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

2
votes
1answer
86 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
votes
1answer
112 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 ...
2
votes
3answers
164 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?
0
votes
1answer
86 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
vote
0answers
32 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
votes
1answer
88 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 ...
8
votes
3answers
426 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
votes
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.
1
vote
2answers
249 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 "...
0
votes
0answers
54 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
votes
1answer
125 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
votes
1answer
404 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?
1
vote
1answer
97 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
99 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
votes
1answer
99 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
votes
0answers
72 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
votes
1answer
192 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, ...
8
votes
2answers
268 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 ...
0
votes
1answer
238 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 ...
1
vote
0answers
39 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
vote
1answer
197 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. ...
13
votes
4answers
677 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
votes
2answers
113 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
326 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
529 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
781 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
votes
3answers
288 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
votes
3answers
737 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 ...
8
votes
3answers
739 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
votes
1answer
378 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
votes
0answers
134 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
votes
1answer
163 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
500 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
votes
2answers
510 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
votes
2answers
145 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
641 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
votes
2answers
245 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 ...
1
vote
0answers
119 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 ...
0
votes
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
votes
7answers
11k 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 ...
0
votes
1answer
174 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
votes
2answers
922 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
votes
1answer
603 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" ...
1
vote
1answer
2k views

What is hinge moment?

What is hinge moment? Why in the process of calculating it we must calculate the coefficient of hinge in 2D? Why the distribution of airfoil thickness at 90%, 95%, and 99% of the line should be ...
1
vote
3answers
969 views

Is there a specific relation between sideslip angle and yaw rate OR how sideslip angle depend on yaw rate?

Since, yaw rate is controlled via rudder and sideslip angle can also be controlled by rudder, I want to know if there is any dependence of sideslip angle on yaw rate in fly by wire aircraft as I am ...
1
vote
2answers
3k views

What does stick fixed and stick free longitudinal stability mean in simple terms?

What is the significance of stick fixed and stick free terms in aircrafts with mechanical control and modern fly-by-wire control?
2
votes
1answer
165 views

What are the factors that determine the speed flutter appears on wings?

I'm doing a study on the flutter phenomenon of airplane wings. I'm interested in factors that influence wing stability, and how one can increase the speed where flutter starts. What are the ...
7
votes
3answers
1k views

When leaving ground effect, why is there a nose-up change in moment?

The Airplane Flight Handbook states: The aircraft leaving ground effect will Require an increase in AOA to maintain the same CL Experience an increase in induced drag and thrust required ...
3
votes
1answer
553 views

Did WWII fighters have inverted airfoils for horizontal stabilizers?

Like would for example the P-47 most likely have symmetric, normal or inverted airfoil as horz. tail? Is my analysis correct?: It has a CG at 25-32% MAC according to manual. Since AC on wings is ...
17
votes
3answers
4k views

Would a stationary WWII fighter fall on its nose with full throttle and brakes on?

Would a stationary WWII fighter fall on its nose with full throttle and brakes on? It's a general question, but I am interested in the Republic P-47.