonic flight? [duplicate]

I understand that for a fighter aircraft, it would have to be inherently unstable. To do this I believe that the neutral point needs to be aft of the cg. I was told that during supersonic flight this ...
0
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1answer
108 views

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 ...
9
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4answers
484 views

Is this paragraph about the dihedral effect in the FAA's Glider Flying Handbook correct?

I've been reading the FAA's Glider Flying Handbook, 2013 (FAA-H-8083-13A). In chapter 3 ("Aerodynamics of Flight"), the book is discussing stability. On page 3-12, it states: Dihedral is the upward ...
41
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5answers
7k views

Why do most biplanes have their top wing slightly forward of the lower wing?

In most of the biplanes, the top wing is located a little forward of the lower wing. What is the use of this? Also, how does this affect stability of the aircraft.
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2answers
256 views

What is the airplane with the best flying characteristics? [closed]

I'm reading Stick and Rudder by Wolfgang Langewiesche, and in Chapter 7 titled, "What the Airplane Wants to Do" he discusses stability. In discussing it, he says that no plane yet built is completely "...
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0answers
57 views

Controlled stall,aileron or rudder input?

I know aileron input in a stall approach is not adviced, what if vortex generators are placed at the wingtip where the ailerons sit meaning there will still be aileron authority even at stall, at this ...
0
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1answer
129 views

At what angle of deflections do rudders become inefficient?

This article (picture) says rudders for ships can deflect 35° max,so at what aoa does an airplane rudder lose its efficiency,at what " angle of deflection " does it start to stall ?
8
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1answer
416 views

Can an aileron stall in-flight?

Horizontal stabilizers stall, so I was wondering, is it possible for an aileron to stall? If yes, at what angle of attack?
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1answer
113 views

Do elevators have cambered airfoils inverted or symmetrical airfoils

Do horizontal stabilizer of ga planes e.g cessna 172(or ultralights e.g lazair) have cambered airfoils inverted to provide the tail downward force or do they have symmetrical airfoils at negative aoi ...
3
votes
1answer
146 views

Where can I get a graph of lift coefficient against AOA for a symmetrical airfoil?

Where can I get get a graph lift coefficient against AOA for a symmetrical airfoil ? I am asking for a source or link to a graph or table of AOA against Cl of any symmetrical airfoil.
3
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1answer
142 views

What is decalage and how it affects airplane performance?

What is decalage in airplanes and how important is it in respect to airplane performance?
0
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0answers
79 views

Which kind of stability have the aerobatic aircraft?

im designing an aerobatic aircraft (similar to EXTRA 330SC) and i would like to know about the stability lateral and longitudinal, estatic and dynamic. I read somewhere that the aerobatic aircraft ...
0
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1answer
278 views

How does angle of incidence affect an aircraft's stability?

How does angle of incidence affect an aircraft's stability? I've tried searching the web for the simplest answer that makes sense but so far I've come up with nothing as yet. I know it sounds simple, ...
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2answers
292 views

What is purpose of engine pylon airfoils on the Hondajet HA-420?

The engine pylons on the Hondajet are aerodynamically shaped so as to provide a lift force laterally and outwardly. Engine pylon as viewed from rear Engine pylon as viewed from front Are these for ...
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1answer
348 views

Which moments are acting on a flying airplane?

I would like to ask some clarifying questions regarding the moments acting on a flying airplane. My understanding is that there are following force: Weight (pointing down and applied to the CG of ...
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0answers
44 views

How to carry out a CFD simulation for determining the stability derivatives of an aeroplane?

I want to create a 3D model of an aircraft to determine the stability derivatives by using a computational fluid dynamics (CFD) simulation. I tried to google for tutorials that explain how it is ...
1
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1answer
260 views

How to calculate the location of C.G. A.C. & N.P. in static longitudinal stability?

We are in the conceptual stage of design and, using Raymer & Nicolai as references, I am doing a rough calculation of "power off" neutral point (N.P.) to find the optimum c.g. and a.c. positions. ...
14
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4answers
715 views

Why don't single-engine jets suffer severe gyroscopic effects?

I was reading up on World War I fighter aircraft, and saw that rotary piston engines, which powered many of those planes, produced extreme gyroscopic effects due to the large, heavy chunk of metal ...
0
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2answers
114 views

Does ducting help to stabilise heavy lift drones?

I'm looking to build a UAV that is extremely stable. It doesn't have to be fast, it doesn't have to be agile, but it will have to carry up to 50lbs (agriculture focused UAV that has to operate for at ...
6
votes
1answer
349 views

Can the fly-by-wire system of a modern airliner handle an unstable condition?

According to this answer airliners/large passenger aircraft such as an A320 are designed such that they are longitudinally, statically stable under normal flying conditions. What if, for some reason, ...
4
votes
3answers
675 views

What are the relations between stability, controllability and maneuverability?

As preparation for my CFI checkride I have been trying to understand aerodynamics very well. One of the things I’m struggling with is stability If I have a stable aircraft, this means is less ...
7
votes
1answer
916 views

Why is deploying speed brakes not recommended with the flaps extended?

I read this in the normal procedures section of the A320 FCOM. Why is it so? When the speed brakes are deployed, extending the flaps beyond FLAPS 1 may induce a slight roll movement, and in calm ...
6
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3answers
317 views

How does one develop artificial stabilization for aircraft uncontrollable without it?

In an answer about the F-117 Peter Kämpf writes F-117 (...) is unstable and uncontrollable without artificial stabilization. I wonder how such an aircraft comes to existence, specifically how one ...
4
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3answers
852 views

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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3answers
891 views

Does static longitudinal stability require download on the tail?

After having encountered this meme too often for comfort, I ask myself today in order to have the possibility to explain the issue in detail.
5
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1answer
401 views

Are there any fly-by-wire airliners with negative or near-neutral pitch stability?

Are any modern commercial airliners with fly-by-wire flight control systems designed with negative or near-neutral pitch stability so that they can take advantage of the capability of such systems to ...
3
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0answers
144 views

Was the Wright Brothers' 1902 machine a working glider or just a kite?

Was the Wright Brothers' 1902 machine a working glider or just a kite? I spent the last days reading the letters and articles of Amos I. Root, the man who claimed he had seen Wilbur Wright flying his ...
4
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1answer
180 views

Documentation about “drag stabilized flying wings using non-reflex airfoils”?

What provides lift is the wing, but it is unstable without one stabilizer. Flying wings airfoils, or reflex airfoils, carry their stabilizer inside them, through a reversed camber of the trailing ...
4
votes
2answers
564 views

Is there a formula to calculate how big a ventral fin should be?

I've been doing some research into vertical stabilizer designs for a university assignment and have come across ventral fins. I've found a fair bit of information on why they're fitted but can't find ...
3
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2answers
541 views

What makes the F/A-XX twin-engined tailless fighter controllable with engines out?

There are operational tailless aircraft such as B-2 spirit, X-45. It seems yaw stability/control at slow speed is achieved aerodynamically, using either split elevons (B-2) or adjacent elevons ...
0
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2answers
155 views

What are the dynamic stability properties of an aircraft with wings exactly at the vertical CoG?

Please ignore for a moment the practical issues with building and operating an aircraft like this. Suppose a fixed-wing aircraft which, when viewed directly along the roll axis, has the wings ...
3
votes
1answer
849 views

Controllability vs. Stability in PHAK. Is it an error?

My understanding on the relationship between stability and controllability has been that greater stability means less controllability and vice versa. This post confirms that. However, I've came across ...
3
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2answers
274 views

How do I calculate propeller effects on pitching moment?

I have read somewhere that propellers have an effect on the pitching moment of the aircraft. Having said that, I have a couple of questions. Is this a significant effect in model aircraft? If so, are ...
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0answers
143 views

What Inertial effects should be considered to achieve blade stability on a Variable Pitch Propeller tailoredby aerodynamic loads?

I am developing a self adjusting variable pitch propeller tailored by its pitching moments due to aerodynamic loads setting the blade rotation axis in an offset from the aerodynamic center as shown ...
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1answer
1k views

How to locate the coordinates of the Center of Gravity of an airfoil?

I am working on the inertial effects on a variable pitch propeller and i need to define the location of the center of gravity on the airfoil to calculate moments of Inertia and angular momentum. What ...
25
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7answers
12k views

Would a helicopter with the blades on the bottom fly the same, if at all?

I've heard that the pendulum rocket fallacy applies to rotorcraft as well. As stated above, I'm curious to know if a helicopter with blades on the bottom of the body would experience any effects from ...
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1answer
201 views

How to find trim condition of a sectional airfoil without knowing the angle of attack?

I am using a reflexed airfoil designed for positive pitching moments to achieve a pitching angle matched to the changing of free-stream velocity (Aerodynamically tailored). I ended up with a pitching ...
6
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2answers
1k views

What makes spiral instability less harmful than Dutch roll?

The FAA Pilot's Handbook of Aeronautical Knowledge says on page 5-20: Because it is more desirable for the aircraft to have “spiral instability” than Dutch roll tendencies, most aircraft are ...
6
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1answer
653 views

What is the relation between aircraft stability and control?

:) My teacher gave the task to figure out the common relation between stability control. I know definitions and only thing I could find on the internet was "Control is directly opposed to stability" ...